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Objectives: The aim of this study was to combine deep T cell phenotyping with assessment of citrulline-reactive CD4+T cells in the pre-rheumatoid arthritis (RA) phase., Methods: 20 anti-CCP2 positive individuals ( HLA-DRB1*04:01 ) presenting musculoskeletal complaints without clinical or ultrasound signs of synovitis; 10 arthritis progressors and 10 matched non-arthritis progressors were included. Longitudinal samples (1-3 time points) of peripheral blood mononuclear cells were assessed using HLA-class II tetramers with 12 different citrullinated candidate autoantigens combined in a >20-colour spectral flow cytometry panel., Results: The baseline CD4+T cell phenotype was similar between individuals who progressed to arthritis (ie, in the pre-RA phase) and the non-progressors, when studying markers associated with Th1, Th17, T-peripheral and T-regulatory cells as well as with T-cell activation. Citrulline-reactive CD4+T cells were present in both groups but at significantly lower frequency in the progressor group. CD4+T cells specific for citrullinated tenascin-C were the most frequently observed among the progressors, and their frequencies diminished during follow-up that is, closer to arthritis onset. Notably, PD-1 and CD95 expression on the memory cit-tenascin-C-specific T cells in this group indicated repeated antigen exposure., Conclusions: Our data lend support to citrullinated tenascin-C as an interesting T cell antigen in RA. Moreover, lower frequency of circulating citrulline-specific cells in arthritis progressing individuals suggest an initiated homing of these cells to the joints and/or their associated lymph nodes in the pre-RA phase and a possible window of opportunity for therapeutic preventive interventions., Competing Interests: Competing interests: ST: scholarships from Swedish Society for Rheumatology (sponsored by Amgen and Galapagos). CDV: EULAR travel grants. LM-A is an employee at Thermo-Fisher. LR: fees from AstraZeneca for consulting and as a speaker. VM: research grant from Pfizer., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY. Published by BMJ.)

Objective: This post hoc analysis compared the immunogenicity of the biosimilar adalimumab-adbm (Cyltezo) with the adalimumab reference product (RP; Humira) across indications, including rheumatoid arthritis (RA), Crohn's disease (CD) and plaque psoriasis (PsO), and by patient sex in the VOLTAIRE trials programme., Methods: In each active-comparator randomised controlled trial (RCT), immunogenicity was assessed at various time points by the proportion of patients with antidrug antibodies (ADAs) and neutralising antibodies (nAbs), using acid dissociation followed by electrochemiluminescence assay. Assay sensitivity was 50 ng/mL, and drug tolerance was ≥30 µg/mL (free drug) at the low positive control level., Results: Minor differences in immunogenicity parameters (ADAs, ADA titres and nAbs) were evident between adalimumab-adbm and adalimumab RP across these three immune-mediated inflammatory diseases (IMIDs). The proportion of ADA-positive and nAb-positive patients increased from baseline over time in all three RCTs, as expected, and was similar in the RA and CD RCTs but with higher numbers of ADA-positive and nAb-positive patients reported in the PsO trial. Subgroup analysis by patient sex showed the same trend., Conclusions: Differences among the RCTs may partially be explained by concomitant background therapy (methotrexate) in the RA trial, stable doses of azathioprine, 6-mercaptopurine or methotrexate in 36% of patients with CD and absence of background therapy in the PsO RCT. The analyses further confirm the biosimilarity of adalimumab-adbm with the adalimumab RP across IMIDs and provide supporting evidence that adalimumab-adbm is an interchangeable biosimilar with consistent clinical results in patients originally treated with the RP., Trial Registration Numbers: VOLTAIRE-RA (NCT02137226; EudraCT 2012-002945-40); VOLTAIRE-CD (NCT02871635; EudraCT 2016-000612-14); VOLTAIRE-PsO (NCT02850965; EudraCT 2016-000613-79)., Competing Interests: Competing interests: VS reports consulting for AbbVie, Amgen, Aria, AstraZeneca, Bayer, Bioventus, BlackRock, BMS, Boehringer Ingelheim, Celltrion, ChemoCentryx, Equillium, Gilead, Genentech/Roche, Glenmark, GSK, Horizon, Inmedix, Janssen, Kiniksa, Kypha, Lilly, Merck, MiMedx, Novartis, Pfizer, Priovant, Regeneron, Rheos, R-Pharma, Samsung, Sandoz, Sanofi, Scipher, Setpoint, Sorrento, Spherix and Tonix. SB reports previous employment by Boehringer Ingelheim Pharmaceuticals. DM reports previous employment by Boehringer Ingelheim Pharmaceuticals., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Introduction: Janus kinase (JAK) inhibitors are an important therapeutic option in the treatment of rheumatoid arthritis, but increase the risk of developing herpes zoster. Although a dry recombinant zoster vaccine (RZV) that can be used under immunosuppressive conditions has recently been developed, its optimal use and appropriate timing in patients scheduled to start JAK inhibitors is still unclear. The present study is designed to clarify the appropriate timing of JAK inhibitor initiation to measure varicella zoster virus (VZV)-specific IgG titers and VZV-specific T cell response in patients with rheumatoid arthritis who start tofacitinib at the first RZV vaccination or at the second one., Methods and Analysis: STOP HZ (Effectiveness and S afe T y O f P rophylactic Recombinant H erpes Z oster Virus Vaccination for Rheumatoid Arthritis Patients with Tofacitinib Treatment) study is a multicentre, open-label, randomised, comparative study in patients with rheumatoid arthritis who are scheduled to start tofacitinib. This study enrols 60 study subjects in 12 sites. Enrolled subjects receive RZV two times on day 1 and week 8 and initiate tofacitinib 5 mg two times a day at the time of their first RZV (day 1, group A) or second RZV (week 8, group B) based on randomisation. The random assignment is performed centrally in a 1:1 ratio. Patients in Group B continue the same treatment until the start of tofacitinib treatment. Primary endpoint is VZV-specific IgG antibody titers at week 12 compared with those at baseline in each group. Secondary endpoints include comparison of VZV-specific IgG antibody between the groups, changes in disease activity of rheumatoid arthritis, VZV-specific T cell response and adverse events., Ethics and Dissemination: The study has been approved by the Certified Review Board of Keio (No. 2022008), and conforms to the Declaration of Helsinki and good clinical practice guidelines. Written informed consent is obtained from participants prior to enrolment. The results of this study are planned to be submitted for publishment in relevant peer-review journals., Trial Registration Number: jRCTs031230329., Competing Interests: Competing interests: STa has received honoraria from Abbvie, Astellas, Eisai, Eli Lilly and Pfizer. KO has received honoraria and research support from Eisai, Gilead and AstraZeneca. KM has received honoraria and research support from AbbVie, Eli Lilly and Company, Eisai and Ono Pharmaceutical Co. Ltd. AI received research grant and speaker fees from AbbVie, Asahikasei, AstraZeneca, Boehringer Ingelheim, Chugai, Eli Lilly, Ono, Pfizer, Tanabe and Taisho pharmaceutical. TMatsui has received honoraria and research support from Pfizer, Chugai Pharmaceutical Co. Ltd and AsahiKASEI Co. Ltd. STo has received honoraria and research support from Pfizer Japan, Abbvie Japan Co. Ltd, Chugai pharmaceutical Co. Ltd, AsahiKASEI Co. Ltd, Mitsubishi-Tanabe Pharm Co, Eisai Co. Ltd. Janssen pharmaceutical K.K. SS has received honoraria, research support from Eisai Pharma and received honoraria from Abbvie, GlaxoSmithKline, Eli lilly, Pfizer, Astellas Pharma. TMatsub has received research support and/or speaker honoraria from Astellas Pharma, Bristol-Myers Squibb., AbbVie GK, Eli Lilly Japan K.K., Pfizer Japan, Gilead Sciences K.K. and AYUMI Pharmaceutical Corporation. KY has received honoraria, consultant fees and research support from Pfizer, Abbvie, GlaxoSmithkline, Eli lilly, Astellas Pharma, Gilead G.K., Eisai Pharma. KA has received honoraria from Pfizer Japan and GlaxoSmithKline. YK has received research grants and speaking fees from AbbVie, Astellas, Eisai, Eli Lilly, Pfizer and Gilead Sciences. JS, TMi and YM have no conflict of interest., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: To discover antibody biomarkers that can predict a lack of response to first-line therapy in rheumatoid arthritis (RA) patients., Methods: Two RA cDNA phage display libraries were screened for novel antibodies in baseline RA sera from the Care in early RA (CareRA) trial, differentiating between patients who did or did not reach remission after first-line therapy (n=20 each). Antibody reactivity to identified University Hasselt (UH)-RA antigens was validated in baseline samples from 136 additional CareRA participants. The novel antibodies' potential to predict failure to reach remission or low disease activity (LDA), according to the Disease Activity Score 28-joint C-reactive protein/erythrocyte sedimentation rate (DAS28CRP/ESR) and Clinical/Simplified Disease Activity Index (CDAI/SDAI), was studied by multivariate analyses. The presence of the antibody targets in RA synovial tissue and the fibroblast-like synoviocyte (FLS) cell line SW982 was determined by immunofluorescence., Results: We identified antibodies to 41 novel antigens. Antibodies against any of three antigens, UH-RA.305/318/329, discriminated between RA patients not reaching week (w)8 DAS28CRP remission and those that did (36% vs 13%,p=0.0031). In all patients, anti-UH-RA.305/318/329 antibody reactivity was associated with failure to reach week 8 DAS28CRP and DAS28ESR remission (OR 3.63,p=0.0031; OR 2.92,p=0.016; respectively), SDAI/CDAI sustained remission (OR 5.59,p=0.039 for both) and DAS28CRP and DAS28ESR sustained LDA (OR 3.7,p=0.009; OR 2.76,p=0.042; respectively). In rheumatoid factor/anti-citrullinated protein antibody (RF/ACPA) seronegative patients, these antibodies were strongly associated with failure to achieve week 8 DAS28CRP remission (OR 17.3,p=0.0029). Anti-UH-RA.305/329 antibodies were shown to target FLS in RA synovial tissue and SW982 cells., Conclusion: We identified three antibody biomarkers that are associated with failure to achieve remission/LDA after first-line RA therapy., Competing Interests: Competing interests: PVandormael, VS and PVerschueren have a patent application filed on the biomarkers described in this report., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

