Background/Purpose:

Recent studies reported that IL-17 producing Th-17 cells appear to play an important role in the generation of several autoimmune arthritis models. We previously reported that T-bet expression regulates the development of collagen induced arthritis by suppression of antigen reactive Th17 cells differentiation via the repression of RORγt expression (Kondo Y et al. Arthritis Rheum 64,162-72, 2012). This observation suggested that RORγt might be pivotal on the development of autoimmune arthritis. The aim of this study is to clarify the effect of RORγt expression on T cells in the development of autoimmune arthritis.

Methods:

 1) Incidence and severity of collagen induced arthritis (CIA) were assessed in C57BL/6 (B6) and T cell specific RORγt transgenic (RORγt Tg) mice under the control of CD2 promoter. 2) Histological assessment of inflamed joints was performed with hematoxilin-eosin staining. 3) Collagen type II (CII) specific antibody in sera was measured with ELISA. 4) Draining lymph node cells were harvested from B6 and RORγt Tg mice at 10 days after the immunization of CII, and cultured in the medium containing CII. Cytokine level in supernatants were analyzed by ELISA. 5) Draining lymph node cells were cultured in vitro as described in 4), transcription factors expression on CD4⁺T cells was analyzed by FACS and real-time PCR. 6) The correlation between the expression of transcription factors and chemokine receptor 6 (CCR6) was analyzed by FACS.

Results:

1) CIA was significantly suppressed in RORγt Tg mice compared with B6 mice. 2) Histological assessments revealed that inflammation and bone destruction were milder in RORγt Tg mice than B6 mice. 3) Anti-CII antibody was significantly lower in RORγt Tg mice than B6 mice (P < 0.05). 4) IL-17 level in supernatant was significantly increased in RORγt Tg mice compared with B6 mice (P < 0.05). 5) FACS analysis showed that RORγt expression on CD4⁺ T cells was significantly higher in RORγt Tg mice than B6 mice. Although there was no significant difference of Foxp3 expression on CD4⁺ T cells between B6 mice and RORγt Tg mice, most of Foxp3⁺ CD4⁺ T cells also expressed RORγt in RORγt Tg mice. Bcl-6 expression on CD4⁺ T cells of RORγt Tg mice was comparable to that of B6 mice. 6) The expression of CCR6 on CD4⁺ T cells was significantly higher in RORγt Tg mice compared with B6 mice (P < 0.01). In particular, CCR6 was remarkably upregulated in Foxp3⁺ CD4⁺ T cells of RORγt Tg mice compared with that of B6 mice (P< 0.01).

Conclusion:

CIA was significantly suppressed in RORγt Tg mice, although IL-17 production from CII reactive T cells was increased. The inhibition of arthritis might be related with the increase in CCR6⁺ Foxp3⁺ CD4⁺ T cells in RORγt Tg mice.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/ccr6-foxp3-regulatory-t-cells-regulate-the-development-of-collagen-induced-arthritis-in-t-cell-specific-ror%ce%b3t-transgenic-mice/