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Objective: To assess the expression levels of autoimmune regulator (Aire) and inducible costimulator molecule ligand (ICOSL), as well as T follicular helper (Tfh) cell numbers in rheumatoid arthritis (RA) patients, and to explore their relationship with RA severity. We also aimed to investigate the effect of Aire on arthritis and its underlying mechanisms., Methods: The expression levels of Aire, ICOSL, and Tfh cell numbers were measured in RA patients. The relationship between these factors and the levels of anticyclic citrullinated peptide antibodies (Anti-CCP) as well as the Disease Activity Score in 28 joints (DAS28) was analyzed. To investigate the effect of Aire on arthritis, Aire-overexpressing bone marrow-derived dendritic cells (Aire-BMDCs) and recombinant ICOSL were transferred into collagen-induced arthritis (CIA) mice, the symptoms, clinical scores, anti-collagen type II antibodies (anti-CII Abs), rheumatoid factor (RF), proportions of Tfh cells, and percentages of germinal center (GC) B cells in CIA mice were examined., Results: The results showed that Aire levels were significantly decreased in CD14 + PBMCs from patients with RA, and there were negative correlations between ICOSL expression levels, Tfh cell numbers, and Aire expression. Additionally, these factors were correlated with Anti-CCP levels and DAS28. Aire-BMDCs could influence Tfh differentiation, GC B cell development, as well as the levels of anti-CII Abs and RF, which further alleviate the symptoms and reduce clinical scores partly through ICOSL in CIA mice., Conclusions: The findings suggest that Aire may alleviate rheumatoid arthritis by inhibiting ICOSL, which further inhibits Tfh cell differentiation and autoantibody production., 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. This work was supported by the following grants: 20230505039ZP from Department of Science and Technology Project, 82471756 from National Natural Science Foundation of China, JJKH20221090KJ from Science and Technology Research Project of Education Department of Jilin Province and 81671548 from National Natural Science Foundation of China., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) mediated by CD4 + T helper (Th) cells, and characterized by immune cell infiltration, demyelination and neurodegeneration, with no definitive cure available. Thus, it is pivotal and imperative to acquire more profound comprehension of the underlying mechanisms implicated in MS. Dysregulated immune responses are widely believed to play a primary role in the pathogenesis of MS. Recently, a plethora of studies have demonstrated the involvement of T follicular helper (Tfh) cells and tertiary lymphoid-like structures (TLSs) in the pathogenesis and progression of MS. Cathepsin C (CatC) is a cysteine exopeptidase which is crucial for the activation of immune-cell-associated serine proteinases in many inflammatory diseases in peripheral system, such as rheumatoid arthritis and septicemia. We have previously demonstrated that CatC is involved in neuroinflammation and exacerbates demyelination in both cuprizone-induced and experimental autoimmune encephalomyelitis (EAE) mouse models. However, the underlying immunopathological mechanism remains elusive. In the present study, we established a recombinant myelin oligodendrocyte glycoprotein 35-55 peptide-induced EAE model using conditional CatC overexpression mice to investigate the effects of CatC on the alteration of CD4 + Th subsets, including Th1, Th2, Th17, Tfh and T regulatory cells. Our findings demonstrated that CatC particularly enhanced the population of Tfh cell in the brain, resulting in the earlier onset and more severe chronic syndrome of EAE. Furthermore, CatC promoted the formation of TLSs in the brain, leading to persistent neuroinflammation and exacerbating the severity of EAE in the chronic phase. Conversely, treatment with AZD7986, a specific inhibitor of CatC, effectively attenuated the syndrome of EAE and its effects caused by CatC both in vivo and in vitro. These findings provide a novel insight into the critical role of CatC in innate and adaptive immunity in EAE, and specific inhibitor of CatC, AZD7986, may contribute to potential therapeutic strategies for MS., 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.)

The autoimmune disorder known as Systemic Lupus Erythematosus (SLE) exhibits intricate features with abnormal immune responses leading to tissue injury. The generation of antibodies and the disruption of immune regulation heavily depend on the pivotal function of T follicular helper (Tfh) cells. Iron dysregulation is significant in autoimmune diseases, impacting immune cell function and disease progression. Our study investigates the role of the HMGA1/EZH2/STAT3/GPX4 axis in modulating Tfh cells and iron homeostasis in SLE. Abnormal Tfh cell populations in SLE patients demonstrate reduced susceptibility to iron-induced cell death, with HMGA1 identified as a key player in Tfh cell proliferation and sensitivity to iron-induced death. Experimental interventions reveal the inhibitory role of the HMGA1 axis in Tfh cells' susceptibility to iron-induced death, suggesting therapeutic avenues for SLE and related autoimmune disorders. Our study underscores the importance of iron homeostasis in autoimmune conditions, providing novel insights and treatment strategies for further research in this field., Competing Interests: Declarations. Ethical: This study followed the relevant international, national, and local laws and regulations concerning the use of animals and received approval from the Animal Use and Protection Committee of the research institution. All animal experiments were conducted with the principles of humane treatment, ensuring a scientifically sound experimental design while minimizing the animals' pain and discomfort. All animal experiments were approved by the Animal Ethics Committee of First Affiliated Hospital, China Medical University. The researchers involved in the study received appropriate training and certification to ensure the proper handling and care of the animals. Consent to participate: Not applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Malaria remains a significant global public health problem. T follicular helper (Tfh) cells, a subset of CD4 + T cells, have the capacity to regulate B cells, plasma cells, and antibody production, among other functions. Myeloid-derived suppressor cells (MDSCs) possess strong immunosuppressive abilities and can negatively regulate various immune responses. However, the role of MDSCs in inhibiting Tfh-cell responses during Plasmodium infection remains unclear. In this study, we investigated the regulatory effect of MDSCs on Tfh cell-mediated immune responses upon Plasmodium infection. We found that the numbers of MDSCs increased upon Plasmodium infection. Further mechanism study revealed that MDSC-derived Arg-1 and PD-L1 prevented Tfh cell proliferation and activation. Conversely, the addition of nor-NOHA or anti-PD-L1 monoclonal antibodies enhanced the proliferation and activation of Tfh cells, indicating that the inhibitory effect of MDSCs on Tfh cells was dependent on Arg-1 and PD-1/PD-L1. In vivo depletion of MDSCs enhanced Tfh-cell responses and antibody production, as well as relieved symptoms of infected mice and improved their survival rates. These findings provide insights into the immunosuppressive role of MDSCs in inhibiting Tfh cell immune responses and further impairing humoral immunity. Our study provides new strategies for malaria prevention and control., (© 2024 Federation of American Societies for Experimental Biology.)

