Abstract: Objective: To observe the effects of methotrexate (MTX) on the secretion of interferon-γ (IFN-γ) and interleukin-4 (IL-4) by rheumatoid arthritis' circum-citrullinated peptide antigen specific T cells (CCP/AST).Methods: The rheumatoid arthritis' blood peripheral lymphocytes (PBLs) were cultured in vitro for 72 h,and divided into three groups:lymphocytes only (RA blank group),lymphocytes with CCP at the final concentration of 20 μg/ml (RA CCP group),lymphocytes with CCP and MTX both at the final concentration of 20 μg/ml (RA MTX group).PBLs from health volunteers were cultured in vitro (abbreviated blank control group).The concentrations of IFN-γ and IL-4 were measured by ELISA.Results: Compared with RA CCP group:IFN-γ level of PBLs was lower and IL-4 was higher in RA MTX group,IFN-γ/IL-4 ratio was down-regulated (P<0.05-P<0.01),which had the statistical significances.Conclusions: MTX can regulate the levels of IFN-γ and IL-4 in rheumatoid arthritis' CCP/AST (P<0.05).MTX can inhibit CCP induced TH1 cytokine,and up-regulate TH2 cytokine expression.The regulation of rheumatoid arthritis' CCP/AST by MTX may be one of the effective pathway in treating arthritis rheumatoid.