BACKGROUND Adipose-derived stem cells (ASCs) from intra-articular adipose tissue of osteoarthritis (OA) and rheumatoid arthritis (RA) patients similarly regulate the proliferation of activated CD4⁺ T lymphocytes and exhibit comparable differentiation potential. This study aimed to assess the impact of ASCs from RA patients on CD4⁺ T cell activation and differentiation into Th17 and T regulatory (Treg) cells. MATERIAL AND METHODS Intra-articular adipose tissue samples were obtained from patients with RA and OA, who underwent knee replacement surgery. ASCs were isolated and cultured either with isolated CD4⁺ cells or with peripheral blood mononuclear cells. After culture, CD4⁺ T cell phenotype was evaluated by flow cytometry, and cytokine concentrations in culture supernatants were analyzed via ELISA. Blocking experiments were conducted to identify the soluble agents responsible for the immunomodulatory effects of ASCs. RESULTS RA- and OA-derived ASCs effectively modulated CD25 and CD69 expression on CD4⁺ cells. RA-derived ASCs failed to induce Tregs, decreased HLA-DR expression, and increased IL-35 production. RA- and OA-derived ASCs reduced TNF and IFN-γ production but increased IL-17 production. The immunomodulatory activities of ASCs were linked to the kynurenine pathway and prostaglandin E2. CONCLUSIONS This study indicates that ASCs modulate the phenotype of CD4⁺ T cells and influence the production of both pro-inflammatory and anti-inflammatory cytokines. However, ASCs from RA patients appear to have impaired immunomodulatory abilities, raising concerns about their therapeutic potential. Further research is needed to enhance our understanding of ASCs biology and their therapeutic utility.

Rheumatoid arthritis (RA), a multigene disorder with a heritability rate of 60 %, is characterized by persistent pain, synovial hyperplasia, and cartilage and bone destruction, ultimately causing irreversible joint deformity. The etiology and pathogenesis of rheumatoid arthritis (RA) are primarily influenced by specific genetic variants, particularly HLA alleles such as HLA-DRB1*01 and DRB1*04. However, other HLA alleles such as HLA-DRB1*10 and DPB*1 have also been found to contribute to increased susceptibility to RA. However, non-HLA genes also confer a comparatively high risk of RA disease manifestation. The most relevant single nucleotide polymorphisms (SNPs) associated with non-HLA genes are PTPN22, TRAF1, CXCL-12, TBX-5, STAT4, FCGR, PADI4, and MTHFR. In conjunction with genetic susceptibility, epigenetic alterations orchestrate paramount involvement in regulating RA pathogenesis. Increasing evidence implicates DNA methylation and histone protein modifications, including acetylation and methylation, as the primary epigenetic mechanisms that drive the pathogenesis and clinical progression of the disease. In addition to genetic and epigenetic changes, autoimmune inflammation also determines the pathological progression of the synovial membrane in joints with RA. Glycosylation changes, such as sialylation and fucosylation, in immune cells have been shown to be relevant to disease progression. Genetic heterogeneity, epigenetic factors, and changes in glycosylation do not fully explain the features of RA. Therefore, investigating the interplay between genetics, epigenetics, and autoimmunity is crucial. This review highlights the significance and interaction of these elements in RA pathophysiology, suggesting their diagnostic potential and opening new avenues for novel therapeutic approaches., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Around 40 % of patients fail to achieve primary clinical outcomes for rheumatoid arthritis (RA). The growth of lymphatic system in the synovial membrane, is a primary response during RA inflammation. It is suggested that a delivery strategy targeting immunosuppressive agents to the synovial lymph nodes and then to the immune cells is beneficial for resolving arthritis. This study introduced a synthetic polypropylene sulfide methotrexate nano-delivery system (PPS-MTX), which was prepared by covalently bonding methotrexate to polypropylene sulfide, with a diameter size range of 36 nm. It enhanced joint accumulation and retention, which can be selectively uptake by antigen-presenting cells in the synovial lymphatic system. The results indicated that PPS-MTX nanoparticles effectively improved arthritis disease progression and restored the immune tolerance microenvironment in the synovial lymphatic system, promoting peripheral tolerance in collagen-induced arthritis mice. Additionally, no systemic toxicity was observed. This study presents a promising targeted strategy for inducing immune tolerance in the treatment of rheumatoid arthritis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Rheumatoid arthritis (RA) is an enduring autoimmune inflammatory condition distinguished by continual joint inflammation, hyperplasia of the synovium, erosion of bone, and deterioration of cartilage.Fibroblast-like synoviocytes (FLSs) exhibiting "tumor-like" traits are central to this mechanism.ADP-ribosylation factor-like 4c (ARL4C) functions as a Ras-like small GTP-binding protein, significantly impacting tumor migration, invasion, and proliferation.However, it remains uncertain if ARL4C participates in the stimulation of RA FLSs exhibiting "tumor-like" features, thereby fostering the advancement of RA. In our investigation, we unveiled, for the inaugural instance, via the amalgamated scrutiny of single-cell RNA sequencing (scRNA-seq) and Bulk RNA sequencing (Bulk-seq) datasets, that activated fibroblast-like synoviocytes (FLSs) showcase high expression of ARL4C, and the ARL4C protein expression in FLSs derived from RA patients significantly surpasses that observed in individuals with osteoarthritis (OA) and traumatic injury (trauma).Silencing of the ARL4C gene markedly impeded the proliferation of RA FLSs by hindered the transition of cells from the G0/G1 phase to the S phase, and intensified cell apoptosis and diminished the migratory and invasive capabilities. Co-culture of ARL4C gene-silenced RA FLSs with monocytes/macrophages significantly inhibited the polarization of monocytes/macrophages toward M1 and the repolarization of M2 to M1.Furthermore, intra-articular injection of shARL4C significantly alleviated synovial inflammation and cartilage erosion in collagen-induced arthritis (CIA) rats. In conclusion, our discoveries propose that ARL4C assumes a central role in the synovial inflammation, cartilage degradation, and bone erosion associated with RA by triggering the PI3K/AKT and MAPK signaling pathways within RA FLSs.ARL4C holds promise as a prospective target for the development of pharmaceutical agents targeting FLSs, with the aim of addressing RA., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Rheumatoid arthritis (RA) is an inflammatory joint disease characterized by persistent synovitis and inflammation. The exact mechanism of mitochondrial function in the presence of inflammation and dysregulation of autophagic processes in the pathogenesis of RA is still unclear. The aim of our study is to determine mitochondrial function, gene and protein levels of biomolecules related to inflammation (YKL-40) and autophagy (LAMPs) and to search a connection between them in the RA context. Twenty newly diagnosed RA patients and ten healthy individuals were included in the study. Disease severity was assessed by ultrasonography. Conventional clinico-laboratory parameters, immunological markers and protein levels of LAMPs and YKL-40 were examined in plasma. Gene expression analysis for the quantitative measurement of LAMPs and YKL-40 were conducted in white blood cells (WBC). A real-time metabolic analysis was performed to assess mitochondrial function and cell metabolism in peripheral blood mononuclear cells (PBMCs). Increase in spare respiratory capacity in PBMCs of RA patients was detected. Decreased LAMPs plasma protein levels and increased protein levels of YKL-40 in RA patients compared to healthy individuals were measured. No significant differences were found in gene expressions. Correlations between mitochondrial, ultrasonographic and protein levels of the biomarkers related with inflammation and autophagy were established. New data on mitochondrial dysfunction in RA patients and links to inflammation and mitophagy are reported. The relationship between dysregulation of mitophagy and joint diseases deserves to be thoroughly investigated as it would be a promising therapeutic approach., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Rheumatoid arthritis (RA) is an autoimmune disease that causes persistent inflammation involving the joints, cartilage, and synovium. In individuals with RA, alterations in the composition of intestinal bacteria suggest the vital role of gut microbiota in immune dysfunction. Multiple therapies commonly used to treat RA can also alter the diversity of gut microbiota, further suggesting the modulation of gut microbiota as a prevention or treatment for RA. Therefore, a better understanding of the changes in the gut microbiota that accompany RA should facilitate the development of novel therapeutic approaches. In this study, B. coagulans BACO-17 not only significantly reduced paw swelling, arthritis scores, and hind paw and forepaw thicknesses but also protected articular cartilage and the synovium against RA degeneration, with a corresponding downregulation of TNF-α expression. The inhibition or even reversing of RA progression highlights B. coagulans BACO-17 as a novel therapeutic for RA worth investigating., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Objective: Helicobacter pylori infection has been reported to aggravate rheumatoid arthritis (RA), but the relevant mechanism remains unclear. This study aimed to investigate the underlying pathogenic mechanism of H. pylori infection in the progression of RA., Methods: The Disease Activity Score (DAS-28) and serum anticitrullinated protein antibody (ACPA) levels were compared between H. pylori -negative and H. pylori -positive patients with RA. MH7A cells were stimulated with polyclonal ACPA purified from the peripheral blood of patients with RA. The citrullination levels were assessed by western blot in GES-1 cells and sera. ChIP, luciferase reporter assays, mass spectrometry and ELISA were applied to explore the molecular mechanism of H. pylori infection in RA progression., Results: The DAS-28 and ACPA levels of patients with RA in the H. pylori -positive group were significantly higher than those in the H. pylori -negative group. Polyclonal ACPA derived from H. pylori -positive patients promoted cell proliferation and induced secretion of IL-6 and IL-8. For the first time, we found that H. pylori infection induces cellular protein citrullination by upregulating protein arginine deiminase type 4 (PAD4). Furthermore, we confirmed a direct functional binding of hypoxia-inducible factor 1α on the PADI4 gene promoter. We demonstrated that PAD4 interacts with and citrullinates keratin 1 (K1), and serum and synovial fluid levels of anti-Cit-K1 antibody were markedly increased in H. pylori -infected patients with RA., Conclusion: Our findings reveal a novel mechanism by which H. pylori infection contributes to RA progression. Therapeutic interventions targeting H. pylori may be a viable strategy for the management of RA., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY. Published by BMJ on behalf of EULAR.)

