Characterization of Effector Memory CD8+ T Cells in the Synovial Fluid of Rheumatoid Arthritis

Phenotypic and functional dysregulations of CD8 + T Cells in myasthenia gravis

Myasthenia Gravis (MG) is a heterogeneous autoimmune disorder characterized by fluctuating muscle weakness caused by autoantibodies targeting neuromuscular junction components. While the role of CD4 + T cells in MG is well established, the contribution of CD8 + T cells remains poorly understood. In this study, we analyze CD8 + T cells in 36 MG patients and 38 age- and gender-matched controls using flow cytometry to evaluate subset distribution, granzyme expression, and cytokine production. MG patients exhibit an altered CD4 + /CD8 + T cell ratio and significant changes in CD8 + T cell subsets, including increased central memory CD8 + T cell (Tcm) proportions and decreased effector memory CD8 + T cell (Tem) proportions. Granzyme B expression in Tcm cells is significantly elevated in MG patients, whereas no significant changes are observed in other subsets or GZMK expression. Cytokine analysis reveals increased IL-21, GM-CSF, and IL-17A production by CD8 + T cells in MG patients. These phenotypic and functional alterations of CD8 + T cells persist during the acute phase of the disease, regardless of immunotherapy usage, and vary between ocular and generalized MG. Subgroup and correlation analyses further identify age-dependent and age-independent dysregulations of CD8 + T cells, indicating complex and subtype-specific roles of CD8 + T cells in the immunopathological processes underlying MG. Our findings provide novel insights into the involvement of CD8 + T cells in MG pathogenesis, laying a foundation for future research and potential therapeutic strategies targeting CD8 + T cells.

Sex differences in CD8+ T cell responses during adaptive immunity

Biological sex is an important variable that influences the immune system's susceptibility to infectious and non-infectious diseases and their outcomes. Sex dimorphic features in innate and adaptive immune cells and their activities may help to explain sex differences in immune responses. T lymphocytes in the adaptive immune system are essential to providing protection against infectious and chronic inflammatory diseases. In this review, T cell responses are discussed with focus on the current knowledge of biological sex differences in CD8+ T cell mediated adaptive immune responses in infectious and chronic inflammatory diseases. Future directions aimed at investigating the molecular and cellular mechanisms underlying sex differences in diverse T cell responses will continue to underscore the significance of understanding sex differences in protective immunity at the cellular level, to induce appropriate T cell-based immune responses in infection, autoimmunity, and cancer. This article is categorized under: Immune System Diseases > Molecular and Cellular Physiology Infectious Diseases > Molecular and Cellular Physiology.

Remodeling of T-cell mitochondrial metabolism to treat autoimmune diseases

T cells are key drivers of the pathogenesis of autoimmune diseases by producing cytokines, stimulating the generation of autoantibodies, and mediating tissue and cell damage. Distinct mitochondrial metabolic pathways govern the direction of T-cell differentiation and function and rely on specific nutrients and metabolic enzymes. Metabolic substrate uptake and mitochondrial metabolism form the foundational elements for T-cell activation, proliferation, differentiation, and effector function, contributing to the dynamic interplay between immunological signals and mitochondrial metabolism in coordinating adaptive immunity. Perturbations in substrate availability and enzyme activity may impair T-cell immunosuppressive function, fostering autoreactive responses and disrupting immune homeostasis, ultimately contributing to autoimmune disease pathogenesis. A growing body of studies has explored how metabolic processes regulate the function of diverse T-cell subsets in autoimmune diseases such as systemic lupus erythematosus (SLE), multiple sclerosis (MS), autoimmune hepatitis (AIH), inflammatory bowel disease (IBD), and psoriasis. This review describes the coordination of T-cell biology by mitochondrial metabolism, including the electron transport chain (ETC), oxidative phosphorylation, amino acid metabolism, fatty acid metabolism, and one‑carbon metabolism. This study elucidated the intricate crosstalk between mitochondrial metabolic programs, signal transduction pathways, and transcription factors. This review summarizes potential therapeutic targets for T-cell mitochondrial metabolism and signaling in autoimmune diseases, providing insights for future studies.

Single-cell characterisation of tissue homing CD4 + and CD8 + T cell clones in immune-mediated refractory arthritis

BACKGROUND

Immune-mediated arthritis is a group of autoinflammatory diseases, where the patient's own immune system attacks and destroys synovial joints. Sustained remission is not always achieved with available immunosuppressive treatments, warranting more detailed studies of T cell responses that perpetuate synovial inflammation in treatment-refractory patients.

METHODS

In this study, we investigated CD4 + and CD8 + T lymphocytes from the synovial tissue and peripheral blood of patients with treatment-resistant immune-mediated arthritis using paired single-cell RNA and TCR-sequencing. To gain insights into the trafficking of clonal families, we compared the phenotypes of clones with the exact same TCRß amino acid sequence between the two tissues.

RESULTS

Our results show that both CD4 + and CD8 + T cells display a more activated and inflamed phenotype in the synovial tissue compared to peripheral blood both at the population level and within individual T cell families. Furthermore, we found that both cell subtypes exhibited clonal expansion in the synovial tissue.

CONCLUSIONS

Our findings suggest that the local environment in the synovium drives the proliferation of activated cytotoxic T cells, and both CD4 + and CD8 + T cells may contribute to tissue destruction and disease pathogenesis.

The complex relationship between large granular lymphocyte leukemia and rheumatic disease

INTRODUCTION

Large granular lymphocytic (LGL) leukemia is a rare lymphoproliferative disorder characterized by an expansion of clonal T or NK lymphocytes. Neutropenia-related infections represent the main clinical manifestation. Even if the disease follows an indolent course, most patients will ultimately need treatment in their lifetime. Interestingly, LGL leukemia is characterized by a high frequency of autoimmune disorders with rheumatoid arthritis being the most frequent.

AREAS COVERED

This review covers the pathophysiology, clinic-biological features and the advances made in the treatment of LGL leukemia. A special focus will be made on the similarities in the pathophysiology of LGL leukemia and the frequently associated rheumatic disorders.

EXPERT OPINION

Recent advances in the phenotypic and molecular characterization of LGL clones have uncovered the key role of JAK-STAT signaling in the pathophysiology linking leukemic cells expansion and autoimmunity. The description of the molecular landscape of T- and NK-LGL leukemia and the improved understanding of the associated rheumatic disorders open the way to the development of new targeted therapies effective on both conditions.

Identification of potential ferroptosis key genes and immune infiltration in rheumatoid arthritis by integrated bioinformatics analysis

Objective

Ferroptosis is of vital importance in the development of Rheumatoid arthritis (RA). The purpose of this project is to clarify the potential ferroptosis-related genes, pathways, and immune infiltration in RA by bioinformatics analysis.

Methods

We acquired ferroptosis-related genes (FRGs) from Ferroptosis database (FerrDb). We obtained the Gene dataset of RA (GSE55235) from the Gene Expression Omnibus (GEO) Database, screened the differentially expressed genes (DEGs) in RA and control samples, and then took the intersection of it and FRGs. Aiming to construct the protein-protein interaction (PPI) networks of the FRGs-DEGs, STRING database and Cytoscape software 3.7.0 would be used. Furthermore, hub genes were identified by CytoNCA, a Cytoscape plug-in. The gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment of FRGs-DEGs were performed.

Results

We identified 34 FRGs-DEGs, including 7 upregulated and 27 downregulated genes by taking the intersection of the FRGs and DEGs. PPI analysis identified a total of 3 hub genes(VEGFA, PTGS2, and JUN). GO enrichment analyses and KEGG Pathway enrichment displayed that the FRGs-DEGs are involved in the response to oxidative stress and corticosteroid, heme binding, FoxO-signal pathway. Results of immune infiltration displayed that increased infiltration of T cells, while Macrophages M2 less may be related to the occurrence of RA.

Conclusion

The hub genes involved in ferroptosis in RA may be VEGFA, PTGS2, and JUN, which are mainly involved in FoxO-signal pathway. T cell, Mac, and plasma cells may be involved in the regulation of RA-joints-synovial-inflammation.

Circulating CD8+ T Cell Subsets in Primary Sjögren's Syndrome

Currently, multiple studies have indicated that CD8+ T lymphocytes play a role in causing damage to the exocrine glands through acinar injury in primary Sjögren's syndrome (pSS). The aim of this research was to assess the imbalance of circulating CD8+ T cell subsets. We analyzed blood samples from 34 pSS patients and 34 healthy individuals as controls. We used flow cytometry to enumerate CD8+ T cell maturation stages, using as markers CD62L, CD28, CD27, CD4, CD8, CD3, CD45RA and CD45. For immunophenotyping of 'polarized' CD8+ T cell subsets, we used the following monoclonal antibodies: CXCR5, CCR6, CXCR3 and CCR4. The findings revealed that both the relative and absolute numbers of 'naïve' CD8+ T cells were higher in pSS patients compared to the healthy volunteers. Conversely, the proportions of effector memory CD8+ T cells were notably lower. Furthermore, our data suggested that among patients with pSS, the levels of cytotoxic Tc1 CD8+ T cells were reduced, while the frequencies of regulatory cytokine-producing Tc2 and Tc17 CD8+ T cells were significantly elevated. Simultaneously, the Tc1 cell subsets displayed a negative correlation with immunoglobulin G, rheumatoid factor, the Schirmer test and unstimulated saliva flow. On the other hand, the Tc2 cell subsets exhibited a positive correlation with these parameters. In summary, our study indicated that immune dysfunction within CD8+ T cells, including alterations in Tc1 cells, plays a significant role in the development of pSS.

