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A20 is a dual‐function ubiquitin‐editing enzyme that maintains immune homeostasis by restraining inflammation. Although A20 serves a similar negative feedback function for T‐cell receptor (TCR) signaling, the molecular mechanisms utilized and their ultimate impact on human T‐cell function remain unclear. TCR engagement triggers the assembly of the CARD11‐BCL10‐MALT1 (CBM) protein complex, a signaling platform that governs the activation of downstream transcription factors including NF‐κB and c‐Jun/AP‐1. Utilizing WT and A20 knockout Jurkat T cells, we found that A20 is required to negatively regulate NF‐κB and JNK. Utilizing a novel set of A20 mutants in NF‐κB and AP‐1‐driven reporter systems, we discovered the ZnF7 domain is crucial for negative regulatory capacity, while deubiquitinase activity is dispensable. Successful inactivation of A20 in human primary effector T cells congruently conferred sustained NF‐κB and JNK signaling, including enhanced upregulation of activation markers, and increased secretion of several cytokines including IL‐9. Finally, loss of A20 in primary human T cells resulted in decreased sensitivity to restimulation‐induced cell death and increased sensitivity to cytokine withdrawal‐induced death. These findings demonstrate the importance of A20 in maintaining T‐cell homeostasis via negative regulation of both NF‐κB and JNK signaling. [ABSTRACT FROM AUTHOR]

Regulatory B cells (Bregs) are a functionally distinct B‐cell subset involved in the maintenance of homeostasis and inhibition of inflammation. Studies, from the last two decades, have increased our understanding of cellular and molecular mechanisms involved in their generation, function, and to a certain extent phenotype. Current research endeavours to unravel the causes and consequences of Breg defects in disease, with increasing evidence highlighting the relevance of Bregs in promoting tumorigenic responses. Here we provide historical and emerging findings of the significance of Bregs in autoimmunity and transplantation, and how these insights have translated into the cancer field. [ABSTRACT FROM AUTHOR]

Summary: Autologous patient‐derived adoptive T‐cell therapies have revolutionized the management of relapsed multiple myeloma (MM). However, the current manufacturing and quality control processes result in lengthy vein‐to‐vein time, making bridging therapy necessary for most patients. Yet the decision and choice of optimal bridging therapy are complex in the heavily pretreated relapsed MM patient. In this perspective piece, the authors provide their approach and considerations while selecting an optimal bridging regimen before autologous chimeric antigen receptor T‐cell therapy. [ABSTRACT FROM AUTHOR]

Atopic dermatitis (AD) is a common inflammatory skin disorder. Mast cells play an important role in AD because they regulate allergic reactions and inflammatory responses. However, whether and how the modulation of mast cell activity affects AD has not been determined. In this study, we aimed to determine the effects and mechanisms of 3‐O‐cyclohexanecarbonyl‐11‐keto‐β‐boswellic acid (CKBA). This natural compound derivative alleviates skin inflammation by inhibiting mast cell activation and maintaining skin barrier homeostasis in AD. CKBA markedly reduced serum IgE levels and alleviated skin inflammation in calcipotriol (MC903)‐induced AD mouse model. CKBA also restrained mast cell degranulation both in vitro and in vivo. RNA‐seq analysis revealed that CKBA downregulated the extracellular signal‐regulated kinase (ERK) signaling in BM‐derived mast cells activated by anti‐2,4‐dinitrophenol/2,4‐dinitrophenol‐human serum albumin. We proved that CKBA suppressed mast cell activation via ERK signaling using the ERK activator (t‐butyl hydroquinone) and inhibitor (selumetinib; AZD6244) in AD. Thus, CKBA suppressed mast cell activation in AD via the ERK signaling pathway and could be a therapeutic candidate drug for AD. [ABSTRACT FROM AUTHOR]

Accumulation of senescent cells (SNCs) with a senescence‐associated secretory phenotype (SASP) has been implicated as a major source of chronic sterile inflammation leading to many age‐related pathologies. Herein, we provide evidence that a bifunctional immunotherapeutic, HCW9218, with capabilities of neutralizing TGF‐β and stimulating immune cells, can be safely administered systemically to reduce SNCs and alleviate SASP in mice. In the diabetic db/db mouse model, subcutaneous administration of HCW9218 reduced senescent islet β cells and SASP resulting in improved glucose tolerance, insulin resistance, and aging index. In naturally aged mice, subcutaneous administration of HCW9218 durably reduced the level of SNCs and SASP, leading to lower expression of pro‐inflammatory genes in peripheral organs. HCW9218 treatment also reverted the pattern of key regulatory circadian gene expression in aged mice to levels observed in young mice and impacted genes associated with metabolism and fibrosis in the liver. Single‐nucleus RNA Sequencing analysis further revealed that HCW9218 treatment differentially changed the transcriptomic landscape of hepatocyte subtypes involving metabolic, signaling, cell‐cycle, and senescence‐associated pathways in naturally aged mice. Long‐term survival studies also showed that HCW9218 treatment improved physical performance without compromising the health span of naturally aged mice. Thus, HCW9218 represents a novel immunotherapeutic approach and a clinically promising new class of senotherapeutic agents targeting cellular senescence‐associated diseases. [ABSTRACT FROM AUTHOR]

One of the mechanisms of cellular dysfunction during the chronization of immune-system-mediated inflammatory diseases is a change in the profile of expression and co-expression of receptors on cells. The aim of this study was to compare patterns of redistribution of TNF receptors (TNFRs) among patients with different durations of rheumatoid arthritis (RA) or asthma. Subgroup analysis was performed on RA (n = 41) and asthma (n = 22) patients with disease duration<10 years and >10 years and on 30 comparable healthy individuals. The co-expression profile of TNFR1 and TNFR2 was assessed in T cells, B cells, monocytes, regulatory T cells, T-helper subsets, and cytotoxic T-lymphocyte subsets. Percentages of cells with different co-expression combinations and receptor density per cell were estimated. Longer disease duration was significantly associated with a redistribution of receptors in immunocompetent cell subsets with an increase in the expression of TNFR1 in asthma but did not correlate with significant unidirectional changes in receptor expression in RA. In asthma, a higher proportion of cells with a certain type of TNF receptor (as compared with the healthy group) was correlated with a simultaneous greater density of this receptor type. In RA, an inverse correlation was observed (compensatory lower receptor density). Mechanisms of long-term changes in the expression of TNF receptors differ significantly between the diseases of autoimmune and allergic etiology. The formation of irreversible morphostructural alterations was strongly correlated with changes in the expression of TNFR1 in asthma and with changes in the expression of TNFR2 in RA. [ABSTRACT FROM AUTHOR]

Introduction : Although CD20 is classically a B cell marker, in the last three decades, dim expression has been noted on a subset of T cells as well that has been independently verified by a number of groups. Our understanding of these cells and their function is not well established. Methods: A thorough review of original articles on CD20+T cells was undertaken of Pubmed by using combination of phrases including "CD20+", "CD20-positive" and "T cells". Articles in English were considered, and there was no time restriction. Results: CD20+T cells express the standard T cell markers and, in comparison to CD20¯ T cells, appear to express greater inflammatory cytokines and markers of effector function. Although the ontogeny of these cells is still being established, the current theory is that CD20 may be acquired by trogocytosis from B cells. CD20+T cells may be found in healthy controls and in a wide range of pathologies including autoimmune diseases, haematological and non-haematological malignancies and human immunodeficiency virus (HIV) infections. One of the best studied diseases where these cells are found is multiple sclerosis (MS) where a number of therapeutic interventions, including anti-CD20 depletion, have been shown to effectively deplete these cells. Conclusion: This review summarises the latest understanding of CD20+T cells, their presence in various diseases, their putative function and how they may be an ongoing target of CD20-depleting agents. Unfortunately, our understanding of these cells is still at its infancy and ongoing study in a wider range of pathologies is required. [ABSTRACT FROM AUTHOR]

