Motomu Hashimoto

Preferential recruitment of CCR6-expressing Th17 cells to inflamed joints via CCL20 in rheumatoid arthritis and its animal model

This report shows that interleukin (IL) 17–producing T helper type 17 (Th17) cells predominantly express CC chemokine receptor (CCR) 6 in an animal model of rheumatoid arthritis (RA). Th17 cells induced in vivo in normal mice via homeostatic proliferation similarly express CCR6, whereas those inducible in vitro by transforming growth factor β and IL-6 additionally need IL-1 and neutralization of interferon (IFN) γ and IL-4 for CCR6 expression. Forced expression of RORγt, a key transcription factor for Th17 cell differentiation, induces not only IL-17 but also CCR6 in naive T cells. Furthermore, Th17 cells produce CCL20, the known ligand for CCR6. Synoviocytes from arthritic joints of mice and humans also produce a large amount of CCL20, with a significant correlation (P = 0.014) between the amounts of IL-17 and CCL20 in RA joints. The CCL20 production by synoviocytes is augmented in vitro by IL-1β, IL-17, or tumor necrosis factor α, and is suppressed by IFN-γ or IL-4. Administration of blocking anti-CCR6 monoclonal antibody substantially inhibits mouse arthritis. Thus, the joint cytokine milieu formed by T cells and synovial cells controls the production of CCL20 and, consequently, the recruitment of CCR6+ arthritogenic Th17 cells to the inflamed joints. These results indicate that CCR6 expression contributes to Th17 cell function in autoimmune disease, especially in autoimmune arthritis such as RA.

T cell self-reactivity forms a cytokine milieu for spontaneous development of IL-17+ Th cells that cause autoimmune arthritis

This report shows that highly self-reactive T cells produced in mice as a result of genetically altered thymic T cell selection spontaneously differentiate into interleukin (IL)-17–secreting CD4+ helper T (Th) cells (Th17 cells), which mediate an autoimmune arthritis that clinically and immunologically resembles rheumatoid arthritis (RA). The thymus-produced self-reactive T cells, which become activated in the periphery via recognition of major histocompatibility complex/self-peptide complexes, stimulate antigen-presenting cells (APCs) to secrete IL-6. APC-derived IL-6, together with T cell–derived IL-6, drives naive self-reactive T cells to differentiate into arthritogenic Th17 cells. Deficiency of either IL-17 or IL-6 completely inhibits arthritis development, whereas interferon (IFN)-γ deficiency exacerbates it. The generation, differentiation, and persistence of arthritogenic Th17 cells per se are, however, insufficient for producing overt autoimmune arthritis. Yet overt disease is precipitated by further expansion and activation of autoimmune Th17 cells, for example, via IFN-γ deficiency, homeostatic proliferation, or stimulation of innate immunity by microbial products. Thus, a genetically determined T cell self-reactivity forms a cytokine milieu that facilitates preferential differentiation of self-reactive T cells into Th17 cells. Extrinsic or intrinsic stimuli further expand these cells, thereby triggering autoimmune disease. Intervention in these events at cellular and molecular levels is useful to treat and prevent autoimmune disease, in particular RA.

Complement drives Th17 cell differentiation and triggers autoimmune arthritis

Activation of serum complement triggers Th17 cell–dependent spontaneous autoimmune disease in an animal model. In genetically autoimmune-prone SKG mice, administration of mannan or β-glucan, both of which activate serum complement, evoked Th17 cell–mediated chronic autoimmune arthritis. C5a, a chief component of complement activation produced via all three complement pathways (i.e., lectin, classical, and alternative), stimulated tissue-resident macrophages, but not dendritic cells, to produce inflammatory cytokines including IL-6, in synergy with Toll-like receptor signaling or, notably, granulocyte/macrophage colony-stimulating factor (GM-CSF). GM-CSF secreted by activated T cells indeed enhanced in vitro IL-6 production by C5a-stimulated macrophages. In vivo, C5a receptor (C5aR) deficiency in SKG mice inhibited the differentiation/expansion of Th17 cells after mannan or β-glucan treatment, and consequently suppressed the development of arthritis. Transfer of SKG T cells induced Th17 cell differentiation/expansion and produced arthritis in C5aR-sufficient recombination activating gene (RAG)−/− mice but not in C5aR-deficient RAG−/− recipients. In vivo macrophage depletion also inhibited disease development in SKG mice. Collectively, the data suggest that complement activation by exogenous or endogenous stimulation can initiate Th17 cell differentiation and expansion in certain autoimmune diseases and presumably in microbial infections. Blockade of C5aR may thus be beneficial for controlling Th17-mediated inflammation and autoimmune disease.

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.