T follicular helper (Tfh) cells abundantly express the immunoreceptor programmed cell death protein 1 (PD-1), and the impact of PD-1 deficiency on antibody (Ab)-mediated immunity in mice is associated with compromised Tfh cell functions. Here, we revisited the role of the PD-1-PD-L1 axis on Ab-mediated immunity. Individuals with inherited PD-1 or PD-L1 deficiency had fewer memory B cells and impaired Ab responses, similar to Pdcd1 -/- and Cd274 -/- Pdcd1lg2 -/- mice. PD-1, PD-L1, or both could be detected on the surface of human naive B cells following in vitro activation. PD-1- or PD-L1-deficient B cells had reduced expression of the transcriptional regulator c-Myc and c-Myc-target genes in vivo, and PD-1 deficiency or neutralization of PD-1 or PD-L1 impeded c-Myc expression and Ab production in human B cells isolated in vitro. Furthermore, B cell-specific deletion of Pdcd1 prevented the physiological accumulation of memory B cells in mice. Thus, PD-1 shapes optimal B cell memory and Ab-mediated immunity through B cell-intrinsic and B cell-extrinsic mechanisms, suggesting that B cell dysregulation contributes to infectious and autoimmune complications following anti-PD-1-PD-L1 immunotherapy., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Hypoxia-induced pulmonary hypertension (HPH) is a subgroup of type 3 pulmonary hypertension that may cause early right ventricular failure and eventual cardiac failure, which lacks potential therapeutic targets. Our previous research demonstrated that T follicular helper (T FH ) cells that produce IL-21 were involved in HPH. However, the molecular mechanisms of T FH /IL-21-mediated pathogenesis of HPH have been elusive. Here we investigate the role of T FH cells and IL-21 in HPH., Methods: Studies were performed in C57BL/6 mice or IL-21 knockout mice exposed to chronic hypoxia to induce PH, and examined by hemodynamics. Molecular and cellular studies were performed in mouse lung and pulmonary arterial smooth muscle cells (PASMCs). M2 signature gene (Fizz1), M1 signature genes (iNos, IL-12β and MMP9), GC B cell and its marker GL-7, caspase-1, M2 macrophages, T FH cells, Bcl-6 and IL-21 level were measured. Proliferation rate of PASMCs was measured by EdU. Pyroptosis was assessed using Hoechst 33,342/PI double fluorescent staining., Results: In response to chronic hypoxia exposure-induced pulmonary hypertension, IL-21 -/- mice or downregulation of T FH cells in WT mice developed blunted pulmonary hypertension, attenuated pulmonary vascular remodelling. Furthermore, chronic hypoxia exposure significantly increased the germinal center (GC) B cell responses, which were not present in IL-21 -/- mice or downregulation of T FH cells in WT mice. Importantly, IL-21 promoted the polarization of primary alveolar macrophages toward the M2 phenotype. Consistently, significantly enhanced expression of M2 macrophage marker Fizz1 were detected in the bronchoalveolar lavage fluid of HPH mice. Moreover, alveolar macrophages that had been cultivated with IL-21 promoted PASMCs proliferation and pyroptosis in vitro, while a selective CX3CR1 antagonist, AZD8797 (AZD), significantly attenuated the proliferation and pyroptosis of the PASMCs. Finally, ECM1 knockdown promoted IL-2-STAT5 signaling and inhibited Bcl-6 signaling to inhibit T FH differentiation in HPH., Conclusions: T FH /IL-21 axis amplified pulmonary vascular remodelling in HPH. This involved M2 macrophage polarization, PASMCs proliferation and pyroptosis. These data suggested that T FH /IL-21 axis may be a novel therapeutic target for the treatment of HPH., Competing Interests: Declarations. Ethics approval: All animals procedures were approved by the Laboratory Animal Ethics Committee of Hunan Provincial People’s Hospital (XSY-2021-42). Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Immune checkpoint blockade (ICB) has revolutionized cancer treatment; however, the mechanisms determining patient response remain poorly understood. Here, we used machine learning to predict ICB response from germline and somatic biomarkers and interpreted the learned model to uncover putative mechanisms driving superior outcomes. Patients with higher infiltration of T-follicular helper cells had responses even in the presence of defects in the MHC class-I (MHC-I). Further investigation uncovered different ICB responses in tumors when responses were reliant on MHC-I versus MHC-II neoantigens. Despite similar response rates, MHC II-reliant responses were associated with significantly longer durable clinical benefits (discovery: median overall survival of 63.6 vs. 34.5 months; P = 0.0074; validation: median overall survival of 37.5 vs. 33.1 months; P = 0.040). Characteristics of the tumor immune microenvironment reflected MHC neoantigen reliance, and analysis of immune checkpoints revealed LAG3 as a potential target in MHC II-reliant but not MHC I-reliant responses. This study highlights the value of interpretable machine learning models in elucidating the biological basis of therapy responses., (©2024 The Authors; Published by the American Association for Cancer Research.)

Follicular helper T (Tfh) cells have been implicated in the pathophysiology of numerous diseases. This study investigated the hypothetical function of peripheral blood IL-21+ Tfh cells in the etiology of focal segmental glomerulosclerosis (FSGS). Tfh cell subsets were identified via flow cytometry in PBMCs from 15 patients with FSGS and 9 healthy controls (HCs). Moreover, a cytometric bead array (CBA) was used to determine the level of IL-21 in the serum. The proportions of IL-21+ cTfh cells, IL-21+ PD-1+ cTfh cells and serum IL-21 were lower in FSGS patients than in HCs. In FSGS patients, the serum IL-21 concentration was positively correlated with the frequency of IL-21+ cTfh cells and IL-21+ PD-1+ cTfh cells. The frequencies of IL-21+ cTfh cells and IL-21+ PD-1+ cTfh cells were negatively associated with 24-h urine protein but positively correlated with eGFR, serum albumin and serum IgG. CONCLUSIONS: An aberrant frequency of IL-21+ Tfh cells was detected in FSGS patients, which may provide a better understanding of FSGS pathogenesis., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background: Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder defined by a diminished platelet count. ITP pathogenesis involves intricate changes to both cellular and humoral immunity. The pivotal roles of follicular helper T (TFH) cells in the maturations of B cells and the production of antibodies are well-established. However, the specific role of TFH to the immunopathogenesis of ITP remain incompletely understood. This study aimed to clarify the association of CXCL13/CXCR5 axis with TFH in adults with ITP., Methods: A total of 97 ITP patients and 41 healthy controls were enrolled. CD4 + CXCR5 + TFH, CD4 + CXCR5 + PD-1 + TFH, CD4 + CXCR5 + Foxp3 + follicular regulatory T cells (TFR), and desialylated platelets in peripheral blood were measured by flow cytometry. Plasma cytokines were assessed by enzyme-linked immunosorbent assay. CD4 + T cells cocultured with chemokine CXCL13 in vitro was performed for the measurement of TFH proliferation. Intracellular production of reactive oxygen species (ROS) was examined by dichlorodihydrofluorescein diacetate (DCFH-DA) probe staining., Results: We observed a significant increase in circulating TFH and a marked decrease in circulating TFR in the entire ITP cohort. The ratio of TFH/TFR was elevated, accompanied by heightened levels of platelet desialylation, cytokines BAFF, HMGB1, and IL-21, while levels of IL-10 were downregulated in adults with ITP. Notably, patients with ITP exhibiting platelet count below 50 × 10 9 /L had dramatically elevated levels in both chemokine CXCL13 and its receptor CXCR5 + TFH compared to those with platelet count above 100 × 10 9 /L. High frequencies of TFH correlated with poor therapeutic response. Furthermore, in vitro CD4 + T cell proliferation assay demonstrated a CXCL13 dose-dependent increase in the frequencies in both CD4 + CXCR5 + TFH and CD4 + CXCR5 + PD-1 + TFH from ITP patients. Intriguingly, DCFH-DA assay illustrated a significant enhancement in intracellular ROS generation in CXCR5 + T cell subsets, especially in CD4 + CXCR5 + PD-1 + TFH from 4 patients with ITP., Conclusions: These results underscore the pivotal role of CXCL13/CXCR5 axis-drived TFH expansion in the pathogenesis of ITP, providing a potential disease severity biomarker., 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 Ltd. All rights reserved.)

Initially, identified as a Hodgkin lymphoma marker, CD30 was subsequently detected on a subset of human B cells within and around germinal centers (GCs). While CD30 expression is typically restricted to a few B cells, expansion of CD30-expressing B cells occurs in certain immune disorders and during viral infections. The role of CD30 in B cells remains largely unclear. To address this gap in knowledge, we established a conditional CD30-knockin mouse strain. In these mice, B-cell-specific CD30 expression led to a normal B-cell phenotype in young mice, but most aged mice exhibited significant expansion of B cells, T cells and myeloid cells and increased percentages of GC B cells and IgG1-switched cells. This may be driven by the expansion of CD4 + senescence-associated T cells and T follicular helper cells, which partially express CD30-L (CD153) and may stimulate CD30-expressing B cells. Inducing CD30 expression in antigen-activated B cells accelerates the GC reaction and augments plasma cell differentiation, possibly through the posttranscriptional upregulation of CXCR4. Furthermore, CD30 expression in GC B cells promoted the expansion of IgG1-switched cells, which displayed either a GC or memory-like B-cell phenotype, with abnormally high IgG1 levels compared with those in controls. These findings shed light on the role of CD30 signaling in GC B cells and suggest that elevated CD30 + B-cell numbers lead to pathological lymphocyte activation and proliferation., Competing Interests: Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Aging, metabolism, and immunity have long been considered distinct domains. Aging is primarily associated with the gradual decline of physiological functions, metabolism regulates energy production and maintains cellular processes, and the immune system manages innate and adaptive responses against pathogens and vaccines. However, recent studies have revealed that these three systems are intricately interconnected, collectively influencing an individual's response to stress and disease. This review explores the interplay between immunometabolism, T follicular helper cells, B cells, and aging, focusing on how these interactions impact immune function in the elderly., Competing Interests: Declaration of Competing Interest The authors declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