Type 1 diabetes (T1D) is an autoimmune disease resulting in the destruction of the insulin-producing pancreatic beta cells. Disease progression occurs along a trajectory from genetic risk, the development of islet autoantibodies, and autoreactive T cells ultimately progressing to clinical disease. Natural history studies and mechanistic studies linked to clinical trials have provided insight into the role of the immune system in disease pathogenesis. Here, we review our current understanding of the underlying etiology of T1D, focusing on the immune cell types that have been implicated in progression from pre-symptomatic T1D to clinical diagnosis and established disease. This knowledge has been foundational for the development of immunotherapies aimed at the prevention and treatment of T1D. This review summarizes the current understanding of the underlying immunopathology of T1D, focusing on the immune cell types implicated in progression from pre-symptomatic T1D to clinical diagnosis and established disease. It also highlights how this knowledge is driving the development of immunotherapies aimed at the prevention and treatment of T1D. [ABSTRACT FROM AUTHOR]

T cells are important to the immune system as they remove foreign pathogens such as bacteria, cancer cells, viruses, and parasites. T cells can change their DNA by undergoing a process called V(D)J recombination. There are two types of T cells: gamma-delta (γδ) and alpha-beta (αβ). Gamma-delta T cells have been eliciting interest in the past few years as they have an important role in autoimmune diseases, various infections, and cancer. I hypothesized that there are many more gammadelta T cell subtypes that haven’t been characterized yet. Certain subsets of gamma-delta T cells can only be found in the liver as they perform specific functions in liver diseases. Their effect on liver diseases depends on the subset and cytokines produced so characterizing them now can be beneficial in developing vaccines in the future. These new subtypes could have an important role in tumor detection and regression. Cluster 1 had T follicular helper cells, cluster 2 had regulatory T cells, cluster 3 had effector memory cells, cluster 4 had activated tissue memory cells, and cluster 7 had T helper 2-like cells. [ABSTRACT FROM AUTHOR]

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Luminal A breast cancer is the most common subtype of the most common cancer in women. Current treatments using surgery and chemotherapy have greatly improved patient outcomes in recent decades but are still far from perfect. mRNA vaccines, which instruct the body to create specific proteins, hold the best promise going forward as a "cure" for luminal A breast cancer. Immunological therapies are emerging in solving problems that chemotherapy, surgery and targeted therapies cannot. The ultimate goal of immunotherapy would be to help the immune system recognize and destroy tumor cells as well as make antigens. In this paper, mRNA's potential for addressing the heterogenous nature of tumors, envisioning how it might be made to effectively elicit an immune response are explored; in particular, how it can be modified quickly to change which mutated genes it targets. This paper also discusses the limitations of this emerging technology and the difficulties of evaluating its efficacy when it has yet to enter clinical trials. Finally, this paper concludes by offering thoughts on how its development might be accelerated, predictions on effective targets, and likely dates for such a vaccine to debut as a real-world treatment. [ABSTRACT FROM AUTHOR]

(1) Background: Pemphigus is a blistering autoimmune disease of the skin and/or mucous membranes, characterised by the presence of specific autoantibodies directed against structural proteins of the human skin. Recent reports indicate that new haematological parameters, termed Extended Inflammation Parameters (EIP), can be used to assess the activation of immune cells during active inflammation. These include parameters assessing both neutrophil activation (NEUT-RI, NEUT-GI) and the number of activated lymphocytes (RE-LYMP). The aim of this study was to investigate the relationship between changes in NEUT-RI, NEUT-GI and RE-LYMP and the disease activity in patients with pemphigus. (2) Results: The study involved 32 patients with diagnosed different types of pemphigus. Neutrophil activation parameters (NEUT-RI and NEUT-GI) and lymphocytes (RE-LYMP) were significantly higher in these patients compared to the parameters in healthy participants (respectively p = 0.0127, p = 0.0011 and p = 0.0033). The increased quantity of activated lymphocytes (RE-LYMP) also correlated significantly with the extent of skin and/or mucosal lesions in patients assessed by the PDAI scale (p < 0.02). (3) Conclusions: The NEUT-RI, NEUT-GI and RE-LYMP parameters proved to be appropriate markers of inflammation severity in pemphigus, also in relation to local lesions, which was not possible with the inflammation markers (CRP, ESR) used so far on a routine basis. [ABSTRACT FROM AUTHOR]

One of the earliest hallmarks of immune aging is thymus involution, which not only reduces the number of newly generated and exported T cells, but also alters the composition and organization of the thymus microenvironment. Thymic T‐cell export continues into adulthood, yet the impact of thymus involution on the quality of newly generated T‐cell clones is not well established. Notably, the number and proportion of medullary thymic epithelial cells (mTECs) and expression of tissue‐restricted antigens (TRAs) decline with age, suggesting the involuting thymus may not promote efficient central tolerance. Here, we demonstrate that the middle‐aged thymic environment does not support rapid motility of medullary thymocytes, potentially diminishing their ability to scan antigen presenting cells (APCs) that display the diverse self‐antigens that induce central tolerance. Consistent with this possibility, thymic slice assays reveal that the middle‐aged thymic environment does not support efficient negative selection or regulatory T‐cell (Treg) induction of thymocytes responsive to either TRAs or ubiquitous self‐antigens. This decline in central tolerance is not universal, but instead impacts lower‐avidity self‐antigens that are either less abundant or bind to TCRs with moderate affinities. Additionally, the decline in thymic tolerance by middle age is accompanied by both a reduction in mTECs and hematopoietic APC subsets that cooperate to drive central tolerance. Thus, age‐associated changes in the thymic environment result in impaired central tolerance against moderate‐avidity self‐antigens, potentially resulting in export of increasingly autoreactive naive T cells, with a deficit of Treg counterparts by middle age. [ABSTRACT FROM AUTHOR]

Background and objective: The purpose of this study was to evaluate whether gingival fibroblasts (GFs) can be differently activated and polarized into distinct functional subtypes by T‐helper (Th) cytokines. Methods: Gingival fibroblasts were stimulated with interferon (IFN)‐γ, interleukin (IL)‐4, IL‐17, and transforming growth factor (TGF)‐β, representative cytokines of Th1, Th2, Th17, and regulatory T cells, respectively, and the gene expression profiles were analyzed by microarray. Differentially expressed genes (DEGs) in GFs stimulated by 4 cytokines were screened, and a gene ontology (GO) analysis of the DEGs was conducted. To confirm the reliability of the microarray results, the DEGs that showed the largest differences compared with non‐stimulated GFs were further analyzed by RT‐PCR. To evaluate the effect of polarization on GFs responses to lipopolysaccharide (LPS), GFs stimulated by 4 cytokines were further stimulated with Escherichia coli LPS and mRNA levels of several genes were analyzed using RT‐PCR. Results: Differentially expressed genes by 4 Th cytokines were enriched in different GO terms, and the patterns of gene expression on GFs were shown functionally different. GFs stimulated with IFN‐γ (GF(IFN‐γ)) up‐regulated the expression of chemokines (chemokine (C‐X‐C motif) ligand (CXCL)9, −10, −11, chemokine (C‐C motif) ligand (CCL)8), molecules involved in antigen presentation, complement component 3 (C3), and other immune response–related molecules, whereas they down‐regulated the expression of several types of collagen, extracellular matrix (ECM) components, and DNA replication and nuclear protein–related molecules. By contrast, GF(IL‐4) up‐regulated the expression of ECM components, cell adhesion molecules, and tissue development–related molecules and down‐regulated the expression of chemokines (CXCL10 and CXCL8) and adaptive immune response–related molecules. GF(IL‐17) up‐regulated the expression of chemokines and other molecules for neutrophil infiltration and activation, the pro‐inflammatory cytokine IL‐6, and C3. GF(TGF‐β) up‐regulated the expression of cell growth–related molecules, ECM components, several types of collagen, and cell adhesion molecules and down‐regulated the expression of molecules related to complement activation and bacterial recognition. GFs stimulated by 4 cytokines responded differently to LPS. Conclusion: These results show that Th cytokines can polarize GFs into cells with functionally distinct features: immune‐activating but tissue‐destructive GF(IFN‐γ), tissue‐reparative, and immune‐inhibiting GF(IL‐4), highly pro‐inflammatory GF(IL‐17), and potent tissue‐reparative GF(TGF‐β). [ABSTRACT FROM AUTHOR]

