OBJECTIVES: To observe the effect of Iguratimod (T-614) on peripheral blood mononuclear cells (PBMCs),Th1 cells and the expression level of IL-8 of rheumatoid arthritis (RA) patients, and to explore the possible mechanism of T-614 in treating RA.METHODS: RESULTS: We found that:  We found that: 1) Iguratimod effectively induced apoptosis in PBMCs in 1h treatment, T-614 100ug/ml was 19.3±2.8% and 1mg/ml 26.4±3.1%,(P<0.05); 2) Compared with control, Iguratimod effectively inhibit CD3+ T cell secretion at 24h, T-641(1mg/ml) 1.33±0.12% and control (without T-614) 2.91±0.13%  P<0.05). 3) Levels of IL-8 in the supernatant of T-614 treated group and control group were tested by ELISA, Iguratimod effectively inhibit IL-8 prodcution and there were significant differences (P<0.05).CONCLUSIONS: The results suggest that T-614 induced PBMC apoptosis and decreasing CD3+ T cell IFN-γ production and secretion of IL-8 in peripheral blood might be the possible mechanism of the effective of T-614 in treatment of RA.