Objectives: Viruses have been considered as important participants in the development of rheumatoid arthritis (RA). However, the profile of enteric virome and its role in RA remains elusive. This study aimed to investigate the atlas and involvement of virome in RA pathogenesis., Methods: Faecal samples from 30 pairs of RA and healthy siblings that minimise genetic interferences were collected for metagenomic sequencing. The α and β diversity of the virome and the virome-bacteriome interaction were analysed. The differential bacteriophages were identified, and their correlations with clinical and immunological features of RA were analysed. The potential involvement of these differential bacteriophages in RA pathogenesis was further investigated by auxiliary metabolic gene annotation and molecular mimicry study. The responses of CD4 + T cells and B cells to the mimotopes derived from the differential bacteriophages were systemically studied., Results: The composition of the enteric bacteriophageome was distorted in RA. The differentially presented bacteriophages correlated with the immunological features of RA, including anti-CCP autoantibody and HLA-DR shared epitope. Intriguingly, the glycerolipid and purine metabolic genes were highly active in the bacteriophages from RA. Moreover, peptides of RA-enriched phages, in particular Prevotella phage and Oscillibacter phage could provoke the autoimmune responses in CD4 + T cells and plasma cells via molecular mimicry of the disease-associated autoantigen epitopes, especially those of Bip., Conclusions: This study provides new insights into enteric bacteriophageome in RA development. In particular, the aberrant bacteriophages demonstrated autoimmunity-provoking potential that would promote the occurrence of the disease., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ on behalf of EULAR.)

Objectives: T helper 9 (Th9) cells are recognised for their characteristic expression of the transcription factor PU.1 and production of interleukin-9 (IL-9), which has been implicated in various autoimmune diseases. However, its precise relationship with rheumatoid arthritis (RA) pathogenesis needs to be further clarified., Methods: The expression levels of PU.1 and IL-9 in patients with RA were determined by ELISA, western blotting (WB) and immunohistochemical staining. PU.1-T cell-conditional knockout (KO) mice, IL-9 KO and IL-9R KO mice were used to establish collagen antibody-induced arthritis (CAIA), respectively. The inhibitor of PU.1 and IL-9 blocking antibody was used in collagen-induced arthritis (CIA). In an in vitro study, the effects of IL-9 were investigated using siRNAs and IL-9 recombinant proteins. Finally, the underlying mechanisms were further investigated by luciferase reporter analysis, WB and Chip-qPCR., Results: The upregulation of IL-9 expression in patients with RA exhibited a positive correlation with clinical markers. Using CAIA and CIA model, we demonstrated that interventions targeting PU.1 and IL-9 substantially mitigated the inflammatory phenotype. Furthermore, in vitro assays provided the proinflammatory role of IL-9, particularly in the hyperactivation of macrophages and fibroblast-like synoviocytes. Mechanistically, we uncovered that PU.1 and IL-9 form a positive feedback loop in RA: (1) PU.1 directly binds to the IL-9 promoter, activating its transcription and (2) Th9-derived IL-9 induces PU.1 via the IL-9R-JAK1/STAT3 pathway., Conclusions: These results support that the PU.1-IL-9 axis forms a positive loop in Th9 dysregulation of RA. Targeting this signalling axis presents a potential target approach for treating RA., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ on behalf of EULAR.)

Interleukin-22 (IL-22) is a vital cytokine that is dysregulated in various autoimmune conditions including rheumatoid arthritis (RA), multiple sclerosis (MS), and Alzheimer's disease (AD). As the starting point for the activation of numerous signaling pathways, IL-22 plays an important role in the initiation and development of autoimmune diseases. Specifically, imbalances in IL-22 signaling can interfere with other signaling pathways, causing cross-regulation of target genes which ultimately leads to the development of immune disorders. This review delineates the various connections between the IL-22 signaling pathway and autoimmune disease, focusing on the latest understanding of the cellular sources of IL-22 and its effects on various cell types. We further explore progress with pharmacological interventions related to targeting IL-22, describing how such therapeutic strategies promise to usher in a new era in the treatment of autoimmune disease., (© The Author(s) 2024. Published by Oxford University Press on behalf of the British Society for Immunology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Objective: Psoriatic arthritis (PsA) and rheumatoid arthritis (RA) are the most common types of inflammatory musculoskeletal disorders that share overlapping clinical features and complications. The aim of this study was to identify shared marker genes and mechanistic similarities between PsA and RA., Methods: We utilized datasets from the Gene Expression Omnibus (GEO) database to identify differentially expressed genes (DEGs) and perform functional enrichment analyses. To identify the marker genes, we applied two machine learning algorithms: the least absolute shrinkage and selection operator (LASSO) and the support vector machine recursive feature elimination (SVM-RFE). Subsequently, we assessed the diagnostic capacity of the identified marker genes using the receiver operating characteristic (ROC) curve and decision curve analysis (DCA). A transcription factor (TF) network was constructed using data from JASPAR, HumanTFDB, and GTRD. We then employed CIBERSORT to analyze the abundance of immune infiltrates in PsA and RA, assessing the relationship between marker genes and immune cells. Additionally, cellular subpopulations were identified by analyzing single-cell sequencing data from RA, with T cells examined for trajectory and cellular communication using Monocle and CellChat, thereby exploring their linkage to marker genes., Results: A total of seven overlapping DEGs were identified between PsA and RA. Gene enrichment analysis revealed that these genes were associated with mitochondrial respiratory chain complex IV, Toll-like receptors, and NF-κB signaling pathways. Both machine learning algorithms identified Ribosomal Protein L22-like 1 (RPL22L1) and Lymphocyte Antigen 96 (LY96) as potential diagnostic markers for PsA and RA. These markers were validated using test sets and experimental approaches. Furthermore, GSEA analysis indicated that gap junctions may play a crucial role in the pathogenesis of both conditions. The TF network suggested a potential association between marker genes and core enrichment genes related to gap junctions. The application of CIBERSORT and single-cell RNA sequencing provided a comprehensive understanding of the role of marker genes in immune cell function. Our results indicated that RPL22L1 and LY96 are involved in T cell development and are associated with T cell communication with NK cells and monocytes. Notably, high expression of both RPL22L1 and LY96 was linked to enhanced VEGF signaling in T cells., Conclusion: Our study identified RPL22L1 and LY96 as key biomarkers for PsA and RA. Further investigations demonstrated that these two marker genes are closely associated with gap junction function, T cell infiltration, differentiation, and VEGF signaling. Collectively, these findings provide new insights into the diagnosis and treatment of PsA and RA., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Zhou et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Aim: Rheumatoid arthritis (RA) is a prevalent autoimmune disease characterized by immune dysegulation, including an immune imbalance due to abnormal activation of non-classical Th1 cells (CD161 + Th1). This study investigated the effects of CCR5 on the activation and proliferation of CD161 + Th1 and their pathogenicity in patients with RA., Methods: The study was conducted on 53 patients with RA and 32 age- and sex-matched healthy controls (HC). The cell phenotype was assessed by flow cytometry and the cytokine levels in the supernatant were detected by ELISA., Results: We demonstrate a marked increase in CD161 + Th1 cells in the synovial fluid of RA patients. These cells exhibit a hyperactivated and hyperproliferative state alongside elevated CCR5 expression. Furthermore, the levels of CD161 + Th1 cells, CD25, and CCR5 in RA synovial fluid show a positive correlation with the disease activity. Additionally, our study reveals that CCR5 facilitates the activation, proliferation, and cytokine production of CD161 + Th1 cells through the pZAP70/NFAT signaling pathway., Conclusion: These findings contribute to a deeper understanding of RA pathogenesis and uncover a novel mechanism that regulates non-classical CD161 + Th1 responses in RA, which may provide a potential therapeutic target., (© 2024 Asia Pacific League of Associations for Rheumatology and John Wiley & Sons Australia, Ltd.)

Introduction: Coronavirus disease 2019 (COVID-19) vaccines aroused concerns about the risk of flares and adverse events in inflammatory arthritis (IA) since the vaccine clinical trials did not specifically investigate this subset of patients., Methods: A systematic literature review and meta-analysis to summarize the data on joint disease flare and adverse events following immunization (AEFI). Two researchers independently evaluated the literature on Pubmed, Scopus, and EMBASE databases from 22 nd March 2020 to 30 th September 2023. A random-effects model was used to pool odds ratios (OR) (with 95% CI) for the risk of joint disease flares and adverse events. Subgroup analyses were performed to evaluate the risk of disease flare between different IA and adverse events. Heterogeneity was assessed by I 2 statistic., Results: A total of 9874 IA patients were included in the study: 6579 (66.6%) patients affected by RA and 3295 (33.4%) spondyloarthritis (SpA). The overall rate of flares was higher in RA vs. SpA (9.1% vs. 5.3%). However, the pooled estimated analysis showed no increased risk of joint disease flare following COVID-19 vaccination in patients affected by RA vs. SpA [OR 0.88, 95% CI: 0.77-1.00]. Furthermore, a subgroup analysis showed an increased risk of joint flares in psoriatic arthritis (PsA) patients vs. RA [OR 0.79, 95% CI: 0.68-0.93, p=0.004]. The pooled estimated analysis revealed no increased risk of AEFI in patients with RA vs. SpA [1.02, 95% CI: 0.63-1.65]., Conclusions: Our meta-analysis summarized the current evidence on joint disease flares and COVID-19 vaccine-associated AEFI in IA patients. Pooled analysis showed an increased risk of disease flares in PsA vs. RA patients., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Hoxha, Striani, Lovisotto, Simioni, Doria and Ramonda.)