T follicular helper (Tfh) cells help direct the production of antibodies by B cells. In addition to promoting antibody responses to vaccination and infection, Tfh cells have been found to mediate antibody production to food antigens. Work over the past decade has delineated the specific phenotypes of Tfh cells that induce antibodies to food while also clarifying the divergent Tfh cell requirement for different food-specific antibody isotypes. Furthermore, Tfh and antibody responses to food can occur at multiple barrier sites - namely, skin, airway, and gut. Depending on the context of food antigen exposure, the immune response to food at these sites can be protective, as in the case of tolerance or immunotherapy, or pathogenic, as in the case of allergy. This review will highlight recent advances in our understanding of how Tfh cells promote antibodies to food as well as future avenues for continued discovery., Competing Interests: Declaration of Competing Interest None., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The main pathogenic features of immunoglobulin A vasculitis (IgAV) are overactive B cells and elevated production of IgA, which requires help from T follicular helper 17 (Tfh17) cells. To evaluate the pathological role of Tfh17 cells in IgAV, we investigated the mechanism responsible for Tfh17 differentiation and explored how to ameliorate IgAV by modulating Tfh17 generation. Peripheral blood mononuclear cells from IgAV patients were analyzed by flow cytometry. In vitro culture was performed to assess the modulation of cytokine-induced phenotypes. IgAV rats were used to explore the therapeutic effects of IL-6 blockade and the regulatory functions of IL-6 in Tfh17 cells. Serum cytokine and IgA levels were measured by ELISA while histopathological changes were evaluated by H&E,PAS or immunofluorescence staining. Frequency of CD4 + CXCR5 + CCR6 + Tfh17 cells were increased in IgAV patients and associated with disease severity. There was also a significant infiltration of Tfh17 cells in the kidney of human IgAV nephritis patients. IL-6 promoted the dendritic cell production of TGF-β and Tfh17 differentiation. In IgAV rats, the in vivo blockade of IL-6 signaling inhibited Tfh17 differentiation, resulting in reduction of the germinal center and IgA production. Suppression of Tfh17 cells using IL-6 blockade greatly ameliorated clinical symptoms such as hemorrhagic rash and bloody stool and decreased IgA deposition and mesangial proliferation in the kidney in IgAV rats. Our findings suggest that suppression of Tfh17 differentiation can alleviate IgA-mediated vasculitis and may permit the development of tailored medicines for treating IgAV., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Nodal T-follicular helper cell lymphoma (nTFHL), a hematologic neoplasm originating from T-follicular helper (TFH) cells, occasionally presents with pulmonary radiographic abnormalities, without neoplastic cellular infiltration. However, the precise mechanisms underlying non-neoplastic pulmonary opacities in patients with nTFHL remain unclear. Previous reports have shown that TFH cell abnormalities are associated with collagen disease and interstitial pneumonia with autoimmune features (IPAF). We herein report a patient with nTFHL accompanied by interstitial pneumonia diagnosed via lung and lymph node biopsies. These findings suggest the need to rule out nTFHL before diagnosing IPAF.

Follicular helper T (Tfh) cells promote B cell differentiation and antibody production in the B cell follicles of secondary lymphoid organs. Tfh cells express their signature transcription factor BCL6, interleukin (IL)-21, and surface molecules including inducible T cell costimulator (ICOS), programmed cell death-1 (PD-1), and C-X-C motif chemokine receptor 5 (CXCR5). Migration of Tfh cells to B cell follicles largely depends on the CXCR5 expression induced by interactions with antigen-presenting dendritic cells in the T cell area. How Tfh cells acquire sufficient levels of CXCR5 expression, however, has remained unclear. Using our in vitro culture system to generate CXCR5low Tfh-like cells from naive CD4+ T cells with IL-6 in the absence of other cell types, we found that the active form of vitamin D, calcitriol, markedly enhanced CXCR5 expression after the release from persistent T cell receptor (TCR) stimulation. CH-223191, an aryl hydrocarbon receptor antagonist, further enhanced CXCR5 expression. IL-12 but not IL-4, in place of IL-6, also supported calcitriol to enhance CXCR5 expression even before the release from TCR stimulation, whereas the cell viability sharply decreased after the release. The Tfh-like cells generated with IL-6 and calcitriol exhibited chemotaxis toward C-X-C motif chemokine ligand 13 (CXCL13), expressed IL-21, and helped B cells to produce IgG antibodies in vitro more efficiently than Tfh-like cells generated without added calcitriol. Calcitriol injections into antigen-primed mice increased the proportion of CXCR5+PD-1+CD4+ cells in their lymphoid organs, and enhanced T cell entry into B cell follicles. These results suggest that calcitriol promotes CXCR5 expression in developing Tfh cells and regulates their functional differentiation., (© The Author(s) 2024. Published by Oxford University Press on behalf of The Japanese Society for Immunology.)

Chronic antigenic stimulation can trigger the formation of interleukin 10 (IL-10)-producing T-regulatory type 1 (TR1) cells in vivo. We have recently shown that murine T-follicular helper (TFH) cells are precursors of TR1 cells and that the TFH-to-TR1 cell transdifferentiation process is characterized by the progressive loss and acquisition of opposing transcription factor gene expression programs that evolve through at least one transitional cell stage. Here, we use a broad range of bulk and single-cell transcriptional and epigenetic tools to investigate the epigenetic underpinnings of this process. At the single-cell level, the TFH-to-TR1 cell transition is accompanied by both, downregulation of TFH cell-specific gene expression due to loss of chromatin accessibility, and upregulation of TR1 cell-specific genes linked to chromatin regions that remain accessible throughout the transdifferentiation process, with minimal generation of new open chromatin regions. By interrogating the epigenetic status of accessible TR1 genes on purified TFH and conventional T-cells, we find that most of these genes, including Il10 , are already poised for expression at the TFH cell stage. Whereas these genes are closed and hypermethylated in Tconv cells, they are accessible, hypomethylated, and enriched for H3K27ac-marked and hypomethylated active enhancers in TFH cells. These enhancers are enriched for binding sites for the TFH and TR1-associated transcription factors TOX-2, IRF4, and c-MAF. Together, these data suggest that the TR1 gene expression program is genetically imprinted at the TFH cell stage., Competing Interests: JG, PS, JY, JM, DM, CF, PS No competing interests declared, PS P. Santamaria is founder, scientific officer and stockholder of Parvus Therapeutics and receives funding from the company. He also has a consulting agreement with Sanofi, (© 2024, Garnica et al.)

The development of T follicular helper (Tfh) cells is an ongoing process resulting in the formation of various Tfh subsets. Despite advancements, the precise impact of T cell receptor (TCR) stimulation on this process remains incompletely understood. This study explores how TCR-CD3 signaling strength influences naive CD4 + T cell differentiation into Tfh-like cells and the concurrent expression of interleukin-21 (IL-21), interleukin-4 (IL-4), and interferon-gamma (IFN-γ). Strong TCR-CD3 stimulation induces proliferation and increased IL-21 expression in Tfh-like cells, which exhibit a characteristic phenotype expressing CXCR5 and PD1. The coexpression of IL-4 and IFN-γ in IL-21-producing Tfh-like cells is controlled by the strength TCR-CD3 stimulation; low stimulation favors IL-4, while strong stimulation enhances IFN-γ secretion. Exogenous addition of the effector cytokines IL-21 and IL-4 further modulate cytokine coexpression. These findings highlight the intricate regulatory mechanisms governing cytokine production and plasticity in Tfh-like cells, providing insights into B cell response modulation. In vivo , antigen availability may regulate Tfh cell plasticity, impacting subsequent B cell differentiation, emphasizing the need for further exploration through animal models or antigen-specific Tfh cell analyses in human lymph node biopsies., 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 Verstegen, Jorritsma, ten Brinke, Barberis and van Ham.)

The nonrandomized phase II study by Ding et al. explored the combination of azacitidine and chidamide with or without GemOx chemotherapy in relapsed/refractory peripheral T cell lymphoma and demonstrated that the dual epigenetic therapy is safe and efficacious, particularly in the angioimmunoblastic T cell lymphoma subset. 1 Further investigation into adding chemotherapy is warranted, building on the promising results seen in this trial., Competing Interests: Declaration of interests Y.W. declares research funding (to institution) from Incyte, InnoCare, LOXO Oncology, Eli Lilly, MorphoSys, Novartis, Genentech, Genmab, AbbVie, BeiGene, and Merck; advisory board membership (compensation to institution) for Eli Lilly, LOXO Oncology, TG Therapeutics, Incyte, InnoCare, Kite, Jansen, BeiGene, AstraZeneca, Genmab, and AbbVie; consultancy fees (compensation to institution) from InnoCare, AbbVie; and honorarium (to institution) from Kite., (Copyright © 2024 Elsevier Inc. All rights reserved.)