Peripheral CD4+ /CD8+ T cell composition distinct from healthy individuals is shared by ankylosing spondylitis and rheumatoid arthritis

OBJECTIVE

Ankylosing spondylitis (AS) and rheumatoid arthritis (RA) are chronic inflammatory joint diseases, linking to the alterations of immune cells. We attempted to assess whether the alterations in the composition of CD4+ /CD8+ T cells are different between AS and RA and identify the characteristic cells between male and female patients.

METHODS

The proportions of CD3+ or double positive T cells, 6 CD4+ T subsets and 9 CD8+ T cell subsets were detected by flow cytometry and compared in 30 healthy individuals, 42 AS patients and 45 RA patients. The differentially altered cells were individually analyzed for associations with disease activity parameters. In addition, their proportions were compared between different genders in the 3 groups.

RESULTS

The proportions of CD4+ T cells, naive CD4+ T cells and central memory CD4+ T cells were lower in AS patients (P = 0.001, P = 0.002 and P = 0.007, respectively) and RA patients (P = 0.032, P < 0.001 and P = 0.016, respectively), but the proportion of effector memory ones was higher when compared with healthy populations (both P < 0.001), as were the decrease of naive/central memory CD8+ T cells in AS (P = 0.003 and P = 0.016, respectively) and RA (P < 0.001 and P = 0.006, respectively), and the increased tendency of terminally differentiated CD8+ T cells. However, these above-mentioned cells, regulatory T (Treg) cells and CD8+ T cells with different CD127 expressions between AS and RA were similar in proportion. Furthermore, naive CD4+ T cells were positively associated with C-reactive protein (CRP) in AS, whereas CD4+ T cells and terminally differentiated CD8+ T of RA patients were associated with CRP in RA. The gender-related alterations predominantly displayed the overexpressions of Treg cells and naive CD8+ T cells in female patients with AS and RA, respectively.

CONCLUSIONS

AS patients and RA patients have some similar peripheral CD4+ /CD8+ T cell subsets but are distinct from healthy individuals, which may contribute to disease severity. Females are respectively characterized by the up-regulation of Treg cells and naive CD8+ T cells in AS patients and RA patients. The study offers an in-depth understanding of the role of T cell subsets in the similarities of the disorders and helps us to monitor disease changes and may offer a theoretical basis of developing novel therapies against common targets.

Clonally expanded PD-1-expressing T cells are enriched in synovial fluid of juvenile idiopathic arthritis patients

Juvenile idiopathic arthritis (JIA) is the most common chronic rheumatic condition in childhood. The disease etiology remains largely unknown; however, a key role in JIA pathogenesis is surely mediated by T cells. T-lymphocytes activity is controlled via signals, known as immune checkpoints. Delivering an inhibitory signal or blocking a stimulatory signal to achieve immune suppression is critical in autoimmune diseases. However, the role of immune checkpoints in chronic inflammation and autoimmunity must still be deciphered. In this study, we investigated at the single-cell level the feature of T cells in JIA chronic inflammation, both at the transcriptome level via single-cell RNA sequencing and at the protein level by flow cytometry. We found that despite the heterogeneity in the composition of synovial CD4+ and CD8+ T cells, those characterized by PD-1 expression were clonally expanded tissue-resident memory (Trm)-like cells and displayed the highest proinflammatory capacity, suggesting their active contribution in sustaining chronic inflammation in situ. Our data support the concept that novel therapeutic strategies targeting PD-1 may be effective in the treatment of JIA. With this approach, it may become possible to target overactive T cells regardless of their cytokine production profile.

Chemical compositions of Souliea vaginata (Maxim) Franch rhizome and their potential therapeutic effects on collagen-induced arthritis in rats

ETHNOPHARMACOLOGICAL REVEVANCE

Rheumatoid arthritis (RA) is a global prevalent chronic autoimmune inflammatory disease and acceptable safety drugs are lack for its treatment. The rhizomes of Souliea vaginata (Maxim) Franch (SV) possess anti-inflammatory functions and are used as substitution of Coptis chinensis Franch. SV is also traditional Chinese medicine and Tibetan medicine for the treatment of conjunctivitis, enteritis and rheumatic. For searching complementary and alternative anti-RA drugs, it is necessary to characterize the potential anti-arthritic activity of SV and underlying mechanism involved.

AIM OF THE STUDY

The aim of the study was to test the chemical compositions, evaluate the anti-arthritic effects and underlying mechanisms of SV.

MATERIALS AND METHODS

The chemical compositions of SV were analyzed using liquid chromatography-ion trap-time of flight tandem mass spectrometry (LCMS-IT-TOF). From day 11 to day 31, SV (0.5, 1.0 and 1.5 g/kg body weight) and Tripterygium glycosidorum (TG, 10 mg/kg body weight) were administered orally to the CIA model rats once a day. Thickness of paw and body weights were measured once every two days from day 1 to day 31. Histopathological changes were measured using hematoxylin-eosin (HE) staining. Effects of SV on the levels of IL-2, TNF-α, IFN-γ, IL-4 and IL-10 in serum of CIA rats were measured by enzyme-linked immunosorbent assay (ELISA) kits. CD3⁺, CD4⁺, CD8⁺ and CD4⁺CD25⁺ T cells populations were measured using flow cytometric analysis. To evaluate the possible hepatotoxicity and nephrotoxicity, the serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea (UREA) and creatinine (CREA) in CIA rats were also tested using blood auto analyzer.

RESULTS

34 compounds were identified from SV based on LCMS-IT-TOF, and triterpenoids are major anti-arthritic compositions. SV significantly relieved CIA rats' paw swelling without obvious influence on the body weight growth. SV decreased the serum levels of IL-2, TNF-α and IFN-γ in CIA rat, and increased the serum levels of IL-4 and IL-10. SV significantly increased and decreased the percentages of CD4⁺ and CD8⁺, with no significant effects on CD3⁺ in lymphocytes of CIA model rats. Moreover, SV simultaneously decreased thymus and spleen indexes and no hepatotoxicity and nephrotoxicity was observed after short-term treatment.

CONCLUSION

These findings suggest that SV possesses preventive and therapeutic effect on RA by modulating the inflammatory cytokines, T-lymphocyte, thymus and spleen indexes and shows no hepatotoxicity and nephrotoxicity.

Cell-Mediated Cytotoxicity in Lyme Arthritis

OBJECTIVE

Obliterative microvascular lesions are found in the synovial tissue of ~50% of patients with post-antibiotic Lyme arthritis (LA) and correlate with autoantibodies to certain vascular antigens. In this study, we identified lymphocytes with cytotoxic potential that may also mediate this feature of synovial pathology.

METHODS

The cytotoxic potential of lymphocytes and their T cell receptor (TCR) Vβ gene usage were determined using samples of peripheral blood mononuclear cells (PBMCs) and synovial fluid mononuclear cells (SFMCs) from patients with antibiotic-responsive or post-antibiotic LA. Cell phenotypes were analyzed using flow cytometry and intracellular cytokine staining. Immunohistochemistry was performed on post-antibiotic synovial tissue samples.

RESULTS

In SFMC and PBMC samples, the percentages of CD8+ T cells and double-negative T cells (primarily γδ T cells) were greater among 22 patients with post-antibiotic LA than in 14 patients with antibiotic-responsive LA. Moreover, CD8+ T cells and γδ T cells often expressed cytotoxic mediators, granzyme A/granzyme B, and perforin. The same 3 TCR Vβ segments were over-represented in both CD4+ T cells and CD8+ T cells in SFMC samples from post-antibiotic LA patients. In synovial tissue samples from 3 patients with post-antibiotic LA, CD8+ T cells intermixed with CD4+ T cells were seen around blood vessels, and 2 patients with microvascular damage had autoantibodies to vascular-associated antigens. One of these 2 patients, the one in whom cytotoxicity appeared to be active, had complement (C5b-9) deposition on obliterated vessels. Very few natural killer cells or γδ T cells were seen.

CONCLUSION

We propose that CD8+ T cell-mediated cytotoxicity, CD4+ T cell help, autoantibodies to vascular antigens, and complement deposition may each have a role in microvasculature damage in post-antibiotic LA.