Introduction and Objective: Peripheral and follicular helper T lymphocytes (Tph and Tfh, respectively) have an important role in B cell immune responses and the pathogenesis of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Although several studies on the number of Tph and Tfh cells in these conditions have been published, different phenotypes have been employed for their analysis. In this study, we assessed the levels and function of Tph and Tfh cells in blood samples from patients with RA and SLE by using an extended immunophenotype., Materials and Methods: In a cross-sectional pilot study, blood samples from twenty-seven patients with RA and fifteen with SLE, and twenty-six healthy controls were studied. The levels of Tph (CD4 + PD-1 + CXCR5 - CD38 + CD69 + ICOS + ) and Tfh (CD4 + PD-1 + CXCR5 + CD38 + CD69 + ICOS + ) cells were analyzed by flow cytometry. In addition, the function of Tph/Tfh cells was estimated by measuring the synthesis of IL-21 by these lymphocytes as well as the number of circulating plasmablasts (CD19 + CD27 + CD20 - CD38 hi )., Results: Increased percentages of Tph and Tfh lymphocytes were detected in patients with RA and SLE. Furthermore, the synthesis of IL-21 tended to be higher in both conditions, and higher levels of plasmablasts were detected in these patients, compared to controls. In patients with SLE, the number of Tph cells was associated with disease activity and with the levels of circulating plasmablasts, whereas in patients with RA a significant correlation between Tph cells and evolution time was observed., Discussion and Conclusions: Our data of Tph and Tfh lymphocytes, based in the analysis of an extended phenotype of these cells, provides further evidence on their involvement in the pathogenesis of RA and SLE., (Copyright © 2024 Elsevier España, S.L.U. and Sociedad Española de Reumatología y Colegio Mexicano de Reumatología. All rights reserved.)

Aim: This study aimed to evaluate the predictive value of serum humoral factors in determining the therapeutic responses to biologic DMARDs (bDMARDs), especially TNF inhibitors (TNFis), in patients with RA., Methods: A cohort of 52 patients with RA who were treated with bDMARDs, including TNFis, abatacept, and tocilizumab, was analyzed. Serum samples were collected at baseline (t1), 5 ± 1 (t2), and 14 ± 2 weeks (t3) after treatment. A bead-based immunoassay was used to quantify serum cytokines/chemokines. Treatment response was determined 1 year after initiation., Results: Distinct patterns of IL-6 behaviors were observed among different bDMARDs. Patients exhibiting IL-6 rebound at 14 weeks were more likely to be non-responders to TNFi after 1 year, and this rebound appeared to be associated with increases in IFN-γ and IL-12 levels. IFN-β was more detectable than IFN-α2 in RA. Additionally, patients with measurable IFN-β at baseline tended to be TNFi responders., Conclusion: Monitoring serum humoral factors may offer valuable insights into the likelihood of therapeutic success of TNFi in patients with RA. IL-6 rebound at 14 weeks might serve as an early indicator of non-responsiveness to TNFi. These findings highlight the potential of personalized treatment strategies for RA based on serum humoral factor profiling. Larger prospective studies are needed to validate these results and elucidate the underlying mechanisms., (© 2024 Asia Pacific League of Associations for Rheumatology and John Wiley & Sons Australia, Ltd.)

Periodontitis (PD) is characterized by the host's inflammatory responses to microbial dental biofilm dysbiosis, potentially resulting in tooth loss if left untreated. Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease leading to synovial inflammation and destruction of joint cartilage and bone. The suggested association between PD and RA is based on the potential of chronic inflammation present in periodontitis, which could induce alterations in proteins through post-translational modifications, leading to the formation of citrullinated and carbamylated protein antigens. Antibodies directed against these antigens can serve as biomarkers for the underlying immunological processes in RA. Recent studies have also focused on bacterial proteolytic enzymes released from PD-associated bacteria, such as Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, which are also sources of these antibodies. Chronic inflammation in PD causes increased levels of inflammatory cytokines (interferon-α, interleukins-6 and 8, tumor necrosis factor-α) and neutrophil extracellular traps (NETs). The oral microbiota in PD is also associated with the release of NETs (a process known as NETosis). Elevated NET levels are a source of citrullinated and carbamylated proteins which highlights their role in an individual's risk of developing RA (pre-RA individuals) and the progression of chronic RA. This narrative review describes periodontitis and the dysbiotic subgingival microbiota and its role in NETosis as risk factors for inducing early RA and the prospects of identifying pre-RA individuals and seronegative RA patients with these risk factors., (© 2024 Asia Pacific League of Associations for Rheumatology and John Wiley & Sons Australia, Ltd.)

Background: Immune factors are crucial in the pathogenesis of rheumatoid arthritis (RA), and immune cells play a key role in the development of RA. However, there is still disagreement regarding the specific roles of each type of immune cell in the pathological process of RA., Methods: This study used bidirectional two-sample Mendelian randomization (MR) analysis to determine the causal relationship between immune cell characteristics and RA. Utilizing publicly available genetic data, we initially treated immune cell characteristics as exposures to investigate their causal effects on the risk of RA. Subsequently, we performed reverse two-sample MR using the positively selected cells from the initial analysis as outcomes, aiming to identify the core immune cells involved. Finally, a comprehensive sensitivity analysis was conducted to validate the robustness, heterogeneity, and horizontal pleiotropy of the results., Results: Using data from 731 immune cells as exposures and cell SNPs as instruments, we independently conducted two-sample MR analysis for each patient with RA. The main analytical method used was the IVW method, with a significance level set at P < 0.05 for inclusion. In total, we identified 42 immune cell phenotypes that were causally associated with the onset of RA. For the reverse MR analysis, we used RA as the exposure factor and focused on 42 immune cell phenotypes as outcomes. Our analysis revealed causal relationships between the onset of RA and 7 immune cell phenotypes. Among these, 6 showed positive causal relationships, while 1 exhibited a negative causal relationship., Conclusions: Our study emphasized the causal relationship between immune cells and RA through bidirectional two-sample MR analysis, identifying the immune cells causally associated with RA., (© 2024. The Author(s).)

Rheumatoid arthritis (RA) is an autoimmune condition that mostly impacts the joints. During the advanced phases of the disorder, it may be accompanied by other problems. While the precise cause of RA is uncertain, various research has been conducted to gain a better understanding of the immunological processes involved in the development of RA. T cells are acknowledged as significant contributors to the progression of RA because of their roles in cytokine secretion, antigen presentation, and facilitating B cells in the manufacture of antibodies. γδ T cells are a small subset of T cells that have significant functions in the context of infection and diseases linked with tumors. γδ T cells have been the subject of investigation in autoimmune disorders in recent years. This review focused on the involvement of γδ T lymphocytes in the development of RA. In this article, we provide an analysis of the immunological capabilities of γδ T cells, intending to comprehend their significance in RA, which could be pivotal in the creation of innovative clinical treatments., (© 2024 Asia Pacific League of Associations for Rheumatology and John Wiley & Sons Australia, Ltd.)

Precision medicine in immune-mediated inflammatory diseases (IMIDs) requires a cellular understanding of treatment response. We describe a therapeutic atlas for Crohn's disease (CD) and ulcerative colitis (UC) following adalimumab, an anti-tumour necrosis factor (anti-TNF) treatment. We generated ~1 million single-cell transcriptomes, organised into 109 cell states, from 216 gut biopsies (41 subjects), revealing disease-specific differences. A systems biology-spatial analysis identified granuloma signatures in CD and interferon (IFN)-response signatures localising to T cell aggregates and epithelial damage in CD and UC. Pretreatment differences in epithelial and myeloid compartments were associated with remission outcomes in both diseases. Longitudinal comparisons demonstrated disease progression in nonremission: myeloid and T cell perturbations in CD and increased multi-cellular IFN signalling in UC. IFN signalling was also observed in rheumatoid arthritis (RA) synovium with a lymphoid pathotype. Our therapeutic atlas represents the largest cellular census of perturbation with the most common biologic treatment, anti-TNF, across multiple inflammatory diseases., (© 2024. The Author(s).)

Objectives: To compare the humoral response after a SARS-CoV-2 infection in an inflammatory rheumatic disease population with a healthy control population in a case-control study., Methods: Cases: between March and September 2021, all consecutive unvaccinated patients followed for rheumatoid arthritis (RA), spondyloarthritis (SpA) or psoriatic arthritis (PsA) in 16 hospitals in France were systematically screened with a SARS-CoV-2 serological test. Patients with a positive test were included in the COVID-RIC-2 cohort., Controls: between June and July 2020, healthcare professionals working in the Toulouse University Hospital were screened with a SARS-CoV-2 serological test. Those with a positive test were included in the COVID-BIOTOUL cohort and matched to those from COVID-RIC-2 by age, sex and time-sampling on infection date., Analyses: total SARS-CoV-2 antibody titres were centrally measured and compared., Results: 95 patients from COVID-RIC-2 (mean age 49 years, 76% females, median delay of COVID infection: 149 days) including 48 RA, 33 SpA and 14 PsA were compared to 95 matched controls. Globally, there was no significant difference of SARS-CoV-2 antibody titres between both populations: 155 Binding Antibody Units (BAU) (IQR:7-376) in COVID-RIC-2 vs. 120 BAU (IQR:35-320) in COVID-BIOTOUL. There was a trend towards higher antibody titres in patients from COVID-RIC-2 with severe COVID-19 symptoms. In COVID-RIC-2, there was no impact of age, sex, time-sampling or underlying disease on antibody titres and patients taking glucocorticoids, abatacept or rituximab trended toward having lower antibody titres after COVID-19 infection., Conclusions: This study provides reassuring data on humoral response after COVID-19 infection in patients treated with disease-modifying anti-rheumatic drugs.

