Yoshinaga Ito

T Cell Receptor Stimulation-Induced Epigenetic Changes and Foxp3 Expression Are Independent and Complementary Events Required for Treg Cell Development

The transcription factor Foxp3 is essential for the development of regulatory T (Treg) cells, yet its expression is insufficient for establishing the Treg cell lineage. Here we showed that Treg cell development was achieved by the combination of two independent processes, i.e., the expression of Foxp3 and the establishment of Treg cell-specific CpG hypomethylation pattern. Both events were induced by T cell receptor stimulation. The Treg cell-type CpG hypomethylation began in the thymus and continued to proceed in the periphery and could be fully established without Foxp3. The hypomethylation was required for Foxp3(+) T cells to acquire Treg cell-type gene expression, lineage stability, and full suppressive activity. Thus, those T cells in which the two events have concurrently occurred are developmentally set into the Treg cell lineage. This model explains how Treg cell fate and plasticity is controlled and can be exploited to generate functionally stable Treg cells.

Gamma/delta T cells are the predominant source of interleukin‐17 in affected joints in collagen‐induced arthritis, but not in rheumatoid arthritis

OBJECTIVE Although interleukin-17 (IL-17)-producing gamma/delta T cells were reported to play pathogenic roles in collagen-induced arthritis (CIA), their characteristics remain unknown. The aim of this study was to clarify whether gamma/delta T cells or CD4+ T cells are the predominant IL-17-producing cells, and to determine what stimulates gamma/delta T cells to secret IL-17 in mice with CIA. The involvement of IL-17-producing gamma/delta T cells in SKG mice with autoimmune arthritis and patients with rheumatoid arthritis (RA) was also investigated. METHODS IL-17-producing cells in the affected joints of mice with CIA were counted by intracellular cytokine staining during 6 distinct disease phases, and these cells were stimulated with various combinations of cytokines or specific antigens to determine the signaling requirements. Similar studies were performed using SKG mice with arthritis and patients with RA. RESULTS Gamma/delta T cells were the predominant population in IL-17-producing cells in the swollen joints of mice with CIA, and the absolute numbers of these cells increased in parallel with disease activity. IL-17-producing gamma/delta T cells expressed CC chemokine receptor 6, were maintained by IL-23 but not by type II collagen in vitro, and were induced antigen independently in vivo. Furthermore, IL-17 production by gamma/delta T cells was induced by IL-1beta plus IL-23 independently of T cell receptor. In contrast to what was observed in mice with CIA, IL-17-producing gamma/delta T cells were nearly absent in the affected joints of SKG mice and patients with RA, and Th1 cells were predominant in the joints of patients with RA. CONCLUSION Gamma/delta T cells were antigen independently stimulated by inflammation at affected joints and produced enhanced amounts of IL-17 to exacerbate arthritis in mice with CIA but not in SKG mice with arthritis or patients with RA.

TREG-cell therapies for autoimmune rheumatic diseases

Naturally occurring Foxp3+CD25+CD4+ regulatory T (TREG) cells maintain immunological self-tolerance and prevent a variety of autoimmune diseases, including rheumatic diseases such as rheumatoid arthritis and systemic lupus erythematosus. In animal models of rheumatic disease, autoimmune responses can be controlled by re-establishing the T-cell balance in favour of TREG cells. Here we discuss three potential strategies for the clinical use of TREG cells to treat autoimmune rheumatic disease: expansion of self-antigen-specific natural TREG cells in vivo; propagation of antigen-specific natural TREG cells ex vivo, by in vitro antigenic stimulation, and subsequent transfer back into the host; or conversion of antigen-specific conventional T cells into TREG cells in vivo or ex vivo. These strategies require depletion of the effector T cells that mediate autoimmunity before initiating TREG-cell-based therapies. Immunotherapies that target TREG cells, and the balance of TREG cells and autoreactive T cells, are therefore an important modality for the treatment of autoimmune rheumatic disease.

Graded Attenuation of TCR Signaling Elicits Distinct Autoimmune Diseases by Altering Thymic T Cell Selection and Regulatory T Cell Function