Background: The co-expression patterns of type 1 and 2 tumor necrosis factor (TNF)-α membrane receptors (TNFR1/TNFR2) are associated with the presence, stage, and activity of allergic diseases. The aim of this study was to assess the expression levels and dynamics of TNFRs on immune cells and to assess associations between their expression and severity of bronchial asthma (BA). Methods: Patients with severe (n = 8), moderate (n = 10), and mild (n = 4) BA were enrolled. As a comparison group, data from 46 healthy volunteers (HV) were accessed. Co-expression of TNFR1/2 was evaluated as a percentage of cells and the number of receptors of each type per cell. Multivariate logistic regression analysis was used to identify diagnostic biomarkers of BA. Results: More than 90% of the monocytes in patients with mild BA were TNFR1+TNFR2+ but had significantly lower TNFR1 expression density compared with HV (7.82- to 14.08-fold, depending on disease severity). Lower percentages of the TNFR+ B-lymphocytes were observed in combination with significantly lower receptors density in BA compared with HV (2.59- to 11.64-fold for TNFR1 and 1.72- to 3.4-fold for TNFR2, depending on disease severity). The final multivariate model for predicting the presence of BA included the percentage of double-positive CD5+ B-lymphocytes and average number of TNFR1 molecules expressed on cytotoxic naive T-lymphocytes and T-helper cells (R2 = 0.87). Conclusions: The co-expression patterns of TNFRs on immune cells in BA differed significantly compared with HV. The expression differences were associated with disease severity. TNFR1 expression changes were key parameters that discriminated patients with BA from those with HV. [ABSTRACT FROM AUTHOR]

Background: We aimed to characterise the adaptive immune response to Mycobacterium abscessus complex (MABSC) and its cross-reactivity with Mycobacterium avium complex (MAC) and Mycobacterium bovis (Bacille Calmette-Guérin, BCG) in cystic fibrosis (CF) patients and non-CF controls in terms of lymphocyte proliferation and immunophenotyping, cytokine production and anti-MABSC IgG plasma levels. Methods: In this cross-sectional analysis, peripheral blood mononuclear cells (PBMC) from CF patients with MABSC (CF/MABSC, n=12), MAC infection history (CF/MAC, n=5), no NTM history (CF/NTM-, n=15), BCG-vaccinated (C/BCG+, n=9) and non-vaccinated controls (C/BCG-, n=8) were cultured for four days under stimulation with an in-house MABSC lysate and we used flow cytometry to assess lymphocyte proliferation (given by lymphoblast formation) and immunophenotypes. Cytokine production was assessed after overnight whole blood stimulation with the same lysate, and anti-MABSC IgG levels were measured in plasma from non-stimulated blood. Results: All CF/MABSC patients had increased CD3+ and CD19+ lymphoblast formation upon PBMC stimulation with MABSC lysate. There was a higher rate of CD3+ than CD19+ lymphoblasts, predominance of CD4+ over CD8+ lymphoblasts, IFN-γ, TNF-α and IL-2 production, low production of the Th17-associated IL-17, and discrete or no production of Th2/B cell-associated cytokines soluble CD40 ligand (CD40L), IL-4 and IL-5, indicating a Th1-dominated phenotype and infection restricted to the lungs. A similar pattern was seen in C/BCG+ controls, and CF/MAC patients, pointing to cross-reactivity. MABSC-IgG levels were higher in CF/MABSC patients than in both control groups, but not CF/NTM- patients, most of whom also had CD3+ and/or CD19+ lymphoblast formation upon PBMC stimulation, indicating previous exposure, subclinical or latent infection with MABSC or other NTM. Conclusion: The anti-MABSC immune response is Th1-skewed and underlines the cross-reactivity in the anti-mycobacterial immune response. The results, together with published clinical observations, indicate that BCG vaccination may cross-react against NTM in CF patients, and this should be investigated. Due to cross-reactivity, it would also be interesting to investigate whether a combination of MABSC-induced cytokine production by blood cells and anti-MABSC IgG measurement can be useful for identifying latent or subclinical infection both with MABSC and other NTM in CF patients. [ABSTRACT FROM AUTHOR]

Coronavirus disease 2019 (COVID-19) is especially severe in aged patients, defined as 65 years or older, for reasons that are currently unknown. To investigate the underlying basis for this vulnerability, we performed multimodal data analyses on immunity, inflammation, and COVID-19 incidence and severity as a function of age. Our analysis leveraged age-specific COVID-19 mortality and laboratory testing from a large COVID-19 registry, along with epidemiological data of ~3.4 million individuals, large-scale deep immune cell profiling data, and single-cell RNA-sequencing data from aged COVID-19 patients across diverse populations. We found that decreased lymphocyte count and elevated inflammatory markers (C-reactive protein, D-dimer, and neutrophil-lymphocyte ratio) are significantly associated with age-specific COVID-19 severities. We identified the reduced abundance of naïve CD8 T cells with decreased expression of antiviral defense genes (i.e., IFITM3 and TRIM22) in aged severe COVID-19 patients. Older individuals with severe COVID-19 displayed type I and II interferon deficiencies, which is correlated with SARS-CoV-2 viral load. Elevated expression of SARS-CoV-2 entry factors and reduced expression of antiviral defense genes (LY6E and IFNAR1) in the secretory cells are associated with critical COVID-19 in aged individuals. Mechanistically, we identified strong TGF-beta-mediated immune-epithelial cell interactions (i.e., secretory-non-resident macrophages) in aged individuals with critical COVID-19. Taken together, our findings point to immuno-inflammatory factors that could be targeted therapeutically to reduce morbidity and mortality in aged COVID-19 patients. [ABSTRACT FROM AUTHOR]

Introduction: Modulating specific biological effects through the changes in cytokine receptors' expression level remains poorly understood. This study aimed to investigate the influence of the dose-dependent effect of TNF on the balance between proapoptotic and proliferation response depending on the parameters of TNFR1/2 expression density. Methods: Tumor cell lines (HEp-2, K-562, MCF-7, ZR-75/1, MOLT-4, IM-9, and Raji) were characterized for TNFR1/2 co-expression using flow cytometry and were studied to reveal the dose-dependent effect of rhTNF on cell cycle and apoptosis parameters. The associations among the studied parameters were estimated by correlation and regression analysis. Results: It was found for ZR-75/1 cells (the cell line characterized by high expression of both types) that a dose-dependent increase in expression of both types of TNF-α receptors on cells reduces the proliferative activity of cells. For MOLT-4 cells (which are characterized by lower expression), an increase in proliferative response of cells was positively associated with the percentage of both TNFR1+ and TNFR2+ cells. However, opposite effects on the cells were shown for the K-562 and MCF-7 lines having a similar expression profile. A similarity (a large percentage of double-positive cells) was revealed for the lines having similar effects (K-562 and ZR-75/1). Conclusions: High expression of TNF receptor type 1 is not always associated with predominant activation of proapoptotic pathways. However, in the case of simultaneous high expression of both types of receptors, the proportion of double-positive cells is crucial for the activation of either the proapoptotic or proliferation pathways. [ABSTRACT FROM AUTHOR]

The term 'macrophage' encompasses tissue cells that typically share dependence on the same transcriptional regulatory pathways (e.g. the transcription factor PU.1) and growth factors (e.g. CSF1/IL‐34). They share a core set of functions that largely arise from a uniquely high phagocytic capacity manifest in their ability to clear dying cells, pathogens and scavenge damaged, toxic or modified host molecules. However, macrophages demonstrate a remarkable degree of tissue‐specific functionality and have diverse origins that vary by tissue site and inflammation status. With our understanding of this diversity has come an appreciation of the longevity and replicative capacity of tissue‐resident macrophages and thus the realisation that macrophages may persist through tissue perturbations and inflammatory events with important consequences for cell function. Here, we discuss our current understanding of the parameters that regulate macrophage survival and function, focusing on the relative importance of the tissue environment versus cell‐intrinsic factors, such as origin, how long a cell has been resident within a tissue and prior history of activation. Thus, we reconsider the view of macrophages as wholly plastic cells and raise many unanswered questions about the relative importance of cell life‐history versus environment in macrophage programming and function. [ABSTRACT FROM AUTHOR]