Comprehensive microRNA Analysis Identifies miR-24 and miR-125a-5p as Plasma Biomarkers for Rheumatoid Arthritis

MicroRNAs (miRNAs) are present in human plasma and known as a non-invasive biomarker for cancer detection. Our study was designed to identify plasma miRNAs specific for rheumatoid arthritis (RA) by a comprehensive array approach. We performed a systematic, array-based miRNA analysis on plasma samples from three RA patients and three healthy controls (HCs). Plasma miRNAs with more than four times change or with significant (P<0.05) change in expression, or detectable only in RA plasma, were confirmed with plasma from eight RA patients and eight HCs using real-time quantitative PCR. Consistently detectable miRNAs that were significantly different between RA patients and HCs were chosen for further validation with 102 RA patients and 104 HCs. The area under curves (AUC) were calculated after plotting the receiver operating characteristic (ROC) curves. To determine if these miRNAs are specific for RA, the concentrations of these miRNAs were analyzed in 24 patients with osteoarthritis (OA), and 11 patients with systemic lupus erythematosus (SLE). The array analysis and the subsequent confirmation in larger patient cohort identified significant alterations in plasma levels of seven miRNAs. The highest AUC was found for miR-125a-5p, followed in order by miR-24 and miR-26a. Multivariable logistic regression analysis showed that miR-24, miR-30a-5p, and miR-125a-5p were crucial factors for making detection model of RA and provided a formula for Estimated Probability of RA by plasma MiRNA (ePRAM), employing miR-24, miR-30a-5p and miR-125a-5p, which showed increased diagnostic accuracy (AUC: 0.89). The level of miR-24, miR-125a-5p, and ePRAM in OA and SLE patients were lower than that in RA. There was no significant difference in detection for anti-citrullinated protein antibody (ACPA)-positive and ACPA-negative RA patients. These results suggest that the plasma concentrations of miR-24 and miR-125a-5p, and ePRAM are potential diagnostic markers of RA even if patients were ACPA-negative.

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.

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

Discordance and accordance between patient’s and physician’s assessments in rheumatoid arthritis

Objectives: The American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) remission criteria for rheumatoid arthritis (RA) are more stringent than index-based criteria, making it more difficult to achieve a patient’s global assessment (PGA) than an evaluator’s global assessment (EGA). We investigated the reason for the discrepancy between the PGA and the EGA in a Japanese clinical cohort. Method: We assessed clinical and laboratory variables in our clinical cohort. The frequency of remission achievement according to the ACR/EULAR remission criteria and predictors of the discrepancy between the PGA and EGA were analysed. Results: Of 370 patients with RA, 89 fulfilled PGA criteria and 167 patients fulfilled EGA criteria. The PGA was highly correlated with the visual analogue scale (VAS) pain score and non-inflammatory variables including Steinbrocker class and the Health Assessment Questionnaire Disability Index (HAQ-DI). Conversely, inflammatory variables, including swollen joint count (SJC), tender joint count (TJC), and C-reactive protein (CRP) levels, were significantly associated with the EGA. The main predictors of the discrepancy between the PGA and the EGA were patient’s VAS pain score, SJC, and functional disability. Conclusions: Increased pain and functional disability led to a discrepancy towards a worse PGA than EGA, whereas increased SJC led to an accordance towards a worse EGA.

Arthritis and pneumonitis produced by the same T cell clones from mice with spontaneous autoimmune arthritis

SKG mice, a newly established model of rheumatoid arthritis (RA), spontaneously develop autoimmune arthritis accompanying extra-articular manifestations, such as interstitial pneumonitis. To examine possible roles of T cells for mediating this systemic autoimmunity, we generated T cell clones from arthritic joints of SKG mice. Two distinct CD8(+) clones were established and both showed in vitro autoreactivity by killing syngeneic synovial cells and a variety of MHC-matched cell lines. Transfer of each clone to histocompatible athymic nude mice elicited joint swelling and histologically evident synovitis accompanying the destruction of adjacent cartilage and bone. Notably, the transfer also produced diffuse severe interstitial pneumonitis. Clone-specific TCR gene messages in the inflamed joints and lungs of the recipients gradually diminished, becoming hardly detectable in 6-11 months; yet, arthritis and pneumonitis continued to progress. Thus, the same CD8(+) T cell clones from arthritic lesions of SKG mice can elicit both synovitis and pneumonitis, which chronically progress and apparently become less T cell dependent in a later phase. The results provide clues to our understanding of how self-reactive T cells cause both articular and extra-articular lesions in RA as a systemic autoimmune disease.

Increase of Hemoglobin Levels by Anti-IL-6 Receptor Antibody (Tocilizumab) in Rheumatoid Arthritis

Objective To compare the effect of tocilizumab (TCZ) with other biologic therapies in improving anemia of rheumatoid arthritis (RA) patients. Methods We compared the change of hemoglobin (Hb) levels in a cohort of 147 consecutive RA patients who were treated with biologics for more than 12 weeks. Twenty eight patients were treated with TCZ, and 119 patients were treated with biologics other than TCZ (87 with TNF inhibitors and 32 with abatacept). The change of Hb levels from baseline to week 12 was compared between the TCZ and the non-TCZ groups. We performed univariate and multivariate analyses with adjustment of potential confounders such as baseline characteristics, concomitant treatment, and the clinical response to treatment. Results Hb levels generally increased after biologic therapies both in the TCZ and the non-TCZ groups. The increase of Hb levels was greater in the TCZ group than in the non-TCZ groups (1.1 g/dL in the TCZ group vs 0.3 g/dL in the non-TCZ group, p = 0.009). Univariate analysis revealed that increase of Hb levels was also significantly associated with lower Hb, higher Low Hemoglobin Density, and higher CRP levels at baseline and greater reduction in the clinical disease activity index. TCZ therapy was significantly associated with the increase of Hb levels even after adjustment for these factors by multivariate analysis (p<0.001, effect size 0.08–0.12). Conclusion TCZ therapy is an independent factor associated with the increase of Hb level after biologic therapies in RA patients. It will help in selecting appropriate biologics for RA patients with anemia.