T follicular helper (Tfh) cells represent an important subset of CD4+ T cells that is crucial to the maturation and differentiation of B cells and the production of high-affinity antibodies. Because B cell activating-factor (BAFF), a vital B cell survival factor, is also crucial to B cell maturation and differentiation, we assessed the effects of BAFF on Tfh cell development and function. We demonstrated that deficiency of BAFF, but not of APRIL, markedly inhibited Tfh cell development, germinal center (GC) formation, and antigen-specific antibody production. The promoting effect of BAFF on Tfh cell development was dependent on expression of BR3 on T cells, and its promoting effect on GC formation was dependent on expression of BR3 on both T cells and B cells. BAFF directly promoted expression of the Tfh cell-characteristic genes via NF-κB signaling. This effect did need BR3 expression. Thus, BAFF not only has direct effects on B cells, but it also has direct effects on Tfh cell differentiation via engagement of BR3, which collectively promoted GC formation and production of high-affinity antibodies. This dual effect of BAFF on B cells and Tfh cells may help explain the clinical utility of BAFF antagonists in the management of certain autoimmune diseases.

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.)

Angioimmunoblastic T-cell lymphoma (AITL), the most common form of peripheral T-cell lymphoma, originates from follicular helper T (Tfh) cells and is notably resistant to current treatments. The disease progression and maintenance, at least in early stages, are driven by a complex interplay between neoplastic Tfh and clusters of B-cells within the tumor microenvironment, mirroring the functional crosstalk observed inside germinal centers. This interaction is further complicated by recurrent mutations, such as TET2 and DNMT3A, which are present in both Tfh cells and B-cells. These findings suggest that the symbiotic relationship between these 2 cell types could represent a therapeutic vulnerability. This review examines the key components and signaling mechanisms involved in the synapses between B-cells and Tfh cells, emphasizing their significant role in the pathobiology of AITL and potential as therapeutic targets., (Copyright © 2024 United States & Canadian Academy of Pathology. Published by Elsevier Inc. All rights reserved.)

Background: De novo donor-specific antibodies (dnDSAs) significantly affect the long-term outcomes of liver transplantation (LT), highlighting the importance of risk prediction. Follicular helper T (Tfh) cells have been implicated in dnDSA formation after transplantation. Considering the influence of immune response gene polymorphisms on transplantation outcomes, we investigated the association between polymorphisms in Tfh cell-related genes and dnDSA formation after LT., Methods: Fifty-three living-donor LT patients were included in this study. Single nucleotide polymorphisms (SNPs) were identified in six Tfh cell-related genes crucial for differentiation and maturation (BCL6, CXCR5, CXCL13, ICOS, CD40L, and IL-21); their association with the development of dnDSA after LT was evaluated., Results: Among the 53 recipients, 9 developed dnDSAs. BCL6 and IL-21 SNPs showed potential associations with dnDSA formation, enabling risk stratification., Conclusions: Variations in Tfh cell-related genes may predispose individuals to dnDSA formation after LT, emphasizing the importance of genetic factors for predicting post-transplant complications., 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 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.)

Purpose: Peripheral helper T (Tph) cells have an important role in the induction of humoral immune responses and autoantibody production. Accordingly, it is feasible that this lymphocyte subset has a relevant role in the pathogenesis of autoimmune thyroid diseases (AITD). In this study we aim to analyze the levels and function of Tph cells in blood samples from patients with AITD., Methods: We performed an observational study with cases and controls. Blood samples were obtained from nineteen patients with Hashimoto's thyroiditis (HT), twenty-four with Graves' disease (GD), and fifteen healthy controls. In addition, the levels of follicular T helper (Tfh) cells and Tph cells, the release of interleukin-21 (IL-21) by these lymphocytes and the number of plasmablasts were analyzed by multi-parametric flow cytometry analyses., Results: Increased percentages of Tfh and Tph lymphocytes were detected in patients with HT and GD. Furthermore, an enhanced synthesis of the cytokine IL-21 by these cells was observed. Accordingly, we detected significant higher percentages of plasmablasts in patients with GD, and these values tended to be also higher in HT patients. Moreover, significant positive associations were observed between the levels of Tfh or Tph and the number of plasmablast or anti-TSHR Ab titers in patients with AITD., Conclusion: Our data suggest that Tph lymphocytes may have a relevant role in the pathogenesis of AITD., (© 2024. The Author(s).)

Background: Plasmodium vivax is the dominant Plasmodium spp. causing malaria throughout tropical and sub-tropical countries. Humoral immunity is induced during P. vivax infection. However, data on longevity of antibody and memory B cell (MBC) responses is lacking. Follicular helper T cells (Tfh) are drivers of high-affinity and long-lived antibody responses. Understanding of Tfh-mediated immunity against malaria is valuable for vaccine development., Methodology/principal Findings: We enrolled 31 acutely infected P. vivax patients in low malaria transmission areas of Thailand to detect frequencies, phenotypes and kinetics of different subsets of circulating Tfh (cTfh) and MBCs, and to evaluate their association with humoral immunity following natural P. vivax infection. Expansion of cTfh2 cells, activated and atypical MBCs were shown during acute malaria. To relate increased cTfh2 cells to humoral immunity, P. vivax-specific MBCs and antibodies were assessed. High anti-PvCSP and -PvDBPII seropositivity was detected and most subjects produced MBCs specific to these antigens. The increased cTfh2 cells were positively related to atypical MBCs, plasmablasts/plasma cells, and anti-PvDBPII IgM and IgG levels. Distributions of memory cTfh cell subsets were altered from central memory (CM) to effector memory (EM) during infection. The highest ratios of cTfh-EM/cTfh-CM were represented in cTfh2 cells. Positive correlation of cTfh17-EM with activated and atypical MBCs was observed, while cTfh2-CM and cTfh17-CM cells were positively related to PvDBPII-specific MBCs and IgM levels., Conclusions/significance: Present study demonstrated that P. vivax infection induced cTfh polarization into cTfh2 subset, and alteration of memory cTfh2 phenotype from CM to EM phase. These P. vivax-induced cTfh responses significantly associated with generation of MBCs and antibody responses. Therefore, cTfh2 cells might possibly influence humoral immunity by inducing expansion of activated and atypical MBCs, and by generating P. vivax-specific MBCs and antibody responses following natural infection., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Thawornpan 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.)

Activated T follicular helper (aTfh) cells are likely important in host immune responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA vaccination. We characterized the immune responses of aTfh cells to the second (D2) and third (booster; D3) doses of an mRNA vaccine in the peripheral blood of 40 kidney transplant recipients (KTRs) and 17 healthy control volunteers (HCs). A significant increase in SARS-CoV-2-specific IgG antibody was seen after D3 in the KTRs; nonetheless, the levels after D2 and D3 were significantly lower than in the HCs. After D2, dramatic increases in activated CD45RA - CXCR5 + ICOS + PD1 + circulating Tfh (acTfh) cells were observed in the HCs, as well as the seropositive patients among the KTRs, when compared with the seronegative patients among the KTRs. Unlike the HCs, KTRs had less prominent immune responses, including the acTfh and T cells that produce interferon gamma, tumor necrosis factor alpha, and interleukin 21. In addition, the increase in acTfh cells was significantly associated with anti-IgG antibody levels after D3. These results indicate impaired SARS-CoV-2-specific responses via acTfh cells in KTRs, and they suggest that acTfh cells in peripheral blood may play an important role in antibody maintenance following SARS-CoV-2 mRNA vaccination., (© 2024. The Author(s).)