Objective: Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease in which activated CD4 + T cells participate in the disease process by inducing inflammation. We aimed to investigate the role of Toll-like receptor 2 (TLR2) on CD4 + T cells in RA patients, and to elucidate the underlying mechanisms by which TLR2 contributes to the pathogenesis of RA., Methods: Serum samples were collected from RA patients and healthy controls. Soluble TLR2 levels were quantified using an enzyme-linked immunosorbent assay (ELISA). Flow cytometry was employed to assess the TLR2 expression level, activation status, cytokine production, reactive oxygen species (ROS) levels, and glucose uptake capacity of CD4 + T cells. Quantitative polymerase chain reaction (qPCR) was used to measure the expression of enzymes associated with glucose and lipid metabolism. The concentration of lactic acid in the culture supernatant was determined using a dedicated detection kit., Results: RA patients had higher levels of TLR2 in their serum, which positively correlated with C-reactive protein and rheumatoid factor. The expression level of TLR2 in CD4 + T cells of RA patients was increased, and TLR2 + cells showed higher activation levels than TLR2- cells. Activation of TLR2 in CD4 + T cells of RA patients promoted their activation, TNF-α secretion, and increased production of ROS. Furthermore, TLR2 activation led to changes in enzymes related to glucose metabolism, causing a shift in glucose metabolism towards the pentose phosphate pathway. Blocking oxidative phosphorylation and the pentose phosphate pathway had varying effects on CD4 + T cell function., Conclusion: TLR2 reprograms the glucose metabolism of CD4 + T cells in RA patients, contributing to the development of RA through ROS-mediated cell hyperactivation and TNF-α secretion. Key Points • TLR2 is upregulated in CD4 + T cells of RA patients and correlates with disease severity markers such as CRP and RF. • Activation of TLR2 in CD4 + T cells promotes cell activation, TNF-α secretion, and increased ROS production, contributing to the pathogenesis of RA. • TLR2 activates glucose metabolism in CD4 + T cells, shifting towards the pentose phosphate pathway, which may be a novel therapeutic target for RA treatment. • Blocking glucose metabolism and ROS production can reduce CD4 + T cell hyperactivation and TNF-α secretion, indicating potential therapeutic strategies for RA management., (© 2024. The Author(s), under exclusive licence to International League of Associations for Rheumatology (ILAR).)

Spliceosome dysfunction and aberrant RNA splicing underline unresolved inflammation and immunopathogenesis. Here, we revealed the misregulation of mRNA splicing via the spliceosome in the pathogenesis of rheumatoid arthritis (RA). Among them, decreased expression of RNA binding motif protein 25 (RBM25) was identified as a major pathogenic factor in RA patients and experimental arthritis mice through increased proinflammatory mediator production and increased hyperinflammation in macrophages. Multiomics analyses of macrophages from RBM25-deficient mice revealed that the transcriptional enhancement of proinflammatory genes (including Il1b, Il6, and Cxcl10) was coupled with histone 3 lysine 9 acetylation (H3K9ac) and H3K27ac modifications as well as hypoxia inducible factor-1α (HIF-1α) activity. Furthermore, RBM25 directly bound to and mediated the 14 th exon skipping of ATP citrate lyase (Acly) pre-mRNA, resulting in two distinct Acly isoforms, Acly Long (Acly L) and Acly Short (Acly S). In proinflammatory macrophages, Acly L was subjected to protein lactylation on lysine 918/995, whereas Acly S did not, which influenced its affinity for metabolic substrates and subsequent metabolic activity. RBM25 deficiency overwhelmingly increased the expression of the Acly S isoform, enhancing glycolysis and acetyl-CoA production for epigenetic remodeling, macrophage overactivation and tissue inflammatory injury. Finally, macrophage-specific deletion of RBM25 led to inflammaging, including spontaneous arthritis in various joints of mice and inflammation in multiple organs, which could be relieved by pharmacological inhibition of Acly. Overall, targeting the RBM25-Acly splicing axis represents a potential strategy for modulating macrophage responses in autoimmune arthritis and aging-associated inflammation., (© 2024. The Author(s), under exclusive licence to CSI and USTC.)

Pain is one of the most debilitating symptoms of rheumatoid arthritis (RA), and yet remains poorly understood, especially when pain occurs in the absence of synovitis. Without active inflammation, experts most often attribute joint pain to central nervous system dysfunction. However, advances in the past 5 years in both immunology and neuroscience research suggest that chronic pain in RA is also driven by a variety of abnormal interactions between peripheral neurons and mediators produced by resident cells in the local joint environment. In this Review, we discuss these novel insights from an interdisciplinary neuro-immune perspective. We outline a potential working model for the peripheral drivers of pain in RA, which includes autoantibodies, resident immune and mesenchymal cells and their interactions with different subtypes of peripheral sensory neurons. We also offer suggestions for how future collaborative research could be designed to accelerate analgesic drug development., (© 2024. Springer Nature Limited.)

The recombinant Staphylococcal protein A (SpA) is widely used in biotechnology to purify polyclonal and monoclonal IgG antibodies. At very low concentrations, the highly-purified form of the protein A can down-regulate the activation of human B-lymphocytes and macrophages which are the key cells in determining autoimmune diseases. In the present study, the efficiency of three different forms of protein A, including native full-length SpA, the recombinant full-length SpA, and a recombinant truncated form of SpA on the reduction of 4 inflammatory cytokines, including IL-8, IL-1β, TNF-α, and IL-6 by peripheral blood mononuclear cell (PBMCs) were studied and compared to an anti-rheumatoid arthritis commercial drug, Enbrel. The recombinant proteins were expressed in E. coli and the native form of SpA was commercially provided. PBMCs were obtained from adult patients with active rheumatoid arthritis (RA) and healthy control donors. Then, the effect of different doses of the three pure forms of SpA in comparison with Enbrel was investigated by analyzing the expression of selected cytokines using ELISA. The results showed that the truncated form of recombinant SpA significantly reduced the expression of cytokines more effectively than the other full-length formulations as well as the commercial drug Enbrel. In silico analysis shows that in the truncated protein, as the radius of gyration increases, the structure of IgG-binding domains become more open and more exposed to IgG. To summarize, our findings indicate that the truncated form of protein A is the most efficient form of SpA as it significantly decreases the secretion of evaluated cytokines from PBMCs in vitro., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

The role of liver X receptors (LXR) in rheumatoid arthritis (RA) remains controversial. We studied the effect of LXR agonists on fibroblast-like synoviocytes (FLS) from RA patients and the K/BxN arthritis model in LXRα and β double-deficient (Nr1h2/3 -/- ) mice. Two synthetic LXR agonists, GW3965 and T0901317, were used to activate LXRs and investigate their effects on cell growth, proliferation and matrix metalloproteinases, and chemokine production in cultured FLS from RA patients. The murine model K/BxN serum transfer of inflammatory arthritis in Nr1h2/3 -/- animals was used to investigate the role of LXRs on joint inflammation in vivo. LXR agonists inhibited the FLS proliferative capacity in response to TNF, the chemokine-induced migration, the collagenase activity in FLS supernatant and FLS CXCL12 production. In the K/BxN mouse model, Nr1h2/3 -/- animals showed aggravated arthritis, histological inflammation, and joint destruction, as well as an increase in synovial metalloproteases and expression of proinflammatory mediators such as IL-1β and CCL2 in joints compared with wild type animals. Taken together, these data underscore the importance of LXRs in modulating the joint inflammatory response and highlight them as potential therapeutic targets in RA., (© 2024 The Author(s). European Journal of Immunology published by Wiley‐VCH GmbH.)

Complexes of extracellular nucleic acids (NAs) with endogenous proteins or peptides, such as LL37, break immune balance and cause autoimmune diseases, whereas NAs with arginine-enriched peptides do not. Inspired by this, we synthesize a polyarginine nanoparticle PEG-TK-NP Arg , which effectively inhibits Toll-like receptor-9 (TLR9) activation, in contrast to LL37. To explore the discrepancy effect of PEG-TK-NP Arg and LL37, we evaluate the periodic structure of PEG-TK-NP Arg -NA and LL37-NA complexes using small-angle X-ray scattering. LL37-NA complexes have a larger inter-NA spacing that accommodates TLR9, while the inter-NA spacing in PEG-TK-NP Arg -NA complexes mismatches with the cavity of TLR9, thus inhibiting an interaction with multiple TLR9s, limiting their clustering and damping immune induction. Subsequently, the inhibitory inflammation effect of PEG-TK-NP Arg is proved in an animal model of rheumatoid arthritis. This work on how the scavenger-NA complexes inhibit the immune response may facilitate proof-of-concept research translating to clinical application., Competing Interests: Competing interests The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Objectives: The early diagnosis of seronegative rheumatoid arthritis (SNRA), characterised by the absence of rheumatoid factor and anti-citrullinated antibody, involves a greater challenge compared to seropositive RA (SPRA). This study aimed to assess the discriminatory potential of anti-human IgG hinge antibodies (AHAs) for patients with early SNRA., Methods: DMARDs-naive patients with SPRA (n=43), SNRA (n=21), and non-RA (n=49), with disease duration < 2 years, were included. Antigens comprised IgG1 or IgG4 F(ab')2 cleaved by pepsin or MMP-3 and their hinge peptide analogues. Eight IgG anti-hinge antibodies (AHAs) against these antigens were measured in sera from the patients and 58 healthy controls (HCs) using ELISA. Serum CRP and MMP-3 levels, and clinical disease activity index (CDAI), were obtained from medical records. The area under the curve (AUC) obtained from logistic regression and receiver operating characteristic curve analyses were used as a discriminant indicator., Results: The levels of the IgG AHAs were as follows: SPRA≥SNRA≈non-RA>HC. None of the AHAs were effective in discriminating SNRA from non-RA. However, the combination of MMP-3 and AHAs against IgG4 hinge peptide analogues demonstrated the utility (AUC=0.94). Furthermore, combination of MMP-3, AHAs against IgG1 hinge peptide analogues and CDAI maximally exerted discriminatory power (AUC=0.997)., Conclusions: Specific AHAs in combination with MMP-3 and CDAI are potentially useful to discriminate SNRA from non-RA.

