Triptolide is a purified component from a traditional Chinese herb Tripterygium wilfordii Hook F. It has been shown to have anti-inflammatory and immunosuppressive activities by its inhibitory effect on T-cells. But the effect of triptolide on enteric mucosal immune responses is not well known. The enteric mucosal immune system, especially the Peyer's patch, is regarded as one of the sites for inducing immunity tolerance, and this intolerance effect has been used to induce oral tolerance, which can considerably reduce arthritis severity in several models of experimental polyarthritis and rheumatoid arthritis (RA) patients. In this study, we investigated the effect of triptolide on the CD4+ and CD8+ cell distribution in Peyer's patch cells and periphery lymphocytes and TGF-beta and IFN-gamma levels in periphery in collagen induced arthritis (CIA) in DA rats. CIA in the rat is a widely studied animal model of inflammatory polyarthritis, with similarities to RA, and the DA rat is one of most susceptible strains for CIA. Our data show that triptolide could lower the arthritic scores of CIA. The more CD8+ cells in the Peyer's patch, the more CD4+ cells in periphery. High level IFN-gamma and low level TGF-beta in periphery are observed in CIA rats, while the less CD4+ and CD8+ cells in the Peyer's patch, the less CD4+ cells in periphery. Low level IFN-gamma and high level TGF-beta in periphery are shown in triptolide-treated rats. The dose dependency of triptolide was observed in periphery CD4 cells and in the arthritic score. Therefore, the effect of triptolide on Peyer's patch immune cells might partially explain some of the immunosuppressive activities of triptolide.