Background: Biliary atresia (BA) has diverse and unclear pathogenesis, which may be related to immune response in response to a foreign stimulus. T follicular helper (Tfh) cells have been found to play an important role in various immune diseases., Aims: To investigate the expression of Tfh cells in BA and non-BA cholestatic diseases in children., Methods: Transcriptome sequencing and Gene Ontology (GO) enrichment analysis were performed to investigate the differences in gene expression between the BA group and the non-BA cholestasis group. Study the distribution of Tfh cells in liver tissues of the BA and non-BA cholestatic groups through single sample gene set enrichment analysis (ssGSEA). Tfh cells (CD3 + Bcl6 + ) in liver tissues from BA patients were labeled by double immunofluorescent staining to verify their distribution in the liver., Results: Transcriptome sequencing showed differences in gene expression between the BA group and the non-BA cholestasis group. A total of 808 genes were up-regulated and 405 genes were down-regulated in BA, suggesting that there might be a specific immune response in BA. GO enrichment analysis showed that BA group had augmented response to foreign stimulus and increased metabolic process compared to the non-BA cholestatic group. The relative proportion of immune cells was analyzed by ssGSEA method. The proportions of Tfh cells, activated B cells, CD4 + T cells, memory B cells and Th2 cells were higher in the BA group than in the non-BA cholestatic group. Fluorescence immunostaining showed that Tfh cells were significantly increased in liver tissue samples of the BA group compared to the non-BA cholestasis group, which was consistent with the transcriptome sequencing results., Conclusion: Tfh cells share in immune cascade involvement in BA. Our work support immune pathogenesis of the in response to a stimulus that might be foreign in BA., (© 2024. The Author(s).)

Objective/main Outcome: To study the expression of OX40 on T follicular helper (Tfh) cells and the ligand OX40L on antigen-presenting cells (APCs) in peripheral blood of patients with type 1 diabetes mellitus (T1DM) and the role of OX40 signaling in promoting Tfh cells to assist B-cell differentiation., Design: Cross-sectional study., Setting: Endocrinology department of a university hospital., Participants: Twenty-five patients with T1DM and 35 with newly diagnosed type 2 diabetes mellitus (T2DM) from January 2021 to December 2021 (39 males, 21 females; mean age: 31.0 ± 4.5, range: 19-46 years)., Interventions: None., Methods: The peripheral blood proportion of CD4+CD25-CD127+CXCR5+PD1+ Tfh cells in patients with T1DM or T2DM and the OX40L expression in CD14+ monocytes and CD19+ B cells were analyzed by flow cytometry. The OX40 signal effect on Tfh-cell function was analyzed by coincubating B cells with Tfh cells under different conditions. Flow cytometry detected the ratio of CD19-CD138+ plasmacytes., Results: The Tfh cells ratio and intracellular IL-21 expression in peripheral blood was significantly higher in patients with T1DM than with T2DM, and the OX40 expression in peripheral Tfh cells and OX40L expression in APC were significantly higher in T1DM. After adding OX40L protein, the CD19-CD138+-plasmacytes percentage was significantly increased and higher in T1DM. Blocking of anti-OX40L monoclonal antibodies significantly reduced the plasmacytes ratio., Conclusion: The peripheral Tfh cells proportion increased and the OX40 expression in peripheral Tfh cells was upregulated in patients with T1DM vs patients with T2DM. OX40/OX40L signaling enhanced the Tfh-cell function to assist B-cell differentiation, which may contribute to the pathogenesis of T1DM., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Endocrine Society.)

The expansion of T follicular helper (Tfh) cells correlates with disease progression in human and murine systemic lupus erythematosus (SLE). Unfortunately, there are no therapies to deplete Tfh cells. Importantly, low-dose rIL-2-based immunotherapy shows potent immunosuppressive effects in SLE patients and lupus-prone mice, primarily attributed to the expansion of regulatory T cells (Tregs). However, IL-2 can also inhibit Tfh cell differentiation. In this study, we investigate the potential of low-dose rIL-2 to deplete Tfh cells and prevent autoantibody responses in SLE. Our data demonstrate that low-dose rIL-2 efficiently depletes autoreactive Tfh cells and prevents autoantibody responses in lupus-prone mice. Importantly, this immunosuppressive effect was independent of the presence of Tregs. The therapeutic potential of eliminating Tfh cells was confirmed by selectively deleting Tfh cells in lupus-prone mice. Our findings demonstrate the critical role of Tfh cells in promoting autoantibody responses and unveil, (to our knowledge), a novel Treg-independent immunosuppressive function of IL-2 in SLE., (Copyright © 2024 by The American Association of Immunologists, Inc.)

T follicular regulatory (TFR) cells are found in the germinal center (GC) response and, along with T follicular helper (TFH) cells, help to control the development of high-affinity antibodies (Ab). Although TFR cells are generally thought to repress GC B cells and the Ab response, we have previously shown that in a mouse food allergy model, TFR cells produce IL-10 and play an essential helper role such that in the absence of TFR cells, IgE responses are diminished. Here we show that in this food allergy response, TFR cells produced IL-4 that promotes the generation of antigen-specific IgE. We show that food allergy-primed TFR cells specifically upregulate IL-4 gene transcription and produce functional IL-4 that promoted IgE responses both in vitro and in vivo. We determined that IgE responses are dependent on a high level of IL-4 produced by follicular T cells in the GC, explaining the need for IL-4 produced by TFR cells in the food allergy response. Overall, our findings have demonstrated that in food allergy, TFR cells can produce IL-4 and regulate IgE in a manner that augments the role of TFH cells in IgE responses.

Rheumatoid arthritis (RA) is frequent, an imbalance between helper cells (Th) and regulatory T cells (Treg) is the fundamental immunological cause of RA. This study investigates how recombinant human programmed cell death 1 (PD-L1) protein affects circulating T follicular helper (cTfh), circulating T follicular regulatory (cTfr), and their equilibrium. Magnetic bead sorting was used to select CD4+CXCR5+T cells from RA patients' and healthy individuals' peripheral blood mononuclear cells for in vitro growth. Recombinant human PD-L1 protein stimulated CD4+CXCR5+T cells. Cell counting kit 8 (CCK-8), flow cytometry surface labeling, ELISA, and RT-PCR were used to measure CD4+CXCR5+T cell proliferation inhibition, cTfh and cTfr frequencies, IL-21 expression, and PI3K, AKT, Bcl-6, and Blimp-1 mRNA levels. The recombinant human PD-L1 protein dose-dependently inhibited the proliferation of CD4+CXCR5+T cells in active RA peripheral blood. However, it has a weaker inhibitory effect on healthy peripheral blood CD4+CXCR5+T cells. PD-L1 protein decreased cTfh in active RA peripheral blood CD4+CXCR5+T overall cultured cells but did not affect cTfr; The cTfr/cTfh ratio increased but did not affect the frequency of cTfh and cTfr in healthy persons' cultured CD4+CXCR5+T cells. PD-L1 protein reduced IL-21 in CD4+CXCR5+T cell culture supernatant from active RA peripheral blood. Recombinant human PD-L1 protein lowered PI3K, AKT, and Bcl-6 mRNA in active RA peripheral blood CD4+CXCR5+T cell culture, including significant differences. But Blinmp-1 mRNA variations were neither substantial nor statistically different. PD-1/PD-L1 limits cTfh proliferation, differentiation, and activation via the PI3K/AKT signaling pathway regulates its immunological balance with cTfr, and corrects the cTfr/cTfh imbalance by controlling their interaction.