Objective: The complement system has been associated with the etiopathogenesis of rheumatoid arthritis (RA). Insulin resistance (IR) and metabolic syndrome (MetS) are prevalent among patients with RA. The aim of this study was to explore the relationship between a comprehensive evaluation of the complement system and IR, as well as MetS, in patients with RA., Methods: A total of 339 nondiabetic patients with RA were recruited. Functional assays of the 3 complement pathways were assessed. Additionally, serum levels of the following individual components of the complement system were measured: C1q (classical); lectin (lectin); C2, C4, and C4b (classical lectin); factor D and properdin (alternative); C3 and C3a (common); C5, C5a, and C9 (terminal); as well as the factor I and C1 inhibitor regulators. IR and β cell function indices were calculated using the homeostatic model assessment. Criteria for MetS were applied. Multivariable linear regression analysis was performed to investigate the association between the complement system and IR in patients with RA., Results: Many elements of the upstream and common complement pathways, but not the functional tests of the 3 routes, correlated positively with higher levels of IR and β cell function. However, after multivariable adjustment for factors associated with IR, these relationships were lost. Conversely, the presence of MetS in patients with RA maintained a relationship with higher levels of C1q, C4, C3, properdin, and factor I after adjusting for confounders., Conclusion: There is a positive correlation between the complement system and MetS among nondiabetic patients with RA. This association is independent of traditional IR factors., (Copyright © 2024 by the Journal of Rheumatology.)

Objectives: To investigate the correlation between innate lymphoid cell (ILC) subsets with T-helper (Th) cells and to explore the effect of ILCs on T cells in rheumatoid arthritis (RA)., Methods: We analysed the frequencies of ILC subsets in RA patients with varying disease activity and their correlation with Th cell subsets. We further investigated this correlation in various organs of collagen-induced arthritis (CIA) mice. The effects of ILCs on CD4+ T cells were determined by in vitro cell co-culture experiments., Results: ILCs were less frequent in RA patients than in healthy controls, with higher levels of group 3 ILCs (ILC3s) in RA (p<0.05). ILC3s correlated positively with Th1 and Th17 cells in RA peripheral blood (p<0.05). In the peripheral blood, spleen, and lymph nodes of CIA, ILC3s decreased and then increased during arthritis progression. ILC3s correlated positively with Th1 and Th17 cells in the spleen and lymph nodes of CIA (p<0.05). NKp46+ ILC3s in the spleen positively correlated with Th1 and Th17 cells (p<0.05). Under Th17 cell differentiation conditions, co-culturing CIA-derived ILC3s directly with naive CD4+ T cells promoted Th17 differentiation and increased IL-17 secretion. However, co-culturing through a transwell insert impeded Th17 differentiation without affecting IL-17 secretion., Conclusions: ILC3s positively correlated with Th1 and Th17 cells in RA. In CIA, the frequencies of ILC3s changed with disease development and showed a positive correlation with Th1 and Th17 cells. ILC3s may facilitate the differentiation of Th17 cells through direct cell-cell contact.

Objective: Synovial fluid (SF)-derived T cells are frequently studied as a proxy for investigating the synovial tissue (ST) T cell infiltrate in inflammatory arthritis. However, because ST is the primary site of inflammatory activity, there is debate as to whether SF provides a true reflection of the ST T cell population., Methods: In this study, we used single-cell RNA sequencing paired with single-cell T cell receptor (TCR) sequencing to directly compare memory T cells from paired samples of SF and ST from six patients with inflammatory arthritis to investigate their similarity in terms of TCR repertoire and T cell subset composition., Results: The TCR repertoires of SF and ST T cells were strikingly similar, particularly for CD8+ T cells. A median of 49% of the total CD8+ TCR repertoire in SF was shared with ST, compared with 20% shared with blood. Similarly, 47% of the ST CD8+ TCR repertoire was shared with SF compared to 25% with blood. Furthermore, once the effect of collagenase digestion on gene expression by ST T cells had been accounted for, the frequencies of specific CD8+ and CD4+ T cell subsets were, in general, similar in SF and ST and were distinct from blood., Conclusion: Our results suggest that T cells migrate and equilibrate between the SF and ST and maintain similar phenotypes in both sites. We conclude that SF is an appropriate proxy for investigating the T cell infiltrate in inflamed synovium, particularly in terms of investigating the TCR repertoire., (© 2024 The Author(s). Arthritis & Rheumatology published by Wiley Periodicals LLC on behalf of American College of Rheumatology.)

Objective: The objective of this study was to discover autoantibodies to non-modified proteins associated with the presence/absence of ACPAs in RA., Methods: The autoantibody repertoire of 80 ACPA-negative and 80 ACPA-positive RA subjects from the Swedish population-based Epidemiological Investigation of RA (EIRA) cohort was screened using a suspension bead array built on protein fragments earlier described as autoimmunity targets. Four autoantibodies positive in the initial screening were validated in another set of EIRA samples containing 317 ACPA-positive, 302 ACPA-negative and 372 age- and sex-matched controls. The relationship between the four autoantibodies and lung abnormalities on high-resolution CT (HRCT) was examined in 93 early-RA patients from the LURA cohort. Association between the autoantibodies, smoking and MHC class II alleles was assessed by logistic regression analysis., Results: Anti-ANOS1 and anti-MURC IgG levels were associated with ACPA-positive status [odds ratio (OR) = 3.02; 95% CI 1.87-4.89; and OR = 1.86; 95% CI 1.16-2.97, respectively] and increased in ACPA-positive patients compared with controls. Anti-ANOS1 IgG was associated with smoking habit (OR = 2.11; 95% CI 1.22-3.69) and anti-MURC IgG with the presence of the MHC class II 'shared-epitope' genes (OR = 1.95; 95% CI 1.11-3.46). Anti-TSPYL4 IgG was associated with being ACPA negative (OR = 0.41; 95% CI 0.19-0.89). Anti-TSPYL4 IgG and anti-MAP2K6 IgG levels were increased in the ACPA-negative patients compared with controls. Presence of anti-MAP2K6 IgG and anti-TSPYL4 IgG correlated negatively with HRCT-defined lung abnormalities., Conclusion: These four autoantibodies may be useful in diagnostics and in predicting clinical phenotypes of RA., (© The Author(s) 2024. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Rheumatoid arthritis (RA) is a systemic autoimmune disease driven by highly active autoantibody-producing B cells. Activation of B cells is maintained within ectopic germinal centres found in affected joints. Fibroblast-like synoviocytes (FLS) present in inflamed joints support B-cell survival, activation, and differentiation. CD27+ memory B cells and naive B cells show very different responses to activation, particularly by CD40 ligand (CD40L). We show that FLS-dependent activation of human B cells is dependent on interleukin-6 (IL-6) and CD40L. FLS have been shown to activate both naive and memory B cells. Whether the activating potential of FLS is different for naive and memory B cells has not been investigated. Our results suggest that FLS-induced activation of B cells is dependent on IL-6 and CD40L. While FLS are able to induce plasma cell differentiation, isotype switching, and antibody production in memory B cells, the ability of FLS to activate naive B cells is significantly lower., (© 2024 The Author(s). Immunology published by John Wiley & Sons Ltd.)

Epstein-Barr virus (EBV) reactivation in COVID-19 patients has been reported, but studies on its clinical significance are lacking. We herein report the occurrence of infectious mononucleosis (IM) due to EBV reactivation in a 60-year-old man with rheumatoid arthritis being treated with methotrexate and tocilizumab. The patient presented with a fever and tested positive for COVID-19. Laboratory findings revealed an increased atypical lymphocyte count, decreased platelet count, and elevated liver enzyme levels. Flow cytometry showed predominant expansion of reactive T cells. EBV reactivation was confirmed using real-time polymerase chain reaction. The patient was treated with remdesivir, and clinical improvement was observed after 10 days of treatment. Follow-up showed a gradual decrease in the EBV-DNA load with no recurrence of atypical lymphocytes. These findings suggest that COVID-19 in immunocompromised patients may lead to unexpected EBV reactivation and IM, even for patients outside the age at which IM is likely to occur., Competing Interests: Declaration of competing interest All authors declare no competing financial interests., (Copyright © 2024 Japanese Society of Chemotherapy, Japanese Association for Infectious Diseases, and Japanese Society for Infection Prevention and Control. Published by Elsevier Ltd. All rights reserved.)

Objective: Individuals positive for anti-cyclic-peptide-antibodies (anti-CCP) and musculoskeletal complaints (MSK-C) are at risk for developing rheumatoid arthritis (RA). In this study we aimed to investigate factors involved in arthritis progression., Methods: Anti-CCP2-positive individuals with MSK-C referred to a rheumatologist were recruited. Individuals lacked arthritis at clinical and ultrasound examination and were followed for ≥3 years or until clinical arthritis diagnosis. Blood samples from inclusion were analysed for nine ACPA reactivities (citrullinated α-1-enolase, fibrinogen, filaggrin, histone, vimentin and tenascin peptides); 92 inflammation-associated proteins; and HLA-shared epitope alleles. Cox regression was applied to the data to identify independent predictors in a model., Results: Two hundred and sixty-seven individuals were included with median follow-up of 49 months (interquartile range [IQR]: 22-60); 101 (38%) developed arthritis after a median of 14 months (IQR: 6-27). The analysis identified that presence of at least one ACPA reactivity (hazard ratio [HR] 8.0; 95% CI: 2.9, 22), ultrasound-detected tenosynovitis (HR 3.4; 95% CI: 2.0, 6.0), IL-6 levels (HR 1.5; 95% CI: 1.2, 1.8) and IL-15 receptor α (IL-15Rα) levels (HR 0.6; 95% CI: 0.4, 0.9) are significant independent predictors for arthritis progression in a prediction model (Harrell's C 0.76 [s.e. 0.02], AUC 0.82 [95% CI: 0.76, 0.89], cross-validated AUC 0.70 [95% CI: 0.56, 0.85])., Conclusion: We propose a high RA risk phase characterized by presence of ACPA reactivity, tenosynovitis, IL-6 and IL-15Rα and suggest that these factors need to be further investigated for their biological effects and clinical values, to identify individuals at particular low risk and high risk for arthritis progression., (© The Author(s) 2024. Published by Oxford University Press on behalf of the British Society for Rheumatology.)