Specialized pro‐resolving mediators actively limit inflammation and support tissue regeneration, but their role in age‐related muscle dysfunction has not been explored. We profiled the mediator lipidome of aging muscle via liquid chromatography‐tandem mass spectrometry and tested whether treatment with the pro‐resolving mediator resolvin D1 (RvD1) could rejuvenate the regenerative ability of aged muscle. Aged mice displayed chronic muscle inflammation and this was associated with a basal deficiency of pro‐resolving mediators 8‐oxo‐RvD1, resolvin E3, and maresin 1, as well as many anti‐inflammatory cytochrome P450‐derived lipid epoxides. Following muscle injury, young and aged mice produced similar amounts of most pro‐inflammatory eicosanoid metabolites of cyclooxygenase (e.g., prostaglandin E2) and 12‐lipoxygenase (e.g., 12‐hydroxy‐eicosatetraenoic acid), but aged mice produced fewer markers of pro‐resolving mediators including the lipoxins (15‐hydroxy‐eicosatetraenoic acid), D‐resolvins/protectins (17‐hydroxy‐docosahexaenoic acid), E‐resolvins (18‐hydroxy‐eicosapentaenoic acid), and maresins (14‐hydroxy‐docosahexaenoic acid). Similar absences of downstream pro‐resolving mediators including lipoxin A4, resolvin D6, protectin D1/DX, and maresin 1 in aged muscle were associated with greater inflammation, impaired myofiber regeneration, and delayed recovery of strength. Daily intraperitoneal injection of RvD1 had minimal impact on intramuscular leukocyte infiltration and myofiber regeneration but suppressed inflammatory cytokine expression, limited fibrosis, and improved recovery of muscle function. We conclude that aging results in deficient local biosynthesis of specialized pro‐resolving mediators in muscle and that immunoresolvents may be attractive novel therapeutics for the treatment of muscular injuries and associated pain in the elderly, due to positive effects on recovery of muscle function without the negative side effects on tissue regeneration of non‐steroidal anti‐inflammatory drugs. [ABSTRACT FROM AUTHOR]

Age impacts alloimmunity. Effects of aging on T‐cell metabolism and the potential to interfere with immunosuppressants have not been explored yet. Here, we dissected metabolic pathways of CD4+ and CD8+ T cells in aging and offer novel immunosuppressive targets. Upon activation, CD4+ T cells from old mice failed to exhibit adequate metabolic reprogramming resulting into compromised metabolic pathways, including oxidative phosphorylation (OXPHOS) and glycolysis. Comparable results were also observed in elderly human patients. Although glutaminolysis remained the dominant and age‐independent source of mitochondria for activated CD4+ T cells, old but not young CD4+ T cells relied heavily on glutaminolysis. Treating young and old murine and human CD4+ T cells with 6‐diazo‐5‐oxo‐l‐norleucine (DON), a glutaminolysis inhibitor resulted in significantly reduced IFN‐γ production and compromised proliferative capacities specifically of old CD4+ T cells. Of translational relevance, old and young mice that had been transplanted with fully mismatched skin grafts and treated with DON demonstrated dampened Th1‐ and Th17‐driven alloimmune responses. Moreover, DON diminished cytokine production and proliferation of old CD4+ T cells in vivo leading to a significantly prolonged allograft survival specifically in old recipients. Graft prolongation in young animals, in contrast, was only achieved when DON was applied in combination with an inhibition of glycolysis (2‐deoxy‐d‐glucose, 2‐DG) and OXPHOS (metformin), two alternative metabolic pathways. Notably, metabolic treatment had not been linked to toxicities. Remarkably, immunosuppressive capacities of DON were specific to CD4+ T cells as adoptively transferred young CD4+ T cells prevented immunosuppressive capacities of DON on allograft survival in old recipients. Depletion of CD8+ T cells did not alter transplant outcomes in either young or old recipients. Taken together, our data introduce an age‐specific metabolic reprogramming of CD4+ T cells. Targeting those pathways offers novel and age‐specific approaches for immunosuppression. [ABSTRACT FROM AUTHOR]

The characterization of cell‐mediated and humoral adaptive immune responses to SARS‐CoV‐2 is fundamental to understand COVID‐19 progression and the development of immunological memory to the virus. In this study, we detected T‐cells reactive to SARS‐CoV‐2 proteins M, S, and N, as well as serum virus‐specific IgM, IgA, IgG, in nearly all SARS‐CoV‐2 infected individuals, but not in healthy donors. Virus‐reactive T cells exhibited signs of in vivo activation, as suggested by the surface expression of immune‐checkpoint molecules PD1 and TIGIT. Of note, we detected antigen‐specific adaptive immune response both in asymptomatic and symptomatic SARS‐CoV‐2 infected subjects. More importantly, symptomatic patients displayed a significantly higher magnitude of both cell‐mediated and humoral adaptive immune response to the virus, as compared to asymptomatic individuals. These findings suggest that an uncontrolled adaptive immune response contribute to the development of the life‐threatening inflammatory phase of the disease. Finally, this study might open the way to develop effective vaccination strategies. [ABSTRACT FROM AUTHOR]

This review article addresses the largely unanticipated convergence of two landmark discoveries. The first is the discovery of interferons, critical signaling molecules for all aspects of both innate and adaptive immunity, discovered originally by Isaacs and Lindenmann at the National Institute for Medical Research, London, in 1957 (Proceedings of the Royal Society of London. Series B: Biological Sciences, 1957, 147, 258). The second, formerly unrelated discovery, by Leonard Hayflick and Paul Moorhead (Wistar Institute, Philadelphia) is that cultured cells undergo an irreversible but viable growth arrest, termed senescence, after a finite and predictable number of cell divisions (Experimental Cell Research, 1961, 25, 585). This phenomenon was suspected to relate to organismal aging, which was confirmed subsequently (Nature, 2011, 479, 232). Cell senescence has broad‐ranging implications for normal homeostasis, including immunity, and for diverse disease states, including cancer progression and response to therapy (Nature Medicine, 2015, 21, 1424; Cell, 2019, 179, 813; Cell, 2017, 169, 1000; Trends in Cell Biology, 2018, 28, 436; Journal of Cell Biology, 2018, 217, 65). Here, we critically address the bidirectional interplay between interferons (focusing on type I) and cell senescence, with important implications for health and healthspan. [ABSTRACT FROM AUTHOR]

The aging process is characterized by a chronic, low‐grade inflammatory state, termed "inflammaging." It has been suggested that macrophage activation plays a key role in the induction and maintenance of this state. In the present study, we aimed to elucidate the mechanisms responsible for aging‐associated changes in the myeloid compartment of mice. The aging phenotype, characterized by elevated cytokine production, was associated with a dysfunction of the hypothalamic–pituitary–adrenal (HPA) axis and diminished serum corticosteroid levels. In particular, the concentration of corticosterone, the major active glucocorticoid in rodents, was decreased. This could be explained by an impaired expression and activity of 11β‐hydroxysteroid dehydrogenase type 1 (11β‐HSD1), an enzyme that determines the extent of cellular glucocorticoid responses by reducing the corticosteroids cortisone/11‐dehydrocorticosterone to their active forms cortisol/corticosterone, in aged macrophages and peripheral leukocytes. These changes were accompanied by a downregulation of the glucocorticoid receptor target gene glucocorticoid‐induced leucine zipper (GILZ) in vitro and in vivo. Since GILZ plays a central role in macrophage activation, we hypothesized that the loss of GILZ contributed to the process of macroph‐aging. The phenotype of macrophages from aged mice was indeed mimicked in young GILZ knockout mice. In summary, the current study provides insight into the role of glucocorticoid metabolism and GILZ regulation during aging. [ABSTRACT FROM AUTHOR]