Transcriptomic profiling of programmed cell death 1 (PD-1) expressing T cells in early rheumatoid arthritis identifies a decreased CD4 + PD-1 + signature post-treatment

Programmed cell death protein 1 (PD-1)-expressing T cells are expanded in individuals with established rheumatoid arthritis (RA). However, little is known about their functional role in the pathogenesis of early RA. To address this, we investigated the transcriptomic profiles of circulating CD4⁺ and CD8⁺ PD-1⁺ lymphocytes from patients with early RA (n = 5) using fluorescence activated cell sorting in conjunction with total RNA sequencing. Additionally, we assessed for alterations in CD4⁺PD-1⁺ gene signatures in previously published synovial tissue (ST) biopsy data (n = 19) (GSE89408, GSE97165) before and after six-months of triple disease modifying anti-rheumatic drug (tDMARD) treatment. Comparisons of gene signatures between CD4⁺PD-1⁺ vs. PD-1^- cells identified significant upregulation of genes including CXCL13 and MAF, and in pathways including Th1 and Th2, cross talk between dendritic cells and NK cells, B cell development and antigen presentation. Gene signatures from early RA ST before and after six-month tDMARD treatment revealed downregulation of the CD4⁺PD-1⁺ signatures following treatment, identifying a mechanism through which tDMARDs exert their effect by influencing T cell populations. Furthermore, we identify factors associated with B cell help that are enhanced in the ST compared with PBMCs, highlighting their importance in driving synovial inflammation.

Cytotoxic CD8+ T cells target citrullinated antigens in rheumatoid arthritis

The immune mechanisms that mediate synovitis and joint destruction in rheumatoid arthritis (RA) remain poorly defined. Although increased levels of CD8+ T cells have been described in RA, their function in pathogenesis remains unclear. Here we perform single cell transcriptome and T cell receptor (TCR) sequencing of CD8+ T cells derived from anti-citrullinated protein antibodies (ACPA)+ RA blood. We identify GZMB+CD8+ subpopulations containing large clonal lineage expansions that express cytotoxic and tissue homing transcriptional programs, while a GZMK+CD8+ memory subpopulation comprises smaller clonal expansions that express effector T cell transcriptional programs. We demonstrate RA citrullinated autoantigens presented by MHC class I activate RA blood-derived GZMB+CD8+ T cells to expand, express cytotoxic mediators, and mediate killing of target cells. We also demonstrate that these clonally expanded GZMB+CD8+ cells are present in RA synovium. These findings suggest that cytotoxic CD8+ T cells targeting citrullinated antigens contribute to synovitis and joint tissue destruction in ACPA+ RA.

T-cell exhaustion in immune-mediated inflammatory diseases: New implications for immunotherapy

Immune-mediated inflammatory diseases(IMIDs) are referred to as highly disabling chronic diseases affecting different organs and systems. Inappropriate or excessive immune responses with chronic inflammation are typical manifestations. Usually in patients with chronic infection and cancer, due to long-term exposure to persistent antigens and inflammation microenvironment, T-cells are continuously stimulated and gradually differentiate into an exhausted state. Exhausted T-cells gradually lose effector function and characteristics of memory T-cells. However, existing studies have found that exhausted T-cells are not only present in the infection and tumor environment, but also in autoimmunity, and are associated with better prognosis of IMIDs. This suggests new prospects for the application of this reversible process of T-cell exhaustion in the treatment of IMID. This review will focus on the research progress of T-cell exhaustion in several IMIDs and its potential application for diagnosis and treatment in IMIDs.

Granzyme K+ CD8 T cells form a core population in inflamed human tissue

T cell-derived pro-inflammatory cytokines are a major driver of rheumatoid arthritis (RA) pathogenesis. Although these cytokines have traditionally been attributed to CD4 T cells, we have found that CD8 T cells are notably abundant in synovium and make more interferon (IFN)-γ and nearly as much tumor necrosis factor (TNF) as their CD4 T cell counterparts. Furthermore, using unbiased high-dimensional single-cell RNA-seq and flow cytometric data, we found that the vast majority of synovial tissue and synovial fluid CD8 T cells belong to an effector CD8 T cell population characterized by high expression of granzyme K (GzmK) and low expression of granzyme B (GzmB) and perforin. Functional experiments demonstrate that these GzmK+ GzmB+ CD8 T cells are major cytokine producers with low cytotoxic potential. Using T cell receptor repertoire data, we found that CD8 GzmK+ GzmB+ T cells are clonally expanded in synovial tissues and maintain their granzyme expression and overall cell state in blood, suggesting that they are enriched in tissue but also circulate. Using GzmK and GzmB signatures, we found that GzmK-expressing CD8 T cells were also the major CD8 T cell population in the gut, kidney, and coronavirus disease 2019 (COVID-19) bronchoalveolar lavage fluid, suggesting that they form a core population of tissue-associated T cells across diseases and human tissues. We term this population tissue-enriched expressing GzmK or TteK CD8 cells. Armed to produce cytokines in response to both antigen-dependent and antigen-independent stimuli, CD8 TteK cells have the potential to drive inflammation.

Intersection Between Large Granular Lymphocyte Leukemia and Rheumatoid Arthritis

Large granular lymphocyte (LGL) leukemia, a rare hematologic malignancy, has long been associated with rheumatoid arthritis (RA), and the diseases share numerous common features. This review aims to outline the parallels and comparisons between the diseases as well as discuss the potential mechanisms for the relationship between LGL leukemia and RA. RA alone and in conjunction with LGL leukemia exhibits cytotoxic T-cell (CTL) expansions, HLA-DR4 enrichment, RA-associated autoantibodies, female bias, and unknown antigen specificity of associated T-cell expansions. Three possible mechanistic links between the pathogenesis of LGL leukemia and RA have been proposed, including LGL leukemia a) as a result of longstanding RA, b) as a consequence of RA treatment, or c) as a driver of RA. Several lines of evidence point towards LGL as a driver of RA. CTL involvement in RA pathogenesis is evidenced by citrullination and granzyme B cleavage that modifies the repertoire of self-protein antigens in target cells, particularly neutrophils, killed by the CTLs. Further investigations of the relationship between LGL leukemia and RA are warranted to better understand causal pathways and target antigens in order to improve the mechanistic understanding and to devise targeted therapeutic approaches for both disorders.

Phenotypic, transcriptomic and functional profiling reveal reduced activation thresholds of CD8+ T cells in giant cell arteritis

OBJECTIVES

Evidence from temporal artery tissue and blood suggests involvement of CD8+ T cells in the pathogenesis of GCA, but their exact role is poorly understood. Therefore, we performed a comprehensive analysis of circulating and lesional CD8+ T cells in GCA patients.

METHODS

Circulating CD8+ T cells were analysed for differentiation status (CD45RO, CCR7), markers of activation (CD69 and CD25) and proliferation (Ki-67) in 14 newly diagnosed GCA patients and 18 healthy controls by flow cytometry. Proliferative capacity of CD8+ T cells upon anti-CD3 and anti-CD3/28 in vitro stimulation was assessed. Single-cell RNA sequencing of peripheral blood mononuclear cells of patients and controls (n = 3 each) was performed for mechanistic insight. Immunohistochemistry was used to detect CD3, CD8, Ki-67, TNF-α and IFN-γ in GCA-affected tissues.

RESULTS

GCA patients had decreased numbers of circulating effector memory CD8+ T cells but the percentage of Ki-67-expressing effector memory CD8+ T cells was increased. Circulating CD8+ T cells from GCA patients demonstrated reduced T cell receptor activation thresholds and displayed a gene expression profile that is concurrent with increased proliferation. CD8+ T cells were detected in GCA temporal arteries and aorta. These vascular CD8+ T cells expressed IFN-γ but not Ki-67.

CONCLUSION

In GCA, circulating effector memory CD8+ T cells demonstrate a proliferation-prone phenotype. The presence of CD8+ T cells in inflamed arteries seems to reflect recruitment of circulating cells rather than local expansion. CD8+ T cells in inflamed tissues produce IFN-γ, which is an important mediator of local inflammatory responses in GCA.

Molecular Mechanisms of Immunosenescene and Inflammaging: Relevance to the Immunopathogenesis and Treatment of Multiple Sclerosis

Aging is characterized, amongst other features, by a complex process of cellular senescence involving both innate and adaptive immunity, called immunosenescence and associated to inflammaging, a low-grade chronic inflammation. Both processes fuel each other and partially explain increasing incidence of cancers, infections, age-related autoimmunity, and vascular disease as well as a reduced response to vaccination. Multiple sclerosis (MS) is a lifelong disease, for which considerable progress in disease-modifying therapies (DMTs) and management has improved long-term survival. However, disability progression, increasing with age and disease duration, remains. Neurologists are now involved in caring for elderly MS patients, with increasing comorbidities. Aging of the immune system therefore has relevant implications for MS pathogenesis, response to DMTs and the risks mediated by these treatments. We propose to review current evidence regarding markers and molecular mechanisms of immunosenescence and their relevance to understanding MS pathogenesis. We will focus on age-related changes in the innate and adaptive immune system in MS and other auto-immune diseases, such as systemic lupus erythematosus and rheumatoid arthritis. The consequences of these immune changes on MS pathology, in interaction with the intrinsic aging process of central nervous system resident cells will be discussed. Finally, the impact of immunosenescence on disease evolution and on the safety and efficacy of current DMTs will be presented.