Background: The presence of ACPA significantly increases the risk of developing RA. Dysregulation of lymphocyte subpopulations was previously described in RA. Our objective was to propose the predictive model for progression to clinical arthritis based on peripheral lymphocyte subsets and ACPA in individuals who are at risk of RA., Methods: Our study included 207 at-risk individuals defined by the presence of arthralgias and either additional ACPA positivity or meeting the EULAR definition for clinically suspect arthralgia. For the construction of predictive models, 153 individuals with symptom duration ≥12 months who have not yet progressed to arthritis were included. The lymphocyte subsets were evaluated using flow cytometry and anti-CCP using ELISA., Results: Out of all individuals with arthralgia, 41 progressed to arthritis. A logistic regression model with baseline peripheral blood lymphocyte subpopulations and ACPA as predictors was constructed. The resulting predictive model showed that high anti-CCP IgG, higher percentage of CD4+ T cells, and lower percentage of T and NK cells increased the probability of arthritis development. Moreover, the proposed classification decision tree showed that individuals having both high anti-CCP IgG and low NK cells have the highest risk of developing arthritis., Conclusions: We propose a predictive model based on baseline levels of lymphocyte subpopulations and ACPA to identify individuals with arthralgia with the highest risk of progression to clinical arthritis. The final model includes T cells and NK cells, which are involved in the pathogenesis of RA. This preliminary model requires further validation in larger at-risk cohorts., (© The Author(s) 2024. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Dietary strategies rich in fiber have been demonstrated to offer benefits to individuals afflicted with rheumatoid arthritis (RA). However, the specific mechanisms through which a high-fiber diet (HFD) mitigates RA's autoimmunity remain elusive. Herein, we investigate the influence of pectin- and inulin-rich HFD on collagen-induced arthritis (CIA). We establish that HFD significantly alleviates arthritis in CIA mice by regulating the Th17/Treg balance. The rectification of aberrant T cell differentiation by the HFD is linked to the modulation of gut microbiota, augmenting the abundance of butyrate in feces. Concurrently, adding butyrate to the drinking water mirrors the HFD's impact on ameliorating CIA, encompassing arthritis mitigation, regulating intestinal barrier integrity, and restoring the Th17/Treg equilibrium. Butyrate reshapes the metabolic profile of CD4 + T cells in an AMPK-dependent manner. Our research underscores the importance of dietary interventions in rectifying gut microbiota for RA management and offers an explanation of how diet-derived microbial metabolites influence RA's immune-inflammatory-reaction., Competing Interests: Declaration of competing interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Part of the figures (Figure. 1A, Figure. 5A and graphical abstract) were created with BioRender.com., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Transmembrane 9 superfamily member 1 (TM9SF1) is involved in inflammation. Since both inflammatory and autoimmune diseases are linked to immune cells regulation, this study investigated the association between TM9SF1 expression and autoimmune disease activity. As B cell differentiation and autoantibody production exacerbate autoimmune disease, the signaling pathways involved in these processes were explored., Methods: Tm9sf1 -/- mouse rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) models were used to verify the relationship between gene expression and disease severity. Peripheral blood mononuclear cells (PBMCs) from 156 RA and 145 SLE patients were used to explore the relationship between TM9SF1 expression and disease activity. The effectiveness of TM9SF1 as a predictor of disease activity was assessed using multiple logistic regression and receiver operating characteristic (ROC) curves. The signaling pathways regulated by TM9SF1 in B cell maturation and antibody production were conducted by plasma cell induction experiment in vitro., Results: The Tm9sf1 -/- RA and SLE model mice produced fewer autoantibodies and showed reduced disease severity relative to wild-type (WT) mice. TM9SF1 levels in PBMCs of patients were higher than those in healthy controls, and were reduced in patients with low disease activity relative to those with active RA and SLE. Furthermore, TM9SF1 levels were positively linked with autoantibody titers and pro-inflammatory cytokine levels in both diseases. ROC analyses indicated TM9SF1 outperformed several important clinical indicators in predicting disease activity (area under the curve (AUC) were 0.858 and 0.876 for RA and SLE, respectively). In vitro experiments demonstrated that Tm9sf1 knockout blocked differentiation of B cells into antibody-producing plasma cells by activating mTOR and inhibiting autophagy, and mTOR inhibitors such as rapamycin could reverse this effect., Conclusions: The primary finding was the identification of the molecular mechanism underlying autophagy regulation in B cells, in which Tm9sf1 knockout was found to modulate mTOR-dependent autophagy to block B cell differentiation into antibody-secreting plasma cells. It was also found that TM9SF1 expression level in PBMCs was an accurate indicator of disease activity in patients with RA and SLE, suggesting its clinical potential for monitoring disease activity in these patients., (© 2024. The Author(s).)

Natural autoantibodies (natAAbs) react with evolutionarily conserved antigens but they do not lead to pathological tissue destruction, contrary to pathological autoantibodies (pathAAbs). NatAAbs usually belong to the IgM isotype, and their network, also known as the "immunological homunculus", is thought to play a role in immunological tolerance. NatAAbs are produced by B1 cells found mostly on the serosa surfaces or the spleen. The exact relation between natAAbs and pathAAbs is still not completely understood. The recombinant human proteoglycan (PG) aggrecan G1 domain (rhG1)-induced arthritis (GIA) is an excellent mouse model for rheumatoid arthritis because it represents most of the clinical, immunological and laboratory parameters of the corresponding human pathology. Recently, we studied the role of the spleen in GIA, and found that a splenectomy modified the development of autoimmunity. To further characterize the possible role of the nAAb levels in tolerance and autoimmunity, in the present study, we set out to measure the nat- and pathAAb levels in GIA. We analyzed the natAAb levels in the serum against cartilage PG aggrecan, Hsp60 and Hsp70, and the mitochondrial citrate synthase (CS) antigens in healthy control and arthritic mice. Furthermore, we studied whether the splenectomy influenced the production of nat- and pathAAbs in mice with GIA. Our results show that the natAAb levels against PG aggrecan, Hsp60, Hsp70 and CS showed age-related variations in healthy BALB/c mice. The induction of autoimmune arthritis did not change the levels of the measured natAAbs significantly. Splenectomy, on the other hand, clearly decreased the levels of all the measured natAAbs. Interestingly, the levels of the pathAAbs showed the opposite change: they were higher in the splenectomized group than in the control arthritic mice. Based on these results, we conclude that the spleen plays a role in setting the balance between nat- and pathAAbs in autoimmune arthritis.

Rheumatoid arthritis (RA) is a chronic autoimmune disease that causes joint inflammation and gradual tissue destruction. New research has shown how important noncoding RNAs (ncRNAs) are for changing immune and inflammatory pathways, such as the WNT signaling pathway, which is important for activating synovial fibroblasts and osteoblasts to work. This article examines the current understanding of several ncRNAs, such as miRNAs, lncRNAs, and circRNAs, that influence NF-κB signaling in the pathogenesis of RA. We investigate how these ncRNAs impact NF-κB signaling components, altering cell proliferation, differentiation, and death in joint tissues. The paper also looks at how ncRNAs can be used as potential early detection markers and therapeutic targets in RA because they can change important pathogenic pathways. This study highlights the therapeutic potential of targeting ncRNAs in RA therapy techniques, with the goal of reducing inflammation and stopping disease progression. This thorough analysis opens up new possibilities for understanding the molecular foundations of RA and designing novel ncRNA-based treatments., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Seyedi, Espandar, Hojatizadeh, Mohammadi, Sadri and Rezaei.)

Objectives: To observe the effects of moxibustion on G protein-coupled receptor 43 (GPR43) and helper T cell 17 (Th17)/regulatory T cell (Treg) balance in rats with adjuvant arthritis (AA), so as to investigate the partial mechanism of moxibustion therapy on rheumatoid arthritis (RA)., Methods: A total of 24 Wistar rats were randomly divided into a normal group, a model group and a moxibustion group, with 8 rats in each group. The AA rat model was replicated using wind, cold and moisture environmental factors + Freund's complete adjuvant (CFA) injection method. In the moxibustion group, moxibustion was performed on bilateral "Zusanli" (ST36) and "Shenshu" (BL23) for 20 min/time, once daily, for 21 d. The changes of joint swelling degree (JSD) and arthritis index (AI) were observed in each group of rats. Transmission electron microscopy and HE staining were used to examine changes in the cellular structure of the ankle joint synovial tissue in each group. Western blot analysis was employed to detect the expression levels of GPR43 in the synovial tissue of the ankle joints. Flow cytometry was used to measure the percentages of Treg and Th17 in peripheral blood. ELISA was used to determine the contents of interleukin-10 (IL-10) and transforming growth factor-β 1 (TGF-β1) in serum., Results: Compared with the normal group, the JSD and AI in the model group increased before and after treatment ( P <0.01), with significant synovial pathological and ultrastruct ural injury observed. Additionally, compared with the normal group, the expression of GPR43 in the synovial tissue decreased ( P <0.01), the Treg percentage in peripheral blood decreased ( P <0.01) and the Th17 percentage increased ( P <0.01), serum IL-10 and TGF-β1 contents decreased in the model group ( P <0.01). Compared with the model group, the moxibustion group exhibited a significant reduction in JSD and AI after treatment ( P <0.01), the degree of pathological and ultrastruct ural damage in the synovium decreased, the expression of GPR43 in the synovial tissue increased ( P <0.05), the Treg percentage in peripheral blood increased ( P <0.01) and the Th17 percentage decreased ( P <0.01), serum IL-10 and TGF-β1 contents increased ( P <0.01). The relative expression of GPR43 in synovial tissue was positively correlated with the percentage of Treg in peripheral blood ( r =0.967, P <0.01)., Conclusions: Moxibustion can significantly improve the inflammatory response in the synovial membrane of AA rats. The mechanism may be related to moxibustion restoring the Th17/Treg balance through regulating GPR43.