Introduction: Density and co-expression of tumor necrosis factor (TNF) receptors may vary among cell populations. However, the role and potential of these changes remain unclear. This study aimed to determine the density of expression and co-expression of TNFR1/2 and the dose-dependent effect of soluble TNF on these parameters. Methods: Epithelial-like (HEp-2, K-562, MCF-7, ZR-75/1) and lymphoblast-like (MOLT-4, HL-60, Raji, RPMI-8226, IM-9) cell lines were characterized for co-expression of TNFR1/2 using a modified flow cytometry protocol. The dose-dependent effects of rhTNF on TNF receptor expression in these lines were studied. Results: This study reports a protocol for the simultaneous quantitative evaluation of the of TNF receptor number and co-expression of membrane-bound TNFR1/2. Cells within one tumor cell line were found to differ regarding their expression of type 1 and 2 TNFα receptors; simultaneously, cells with all 4 variants of co-expression may be present in culture. Conclusion: We demonstrated a dose-dependent effect of TNF on changes in the expression of TNFR1/2 by the percentage of positive cells and by the number of receptors, which may be used to control TNF-mediated processes in target cells. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this present study was to evaluate the levels of Netrin‐1 and Unc5b in periodontal health and disease. Background: Netrin‐1, acting via its receptor UNC5b, regulates the inflammatory response and takes apart in bone destructive diseases. Methods: Samples of gingival crevicular fluid (GCF), whole saliva, and serum were taken from systemically healthy, nonsmoking 20 periodontitis , 20 gingivitis patients, and 20 periodontally healthy subjects at baseline and 4 weeks after nonsurgical periodontal treatment (NSPT). Whole‐mouth and site‐specific clinical periodontal parameters were recorded. Netrin‐1 and Unc5b levels were measured by enzyme‐linked immunosorbent assay. Data were analyzed by nonparametric tests. Results: Total amount of Netrin‐1 in GCF was significantly higher in periodontitis than the others, and the levels were significantly reduced after NSPT. Salivary and serum concentrations of Netrin‐1 were significantly different among the study groups (P =.000), and NSPT significantly increased the concentration levels of both salivary and serum Netrin‐1 (P <.05). Healthy subjects had significantly lower GCF (P =.001) and conversely, higher salivary and serum levels of Unc5b than the other groups (P =.002). The GCF levels of Unc5b were significantly reduced (P <.01), and conversely, serum concentrations were significantly increased after NSPT (P <.05). GCF Netrin‐1 and Unc5b total amounts were positively correlated with clinical parameters (P <.01 and P <.05) whereas salivary Netrin‐1 and Unc5b concentrations were negatively correlated with clinical parameters (P <.01 and P <.05). Conclusions: The results of this study indicate that Netrin‐1 and its receptor Unc5b may have essential roles in periodontal inflammation and those can be assumed as useful therapeutic agent to control inflammation and periodontal breakdown. [ABSTRACT FROM AUTHOR]

Summary: There is currently scarce knowledge of the immunological profile of patients with latent autoimmune diabetes mellitus in the adult (LADA) when compared with healthy controls (HC) and patients with classical type 1 diabetes (T1D) and type 2 diabetes (T2D). The objective of this study was to investigate the cellular immunological profile of LADA patients and compare to HC and patients with T1D and T2D. All patients and age‐matched HC were recruited from Uppsala County. Peripheral blood mononuclear cells were isolated from freshly collected blood to determine the proportions of immune cells by flow cytometry. Plasma concentrations of the cytokine interleukin (IL)‐35 were measured by enzyme‐linked immunosorbent assay (ELISA). The proportion of CD11c+CD123– antigen‐presenting cells (APCs) was lower, while the proportions of CD11c+CD123+ APCs and IL‐35+ tolerogenic APCs were higher in LADA patients than in T1D patients. The proportion of CD3–CD56highCD16+ natural killer (NK) cells was higher in LADA patients than in both HC and T2D patients. The frequency of IL‐35+ regulatory T cells and plasma IL‐35 concentrations in LADA patients were similar to those in T1D and T2D patients, but lower than in HC. The proportion of regulatory B cells in LADA patients was higher than in healthy controls, T1D and T2D patients, and the frequency of IL‐35+ regulatory B cells was higher than in T1D patients. LADA presents a mixed cellular immunological pattern with features overlapping with both T1D and T2D. [ABSTRACT FROM AUTHOR]

Tumor-infiltrating lymphocytes (TILs), found in patients with advanced pancreatic ductal adenocarcinoma (PDAC), are shown to correlate with overall survival (OS) rate. Although majority of TILs consist of CD8+/CD4+ T cells, the presence of NK cells and their role in the pathogenesis of PDAC remains elusive. We performed comprehensive analyses of TIL, PBMC, and autologous tumor cells from 80 enrolled resectable PDAC patients to comprehend the NK cell defects within PDAC. Extremely low frequencies of NK cells (<0.5%) were found within PDAC tumors, which was attributable not to the low expression of tumor chemokines, but to the lack of chemokine receptor, CXCR2. Forced expression of CXCR2 in patients' NK cells rendered them capable of trafficking into PDAC. Furthermore, NK cells exhibited impaired cell-mediated killing of autologous PDAC cells, primarily due to insufficient ligation of NKG2D and DNAM-1, and failed to proliferate within the hypoxic tumor microenvironment. Importantly, these defects could be overcome by ex-vivo stimulation of NK cells from such patients. Importantly, when the proliferative capacity of NK cells in vitro was used to stratify patients on the basis of cell expansion, patients whose NK cells proliferated <250-fold experienced significantly lower DFS and OS than those with ≥250-fold. Ex-vivo activation of NK cells restored tumor trafficking and reactivity, hence provided a therapeutic modality while their fold expansion could be a potentially significant prognostic indicator of OS and DFS in such patients. [ABSTRACT FROM AUTHOR]

The expression of cytokine receptors has a crucial role in many cellular processes. Recent studies reported that changes of receptor expression could control the action of mediators on target cells. The initiation of different signaling pathways and, therefore, specific effects on cells, depends on certain components forming the cytokine-receptor complex. These mechanisms control the immune response and affect both the course of diseases (oncological, autoimmune, inflammatory) and the effectiveness of therapy. This review describes the potential of immune mediator receptors to regulate the efficiency of cytokine activity during pathologic processes and ensure the variability of their biological effects. Our aim was to investigate the spectrum of potential roles of changes in mediator receptor expression for main classes of pathologies. For all major types of immune mediators (cytokines, interleukins, chemokines, growth factors, and tumor necrosis factors), it has been shown that changes in their receptor expression are associated with impaired functioning of the organism in chronic diseases. [ABSTRACT FROM AUTHOR]

The role of HIV-specific CD8 T cell activity in the course of HIV infection and the way it affects the virus that resides in the latent reservoir resting memory cells is debated. The PBMC of HIV-infected patients contain HIV-specific CD8 T cells and their potential targets, CD4 T cells latently infected by HIV. CD4 T cells and CD8 T cells procured from PBMC of HIV-infected patients were co-incubated and analyzed: Formation of CD8 T cells and HIV-infected CD4 T cell conjugates and apoptosis of these CD4 T cells were observed by fluorescence microscopy with in situ PCR of HIV LTR DNA. Furthermore, conjugation of CD8 T cells with CD4 T cells and apoptosis of CD4 T cells was observed and quantified by imaging flow cytometry using anti-human activated caspase 3 antibody and TUNEL assay. The conjugation activity and apoptosis were found to be much higher in patients with acute HIV infection or AIDS compared to patients in chronic infection on antiretroviral therapy (ART) or not. Patients on ART had low grade conjugation and apoptosis of isolated CD69, CD25, and HLA-DR-negative CD4 T cells (latent reservoir cells) by CD8 T cells. Using in situ PCR The latent reservoir CD4 T cells were shown to contain most of the HIV DNA. We demonstrate in HIV-infected patients, that CD8 T cells conjugate with and kill HIV-infected CD4 T cells, including HIV-infected resting memory CD4 T cells, throughout the course of HIV infection. We propose that in HIV-infected patients CD4 T cell annihilation is caused in part by ongoing activity of HIV-specific CD8 T cells. HIV Nef protein interacts with ASK 1 and inhibits its pro-apoptotic death signaling by Fas/FasL, thus protecting HIV-infected cells from CD8 T cells killing. A peptide that interrupts Nef-ASK1 interaction that had been delivered into CD4 T cells procured from patients on ART resulted in the increase of their apoptosis inflicted by autologous CD8 T cells. We suggest that elimination of the HIV-infected latent reservoir CD4 T cells can be achieved by Nef inhibition. [ABSTRACT FROM AUTHOR]