OX40-Fc Fusion Protein Alleviates PD-1-Fc-Aggravated Rheumatoid Arthritis by Inhibiting Inflammatory Response

BACKGROUND

Researches have confirmed that the abnormal signals of OX40 and PD-1 lead to the changes of T cell biological behavior, thus participating the immunopathological process of RA. However, the pathogenesis of RA immunopathological process has not been clarified yet.

METHODS

30 DBA/1 mice were randomly divided into 5 groups (6 mice per group): control group, collagen-induced arthritis (CIA) group, PD-1-Fc/CIA group, OX40-Fc/CIA group, and PD-1-Fc + OX40-Fc/CIA group. The pathological changes in mice joints were observed by H&E staining. The proportion of CD4+ T, CD8+ T, CD28+, and CD19+ cells in peripheral blood mononuclear cells (PBMCs) was detected by flow cytometry. Serum inflammatory factors (CRP, IL-2, IL-4, IL-1β, INF-γ) and bone metabolism-related genes (CTX-I, TRACP-5b, BALP) were detected by ELISA assay. Western blotting was applied to measure the NF-κB signaling pathway-related protein (p-IKKβ, p-IκBα, p50) expression in synovial tissue of mice joint.

RESULTS

Compared with the control group, CIA mice showed significant increases in arthritis score and pathological score. In the CIA group, a marked decrease was identified in the proportion of CD8+ T, CD19+, and CD68+ cells. Additionally, the CIA group was associated with upregulation of secretion of inflammatory factors in serum and expression of bone metabolism-related genes and NF-κB pathway-related proteins. Compared with the CIA group, the same indexes above showed a further aggravation in the PD-1-Fc group while all indexes improved in the OX40-Fc group. Besides, OX40-Fc fusion protein slowed down significantly the further deterioration of CIA mouse pathological process caused by PD-1-Fc fusion protein.

CONCLUSION

OX40-Fc fusion protein alleviates PD-1-Fc-aggravated RA by inhibiting inflammatory response. This research provides biological markers with clinical significance for diagnosis and prognosis of RA, as well as offers theoretical and experimental foundation to the new targets for immune intervention.

Tc17 CD8+ T cells accumulate in murine atherosclerotic lesions, but do not contribute to early atherosclerosis development

AIMS

CD8+ T cells can differentiate into subpopulations that are characterized by a specific cytokine profile, such as the Tc17 population that produces interleukin-17. The role of this CD8+ T-cell subset in atherosclerosis remains elusive. In this study, we therefore investigated the contribution of Tc17 cells to the development of atherosclerosis.

METHODS AND RESULTS

Flow cytometry analysis of atherosclerotic lesions from apolipoprotein E-deficient mice revealed a pronounced increase in RORγt+CD8+ T cells compared to the spleen, indicating a lesion-specific increase in Tc17 cells. To study whether and how the Tc17 subset affects atherosclerosis, we performed an adoptive transfer of Tc17 cells or undifferentiated Tc0 cells into CD8-/- low-density lipoprotein receptor-deficient mice fed a Western-type diet. Using flow cytometry, we showed that Tc17 cells retained a high level of interleukin-17A production in vivo. Moreover, Tc17 cells produced lower levels of interferon-γ than their Tc0 counterparts. Analysis of the aortic root revealed that the transfer of Tc17 cells did not increase atherosclerotic lesion size, in contrast to Tc0-treated mice.

CONCLUSION

These findings demonstrate a lesion-localized increase in Tc17 cells in an atherosclerotic mouse model. Tc17 cells appeared to be non-atherogenic, in contrast to their Tc0 counterpart.

Recent Advances in Understanding the Pathogenesis of Rheumatoid Arthritis: New Treatment Strategies

Rheumatoid arthritis (RA) is considered a chronic systemic, multi-factorial, inflammatory, and progressive autoimmune disease affecting many people worldwide. While patients show very individual courses of disease, with RA focusing on the musculoskeletal system, joints are often severely affected, leading to local inflammation, cartilage destruction, and bone erosion. To prevent joint damage and physical disability as one of many symptoms of RA, early diagnosis is critical. Auto-antibodies play a pivotal clinical role in patients with systemic RA. As biomarkers, they could help to make a more efficient diagnosis, prognosis, and treatment decision. Besides auto-antibodies, several other factors are involved in the progression of RA, such as epigenetic alterations, post-translational modifications, glycosylation, autophagy, and T-cells. Understanding the interplay between these factors would contribute to a deeper insight into the causes, mechanisms, progression, and treatment of the disease. In this review, the latest RA research findings are discussed to better understand the pathogenesis, and finally, treatment strategies for RA therapy are presented, including both conventional approaches and new methods that have been developed in recent years or are currently under investigation.

Immune cell profiles in synovial fluid after anterior cruciate ligament and meniscus injuries

Background

Anterior cruciate ligament (ACL) and meniscus tears are common knee injuries. Despite the high rate of post-traumatic osteoarthritis (PTOA) following these injuries, the contributing factors remain unclear. In this study, we characterized the immune cell profiles of normal and injured joints at the time of ACL and meniscal surgeries.

Methods

Twenty-nine patients (14 meniscus-injured and 15 ACL-injured) undergoing ACL and/or meniscus surgery but with a normal contralateral knee were recruited. During surgery, synovial fluid was aspirated from both normal and injured knees. Synovial fluid cells were pelleted, washed, and stained with an antibody cocktail consisting of fluorescent antibodies for cell surface proteins. Analysis of immune cells in the synovial fluid was performed by polychromatic flow cytometry. A broad spectrum immune cell panel was used in the first 10 subjects. Based on these results, a T cell-specific panel was used in the subsequent 19 subjects.

Results

Using the broad spectrum immune cell panel, we detected significantly more total viable cells and CD3 T cells in the injured compared to the paired normal knees. In addition, there were significantly more injured knees with T cells above a 500-cell threshold. Within the injured knees, CD4 and CD8 T cells were able to be differentiated into subsets. The frequency of total CD4 T cells was significantly different among injury types, but no statistical differences were detected among CD4 and CD8 T cell subsets by injury type.

Conclusions

Our findings provide foundational data showing that ACL and meniscus injuries induce an immune cell-rich microenvironment that consists primarily of T cells with multiple T helper phenotypes. Future studies investigating the relationship between immune cells and joint degeneration may provide an enhanced understanding of the pathophysiology of PTOA following joint injury.

Therapeutic effect of various ginsenosides on rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is an autoimmune disease which causes disability and threatens the health of humans. Therefore, it is of great significance to seek novel effective drugs for RA. It has been reported that various ginsenoside monomers are able to treat RA. However, it is still unclear which ginsenoside is the most effective and has the potential to be developed into an anti-RA drug.

Methods

The ginsenosides, including Rg1, Rg3, Rg5, Rb1, Rh2 and CK, were evaluated and compared for their therapeutic effect on RA. In in vitro cell studies, methotrexate (MTX) and 0.05% dimethyl sulfoxide (DMSO) was set as a positive control group and a negative control group, respectively. LPS-induced RAW264.7 cells and TNF-α-induced HUVEC cells were cultured with MTX, DMSO and six ginsenosides, respectively. Cell proliferation was analyzed by MTT assay and cell apoptosis was carried out by flow cytometry. CIA mice model was developed to evaluate the therapeutic efficacy of ginsenosides. The analysis of histology, immunohistochemistry, flow cytometry and cytokine detections of the joint tissues were performed to elucidate the action mechanisms of ginsenosides.

Results

All six ginsenosides showed good therapeutic effect on acute arthritis compared with the negative control group, Ginsenoside CK provided the most effective treatment ability. It could significantly inhibit the proliferation and promote the apoptosis of RAW 264.7 and HUVEC cells, and substantially reduce the swelling, redness, functional impairment of joints and the pathological changes of CIA mice. Meanwhile, CK could increase CD8 + T cell to down-regulate the immune response, decrease the number of activated CD4 + T cell and proinflammatory M1-macrophages, thus resulting in the inhibition of the secretion of proinflammatory cytokine such as TNF-α and IL-6.

Conclusion

Ginsenoside CK was proved to be a most potential candidate among the tested ginsenosides for the treatment of RA, with a strong anti-inflammation and immune modulating capabilities.