Clinical evidence suggests anti-Hsp60 antibodies could contribute to atherosclerosis (AS) development, with unclear mechanisms. This study aims to explore the role of anti-HSP60-mediated autoimmunity in AS progression. HSP60-MHC tetramers were used to characterize HSP60-specific CD4 + T cells and assess TCR responses in mice. These cells were transplanted into AS mice to examine immune cell differentiation and infiltration in plaques and blood. Mice were injected with recombinant HSP60 or anti-HSP60 sera to evaluate effects on plaque progression and macrophage activity. Experiments with muMT -/- Apoe -/- mice examined humoral immunity's role in this autoimmunity. HSP60-reactive CD4 + T cells in AS mice differentiated into follicular helper cells, not Th1/Th17. Anti-HSP60 treatments increased macrophage infiltration and M1 polarization, indicating an anti-HSP60-driven inflammatory progression, dependent on humoral immunity. Anti-HSP60 influences macrophage infiltration, polarization, and plaque formation via humoral immunity, shedding light on its potential role in AS progression., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background: Oral consumption of peanut products early in life reduces the incidence of peanut allergy in children. However, little is known about whether exposure via the oral mucosa alone is sufficient or whether the gastrointestinal tract must be engaged to protect against peanut allergy., Objective: We used a mouse model and examined the effects of peanut allergen administration to only the oral cavity on allergy development induced by environmental exposure., Methods: Naive BALB/c mice were administered peanut flour (PNF) sublingually, followed by epicutaneous exposure to PNF to mimic a human condition. The sublingual volume was adjusted to engage only the oral cavity and prevent it from reaching the esophagus or gastrointestinal tract. The efficacy was evaluated by examining the anaphylactic response, antibody titers, and T follicular helper cells., Results: The mice exposed epicutaneously to PNF developed peanut allergy, as demonstrated by increased plasma levels of peanut-specific IgE and the manifestation of acute systemic anaphylaxis following intraperitoneal challenge with peanut extract. The development of peanut allergy was suppressed when mice had been given PNF sublingually before epicutaneous exposure. There were fewer T follicular helper cells in the skin-draining lymph nodes of mice that received sublingual PNF than in the mice that received PBS. Suppression of IgE production was observed with sublingual PNF at 1/10 of the intragastric PNF dose., Conclusion: Administration of peanut allergens only to the oral cavity effectively prevents the development of peanut allergy. The capacity of the oral mucosa to promote immunologic tolerance needs to be evaluated further to prevent food allergy., (Copyright © 2024 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Objective: We focused to analyze the time-course changes at pre- and post-flare of T peripheral helper (Tph) cells and circulating T follicular helper (Tfh) cells in the blood of patients with systemic lupus erythematosus (SLE) with lupus low disease activity state (LLDAS) before flare., Methods: This study included inactive (n = 29) and active (n = 55) patients with SLE. Tph subsets, Tfh subsets, CD11c hi B cells, and plasma cells in the blood were determined by flow cytometry. The blood levels of cytokines including interferons (IFNs) were measured by electrochemiluminescence assay or cytokine beads array., Results: Active SLE patients exhibited the increased frequency of Tph1, Tph2, Tfh1, and Tfh2 subsets when compared to inactive patients, but no clear changes in the other subsets. During the treatment with medications, Tph1, Tph2, and Tfh2 subsets were significantly reduced along with disease activity and Tph1 and Tph2 subsets were positively correlated with SLE disease activity index (SLEDAI). The time course analysis of patients at pre- and post-flare revealed that in the patients at LLDAS before flare, Tph subsets and Tfh subsets were relatively low levels. At the flare, Tph cells, particularly Tph1 and Tph2 subsets, were increased and correlated with SLEDAI. Furthermore, the blood levels of IFN-α2a, IFN-γ, and IFN-λ1 were low in the patients with LLDAS before flare but these IFNs, particularly IFN-λ1, were increased along with flare., Conclusion: Increased frequency of Tph1 and Tph2 subsets and elevated levels of serum IFN-λ1 are presumably critical for triggering of flare in SLE., 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.)

Renal transplantation is the preferred treatment option for patients with end-stage renal disease (ESRD) in a clinical setting. Antibody mediated rejection (AMR) is one of the leading causes of graft dysfunction. To address the current shortcomings in the early diagnosis and treatment of AMR in clinical practice, this article analyzes the distribution of different circulating T follicular helper (cTfh) cell subtypes and B cell subpopulations in peripheral blood and detects the cytokine levels of chemokine ligand 13 (CXCL13), interleukin-21 (IL-21), and interleukin-4 (IL-4) related to cTfh cells in peripheral blood of kidney transplant recipients. Moreover, we also explore the correlation between cTfh cells, peripheral blood memory B cells, and AMR, their value as early predictive indicators of AMR, and explore potential therapeutic targets for AMR patients. Our results indicate that the proportion of cTfh cells increased at the onset of AMR, which plays an important role in antigen-specific B-cell immune regulation. Activation of cTfh cells in AMR patients correlates with phenotypes of memory B cells and plasma blasts. cTfh cells and memory B cells have promising diagnostic efficacies and predictive values for AMR. The proportion of cTfh cells to CD4 + T cells and the proportion of memory B cells to CD19 + B cells are correlated with serum creatinine levels, indicating that cTfh cells and memory B cells may be involved in the progression of AMR. In addition, the CXCL13, IL-21, and IL-4, which were associated with cTfh cells, may be involved in the onset of AMR., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2024. Published by Elsevier B.V.)

Antigen-specific humoral responses are orchestrated through complex interactions among immune cells in lymphoid tissues, including the collaboration between B cells and T follicular helper (Tfh) cells. Accumulating evidence indicates a crucial role for interleukin-9 (IL-9) in the formation of germinal centers (GCs), enhancing the generation of class-switched high-affinity antibodies. However, the exact function of IL-9 in Tfh cell regulation remains unclear. In this study, we examined the humoral immune responses of CD4 Cre/+ Il9ra fl/fl mice, which lack an IL-9-specific receptor in Tfh cells. Upon intraperitoneal immunization with sheep red blood cells (SRBCs), CD4 Cre/+ Il9ra fl/fl mice displayed diminished levels of SRBC-specific IgG antibodies in their sera, along with reduced levels of GC B cells and plasma cells. Notably, Il9ra-deficient Tfh cells in the spleen exhibited decreased expression of their signature molecules such as B-cell lymphoma 6, C-X-C chemokine receptor 5, IL-4, and IL-21 compared to control mice. In models of allergic asthma induced by house dust mite (HDM) inhalation, CD4 Cre/+ Il9ra fl/fl mice failed to elevate serum levels of HDM-specific IgE and IgG. This was accompanied by reductions in Tfh cells, GC B cells, and plasma cells in mediastinal lymph nodes. Furthermore, group 2 innate lymphoid cells (ILC2s) were identified as producers of IL-9 under immunizing conditions, possibly induced by leukotrienes released by activated IgD + B cells around the T-B border. These observations may indicate the critical role of IL-9 receptor signaling in the activation of Tfh cells, with ILC2s potentially capable of supplying IL-9 in organized lymphoid tissues., 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 Sato, Ikegami, Yanagi, Ohyu, Sugaya, Shirato, Tanemoto, Kamiya, Kikuchi, Kamada, Nakata, Kamekura, Sato, Takano, Miyajima, Watanabe and Ichimiya.)

Chronic lymphocytic leukemia (CLL) presents with heterogeneous clinical outcomes, suggesting varied underlying pathogenic mechanisms. This study aims to elucidate the impact of T follicular helper (Tfh) cells on CLL progression and prognosis. Gene expression profile data for CLL were collected from GSE22762 and GSE39671 datasets. Patients were divided into high and low groups using Tfh levels using the optimal cutoff value based on overall survival (OS) and time-to-first treatment (TTFT). Differential expression analysis was performed between these groups, followed by co-expression network analysis and single-sample Gene Set Enrichment Analysis (ssGSEA). Marker genes of Tfh cells were used to construct prognostic models. Additionally, 40 CLL patients were recruited and categorized based on median Tfh levels. Marker gene expression was assessed using RT-qPCR and Western Blot, and immune cell levels were determined through flow cytometry. The high group showed better prognosis compared to the low group. Among the 1121 differentially expressed genes identified, five co-expression networks were constructed, with the turquoise module showing the highest correlation with Tfh cells. Genes within this module significantly participate in cytokine-cytokine receptor interaction, PI3K-Akt signaling pathway, and natural killer cell mediated cytotoxicity. Tfh cells were significantly negatively correlated with activated B cells and positively correlated with Tregs. The Random Survival Forest (RSF) model identified 10 marker genes, and further analysis using Lasso regression and nomogram selected CLEC4A, RAE1, CD84, and PRDX1 as prognostic markers. In the high group, levels of CLEC4A and RAE1 were higher than in the low group, whereas CD84 and PRDX1 were lower. Flow cytometry revealed that the level of activated B cells in the high Tfh group was significantly lower than in the low Tfh group, while the level of Tregs is significantly higher in the high Tfh group. This study seeks to contribute to a more detailed understanding of the pathogenesis of CLL, delving into the prognostic significance of Tfh., (© 2024. The Author(s).)