Mice with a mutation of the ζ-associated protein of 70 kDa gene (skg mutation) are genetically prone to develop autoimmune arthritis, depending on the environment. In a set of mice with the mutation, the amount of ζ-associated protein of 70 kDa protein as well as its tyrosine phosphorylation upon TCR stimulation decreased from +/+, skg/+, skg/skg, to skg/− mice in a stepwise manner. The reduction resulted in graded alterations of thymic positive and negative selection of self-reactive T cells and Foxp3+ natural regulatory T cells (Tregs) and their respective functions. Consequently, skg/− mice spontaneously developed autoimmune arthritis even in a microbially clean environment, whereas skg/skg mice required stimulation through innate immunity for disease manifestation. After Treg depletion, organ-specific autoimmune diseases, especially autoimmune gastritis, predominantly developed in +/+, at a lesser incidence in skg/+, but not in skg/skg BALB/c mice, which suffered from other autoimmune diseases, especially autoimmune arthritis. In correlation with this change, gastritis-mediating TCR transgenic T cells were positively selected in +/+, less in skg/+, but not in skg/skg BALB/c mice. Similarly, on the genetic background of diabetes-prone NOD mice, diabetes spontaneously developed in +/+, at a lesser incidence in skg/+, but not in skg/skg mice, which instead succumbed to arthritis. Thus, the graded attenuation of TCR signaling alters the repertoire and the function of autoimmune T cells and natural Tregs in a progressive manner. It also changes the dependency of disease development on environmental stimuli. These findings collectively provide a model of how genetic anomaly of T cell signaling contributes to the development of autoimmune disease.

Dysbiosis contributes to arthritis development via activation of autoreactive T cells in the intestine.

The intestinal microbiota is involved in the pathogenesis of arthritis. Altered microbiota composition has been demonstrated in patients with rheumatoid arthritis (RA). However, it remains unclear how dysbiosis contributes to the development of arthritis. The aim of this study was to investigate whether altered composition of human intestinal microbiota in RA patients contributes to the development of arthritis.

Detection of T cell responses to a ubiquitous cellular protein in autoimmune disease

T cells that mediate autoimmune diseases such as rheumatoid arthritis (RA) are difficult to characterize because they are likely to be deleted or inactivated in the thymus if the self antigens they recognize are ubiquitously expressed. One way to obtain and analyze these autoimmune T cells is to alter T cell receptor (TCR) signaling in developing T cells to change their sensitivity to thymic negative selection, thereby allowing their thymic production. From mice thus engineered to generate T cells mediating autoimmune arthritis, we isolated arthritogenic TCRs and characterized the self antigens they recognized. One of them was the ubiquitously expressed 60S ribosomal protein L23a (RPL23A), with which T cells and autoantibodies from RA patients reacted. This strategy may improve our understanding of the underlying drivers of autoimmunity. In a mouse model of rheumatoid arthritis, autoimmune T cells recognize a protein from the ribosome. Finding the targets of T cells gone bad Autoimmune diseases such as rheumatoid arthritis can result when the immune system attacks its own body. If we could identify the specific proteins targeted by autoimmune T cells, we might then be able to block this interaction, which might be useful therapeutically. Ito et al. identified one such target in mice that develop a disease similar to rheumatoid arthritis. Disease-causing T cells recognized a protein that is part of the ribosome, a large protein complex that catalyzes protein synthesis. They also found T cells specific for this protein in people with rheumatoid arthritis. Science, this issue p. 363

Overexpression of a Minimal Domain of Calpastatin Suppresses IL-6 Production and Th17 Development via Reduced NF-κB and Increased STAT5 Signals

Calpain, a calcium-dependent cysteine protease, is reportedly involved in the pathophysiology of autoimmune diseases such as rheumatoid arthritis (RA). In addition, autoantibodies against calpastatin, a natural and specific inhibitor of calpain, are widely observed in RA. We previously reported that E-64-d, a membrane-permeable cysteine protease inhibitor, is effective in treating experimental arthritis. However, the exact role of the calpastatin-calpain balance in primary inflammatory cells remains unclear. Here we investigated the effect of calpain-specific inhibition by overexpressing a minimal functional domain of calpastatin in primary helper T (Th) cells, primary fibroblasts from RA patients, and fibroblast cell lines. We found that the calpastatin-calpain balance varied during Th1, Th2, and Th17 development, and that overexpression of a minimal domain of calpastatin (by retroviral gene transduction) or the inhibition of calpain by E-64-d suppressed the production of IL-6 and IL-17 by Th cells and the production of IL-6 by fibroblasts. These suppressions were associated with reductions in RORγt expression and STAT3 phosphorylation. Furthermore, inhibiting calpain by silencing its small regulatory subunit (CPNS) suppressed Th17 development. We also confirmed that overexpressing a minimal domain of calpastatin suppressed IL-6 by reducing NF-κB signaling via the stabilization of IκBα, without affecting the upstream signal. Moreover, our findings indicated that calpastatin overexpression suppressed IL-17 production by Th cells by up-regulating the STAT5 signal. Finally, overexpression of a minimal domain of calpastatin suppressed IL-6 production efficiently in primary fibroblasts derived from the RA synovium. These findings suggest that inhibiting calpain by overexpressing a minimal domain of calpastatin could coordinately suppress proinflammatory activities, not only those of Th cells but also of synovial fibroblasts. Thus, this strategy may prove viable as a candidate treatment for inflammatory diseases such as RA.