Recent advances on the role of cytotoxic T lymphocytes in the pathogenesis of spondyloarthritis

Spondyloarthritis (SpA) is a chronic inflammatory disorder with complex etiology and pathogenesis. Its pathogenesis likely involves a combination of different factors. These factors include host genetics, environmental triggers, and immune and microbiota dysregulation. One of the strongest genetic associations with SpA is HLA-B27, implicating the involvement of cytotoxic T lymphocytes (CTLs) in SpA pathogenesis. Despite this discovery dating back decades ago, the CTL compartment that underlies SpA inflammation has yet to be fully defined until recently. Indeed, recent published studies support a significant role that CTLs play in contributing to chronic joint inflammation, which is a hallmark of SpA pathology. In this review chapter, we discuss emerging evidence that supports a newfound role of CTLs in SpA pathogenesis. This emerging evidence includes enrichment of CTL-related genes from genome-wide association studies, overrepresentation of pathogenic synovial CTL phenotype, clonal expansion, and immune dysregulation of CTLs. The discoveries of this mounting evidence suggest that CTL homeostasis is altered, and a disrupted adaptive immunity underlies the chronic inflammatory features seen in SpA pathology.

CD8+ T Lymphocytes: Crucial Players in Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease associated with damage to multiple organs and glands. The most common clinical manifestations are dry eyes, dry mouth, and enlarged salivary glands. Currently, CD4+ T lymphocytes are considered to be key factors in the immunopathogenesis of pSS, but various studies have shown that CD8+ T lymphocytes contribute to acinar injury in the exocrine glands. Therefore, in this review, we discussed the classification and features of CD8+ T lymphocytes, specifically describing the role of CD8+ T lymphocytes in disease pathophysiology. Furthermore, we presented treatment strategies targeting CD8+ T cells to capitalize on the pathogenic and regulatory potential of CD8+ T lymphocytes in SS to provide promising new strategies for this inflammatory disease.

High-flow hydrogen inhalation might suppresses the immune function of middle-aged participants: a self-controlled study

Hydrogen inhalation therapy has been proven to be safe and effective in disease treatment in multiple clinical reports, but the gas flow rates used in different studies vary greatly. Since there is no upper limit for the safe concentration of hydrogen, this study tested the effects of high-flow (not high concentration) hydrogen inhalation on immune function. From October 2019 to January 2020, 20 adult participants (31-60 years old) were enrolled in a self-controlled study to check the immune function in peripheral blood lymphocyte subsets before and after a 2-week hydrogen inhalation protocol. The participants inhaled hydrogen for 2 or 4 hours each day. After 2 weeks of hydrogen inhalation, statistically significant changes were observed in follicular helper T cells, helper and cytotoxic T cells, natural killer and natural killer T cells, and gamma delta T cells, generally suggesting a decrease in their proportions. These results show that high-flow hydrogen inhalation has an inhibitory effect on the immune function of healthy participants. The study protocol received ethical approval from the Ethics Committee of Fuda Cancer Hospital, Jinan University on December 7, 2018 (approval No. Fuda20181207).

Comprehensive Phenotyping of Peripheral Blood T Lymphocytes in Healthy Mice

T lymphocytes play a central role in antigen-specific immune responses. They modulate the function of different immune cells both through a direct contact (receptor binding) and through the secretion of cytokines. At the same time, they are deeply involved in the direct killing of aberrant target cells. T lymphocytes derive from a bone marrow precursor that migrates in the thymus where the main differentiation steps take place. Mature CD4 and CD8 single-positive cells, then, leave the thymus to reach the secondary lymphoid organs. T-cell subsets and their maturation steps can be identified mainly based on the expression of extracellular markers, intracellular transcription factors and cytokine production profiles. In this review, we report, from a cytometric point of view, an overview of the most important T-cell subpopulations and their differentiation state. © 2020 International Society for Advancement of Cytometry.

The role of CD8 + T lymphocytes in chronic obstructive pulmonary disease: a systematic review

OBJECTIVE AND DESIGN

This systematic review aims to establish the role of CD8 + T lymphocytes in COPD.

METHODS

Forty-eight papers published in the last 15 years were identified for inclusion.

RESULTS

CD8 + T-cells are increased in the lungs of patients with COPD (17 studies, 16 positive) whereas in the circulation, findings were inconclusive. Activation of CD8 + T-cells was enhanced in lungs (four studies, three positive) but cell phenotype was unclear. There was substantial evidence of a higher proportion of type 1 CD8 + (Tc1) cells in COPD (11 studies, 9 positive), though the population of type 2 (Tc2) cells was also increased (5 studies, 4 positive). CD8 + T-cells in COPD exhibited greater expression of cytotoxic proteins (five studies, five positive). Studies assessed a variety of questions so evidence was insufficient to draw firm conclusions. The role of CD8 + T-cells at acute exacerbation of COPD and also their contribution to alveolar destruction can only be hypothesised at this stage.

CONCLUSIONS

Not only is the number of CD8 + T-cells increased in COPD, these cells have increased capacity to exert effector functions and are likely to contribute to disease pathogenesis. Several mechanisms highlighted show promise for future investigation to consolidate current knowledge.

cDC1 are required for the initiation of collagen-induced arthritis

Rheumatoid arthritis (RA) is chronic autoimmune disease which etiology remains unknown. Several cell types have been described to potentiate/aggravate the arthritic process however the initiating event in synovial inflammation is still elusive. Dendritic cells (DCs) are essential for the initiation of primary immune responses and thus we hypothesized that these cells might be crucial for RA induction. DCs are a heterogeneous population of cells comprising different subsets with distinct phenotype and function. Here we investigated which DC subset(s) is/are crucial for the initiation of the arthritic process.

We have previously demonstrated that Flt3−/− mice, with reduced DCs, were protected from collagen induced arthritis (CIA). Here we have shown that GM-CSF derived DCs in Flt3L−/− mice are functional but not sufficient to induce arthritis. Batf3^−/− mice lacking both CD103⁺ and CD8α⁺ cDC1 were resistant to collagen induced arthritis (CIA), demonstrating that this DC subset is crucial for arthritis development. CEP-701 (a Flt3L inhibitor) treatment prevented CIA induction, and reduced dramatically the numbers CD103⁺ cDC1s present in the lymph nodes and synovium. Hence this study identified cDC1 as the main subset orchestrating the initiation of cell-mediated immunity in arthritis.

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Flt3L independent DCs present in Flt3L−/− mice are functional but are not sufficient to induce arthritis.

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BATF3−/− mice lacking cDC1 are protected from arthritis development indicating that cDC1 are necessary for disease induction.

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Treatment with a Flt3L inhibitor, CEP701, reduced cDC1 populations and prevented arthritis induction.

Synovial fluid CD69+CD8+ T cells with tissue-resident phenotype mediate perforin-dependent citrullination in rheumatoid arthritis

Objectives

Although the importance of tissue-resident memory T (T_RM) cells in organ-specific chronic inflammation has been recognised, little is known about their role in rheumatoid arthritis (RA). Here, we examined the characteristics of synovial fluid CD8⁺ T cells that express canonical T_RM markers CD69 and CD103, and their role in the pathogenesis of RA.

Methods

Synovial fluid mononuclear cells (SFMCs) were obtained from patients with RA. Flow cytometric analysis of surface markers and cytotoxic molecules of CD8⁺ T cells was performed. TCR repertoire of CD8⁺ T cells was analysed by TCRVβ CDR3 sequencing. Citrullination with the formation of neutrophil extracellular trap (NET) was evaluated by immunofluorescence staining.

Results

The frequency of CD8⁺ T cells was increased in SFMCs, and these CD8⁺ T cells were primarily comprised of CD45RA^- memory T cells expressing CD69 and/or CD103. CD69⁺CD8⁺ T cells exhibited T_RM phenotypes, including upregulation of CXCR6, CD49a and CD101, and downregulation of S1PR1 and KLF2. TCR repertoire analysis showed that these cells were an oligoclonally expanded population with increased expression of cytotoxic molecules. The treatment of neutrophils with supernatant from IL-15-stimulated CD69⁺CD8⁺ T cells induced perforin-mediated histone citrullination and NET formation irrespective of their CD103 expression. The frequency of perforin-expressing cells among CD69⁺CD8⁺ T cells in SFMCs was significantly higher in patients with anti-citrullinated protein antibody (ACPA) than in those without ACPA.

Conclusion

CD69⁺CD8⁺ T cells in the SFMCs of RA patients exhibit T_RM-like features. These cells may participate in the pathogenesis of RA via perforin-mediated citrullination.