Materials and Methods: Using flow cytometry, we identified and quantified Group 2 innate lymphocytes, T helper 2 cells, follicular helper T cells, and T helper 17 cells in peripheral blood samples from 49 individuals with asthma. We then conducted cross-sectional analyses to assess relationships between levels of these immune cells and lung function parameters, including the percentage predicted forced expiratory volume in 1 s (%FEV1). We also examined correlations between the proportions of immune cells and type 2 biomarkers., Results: Proportions of CXCR5 + follicular helper T cells in human peripheral blood, as opposed to Group 2 innate lymphoid cells (ILC2) or T helper 2 cells, were significantly higher in cases with %FEV1 < 80% compared to those with %FEV1 ≥ 80%. Further, these proportions correlated negatively with %FEV1 and positively with blood eosinophil counts., Conclusions: The proportion of circulating follicular helper T cells, but not T helper 2 cells or Group 2 innate lymphoid cells, may reflect the presence of airway obstruction caused by persistent type 2 inflammation., Competing Interests: Akihito Yokoyama receives speaker fees from AstraZeneca, Boehringer Ingelheim, GSK, Novartis, and Sanofi. The rest of the authors declare that they have no relevant conflicts of interest., (Copyright © 2024 Tsukie Kin Tsukuda et al.)

Despite decades of intense research, our understanding of the correlates of protection against Salmonella Typhi ( S . Typhi) infection and disease remains incomplete. T follicular helper cells (T FH ), an important link between cellular and humoral immunity, play an important role in the development and production of high affinity antibodies. While traditional T FH cells reside in germinal centers, circulating T FH (cT FH ) (a memory subset of T FH ) are present in blood. We used specimens from a typhoid controlled human infection model whereby participants were immunized with Ty21a live attenuated S . Typhi vaccine and then challenged with virulent S . Typhi. Some participants developed typhoid disease (TD) and some did not (NoTD), which allowed us to assess the association of cT FH subsets in the development and prevention of typhoid disease. Of note, the frequencies of cT FH were higher in NoTD than in TD participants, particularly 7 days after challenge. Furthermore, the frequencies of cT FH 2 and cT FH 17, but not cT FH 1 subsets were higher in NoTD than TD participants. However, we observed that ex-vivo expression of activation and homing markers were higher in TD than in NoTD participants, particularly after challenge. Moreover, cT FH subsets produced higher levels of S . Typhi-specific responses (cytokines/chemokines) in both the immunization and challenge phases. Interestingly, unsupervised analysis revealed unique clusters with distinct signatures for each cT FH subset that may play a role in either the development or prevention of typhoid disease. Importantly, we observed associations between frequencies of defined cT FH subsets and anti- S. Typhi antibodies. Taken together, our results suggest that circulating T FH 2 and T FH 17 subsets might play an important role in the development or prevention of typhoid disease. The contribution of these clusters was found to be distinct in the immunization and/or challenge phases. These results have important implications for vaccines aimed at inducing long-lived protective T cell and antibody responses., Competing Interests: ML: Co-inventor of a live attenuated S. Typhi vaccine strain CVD 909 and a S. Paratyphi A vaccine strain CVD 1902 that have been licensed to Bharat Biotech International BBI, Hyderabad, India for clinical development. ML is also a co-inventor of a Trivalent Salmonella Conjugate vaccine that includes S. Enteritidis, S. Typhimurium conjugates core plus O-polysaccharide covalently linked to FliC flagellin subunits of the homologous serovars in combination with BBI’s Vi conjugate Typbar TCV. AP: is chair of the UK department of Health and Social Cares Joint Committee on vaccination and immunisation. He has research grants on typhoid/paratyphoid vaccines from Serum Institute of India, Medical Research Council, Wellcome Trust and Bill & Melinda gates Foundation. Author MM was employed by company Sanofi. Authors SF and CB were employed by company GlaxsoSmithKline. Author RR is presently employed at Moderna Therapeutics and owns shares/options. Her contributions to this project were made prior to her employment at Moderna. The remaining 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 Booth, Rapaka, McArthur, Fresnay, Darton, Blohmke, Jones, Waddington, Levine, Pollard and Sztein.)

Background: Systemic lupus erythematosus (SLE) is the quintessential autoimmune disease, as it is characterized by hyperactivity of CD4 + T cells and subsequently drives lupus pathology. Follicular helper T (TFH) cells play an important role in B cell maturation and antibody production. However, which specific subset of cTFH cells drives B cell function and contributes to the development of anti-dsDNA antibodies and SLE pathogenesis remains unclear., Methods: Peripheral blood mononuclear cells from SLE patients with inactive (n = 11) and active (n = 21) were used to determine and detect frequencies and phenotypes of circulating TFH cells (cTFH), memory cTFH, and B cell subsets. The correlations among cTFH cell subsets and phenotypes, B cell subsets, anti-dsDNA autoantibodies, and clinical parameters were analyzed., Results: In subjects with active SLE, cTFH1 and cTFH17 cells were significantly expanded and activated. These expanded cTFH cells expressed memory phenotypes; cTFH1 cells were predominantly central memory (CM) type, while cTFH17 cells were largely effector memory (EM) type. Phenotyping B cell subsets in these patients showed increased frequencies of aNAV and DN2 B cells. Clinically, ICOS + cTFH1, ICOS + cTFH17 cells, and SLEDAI-2k scores were found to be correlated. Analysis of cTFH-B cell relationship revealed positive correlations among ICOS + cTFH1 cells, aNAV B cells, and anti-dsDNA antibodies. Activation of ICOS + cTFH17 cells was significantly related to the expansion of aNAV and DN2 B cells. The presence of CM cells in cTFH1 and cTFH17 subsets was correlated with aNAV and DN2 B cell frequencies., Conclusion: SLE cTFH cells were found to be polarized toward cTFH1 and cTFH17 cells; activation of these cTFH subsets was significantly associated with disease activity score, aNAV, DN2 B cell expansion, and anti-dsDNA antibody level. Thus, the interactions among cTFH1, cTFH17, and B cells likely contribute to the development of autoantibodies and the pathogenesis in SLE., (© 2024. The Author(s).)

Follicular helper and regulatory T cells (Tfh/TFR) cells are distinct subsets of CD4 + cells that have been recognized for their critical role in regulating cellular reactions within the germinal centers of lymphoid follicles. In the present study, we aimed to determine the presence and the frequency of these cells in draining lymph nodes of patients with bladder cancer (BC). Forty-six patients with BC who had undergone radical cystectomy and pelvic lymph node dissection were enrolled. Following routine pathological examination, a portion of the dissected lymph nodes was minced to obtain a single-cell suspension. Mononuclear cells were then separated using Ficoll-Hypaque gradient centrifugation, and the samples with proper viability (> 95%) were subjected to further analysis. To phenotype the follicular subsets, cells were stained with appropriate fluorochrome-conjugated antibodies specific for CD4, CXCR5, BCL6, and FOXP3. The cells were then acquired on a four-color flow cytometer. The data were analyzed with the FlowJo software version 10.8.1 package. Our analysis indicated that, on average 37.89 ± 16.36% of CD4 + lymphocytes in draining lymph nodes of patients with BC expressed CXCR5. The majority of them were negative for FOXP3, representing helper subsets (28.73 ± 13.66). A small percent simultaneously expressed BCL6 transcription factor (1.65% ± 1.35), designated as Tfh (CD4 + BCL6 + CXCR5 + FOXP3 - ). While less than 10% of CD4 + lymphocytes expressed CXCR5 and FOXP3, 1.78 ± 2.54 were also positive for BCL6, known as TFR. Statistical analysis revealed that the frequency of both Tfh and TFR cells was higher in draining lymph nodes of patients with tumor-infiltrated nodes (P = 0.035 and P = 0.079, respectively) compared to those with negative ones. The percentage of these cells was also higher in high-grade tumors compared to low-grade ones (P = 0.031 for both). Our data collectively indicated that however approximately one third of CD4 + lymphocytes expressed CXCR5 and accordingly had the capacity to enter the follicles, less than 2% of them represented Tfh and TFR phenotypes. The percentage of these cells increased in progressed tumors and showed an association with negative prognostic factors., (© 2024. The Author(s).)

The differentiation and specificity of human CD4 + T follicular helper cells (T FH cells) after influenza vaccination have been poorly defined. Here we profiled blood and draining lymph node (LN) samples from human volunteers for over 2 years after two influenza vaccines were administered 1 year apart to define the evolution of the CD4 + T FH cell response. The first vaccination induced an increase in the frequency of circulating T FH (cT FH ) and LN T FH cells at week 1 postvaccination. This increase was transient for cT FH cells, whereas the LN T FH cells further expanded during week 2 and remained elevated in frequency for at least 3 months. We observed several distinct subsets of T FH cells in the LN, including pre-T FH cells, memory T FH cells, germinal center (GC) T FH cells and interleukin-10 + T FH cell subsets beginning at baseline and at all time points postvaccination. The shift toward a GC T FH cell phenotype occurred with faster kinetics after the second vaccine compared to the first vaccine. We identified several influenza-specific T FH cell clonal lineages, including multiple responses targeting internal influenza virus proteins, and found that each T FH cell state was attainable within a clonal lineage. Thus, human T FH cells form a durable and dynamic multitissue network., (© 2024. The Author(s).)