Interferon-gamma release assay for diagnosing Mycobacterium tuberculosis infections in patients with systemic lupus erythematosus

Our aim was to analyze the performance of an interferon-gamma release assay, QuantiFERON-TB Gold (QFT-2G), for diagnosing Mycobacterium tuberculosis (MTB) infection in patients with systemic lupus erythematosus (SLE). We performed the QFT-2G and tuberculin skin test (TST) in 71 SLE patients. The QFT-2G results of 279 patients with other connective tissue diseases (CTD) and 35 healthy controls were analyzed. Of the 71 SLE patients, two (2.8%) were positive and 46 (64.8%) were negative by QFT-2G. All SLE patients had no evidence of active MTB infection, apart from one. QFT-2G produced a significantly higher number of indeterminate results in patients with SLE (23/71, 32.4%) compared with those with other CTD (5.7%) or healthy controls (0%) (p < 0.0001 and p < 0.0001). Decreased lymphocyte counts and high SLEDAI scores in SLE patients were shown to be risk factors for indeterminate results by multivariate analysis (p = 0.02 and p = 0.04). Among all patients with CTD, SLE itself and lymphocytopenia were found to be independent risks for indeterminate results (p = 0.00000625 and p = 0.000107). In conclusion, QFT-2G may have more potential to assist in the diagnosis of active and latent MTB infection than TST in SLE patients. However, because of the high frequency of indeterminate results, caution must be used when interpreting the results of QFT-2G among SLE patients, especially those who have parallel or subsequent flares.

Thymus, innate immunity and autoimmune arthritis: Interplay of gene and environment

A hypomorphic mutation of the gene encoding zeta‐associated protein‐70 (ZAP‐70), a signaling molecule in T cells, produces autoimmune arthritis in mice under a microbially conventional condition but not in a clean environment. The genetic anomaly alters thymic selection of self‐reactive T cells as well as natural regulatory T cells and their respective functions. Highly self‐reactive polyclonal T cells, including arthritogenic ones, thus produced by the thymus strongly recognize self‐antigens presented by antigen‐presenting cells, stimulate them to up‐regulate co‐stimulatory molecules and secrete cytokines that drive naïve self‐reactive T cells to differentiate into autoimmune effector Th17 cells. Administration of microbial products and activation of complement can facilitate the differentiation, evoking clinically overt arthritis in a microbially clean environment. Furthermore, mutation‐dependent graded attenuation of T cell receptor signaling alters disease phenotypes and the dependency of disease occurrence on the environment. These findings provide a model of how genetic and environmental factors, in association, cause autoimmune diseases such as rheumatoid arthritis.

Autoimmune Th17 Cells Induced Synovial Stromal and Innate Lymphoid Cell Secretion of the Cytokine GM-CSF to Initiate and Augment Autoimmune Arthritis

&NA; Despite the importance of Th17 cells in autoimmune diseases, it remains unclear how they control other inflammatory cells in autoimmune tissue damage. Using a model of spontaneous autoimmune arthritis, we showed that arthritogenic Th17 cells stimulated fibroblast‐like synoviocytes via interleukin‐17 (IL‐17) to secrete the cytokine GM‐CSF and also expanded synovial‐resident innate lymphoid cells (ILCs) in inflamed joints. Activated synovial ILCs, which expressed CD25, IL‐33Ra, and TLR9, produced abundant GM‐CSF upon stimulation by IL‐2, IL‐33, or CpG DNA. Loss of GM‐CSF production by either ILCs or radio‐resistant stromal cells prevented Th17 cell‐mediated arthritis. GM‐CSF production by Th17 cells augmented chronic inflammation but was dispensable for the initiation of arthritis. We showed that GM‐CSF‐producing ILCs were present in inflamed joints of rheumatoid arthritis patients. Thus, a cellular cascade of autoimmune Th17 cells, ILCs, and stromal cells, via IL‐17 and GM‐CSF, mediates chronic joint inflammation and can be a target for therapeutic intervention. Graphical Abstract Figure. No caption available. HighlightsT cell production of GM‐CSF is dispensable for the initiation of arthritisGM‐CSF from stromal cells is crucial for the initiation of autoimmune arthritisGM‐CSF‐producing synovial‐resident ILCs augment autoimmune arthritisILC production of GM‐CSF is stimulated by IL‐2, IL‐33, or TLR9 ligands &NA; It remains obscure how joint inflammation in rheumatoid arthritis is initiated and progressing. In this study, Hirota et al. identified in an animal model of rheumatoid arthritis an inflammatory cellular cascade instigated by an arthritogenic T helper subset and enhanced by GM‐CSF‐producing synovial‐resident innate lymphoid cells.