SAT0066 DEFICIENCY OF TRANSCRIPTIONAL FACTOR T-BET ACCELERATES THE DEVELOPMENT OF COLLAGEN-INDUCED ARTHRITIS BY INDUCING T HELPER TYPE 17 DIFFERENTIATION

Abstract

Background The transcriptional factor T-bet is required for Th-1 differentiation and important for regulating Th-17 differentiation, which plays a critical role in the development of collagen-induced arthritis (CIA). Previous studies reported that overexpression of T-bet suppresses Th-17 differentiation via inhibition of retinoic acid-related orphan receptor (ROR) γt and aryl hydrocarbon receptor (AhR) (1, 2). However, the function of T-bet in the development of CIA remains largely unknown. Objectives To clarify the role of T-bet on the pathogenesis of CIA. Methods 1) T-bet knockout (T-bet-/-) mice (C57BL/6, B6 background) were generated as previously described (3). T-bet-/- mice were immunized with CII with CFA, and the incidence and severity of CIA was assessed. 2) Anti-CII antibodies in the sera from T-bet-/- mice on day 60 after the first immunization were measured. 3) Lymph node cells from B6 or T-bet-/- mice immunized with CII were analyzed by flow cytometry using antibodies specific for CD3, CD4, CD8, CD11b, CD11c, CD19, Gr1 and NK1.1. 4) The lymph node cells described above were cultured in the CII containing medium, then the cytokine production was assayed by ELISA. Results 1) CIA developed in the T-bet-/- mice was more severe than that of B6 wild-type mice and the incidence of arthritis was around 1.5-fold higher. 2) The levels of total IgG, IgG1, IgG2b, IgG3 antibodies against native chicken CII were significantly higher in T-bet-/- mice. However, IgG2a antibody production was significantly lower in T-bet-/- mice compared to B6 mice. 3) The number of CD4+ T (CD3+CD4+), CD8+ T (CD3+CD8+), B (CD19+), dendritic cells (CD11c+), macrophage (CD11c-CD11b+Gr1-), neutrophil (CD11c-CD11b+Gr1+), NK cell (CD3-NK1.1+) in the lymph node was not different but the number of NKT (CD3+NK1.1+) cells was significantly decreased in T-bet-/- mice. 4) The level of IL-17 and IL-22 in the culture supernatant was significantly higher in T-bet-/- mice, whereas that of IFNγ was comparable in the two groups. Conclusion CIA was significantly severe in T-bet-/- mice. The mechanisms of severe arthritis might be mediated through the up-regulation of IL-17 and IL-22 by Th-17 differentiation in the T-bet deficient and IFNγ independent manner or the decrease of NKT cells.