Germline Features Associated with Immune Infiltration in Solid Tumors

The immune composition of the tumor microenvironment influences response and resistance to immunotherapies. While numerous studies have identified somatic correlates of immune infiltration, germline features that associate with immune infiltrates in cancers remain incompletely characterized. We analyze seven million autosomal germline variants in the TCGA cohort and test for association with established immune-related phenotypes that describe the tumor immune microenvironment. We identify one SNP associated with the amount of infiltrating follicular helper T cells; 23 candidate genes, some of which are involved in cytokine-mediated signaling and others containing cancer-risk SNPs; and networks with genes that are part of the DNA repair and transcription elongation pathways. In addition, we find a positive association between polygenic risk for rheumatoid arthritis and amount of infiltrating CD8+ T cells. Overall, we identify multiple germline genetic features associated with tumor-immune phenotypes and develop a framework for probing inherited features that contribute to differences in immune infiltration.

Characterization of Phenotypes and Functional Activities of Leukocytes From Rheumatoid Arthritis Patients by Mass Cytometry

Background: Rheumatoid arthritis (RA) is the most common autoimmune rheumatic disease and leads to persistent chronic inflammation. The pathophysiology of the disease is complex, involving both adaptive and innate immunity. Among innate immune cells, neutrophils have been rarely studied due to their sensitivity to freezing and they are not being collected after Ficoll purification. Methods: We used mass cytometry to perform a multidimensional phenotypic characterization of immune cells from RA-treated patients, which included the simultaneous study of 33 intra- or extra-cellular markers expressed by leukocytes. We were able to focus our study on innate immune cells, especially neutrophils, due to a specific fixation method before freezing. In addition, blood samples were stimulated or not with various TLR agonists to evaluate whether RA-dependent chronic inflammation can lead to immune-cell exhaustion. Results: We show that RA induces the presence of CD11blow neutrophils (33.7 and 9.2% of neutrophils in RA and controls, respectively) associated with the duration of disease. This subpopulation additionally exhibited heterogeneous expression of CD16. We also characterized a CD11ahigh Granzyme Bhigh T-cell subpopulation possibly associated with disease activity. There was no difference in cytokine expression after the stimulation of immune cells by TLR agonists between RA and controls. Conclusion: Mass cytometry and our fixation method allowed us to identify two potential new blood subpopulations of neutrophils and T-cells, which could be involved in RA pathology. The phenotypes of these two potential new subpopulations need to be confirmed using other experimental approaches, and the exact role of these subpopulations is yet to be studied.

Anti-PD-1 Immunotherapy-Induced Flare of a Known Underlying Relapsing Vasculitis Mimicking Recurrent Cancer

Safe use of immune checkpoint blockade in patients with cancer and autoimmune disorders requires a better understanding of the pathophysiology of immunologic activation. We describe the immune correlates of reactivation of granulomatosis with polyangiitis (GPA)-an antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis-in a patient with metastatic urothelial carcinoma treated with pembrolizumab. After PD-1 blockade, an inflammatory pulmonary nodule demonstrated a granulomatous, CD4+ T-cell infiltrate, correlating with increased CD4+ and CD8+ naïve memory cells in the peripheral blood without changes in other immune checkpoint receptors. Placed within the context of the existing literature on GPA and disease control, our findings suggest a key role for PD-1 in GPA self-tolerance and that selective strategies for immunotherapy may be needed in patients with certain autoimmune disorders. We further summarize the current literature regarding reactivation of autoimmune disorders in patients undergoing immune checkpoint blockade, as well as potential immunosuppressive strategies to minimize the risks of further vasculitic reactivation upon rechallenge with anti-PD-1 blockade. KEY POINTS: Nonspecific imaging findings in patients with cancer and rheumatological disorders may require biopsy to distinguish underlying pathology.Patients with rheumatologic disorders have increased risk of reactivation with PD-(L)1 immune checkpoint blockade, requiring assessment of disease status before starting treatment.Further study is needed to evaluate the efficacy of treatment regimens in preventing and controlling disease reactivation.

T-Cell Compartmentalization and Functional Adaptation in Autoimmune Inflammation: Lessons From Pediatric Rheumatic Diseases

Chronic inflammatory diseases are characterized by a disturbed immune balance leading to recurring episodes of inflammation in specific target tissues, such as the joints in juvenile idiopathic arthritis. The tissue becomes infiltrated by multiple types of immune cell, including high numbers of CD4 and CD8 T-cells, which are mostly effector memory cells. Locally, these T-cells display an environment-adapted phenotype, induced by inflammation- and tissue-specific instructions. Some of the infiltrated T-cells may become tissue resident and play a role in relapses of inflammation. Adaptation to the environment may lead to functional (re)programming of cells and altered cellular interactions and responses. For example, specifically at the site of inflammation both CD4 and CD8 T-cells can become resistant to regulatory T-cell-mediated regulation. In addition, CD8 and CD4 T-cells show a unique profile with pro- and anti-inflammatory features coexisting in the same compartment. Also regulatory T-cells are neither homogeneous nor static in nature and show features of functional differentiation, and plasticity in inflammatory environments. Here we will discuss the recent insights in T-cell functional specialization, regulation, and clonal expansion in local (tissue) inflammation.

Effector Functions of CD4+ T Cells at the Site of Local Autoimmune Inflammation-Lessons From Rheumatoid Arthritis

Infiltration of memory CD4+ T cells in synovial joints of Rheumatoid Arthritis (RA) patients has been reported since decades. Moreover, several genome wide association studies (GWAS) pinpointing a key genetic association between the HLA-DR locus and RA have led to the generally agreed hypothesis that CD4+ T cells are directly implicated in the disease. Still, RA is a heterogeneous disease and much effort has been made to understand its different facets. T cell differentiation is driven by mechanisms including antigen stimulation, co-stimulatory signals and cytokine milieu, all of which are abundant in the rheumatic joint, implying that any T cells migrating into the joint may be further affected locally. In parallel to the characterization and classification of T-cell subsets, the contribution of different effector T cells to RA has been investigated in numerous studies though sometimes with contradictory results. In particular, the frequency of Th1 and Th17 cells has been assessed in the synovial joints with various results that could, at least partly, be explained by the stage of the disease. For regulatory T cells, it is largely accepted that they accumulate in RA synovial fluid and that the equilibrium between regulatory T cells and effector cells is a key factor in controlling inflammation processes involved in RA. Recent phenotypic studies describe the possible implication of a novel subset of peripheral T helper cells (Tph) important for T-B cell cross talk and plasma cell differentiation in the RA joint of ACPA+ (autoantibodies against citrullinated proteins) RA patients. Finally, cytotoxic CD4+ T cells, historically described as increased in the peripheral blood of RA patients have attracted new attention in the last years. In view of the recently identified peripheral T-cell subsets, we will integrate immunological data as well as information on genetic variants and therapeutic strategy outcomes into our current understanding of the width of effector T cells. We will also integrate tissue-resident memory T cell aspects, and discuss similarities and differences with inflammatory conditions in skin (psoriasis) and mucosal organs (Crohn's disease).

PD-1+CD8+ T cells are clonally expanding effectors in human chronic inflammation

Chronic inflammatory diseases are characterized by recurrent inflammatory attacks in the tissues mediated by autoreactive T cells. Identity and functional programming of CD8+ T cells at the target site of inflammation still remain elusive. One key question is whether, in these antigen-rich environments, chronic stimulation leads to CD8+ T cell exhaustion comparable to what is observed in infectious disease contexts. In the synovial fluid (SF) of juvenile idiopathic arthritis (JIA) patients, a model of chronic inflammation, an overrepresentation of PD-1+CD8+ T cells was found. Gene expression profiling, gene set enrichment analysis, functional studies, and extracellular flux analysis identified PD-1+CD8+ T cells as metabolically active effectors, with no sign of exhaustion. Furthermore, PD-1+CD8+ T cells were enriched for a tissue-resident memory (Trm) cell transcriptional profile and demonstrated increased clonal expansion compared with the PD-1- counterpart, suggesting antigen-driven expansion of locally adapted cells. Interestingly, this subset was also found increased in target tissues in other human chronic inflammatory diseases. These data indicate that local chronic inflammation drives the induction and expansion of CD8+ T cells endowed with potential detrimental properties. Together, these findings lay the basis for investigation of PD-1-expressing CD8+ T cell targeting strategies in human chronic inflammatory diseases.

Therapeutic effects of anti-CD154 antibody in cynomolgus monkeys with advanced rheumatoid arthritis

Rheumatoid arthritis is one major chronic inflammatory systemic autoimmune disease. The CD154-CD40 interactions play a critical role in the regulation of immune responses and the maintenance of autoimmunity. Therefore, we aimed to determine whether anti-CD154 antibody treatment show positive effects on immunomodulation and clinical improvement of sustained severe rheumatoid arthritis in cynomolgus monkeys. Arthritis was induced using chicken type II collagen (CII) and arthritic monkey were divided into control and anti-CD154 treatment groups based on their concentrations of anti-CII antibodies on week 7 post-immunization. Blood and tissue samples were collected on week 16 post-immunization. Anti-CD154 antibody treatment improved arthritis and movement, and significantly decreased the numbers of proliferating B cells and the serum levels of anti-type II collagen antibody and sCD154 compared with non-treatment group. Further anti-CD154 antibody treatment significantly decreased the percentage of CD4+ cells and the ratio of CD4+ to CD8+ T cells and significantly increased the percentage of CD8+ cells and effector memory CD8+ cells in peripheral blood. We have shown for the first time in a nonhuman primate model of RA that CD154 blockade has beneficial effects. This study might be valuable as preclinical data of CD154 blockade in nonhuman primate models of severe rheumatoid arthritis.

