Abstract: Objective This study was to investigate the effect of leflunomide on the shift of Th1 and Th2 cells in collagen-induced arthritis(CIA) rats. Methods CIA was induced, and leflunomide was given intragastrically to CIA rats. Histopathological examinations of joint synovim were scored after HE staining. The weight of the body and the spleen were measured to calculate the index of spleen. RT-PCR was used to determine the expression of T-bet and GATA-3 mRNA in the splenocytes of CIA rats. ELISA was used to detect the secretion of IFN-γ and IL-4 in Con A-induced splenocytes from CIA rats. Results Compared with model CIA rats, leflunomide(2 mg/kg/day, ig× 15 days) significantly decreased the scores of histopathological examinations of joint synovim and the index of spleen in CIA rats. Administration of leflunomide significantly improved the expression of GATA-3 mRNA and the secretion of IL-4, and decreased the expression of T-bet mRNA and the secretion of IFN-γ in Con A-induced splenocytes from CIA rats. Conclusion The inhibition of arthritis by leflunomide may be related to maintain the balance of Th subtypes.

Key words: arthritis, leflunomide, Th1, Th2