Objective: Collagen-induced arthritis (CIA) model was induced in C57BL/6 wild-type (wt) and C57BL/6 miR-204/-211 double-knockout (dKO) mice to investigate the role of miR-204/-211 in suppressing splenic inflammation in rheumatoid arthritis (RA)., Methods: Differences of miR-204/-211 and structure-specific recognition protein 1 (SSRP1) in the spleen of DBA/1J wt and CIA mice were detected via PCR and immunohistochemistry. CIA was induced in both C57BL/6 wt and C57BL/6 miR-204/-211 dKO mice, and the onset of CIA and disease severity were statistically analyzed. Immunohistochemistry staining of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and SSRP1 in spleen or knee joints was performed and analyzed. In CIA miR-204/-211 dKO mice, AAV-shSSRP1 was intra-articularly injected, with both the AAV-shRNA Ctrl and AAV-shRNA Ctrl CIA groups receiving the same dose of AAV-shRNA. Spleen sections were stained with hematoxylin and eosin (H&E)., Results: Compared to wt mouse spleens, aberrant expression of miR-204/-211 and SSRP1 was observed in the spleens of CIA mice. Immunized dKO mice exhibited a higher incidence of CIA onset and a more exacerbated RA disease phenotype, characterized by increased spleen inflammation score and elevated levels of IL-1β, TNF-α, and SSRP1 expression. AAV-shSSRP1 injection in CIA dKO mice significantly reduced spleen inflammation scores, IL-1β and TNF-α expression levels, and down-regulated Ki-67 expression compared to CIA dKO mice., Conclusion: Knockout of miR-204/-211 exacerbated the onset of CIA in C57BL/6 mice, while miR-204/-211 played a protective role against the progression of splenic inflammatory and proliferative progression in RA by targeting SSRP1., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The dysregulation of the immune system plays a crucial role in the pathogenesis of manyfold diseases, among which we find rheumatoid arthritis (RA), an autoimmune disease characterized by chronic inflammation in synovial joints, leading to pain and disability. Immune cells such as pro-inflammatory macrophages and T helper 1 (Th1) cells drive the inflammatory cascade. Thus, including immune system in in vitro models is pivotal to recapitulate and better understand the complex interactions between these immune cell subsets and their secreted mediators. Here, a compartmentalized microfluidic platform is presented, for precise confinement of circulating immune cells in organs-on-chip. The integration of innovative normally-closed sieving valves allows, through minimal waste of biological material, to co-culture different immune cell types (e.g. macrophages and Th1). Moreover, the platform allows to stimulate cell subsets separately, and to assess their cross-talk at desired time points. Functional validation of the platform demonstrates its ability to create stable chemotactic gradients, allowing for induction and evaluation of Th1 cells migration. In a proof-of-concept study, the platform allowed to assess Th1 T cells migration towards pro-inflammatory macrophages, thus replicating a characteristic interaction among immune cells triggered during RA onset. These results thus support the suitability of the platform to study immune cells cross-talk and migration phenomena, being potentially applicable to a manyfold immune cell mechanisms, both involved in RA progression and in different immune-mediated pathologies., (Creative Commons Attribution license.)

Objective: Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) is a significant pulmonary complication of RA. This study tried to elucidate the mechanisms enhancing inflammation and causing lung injury in RA-ILD, focusing on the role of neutrophil extracellular traps (NETs). The study also investigated the potential benefits of nintedanib in advanced disease., Methods: Nine RA-ILD patients and nine healthy controls were included in the study. Inflammatory markers in patients' circulation were evaluated with immunoassays. The formation of NETs was examined using a citrullinated histone H3 (CitH3) ELISA and cell immunofluorescence. Inflammatory proteins expressed in neutrophils/NETs were studied with real-time qPCR and NET ELISA. To assess the effect of nintedanib, an intracellular tyrosine kinase inhibitor with antifibrotic properties, in RA-ILD a paired study was conducted in five patients before treatment administration and 16 weeks later., Results: The soluble terminal complement complex sC5b-9 and the levels of CitH3 were significantly elevated in patients with RA-ILD, compared to healthy controls. In addition, neutrophils isolated from RA-ILD patients released NETs enriched with tissue factor and interleukin-17A. Inflammatory NETs had a dynamic role, increasing the fibrotic potential of human pulmonary fibroblasts (HPFs). On the other hand, nintedanib treatment decreased NETs and sC5b-9 levels in RA-ILD patients., Conclusion: The findings propose an interplay between circulating NETs and HPFs, establishing the immunofibrotic aspects of RA-ILD. They also support the effectiveness of nintedanib in reducing key pathological processes of the disease. Further research is needed to fully understand these mechanisms and optimize treatment strategies for RA-ILD., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Venetsanopoulou, Ntinopoulou, Papagianni, Koletsos, Voulgari and Chrysanthopoulou.)

Rheumatoid arthritis (RA) is marked by joint damage and inflammation, with B cells playing a key role by generating autoantibodies. This study shows that G protein-coupled receptor 40 (GPR40) deficiency in B cells leads to increased activation, proliferation, antibody production, germinal center formation, and class switch recombination. GPR40 regulates Plcγ2 phosphorylation and intracellular calcium flux downstream of the B cell receptor by binding to the Gαq protein. In GPR40-deficient mice, susceptibility to collagen-induced arthritis was higher. GPR40 agonists showed potential as therapeutic agents, and their reduced expression in patients with RA correlated with disease onset, suggesting GPR40 as a potential therapeutic target and diagnostic marker., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Objectives: Large granular lymphocyte (LGL) leukemia is a rare hematologic malignancy characterized by clonal expansion of cytotoxic T-cells frequent somatic activating STAT3 mutations. Based on the disease overlap between LGL leukemia rheumatoid arthritis (RA)a putative role for CD8+ T-cells in RA we hypothesized that STAT3 mutations may be detected in RA patient CD8+ T-cells correlate with clinical characteristics., Methods: Blood samples, clinical parameters, and demographics were collected from 98 RA patients and 9 healthy controls (HCs). CD8+ cell DNA was isolated and analyzed via droplet digital (dd)PCR to detect STAT3 mutations common in LGL leukemia: Y640F, D661Y, and the S614 to G618 region. STAT3 data from 99 HCs from a public dataset supplemented our 9 HCs., Results: RA patients had significantly increased presence of STAT3 mutations compared to controls (Y640F p=0.0005, D661Y p=0.0005). The majority of these were low variant allele frequency (VAF) (0.008-0.05%) mutations detected in a higher proportion of the RA population (31/98 Y640F, 17/98 D661Y) vs. HCs (0/108 Y640F, 0/108 D661Y). In addition, 3/98 RA patients had a STAT3 mutation at a VAF >5% compared to 0/108 controls. Serological markers, RF and anti-CCP positivity, were more frequently positive in RA patients with STAT3 mutation relative to those without (88% vs 59% RF, p=0.047; 92% vs 58% anti-CCP, p=0.031, respectively)., Conclusions: STAT3 activating mutations were detected in RA patient CD8+ cells and associated with seropositivity. Thus, STAT3 activating mutations may play a role in disease pathogenesis in a subset of RA patients., Competing Interests: TL has received Scientific Advisory Board membership, consultancy fees, honoraria, and/or stock options from Keystone Nano, Flagship Labs 86, Dren Bio, Recludix Pharma, Kymera Therapeutics, and Prime Genomics. DF has received research funding, honoraria, and/or stock options from AstraZeneca, Dren Bio, Recludix Pharma, and Kymera Therapeutics. AR has received research funding, consultancy fees, and Honoria from AstraZeneca and MedGenome Labs. DK has served on the Aurinia Lupus Center Advisory Board, and Clinical Advisory Board for Landos Biopharma; and is a member of the Amgen Speaker’s Bureau. ED has also received grants from Pfizer and Bristol-Myers Squibb related to RA, personal fees from Celgene and Gilead outside of the submitted work and is a current employee of AstraZeneca. FA has received consulting fees and/or royalties from Celgene, Inova, Advise Connect Inspire, and Hillstar Bio, Inc. ED and FA are authors on licensed patent no. 8,975,033, entitled “Human autoantibodies specific for pad3 which are cross-reactive with pad4 and their use in the diagnosis and treatment of rheumatoid arthritis and related diseases”. There are no conflicts of interest with the work presented in this manuscript. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be constructed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Moosic, Olson, Freijat, Khalique, Hamele, Shemo, Boodoo, Baker, Khurana, Schmachtenberg, Duffy, Ratan, Darrah, Andrade, Jones, Olson, Feith, Kimpel and Loughran.)

For many diseases, including cancer, infections, and auto-immune diseases, the immune response is a major determinant of disease progression, response to therapy, and clinical outcome. Innate and adaptive immune responses are controlled by coordinated activity of different immune cell types. The functional activity state of immune cells is determined by Signal Transduction Pathways (STPs). A recently developed technology (Simultaneous Transcriptome-based Activity Profiling of Signal Transduction Pathways, STAP-STP) enables simultaneous and quantitative activity measurement of relevant STPs in immune cells based on mRNA-analysis. STAP-STP technology was used to analyze public transcriptome data of a variety of immune cell types in resting and activated functional state. In addition, a clinical study on rheumatoid arthritis (RA) was analyzed to illustrate utility of the technology. Per sample, activity of androgen and estrogen receptor, PI3K, MAPK, TGFβ, Notch, NFκB, JAK-STAT1/2, and JAK-STAT3 STPs was calculated, generating an STP activity profile (SAP) consisting of 9 activity scores. Each analyzed immune cell type, i.e. naive/resting and immune-activated CD4 + and CD8 + T cells, T helper cells, B cells, NK cells, monocytes, macrophages, and dendritic cells, had a reproducible and characteristic SAP, reflecting both cell type and its activity state. Analysis of clinical RA samples revealed increased TGFβ STP activity in whole blood samples. In conclusion, STAP-STP technology enables quantitative measurement of the functional activity state of immune cells of the innate and adaptive immune system. Aside from diagnostic applications, utility lies in unravelling abnormal immune function in disease and immunomodulatory drug development., (© 2024. The Author(s).)