Interleukin-7 Induces Osteoclast Formation via STAT5, Independent of Receptor Activator of NF-kappaB Ligand

Interleukin-7 (IL-7), which is required for the development and survival of T cells in the thymus and periphery, plays a role in joint destruction. However, it remains unclear how IL-7 affects osteoclast formation. Thus, we investigated the mechanism by which IL-7 induced osteoclast formation through IL-7 receptor α (IL-7Rα) in osteoclast precursors. We cultured peripheral blood mononuclear cells or synovial fluid mononuclear cells with IL-7 in the presence or absence of an appropriate inhibitor to analyze osteoclast formation. We also constructed IL-7Rα-expressing RAW264.7 cells to uncover the mechanism(s) by which IL-7 induced osteoclast formation differed from that of receptor activator of nuclear factor κB ligand (RANKL). We found that IL-7 induced osteoclast formation of human monocytes from peripheral blood or synovial fluid in a RANKL-independent and a signal transducer and activator of transcription 5 (STAT5)-dependent manner. IL-7-induced osteoclasts had unique characteristics, such as small, multinucleated tartrate-resistant acid phosphatase positive cells and no alterations even when RANKL was added after IL-7 pretreatment. RAW264.7 cells, if overexpressing IL-7Rα, also were able to differentiate into osteoclasts by IL-7 through a STAT5 signaling pathway. Furthermore, IL-7-induced osteoclast formation was repressed by inhibitors of the IL-7R signaling molecules Janus kinase and STAT5. Our findings demonstrate that IL-7 is a truly osteoclastogenic factor, which may induce osteoclast formation via activation of STAT5, independent of RANKL. We also suggest the possibility that an IL-7R pathway blocker could alleviate joint damage by inhibiting osteoclast formation, especially in inflammatory conditions.

Inflammatory cytokines compromise programmed cell death-1 (PD-1)-mediated T cell suppression in inflammatory arthritis through up-regulation of soluble PD-1

The programmed cell death 1 (PD‐1) receptor plays a major role in regulating T cell activation. Our aim was to determine how inflammation influences PD‐1‐mediated T cell suppression. Flow cytometry analysis of rheumatoid arthritis (RA) and psoriatic arthritis (PsA) synovial fluid (SF) mononuclear cells showed an increase in the percentage of PD‐1⁺ cells within the CD4⁺ and CD8⁺ T cell compartment compared to paired peripheral blood (PB). Upon in‐vitro T cell receptor (TCR) stimulation of healthy control (HC) CD4⁺ T cells in the presence of plate‐bound PD‐L1fc chimera, significantly decreased proliferation and interferon (IFN)‐γ secretion was observed. In contrast, CD4⁺ T cells from RA and PsA PB and SF appeared resistant to such PD‐1‐mediated inhibition. Addition of the proinflammatory cytokines tumour necrosis factor (TNF)α, interleukin (IL)‐6 and IL‐1β, which were increased in RA and PsA SF compared to osteoarthritis (OA) SF, consistently abrogated PD‐1‐mediated suppression in HC CD4⁺ T cell cultures. This effect was reversed by inhibitors of these cytokines. Soluble PD‐1 (sPD‐1) levels were increased in cell culture supernatants from TNFα and IL‐6‐stimulated cultures compared to untreated controls, and also in RA and PsA, but not in OA, serum and SF. Functionally, addition of sPD‐1fc counteracted PD‐1‐mediated suppression of HC CD4⁺ T cells, and increased T cell proliferation in HC CD4⁺ T cell/monocyte co‐cultures. These in‐vitro findings indicate that CD4⁺ T cells from patients with RA and PsA show increased resistance to PD‐1‐mediated suppression, which may be explained in part by the presence of soluble PD‐1 in the inflammatory environment.

CD8(+) T cells with distinct cytokine-producing features and low cytotoxic activity in eosinophilic and non-eosinophilic chronic rhinosinusitis with nasal polyps

BACKGROUND

CD8(+) T cells are important effectors of cell-mediated immunity; however, their contribution to the pathogenesis of CRS is unclear.

OBJECTIVE

This study aimed to characterize the cytokine-producing features and cytotoxic activity of CD8(+) T cells, and their correlation with inflammation patterns in CRS with nasal polyps.

METHODS

The expression of IFN-γ, IL-4, IL-5, IL-17A, forkhead box P3 (FOXP3), perforin, and granzyme B in CD8(+) T cells was studied by means of flow cytometry, immunohistochemistry, and immunofluorescence. The expression of CD8(+) T-cell subset relevant chemokines and chemokine receptors was detected by means of real-time RT-PCR or ELISA. The cytotoxic activity of sorted CD8(+) T cells was defined by anti-CD3-redirected killing assay.

RESULTS

Compared with controls, elevated percentages of total CD8(+) T cells and cytotoxic T lymphocyte (Tc) 1 (IFN-γ(+) ), Tc2 (IL-4(+) ), and Tc17 (IL-17A(+) ) cell subset, and decreased percentages of FOXP3(+) CD8(+) regulatory T cells, were found in both eosinophilic and non-eosinophilic polyps with a Tc2-skewed and Tc1/Tc17-dominated response in eosinophilic and non-eosinophilic polyps, respectively. Nasal CD8(+) T cells were found to produce similar or even higher levels of IFN-γ and IL-4 compared with CD4(+) T cells. Tc1 and Tc17, and Tc2 (IL-4(+) and IL-5(+) ) cell subset percentages positively correlated with neutrophil and eosinophil counts in sinonasal mucosa, respectively. Strikingly, the expression of perforin and granzyme B and cytotoxic activity were significantly reduced in nasal CD8(+) T cells compared with their counterparts in peripheral blood. The expression of CXCL16, CCL17, and CCL20 positively correlated with Tc1, Tc2, and Tc17 cell subset number in sinonasal mucosa, respectively.

CONCLUSION AND CLINICAL RELEVANCE

CD8(+) T cells have low cytotoxic activity; nevertheless, they are a significant and previously underappreciated source of inflammatory cytokine production in polyps. Different Tc cell subset domination may contribute to distinctly biased granulocyte inflammation in eosinophilic and non-eosinophilic polyps.

CD8(+) T cells in human autoimmune arthritis: the unusual suspects

CD8(+) T cells are key players in the body's defence against viral infections and cancer. To date, data on the role of CD8(+) T cells in autoimmune diseases have been scarce, especially when compared with the wealth of research on CD4(+) T cells. However, growing evidence suggests that CD8(+) T-cell homeostasis is impaired in human autoimmune diseases. The contribution of CD8(+) T cells to autoimmune arthritis is indicated by the close association of MHC class I polymorphisms with disease risk, as well as the correlation between CD8(+) T-cell phenotype and disease outcome. The heterogeneous phenotype, resistance to regulation and impaired regulatory function of CD8(+) T cells - especially at the target organ - might contribute to the persistence of autoimmune inflammation. Moreover, newly identified populations of tissue-resident CD8(+) T cells and their interaction with antigen-presenting cells might have a key role in disease pathology. In this Review, we assess the link between CD8(+) T cells, autoimmune arthritis and the basis of their homeostatic changes under inflammatory conditions. Improved insight into CD8(+) T cell-specific pathogenicity will be essential for a better understanding of autoimmune arthritis and the identification of new therapeutic targets.

Self-Sustained Resistance to Suppression of CD8+ Teff Cells at the Site of Autoimmune Inflammation Can Be Reversed by Tumor Necrosis Factor and Interferon-γ Blockade

OBJECTIVE

Resistance of Teff cells to Treg cell-mediated suppression contributes to the breakdown of peripheral tolerance in the inflamed joints of patients with juvenile idiopathic arthritis (JIA). However, unanswered questions are whether this resistant phenotype is self-sustained and whether CD8+ and CD4+ Teff cells share the same mechanism of resistance to suppression. We undertook this study to investigate intrinsic resistance of CD8+ Teff cells to suppression and to determine how this can be targeted therapeutically.

METHODS

CD8+ or CD4+ Teff cells were cultured with or without antigen-presenting cells (APCs) in Treg cell-dependent and -independent suppression assays. Synovial fluid (SF)-derived Teff cells were crosscultured with peripheral blood (PB) Treg cells from JIA patients or healthy controls. Tumor necrosis factor (TNF) or interferon-γ (IFNγ) blocking agents were used to restore Teff cell responsiveness to suppression.