Immune responses are a double-edged sword. Effective and appropriate immune responses capable of controlling viral infection while also largely preserving tissue integrity, are critical for host survival. Too strong immune responses might result in immune pathology, while too weak immune responses might cause viral persistence. Physiologic ageing is accompanied with a decline in the normal functioning of the immune system, which is termed as "immunosenescence". We show that aged mice (16-19 months old) are more resistant to influenza A virus (IAV) infection than the young mice. Strong immune responses in the young mice after IAV infection result in faster clearance of virus, but also cause severe lung injury and higher mortality rate. While in the aged mice, the delayed and milder immune responses contribute to reduced pulmonary damage, and are still capable to clear the infection even with a slower kinetics, displaying a more resistant phenotype during IAV infection. Hence, our work demonstrates that moderate immune responses as a decline with ageing in the aged mice balance the immune pathology and viral clearance, might be beneficial for the host during certain circumstances. Our results provide important insight to our basic knowledge of immunosenescence and immune defenses to invading pathogens. Further, our results indicate that age factors should be considered when investigating the vaccination and therapeutic strategies for severe IAV infection. [ABSTRACT FROM AUTHOR]

Calorie restriction (CR) without malnutrition increases life span and health span in multiple model organisms. In non-human and human primates, CR causes changes that protect against several age-related pathologies, reduces inflammation, and preserves or improves cell-mediated immunity. However, CR has also been shown to exhibit adverse effects on certain organs and systems, including the immune system, and to impact genetically different organisms of the same species differentially. Alternately, short periods of fasting followed by refeeding may result in the proliferation of bone marrow stem cells, suggesting a potential rejuvenation effect that could impact the hematopoietic compartment. However, the global consequences of CR followed by refeeding on the immune system have not been carefully investigated. Here, we show that individuals practicing long-term CR with adequate nutrition have markedly lower circulating levels of total leukocytes, neutrophils, lymphocytes, and monocytes. In 10-month-old mice, short-term CR lowered lymphocyte cellularity in multiple lymphoid tissues, but not in bone marrow, which appears to be a site of influx, or a “safe haven” for B, NK, and T cells during CR. Cellular loss and redistribution was reversed within the first week of refeeding. Based on BrdU incorporation and Ki67 expression assays, repopulating T cells exhibited high proliferation in the refeeding group following CR. Finally, we demonstrated that the thymus was not essential for T cell repopulation following refeeding. These findings are of potential relevance to strategies to rejuvenate the immune system in mammals and warrant further investigation. [ABSTRACT FROM AUTHOR]

The use of preemptive antiviral therapy to prevent cytomegalovirus ( CMV) disease in allogeneic hematopoietic stem cell transplantation (allo- HSCT) recipients might result in over-treatment, inducing drug-related toxicity and viral resistance. A search for predictive markers is needed to determine requirement for antiviral therapy. Clinical follow-up, in combination with the use of streptamers ( STs) and cytokine-intracellular staining, could help to identify patients at high risk for CMV reactivations. To study the immune response and reactivation control by CMV-specific CD8+ T-cell ( CMV- CTL) populations, we monitored 25 patients who have undergone allo- HSCT by using ST multimer and intracellular cytokine staining. Our study has revealed that the presence of functional CMV-specific T cells, determined by early interferon γ production or by significant T-cell expansion after first CMV reactivation, correlated with short CMV viremia duration and low number of CMV reactivations. By contrast, the absence of functional CMV- CTLs does correlate with CMV recurrence. These results support that behavior of CMV-specific subpopulations after reactivation influences reactivations and can guide preemptive therapy. [ABSTRACT FROM AUTHOR]

The contribution of macrophages in the gastrointestinal tract to disease control or progression in HIV infection remains unclear. To address this question, we analyzed CD163+ macrophages in ileum and mesenteric lymph nodes (LN) from SIV-infected rhesus macaques with dichotomous expression of controlling MHC class I alleles predicted to be SIV controllers or progressors. Infection induced accumulation of macrophages into gut mucosa in the acute phase that persisted in progressors but was resolved in controllers. In contrast, macrophage recruitment to mesenteric LNs occurred only transiently in acute infection irrespective of disease outcome. Persistent gut macrophage accumulation was associated with CD163 expression on α4β7+CD16+ blood monocytes and correlated with epithelial damage. Macrophages isolated from intestine of progressors had reduced phagocytic function relative to controllers and uninfected macaques, and the proportion of phagocytic macrophages negatively correlated with mucosal epithelial breach, lamina propria Escherichia coli density, and plasma virus burden. Macrophages in intestine produced low levels of cytokines regardless of disease course, while mesenteric LN macrophages from progressors became increasingly responsive as infection advanced. These data indicate that noninflammatory CD163+ macrophages accumulate in gut mucosa in progressive SIV infection in response to intestinal damage but fail to adequately phagocytose debris, potentially perpetuating their recruitment. [ABSTRACT FROM AUTHOR]

Regulatory T-cells (Treg) are essential for maintaining immune homeostasis and tolerance. Surface glycosylation is ubiquitous on mammalian cells and regulates diverse biological processes. While it is currently well accepted that surface glycan expression influences multiple aspects of T-cell function, little is known about the relevance of glycosylation to Treg biology. This study aimed to profile the surface glycosylation characteristics of Treg in various lymphoid compartments of mouse and in human peripheral blood with comparison to non-regulatory, conventional CD4+ T-cells (Tconv). It also sought to determine the relationship between the surface glycosylation characteristics and suppressive potency of Treg. Lectin-based flow cytometric profiling demonstrated that Treg surface glycosylation differs significantly from that of Tconv in the resting state and is further modified by activation stimuli. In mouse, the surface glycosylation profiles of FoxP3+ Treg from spleen and lymph nodes were closely comparable but greater variability was observed for Treg in thymus, bone marrow, and blood. Surface levels of tri/tetra-antennary N-glycans correlated with expression of proteins known to be involved in Treg suppressive functions, including GITR, PD-1, PD-L1, CD73, CTLA-4, and ICOS. In coculture experiments involving purified Treg subpopulations and CD4+ or CD8+ Tconv, higher surface tri/tetra-antennary N-glycans was associated with greater Treg suppressive potency. Enzymatic manipulation of mouse Treg surface glycosylation resulting in a temporary reduction of surface N-glycans significantly reduced Treg capacity to suppress Tconv activation through contact-dependent mechanisms. Overall, these findings demonstrate that Treg have distinctive surface glycan characteristics that show variability across anatomical locations and are modulated by activation events. They also provide evidence of an important role for surface glycosylation in determining Treg phenotype and suppressive potency. These insights may prove relevant to the analysis of Treg in disease settings and to the further development of Treg-based immunotherapies. [ABSTRACT FROM AUTHOR]

Lymphocyte migration, which is essential for effective immune responses, belongs to the so-called amoeboid migration. The lymphocyte migration is up to 100 times faster than between mesenchymal and epithelial cell types. Migrating lymphocytes are highly polarized in three well-defined structural and functional zones: uropod, medial zone, and leading edge (LE). The actiomyosin-dependent driving force moves forward the uropod, whereas massive actin rearrangements protruding the cell membrane are observed at the LE. These actin rearrangements resemble those observed at the immunological synapse driven by clathrin, a protein normally involved in endocytic processes. Here, we used cell lines as well as primary lymphocytes to demonstrate that clathrin and clathrin adaptors colocalize with actin at the LE of migrating lymphocytes, but not in other cellular zones that accumulate both clathrin and actin. Moreover, clathrin and clathrin adaptors, including Hrs, the clathrin adaptor for multivesicular bodies, drive local actin accumulation at the LE. Clathrin recruitment at the LE resulted necessary for a complete cell polarization and further lymphocyte migration in both 2D and 3D migration models. Therefore, clathrin, including the clathrin population associated to internal vesicles, controls lymphocyte migration by regulating actin rearrangements occurring at the LE. [ABSTRACT FROM AUTHOR]

Regulatory T cells (Treg cells) limit contact between dendritic cells (DCs) and conventional T cells (Tcons), decreasing the formation of aggregates as well as down-modulating the expression of co-stimulatory molecules by DCs, thus decreasing DC immunogenicity and abrogating T-cell activation. Despite the importance of this Treg-cell function, the capacity of Treg cells from term and preterm neonates to suppress DCs, and the suppressive mechanisms they use, are still undefined. We found that, relative to adult Treg cells, activated Treg cells from human neonates expressed lower FOXP3 and CTLA-4, but contained higher levels of cAMP. We developed an in vitro model in which Treg function was measured at a physiological ratio of 1 Treg for 10 Tcon and 1 monocyte-derived DC, as Treg target. Term and preterm Treg cells failed to suppress the formation of DC-Tcon aggregates, in contrast to naïve and memory Treg cells from adults. However, neonatal Treg cells diminished DC and Tcon activation as well as actin polymerization at the immunological synapses. In addition, CTLA-4 and cAMP were the main suppressive molecules used by neonatal Treg. Altogether, both preterm and term neonatal Treg cells appear less functional than adult Treg cells, and this defect is consistent with the general impairment of CD4 cell function in newborns. [ABSTRACT FROM AUTHOR]

