Immunosuppression of triptolide and its effect on skin allograft survival.

In this study the immunosuppressive properties of triptolide were evaluated. Triptolide was found to inhibit skin allograft rejection in a dose-dependent manner. This inhibitory effect was time dependent. Triptolide at 0.1 mg/kg/day significantly prolonged the graft survival when triptolide was given for 9 days after transplantation, but not before transplantation. In vitro studies showed that triptolide markedly suppressed cytotoxic T-lymphocyte (CTL) induction and mixed lymphocyte reaction (MLR) at concentrations ranging from 0.08 to 10 ng/ml. The inhibition on MLR was also significant when triptolide was added to the cultures at 36 h after initial incubation. Furthermore, exogenous IL-2 did not reverse this inhibitory effect of triptolide. Our results suggest that triptolide inhibits lymphocyte activation at a relatively late stage, and its effect on immune response is not exerted through altering IL-2 production.