RESULTS

Suppression of cell proliferation and cytokine production in CD8+ Teff cells from the SF of JIA patients was severely impaired compared to that in CD8+ Teff cells from the PB of JIA patients, regardless of the presence of APCs and CD4+ Teff cells. Similar to CD4+ Teff cells, impaired suppression of CD8+ Teff cells was shown to be an intrinsic feature of this cell population. While TNF blockade restored both CD8+ and CD4+ Teff cell susceptibility to suppression, autocrine release of IFNγ selectively sustained CD8+ Teff cell resistance, which could be relieved by IFNγ blockade.

CONCLUSION

Unlike CD4+ Teff cells, resistance of CD8+ Teff cells to suppression at the site of autoimmune inflammation is maintained by autocrine release of IFNγ, and blockade of IFNγ restores CD8+ Teff cell responsiveness to suppression. These findings indicate a potential therapeutic value of blocking IFNγ to restore immune regulation in JIA.

Human lymph-node CD8(+) T cells display an altered phenotype during systemic autoimmunity

Although many studies are focused on auto-reactive CD4(+) T cells, the precise role of CD8(+) T cells in autoimmunity is poorly understood. The objective of this study is to provide more insight into the phenotype and function CD8(+) T cells during the development of autoimmune disease by studying CD8(+) T cells in human lymph-node biopsies and peripheral blood obtained during the earliest phases of rheumatoid arthritis (RA). Here, we show that lymphoid pro-inflammatory CD8(+) T cells exhibit a less-responsive phenotype already during the earliest phases of autoimmunity compared with healthy individuals. We found an increase in CD8(+) memory T cells in lymphoid tissue during the earliest phases of autoimmunity, even before clinical onset of RA, accompanied by an increased frequency of non-circulating or recently activated (CD69(+)) CD8(+) T cells in lymphoid tissue and peripheral blood. Importantly, lymphoid pro-inflammatory CD8(+)IL-17A(+) T cells displayed a decreased capacity of cytokine production, which was related to disease activity in early RA patients. In addition, a decreased frequency of regulatory CD8(+)IL-10(+) T cells in peripheral blood was also related to disease activity in early RA patients. Our results suggest that different CD8(+) T-cell subsets are affected already during the earliest phases of systemic autoimmunity.

CD8(+) T-Cells as Immune Regulators of Multiple Sclerosis

The vast majority of studies regarding the immune basis of MS (and its animal model, EAE) have largely focused on CD4(+) T-cells as mediators and regulators of disease. Interestingly, CD8(+) T-cells represent the predominant T-cell population in human MS lesions and are oligoclonally expanded at the site of pathology. However, their role in the autoimmune pathologic process has been both understudied and controversial. Several animal models and MS patient studies support a pathogenic role for CNS-specific CD8(+) T-cells, whereas we and others have demonstrated a regulatory role for these cells in disease. In this review, we describe studies that have investigated the role of CD8(+) T-cells in MS and EAE, presenting evidence for both pathogenic and regulatory functions. In our studies, we have shown that cytotoxic/suppressor CD8(+) T-cells are CNS antigen-specific, MHC class I-restricted, IFNγ- and perforin-dependent, and are able to inhibit disease. The clinical relevance for CD8(+) T-cell suppressive function is best described by a lack of their function during MS relapse, and importantly, restoration of their suppressive function during quiescence. Furthermore, CD8(+) T-cells with immunosuppressive functions can be therapeutically induced in MS patients by glatiramer acetate (GA) treatment. Unlike CNS-specific CD8(+) T-cells, these immunosuppressive GA-induced CD8(+) T-cells appear to be HLA-E restricted. These studies have provided greater fundamental insight into the role of autoreactive as well as therapeutically induced CD8(+) T-cells in disease amelioration. The clinical implications for these findings are immense and we propose that this natural process can be harnessed toward the development of an effective immunotherapeutic strategy.

DNA Methylation Regulates the Differential Expression of CX3CR1 on Human IL-7Rαlow and IL-7Rαhigh Effector Memory CD8+ T Cells with Distinct Migratory Capacities to the Fractalkine

DNA methylation is an epigenetic mechanism that modulates gene expression in mammalian cells including T cells. Memory T cells are heterogeneous populations. Human effector memory (EM) CD8(+) T cells in peripheral blood contain two cell subsets with distinct traits that express low and high levels of the IL-7Rα. However, epigenetic mechanisms involved in defining such cellular traits are largely unknown. In this study, we use genome-wide DNA methylation and individual gene expression to show the possible role of DNA methylation in conferring distinct traits of chemotaxis and inflammatory responses in human IL-7Rα(low) and IL-7Rα(high) EM CD8(+) T cells. In particular, IL-7Rα(low) EM CD8(+) T cells had increased expression of CX3CR1 along with decreased DNA methylation in the CX3CR1 gene promoter compared with IL-7Rα(high) EM CD8(+) T cells. Altering the DNA methylation status of the CX3CR1 gene promoter changed its activity and gene expression. IL-7Rα(low) EM CD8(+) T cells had an increased migratory capacity to the CX3CR1 ligand fractalkine compared with IL-7Rα(high) EM CD8(+) T cells, suggesting an important biological outcome of the differential expression of CX3CR1. Moreover, IL-7Rα(low) EM CD8(+) T cells induced fractalkine expression on endothelial cells by producing IFN-γ and TNF-α, forming an autocrine amplification loop. Overall, our study shows the role of DNA methylation in generating unique cellular traits in human IL-7Rα(low) and IL-7Rα(high) EM CD8(+) T cells, including differential expression of CX3CR1, as well as potential biological implications of this differential expression.

Correlation of low CD73 expression on synovial lymphocytes with reduced adenosine generation and higher disease severity in juvenile idiopathic arthritis

Objective

To investigate the expression and adenosine‐generating activity of the ecto‐5′‐nucleotidase CD73 on synovial fluid mononuclear cells (SFMCs) and peripheral blood mononuclear cells (PBMCs) from children with juvenile idiopathic arthritis (JIA).

Methods

Given the role of CD73 protein in the production of antiinflammatory adenosine and its intersection with inflammatory biologic pathways, the expression of CD73 on SF and PB lymphocytes from patients with JIA and PB lymphocytes from healthy control subjects was determined by flow cytometry. The AMPase activity of CD73 on PBMCs and SFMCs was measured by high‐performance liquid chromatography. The effects of cell activation on CD73 expression were examined by in vitro culture of PBMCs.

Results

CD8+ and CD19+ SFMCs from patients with JIA expressed decreased levels of CD73 when compared to paired PBMCs from JIA patients and PBMCs from healthy controls. When the percentages of CD73+ synovial lymphocytes were compared between the 2 clinical forms of oligoarthritis, children with extended oligoarthritis showed lower CD73 expression compared to those with the milder form of the disease. CD8+ SFMCs had a lower ability to produce adenosine from etheno‐AMP compared to CD8+ PBMCs. T cell activation through the T cell receptor (TLR) of CD8+CD73+ cells and B cell activation through TLR‐9 resulted in reduced expression of CD73. This down‐regulation occurred on dividing cells.

Conclusion

These findings show that low CD73 expression on T and B cells in the inflamed site is related to cell proliferation and is correlated with the clinical severity of oligoarticular JIA. The decreased CD73 expression on SFMCs, in turn, results in reduced adenosine production, which leads to a decreased potential for antiinflammatory activity.

Immune regulation of multiple sclerosis by CD8+ T cells

The role of CD8+ T cells in the process of autoimmune pathology has been both understudied and controversial. Multiple sclerosis (MS) is an inflammatory, demyelinating disorder of the central nervous system (CNS) with underlying T cell-mediated immunopathology. CD8+ T cells are the predominant T cells in human MS lesions, showing oligoclonal expansion at the site of pathology. It is still unclear whether these cells represent pathogenic immune responses or disease-regulating elements. Through studies in human MS and its animal model, experimental autoimmune encephalomyelitis (EAE), we have discovered two novel CD8+ T cell populations that play an essential immunoregulatory role in disease: (1) MHC class Ia-restricted neuroantigen-specific "autoregulatory" CD8+ T cells and (2) glatiramer acetate (GA/Copaxone(®)) therapy-induced Qa-1/HLA-E-restricted GA-specific CD8+ T cells. These CD8+ Tregs suppress proliferation of pathogenic CD4+ CD25- T cells when stimulated by their cognate antigens. Similarly, CD8+ Tregs significantly suppress EAE when transferred either pre-disease induction or during peak disease. The mechanism of disease inhibition depends, at least in part, on an antigen-specific, contact-dependent process and works through modulation of CD4+ T cell responses as well as antigen-presenting cells through a combination of cytotoxicity and cytokine-mediated modulation. This review provides an overview of our understanding of CD8+ T cells in immune-mediated disease, focusing particularly on our findings regarding regulatory CD8+ T cells both in MS and in EAE. Clinical relevance of these novel CD8-regulatory populations is discussed, providing insights into a potentially intriguing, novel therapeutic strategy for these diseases.