T cells recognize antigens at the two-dimensional (2D) interface with antigen-presenting cells (APCs), which trigger T-cell effector functions. T-cell functional outcomes correlate with 2D kinetics of membrane-embedded T-cell receptors (TCRs) binding to surface-tethered peptide-major histocompatibility complex molecules (pMHCs). However, most studies have measured TCR-pMHC kinetics for recombinant TCRs in 3D by surface plasmon resonance, which differs drastically from 2D measurements. Here, we compared pMHC dissociation from native TCR on the T-cell surface to recombinant TCR immobilized on glass surface or in solution. Force on TCR-pMHC bonds regulated their lifetimes differently for native than recombinant TCRs. Perturbing the cellular environment suppressed 2D on-rates but had no effect on 2D off-rate regardless of whether force was applied. In contrast, for the TCR interacting with its monoclonal antibody, the 2D on-rate was insensitive to cellular perturbations and the force-dependent off-rates were indistinguishable for native and recombinant TCRs. These data present novel features of TCR-pMHC kinetics that are regulated by the cellular environment, underscoring the limitations of 3D kinetics in predicting T-cell functions and calling for further elucidation of the underlying molecular and cellular mechanisms that regulate 2D kinetics in physiological settings. [ABSTRACT FROM AUTHOR]

Immune dysfunctions in the elderly result in increased susceptibility to infectious diseases, cancer, and autoimmune diseases. Natural killer ( NK) cells are bone marrow-derived lymphocytes crucial for host defense against several infections and cancer. We have previously shown that compared to young, aged C57 BL/6 mice have decreased numbers of mature NK cells in the blood, spleen, and bone marrow, resulting in susceptibility to mousepox, a lethal disease caused by ectromelia virus. Here, we describe further age-related defects in NK cells including reduced proliferation in vivo, additional signs of immaturity, and dysregulated expression of activating and inhibitory receptors. Aging also alters the expression of collagen-binding integrins in conventional NK cells and the frequency and phenotype of liver tissue-resident NK cells. We additionally show that the defect in NK maturation is the consequence of deficient maturational cues provided by bone marrow stromal cells. Moreover, we demonstrate that in aged mice, treatment with complexes of the cytokine IL-15 and IL-15Rα induce massive expansion of the NK cells, but most of these NK cells remain immature and are unable to restore resistance to mousepox. The use of rodent model to understand immunosenescence may help the development of treatments to improve the immune fitness of the aged. Our work with NK cells should contribute toward this goal. [ABSTRACT FROM AUTHOR]

Natural killer ( NK) cells are critical in eliminating tumors and viral infections, both of which occur at a high incidence in the elderly. Previous studies showed that aged NK cells are less cytotoxic and exhibit impaired maturation compared to young NK cells. We evaluated whether extrinsic or intrinsic factors were responsible for the impaired maturation and function of NK cells in aging and whether impaired maturation correlated with functional hyporesponsiveness. We confirmed that aged mice have a significant decrease in the frequency of mature NK cells in all lymphoid organs. Impaired NK cell maturation in aged mice correlated with a reduced capacity to eliminate allogeneic and B16 tumor targets in vivo. This could be explained by impaired degranulation, particularly by mature NK cells of aged mice. Consistent with impaired aged NK cell maturation, expression of T-bet and Eomes, which regulate NK cell functional maturation, was significantly decreased in aged bone marrow ( BM) NK cells. Mixed BM chimeras revealed that the nonhematopoietic environment was a key determinant of NK cell maturation and T-bet and Eomes expression. In mixed BM chimeras, NK cells derived from both young or aged BM cells adopted an 'aged' phenotype in an aged host, that is, were hyporesponsive to stimuli in vitro, while adopting a 'young' phenotype following transfer in young hosts. Overall, our data suggest that the aged nonhematopoietic environment is responsible for the impaired maturation and function of NK cells. Defining these nonhematopoietic factors could have important implications for improving NK cell function in the elderly. [ABSTRACT FROM AUTHOR]

Aging of the world population and a concomitant increase in age-related diseases and disabilities mandates the search for strategies to increase healthspan, the length of time an individual lives healthy and productively. Due to the age-related decline of the immune system, infectious diseases remain among the top 5–10 causes of mortality and morbidity in the elderly, and improving immune function during aging remains an important aspect of healthspan extension. Calorie restriction (CR) and more recently rapamycin (rapa) feeding have both been used to extend lifespan in mice. Preciously few studies have actually investigated the impact of each of these interventions upon in vivo immune defense against relevant microbial challenge in old organisms. We tested how rapa and CR each impacted the immune system in adult and old mice. We report that each intervention differentially altered T-cell development in the thymus, peripheral T-cell maintenance, T-cell function and host survival after West Nile virus infection, inducing distinct but deleterious consequences to the aging immune system. We conclude that neither rapa feeding nor CR, in the current form/administration regimen, may be optimal strategies for extending healthy immune function and, with it, lifespan. [ABSTRACT FROM AUTHOR]

Natural Treg cells acquire their lineage-determining transcription factor Foxp3 during development in the thymus and are important in maintaining immunologic tolerance. Here, we analyzed the composition of the thymic Treg-cell pool using RAG2- GFP/ Fox P3- RFP dual reporter mice and found that a population of long-lived GFP− Treg cells exists in the thymus. These long-lived Treg cells substantially increased with age, to a point where they represent >90% of the total thymic Treg-cell pool at 6 months of age. In contrast, long-lived conventional T cells remained at ∼15% of the total thymic pool at 6 months of age. Consistent with these studies, we noticed that host-derived Treg cells represented a large fraction (∼10%) of the total thymic Treg-cell pool in bone marrow chimeras, suggesting that long-lived Treg cells also reside in the thymus of these mice. The pool of long-lived Treg cells in the thymus was sustained by retention of Treg cells in the thymus and by recirculation of peripheral Treg cells back into the thymus. These long-lived thymic Treg cells suppressed T-cell proliferation to an equivalent extent to splenic Treg cells. Together, these data demonstrate that long-lived Treg cells accumulate in the thymus by both retention and recirculation. [ABSTRACT FROM AUTHOR]

Purpose: Primary immune thrombocytopenic purpura (ITP), caused by immune system dysfunction, is recognized as the leading cause of thrombocytopenia in pediatric population. Nonetheless, inadequate studies have been performed on bone marrow immunophenotyping of children with ITP. In this study, we aimed to investigate the immunophenotype of bone marrow lymphocytes in these children. Patients and methods: Between 2008 and 2012, 35 children with ITP and 26 age and sex matched healthy controls were recruited. All participants underwent bone marrow aspiration. Appropriate B-cell, T-cell, and myeloid lineage monoclonal antibodies were employed to determine the immunophenotype of these patients. Results: CD10, CD19, and CD20, all indicative of premature B-cell markers, were significantly greater in children with ITP. CD22, mainly expressed on mature B cells was slightly, but not significantly reduced in the patients' group ( P = .42). On the other hand, T cell markers including CD2, CD3, CD5, and CD7 were underexpressed. CD33, a specific marker for myeloid lineage, was underexpressed in the patients' group (5.6 ± 4.7 vs. 12.9 ± 7.3, P < .001). Noteworthy, the immunophenotype did not significantly differ between acute and persistent cases. Conclusion: Overall, a phenotype characterized by increased pre-B-cell markers along with decreased T cell immunophenotypic markers was observed in bone marrow lymphocytes of children with ITP in the present study. Further larger scale studies are recommended to confirm our findings, as precise mapping of the immunophenotype of lymphocytes in these patients would pave the road to improved diagnosis and treatment. [ABSTRACT FROM AUTHOR]