Background: T follicular helper (Tfh) cells are a subdivision of T helper cells involved in antigen-specific B cell immunity. Tfh cells play an essential role in the interaction of T cells/B cells in the germinal centers (GC), and dysregulation of Tfh actions can offer pathogenic autoantibody formation and lead to the development of autoimmune diseases. This study seeks to evaluate changes in Tfh frequency and its related cytokines in autoimmune disease, its association with disease phase, severity, prognosis, and the effect of immunosuppressive treatment on the Tfh population., Method: The study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 Statement. Electronic databases, including PubMed, Scopus, Web of Science, and Embase, were systematically searched for potentially eligible studies up to January 1, 2024., Results: We identified 4998 articles in the initial search, from which 1686 similar titles were removed. A total of 3312 articles were initially screened, and 3051 articles were excluded by title/abstract screening. A total of 261 studies were considered for full-text assessment, and 205 articles were excluded by reason. Finally, a total of 56 studies were included in our review., Conclusion: The population of Tfh cells is generally higher in autoimmune diseases versus Health control. Moreover, the number of Tfh cells is associated with the disease severity and can be considered for determining the prognosis of studies. Also, peripheral blood circulating Tfh (cTfh) cells are an available sample that can be used as an indicator for diagnosing diseases., 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 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.)

Overwhelming evidence has shown that aging is a significant risk factor for COVID-19-related hospitalizations, death and other adverse health outcomes. Particular T cell subsets that susceptible to aging and associated with COVID-19 disease severity requires further elucidation. Our study recruited 57 elderly patients with acute COVID-19 and 27 convalescent donors. Adaptive immunity was assessed across the COVID-19 severity spectrum. Patients underwent age-dependent CD4 + T lymphopenia, preferential loss of circulating T follicular regulatory cells (cTfh) subsets including cTfh-em, cTfh-cm, cTfh1, cTfh2, cTfh17 and circulating T follicular regulatory cells (cTfr), which regulated antibody production through different pathways and correlated with COVID-19 severity, were observed. Moreover, vaccination improved cTfh-cm, cTfh2, cTfr proportion and promoted NAb production. In conclusion, the elderly had gone through age-dependent cTfh subsets deficiency, which impeded NAb production and enabled aggravation of COVID-19 to critical illness, whereas SARS-CoV-2 vaccine inoculation helped to rejuvenate cTfh, cTfr and intensify NAb responses., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Introduction: Adjuvants added to subunit vaccines augment antigen-specific immune responses. One mechanism of adjuvant action is activation of pattern recognition receptors (PRRs) on innate immune cells. Bordetella colonization factor A (BcfA); an outer membrane protein with adjuvant function, activates T H 1/T H 17-polarized immune responses to protein antigens from Bordetella pertussis and SARS CoV-2. Unlike other adjuvants, BcfA does not elicit a T H 2 response., Methods: To understand the mechanism of BcfA-driven T H 1/T H 17 vs. T H 2 activation, we screened PRRs to identify pathways activated by BcfA. We then tested the role of this receptor in the BcfA-mediated activation of bone marrow-derived dendritic cells (BMDCs) using mice with germline deletion of TLR4 to quantify upregulation of costimulatory molecule expression and cytokine production in vitro and in vivo. Activity was also tested on human PBMCs., Results: PRR screening showed that BcfA activates antigen presenting cells through murine TLR4. BcfA-treated WT BMDCs upregulated expression of the costimulatory molecules CD40, CD80, and CD86 and produced IL-6, IL-12/23 p40, and TNF-α while TLR4 KO BMDCs were not activated. Furthermore, human PBMCs stimulated with BcfA produced IL-6. BcfA-stimulated murine BMDCs also exhibited increased uptake of the antigen DQ-OVA, supporting a role for BcfA in improving antigen presentation to T cells. BcfA further activated APCs in murine lungs. Using an in vitro T H cell polarization system, we found that BcfA-stimulated BMDC supernatant supported T FH and T H 1 while suppressing T H 2 gene programming., Conclusions: Overall, these data provide mechanistic understanding of how this novel adjuvant activates immune responses., 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 Shamseldin, Read, Hall, Tuazon, Brown, Guo, Gupta, Deora, Oestreich and Dubey.)

Competing Interests: Conflicts of interest The authors declare no conflicts of interest.

Th17 cell plasticity is crucial for development of autoinflammatory disease pathology. Periodontitis is a prevalent inflammatory disease where Th17 cells mediate key pathological roles, yet whether they exhibit any functional plasticity remains unexplored. We found that during periodontitis, gingival IL-17 fate-mapped T cells still predominantly produce IL-17A, with little diversification of cytokine production. However, plasticity of IL-17 fate-mapped cells did occur during periodontitis, but in the gingiva draining lymph node. Here, some Th17 cells acquired features of Tfh cells, a functional plasticity that was dependent on IL-6. Notably, Th17-to-Tfh diversification was important to limit periodontitis pathology. Preventing Th17-to-Tfh plasticity resulted in elevated periodontal bone loss that was not simply due to increased proportions of conventional Th17 cells. Instead, loss of Th17-to-Tfh cells resulted in reduced IgG levels within the oral cavity and a failure to restrict the biomass of the oral commensal community. Thus, our data identify a novel protective function for a subset of otherwise pathogenic Th17 cells during periodontitis., (© 2024 McClure et al.)

Background: Head and neck squamous cell carcinoma (HNSCC) typically present with a complex anatomical distribution, often accompanied by insidious symptoms. This combination contributes to its high incidence and poor prognosis. It is now understood that the immune features of cellular components within the tumor ecosystem and their complex interactions are critical factors influencing both tumor progression and the effective immune response., Methods: We obtained single-cell RNA sequencing data of 26,496 cells from three tumor tissues and five normal tissues and performed subsequent analyses. Immunohistochemical staining on tumor sections was used to validate the presence of malignant cells. Additionally, we included bulk RNA sequencing data from 502 HNSCC patients. Kaplan-Meier analysis and the log-rank test were employed to assess predictors of patient outcomes., Results: We identified three epithelial subclusters exhibiting immune-related features. These subclusters promoted the infiltration of T cells, dendritic cells, and monocytes into the tumor microenvironment. Additionally, cancer-associated fibroblasts displayed tumor-promoting and angiogenesis characteristics, contrasting with the predominant antigen-presenting and inflammatory roles observed in fibroblasts from normal tissues. Furthermore, tumor endothelial subsets exhibited a double-sided effect, promoting tumor progression and enhancing the effectiveness of immune response. Finally, follicular helper T cells and T helper 17 cells were found to be significantly correlated with improved outcomes in HNSCC patients. These CD4 + T cell subpopulations could promote the anti-tumor immune response by recruiting and activating B and T cells., Conclusion: Our findings provide deeper insights into the immune features of the tumor ecosystem and reveal the prognostic significance of follicular helper T cells and T helper 17 cells. These findings may pave the way for the development of therapeutic approaches., (© 2024. The Author(s).)

The immunological mechanisms underlying chronic colitis are poorly understood. T follicular helper (T FH ) cells are critical in helping B cells during germinal center reactions. In a T cell transfer colitis model, a lymphoid structure composed of mature dendritic cells (DCs) and T FH cells was found within T cell zones of colonic lymphoid follicles. T FH cells were required for mature DC accumulation, the formation of DC-T cell clusters and colitis development. Moreover, DCs promoted T FH cell differentiation, contributing to colitis development. A lineage-tracing analysis showed that, following migration to the lamina propria, T FH cells transdifferentiated into long-lived pathogenic T H 1 cells, promoting colitis development. Our findings have therefore demonstrated the reciprocal regulation of T FH cells and DCs in colonic lymphoid follicles, which is critical in chronic colitis pathogenesis., (© 2024. The Author(s), under exclusive licence to Springer Nature America, Inc.)