Functional decline of the hematopoietic system occurs during aging and contributes to clinical consequences, including reduced competence of adaptive immunity and increased incidence of myeloid diseases. This has been linked to aging of the hematopoietic stem cell ( HSC) compartment and has implications for clinical hematopoietic cell transplantation as prolonged periods of T-cell deficiency follow transplantation of adult mobilized peripheral blood (PB), the primary transplant source. Here, we examined the gene expression profiles of young and aged HSCs from human cord blood and adult mobilized PB, respectively, and found that Wnt signaling genes are differentially expressed between young and aged human HSCs, with less activation of Wnt signaling in aged HSCs. Utilizing the OP9- DL1 in vitro co-culture system to promote T-cell development under stable Notch signaling conditions, we found that Wnt signaling activity is important for T-lineage differentiation. Examination of Wnt signaling components and target gene activation in young and aged human HSCs during T-lineage differentiation revealed an association between reduced Wnt signal transduction, increasing age, and impaired or delayed T-cell differentiation. This defect in Wnt signal activation of aged HSCs appeared to occur in the early T-progenitor cell subset derived during in vitro T-lineage differentiation. Our results reveal that reduced Wnt signaling activity may play a role in the age-related intrinsic defects of aged HSCs and early hematopoietic progenitors and suggest that manipulation of this pathway could contribute to the end goal of improving T-cell generation and immune reconstitution following clinical transplantation. [ABSTRACT FROM AUTHOR]

Th17 cytokines can play both protective and pathologic roles in the airways. An emerging theme in Th17 cytokine biology is that these responses can mediate tissue pathology when downstream effector cells are dysfunctional, such as neutrophils lacking functional NADPH oxidase in the case of chronic granulomatous disease, or epithelial cells lacking appropriate ion transport as in the case of cystic fibrosis. In this Mini-Review we highlight recent advances in the protective and pathologic roles of Th17 cytokines in the context of infection at the pulmonary barrier. [ABSTRACT FROM AUTHOR]

Autoimmunity increases with aging indicative of reduced immune tolerance, but the mechanisms involved are poorly defined. In recent years, subsets of B cells with immunoregulatory properties have been identified in murine models of autoimmune disorders, and these cells downregulate immune responses via secretion of IL10. In humans, immature transitional B cells with a CD19+ CD24hi CD38hi phenotype have been reported to regulate immune responses via IL10 production. We found the frequency and numbers of CD19+ CD24hi CD38hi cells were reduced in the PBMC pool with age. IL10 expression and secretion following activation via either CD40, or Toll-like receptors was also impaired in CD19+ CD24hi CD38hi B cells from healthy older donors. When investigating the mechanisms involved, we found that CD19+ CD24hi CD38hi B-cell function was compromised by age-related effects on both T cells and B cells: specifically, CD40 ligand expression was lower in CD4 T cells from older donors following CD3 stimulation, and signalling through CD40 was impaired in CD19+ CD24hi CD38hi B cells from elders as evidenced by reduced phosphorylation ( Y705) and activation of STAT3. However, there was no age-associated change in expression of costimulatory molecules CD80 and CD86 on CD19+ CD24hi CD38hi cells, suggesting IL10-dependent immune suppression is impaired, but contact-dependent suppressive capacity is intact with age. Finally, we found a negative correlation between CD19+ CD24hi CD38hi B-cell IL10 production and autoantibody ( Rheumatoid factor) levels in older adults. We therefore propose that an age-related decline in CD19+ CD24hi CD38hi B cell number and function may contribute towards the increased autoimmunity and reduced immune tolerance seen with aging. [ABSTRACT FROM AUTHOR]

The efficiency of antigen ( Ag) processing by dendritic cells ( DCs) is vital for the strength of the ensuing T-cell responses. Previously, we and others have shown that in comparison to protein vaccines, vaccination with synthetic long peptides ( SLPs) has shown more promising (pre-)clinical results. Here, we studied the unknown mechanisms underlying the observed vaccine efficacy of SLPs. We report an in vitro processing analysis of SLPs for MHC class I and class II presentation by murine DCs and human monocyte-derived DCs. Compared to protein, SLPs were rapidly and much more efficiently processed by DCs, resulting in an increased presentation to CD4+ and CD8+ T cells. The mechanism of access to MHC class I loading appeared to differ between the two forms of Ag. Whereas whole soluble protein Ag ended up largely in endolysosomes, SLPs were detected very rapidly outside the endolysosomes after internalization by DCs, followed by proteasome- and transporter associated with Ag processing-dependent MHC class I presentation. Compared to the slower processing route taken by whole protein Ags, our results indicate that the efficient internalization of SLPs, accomplished by DCs but not by B or T cells and characterized by a different and faster intracellular routing, leads to enhanced CD8+ T-cell activation. [ABSTRACT FROM AUTHOR]

Pre-transplant conditioning regimens play a major role in triggering graft-versus-host disease ( GVHD). This study investigated the effect of irradiation on donor T cell trafficking to lymphoid and non-lymphoid tissues by comparing the migration of carboxy-fluorescein diacetate succinimidyl ester-labelled, naïve donor T lymphocytes in vivo in irradiated and non-irradiated syngeneic mice recipients. Recruitment of adoptively transferred naïve T cells to secondary lymphoid organs was increased in irradiated mice and naïve T cells also aberrantly localized to non-lymphoid tissues. Irradiation also induced aberrant effector memory T cell migration into lymph nodes and their localization to homing-privileged non-lymphoid sites, such as the gut. The presence of a minor histocompatibility mismatch further enhanced the aberrant accumulation of T cells in both lymphoid and non-lymphoid tissue, whilst their migratory pattern was not modified as compared to fully matched irradiated recipients. These effects correlated with decreased permeability of, and the secretion of chemotactic factors by the endothelium. Our findings are consistent with the possibility that excessive, dysregulated extravasation of T cells induced by irradiation promotes the development of GVHD. [ABSTRACT FROM AUTHOR]

Germinal center development, critical for long-term humoral immunity, requires the trafficking of T and B lymphocytes to defined tissues and locations after antigenic challenge. The molecular mechanisms that support lymphocyte trafficking through the linkage of extracellular chemotactic and adhesive cues to the actin cytoskeleton are not yet fully defined. We have previously identified the actin-bundling protein L-plastin ( LPL) as a requisite intermediary in both naive B and T lymphocyte migration and in T-cell activation. We tested the hypothesis that humoral immunity would require LPL. We show that mice lacking LPL demonstrated defective germinal center formation and reduced production of T-cell-dependent antibodies. T cells from LPL−/− mice exhibited defective expansion of the follicular helper T population. Reduced expansion of LPL−/− follicular helper T cells correlated with impaired trafficking to or retention of cells in the spleen following challenge, highlighting the importance of initial lymphocyte recruitment to the eventual success of the immune response. Furthermore, LPL−/− B cells demonstrated cell-intrinsic defects in population expansion and in differentiation into germinal center B cells. LPL thus modulates both T- and B-cell function during the germinal center reaction and the production of T-cell-dependent antibody responses. [ABSTRACT FROM AUTHOR]

In the adult thymus, the development of self-tolerant thymocytes requires interactions with thymic epithelial cells (TECs). Although both cortical and medullary TECs (cTECs/mTECs) are known to arise from common bipotent TEC progenitors, the phenotype of these progenitors and the timing of the emergence of these distinct lineages remain unclear. Here, we have investigated the phenotype and developmental properties of bipotent TEC progenitors during cTEC/mTEC lineage development. We show that TEC progenitors can undergo a stepwise acquisition of first cTEC and then mTEC hallmarks, resulting in the emergence of a progenitor population simultaneously expressing the cTEC marker CD205 and the mTEC regulator Receptor Activator of NF-κB (RANK). In vivo analysis reveals the capacity of CD205+ TECs to generate functionally competent cortical and medullary microenvironments containing both cTECs and Aire+ mTECs. Thus, TEC development involves a stage in which bipotent progenitors can co-express hallmarks of the cTEC and mTEC lineages through sequential acquisition, arguing against a simple binary model in which both lineages diverge simultaneously from bipotent lineage negative TEC progenitors. Rather, our data reveal an unexpected overlap in the phenotypic properties of these bipotent TECs with their lineage-restricted counterparts. [ABSTRACT FROM AUTHOR]