Os autores gostariam de agradecer aos Drs. Augusto C. A. Mota e Washington L. C. Santos que gentilmente ajudaram com as análises estatísticas.Este trabalho foi financiado pelo CNPq, pelo Instituto do Milênio do Semiárido(IMSEAR-MCT) e pela FIOCRUZ (PDTIS).Physalis angulata is a solanaceae widely used in folk medicine in various tropical countries in the world. We have previously described that seco-steroids (physalins) purified from P. angulata are potent inhibitors of macrophage activation, blocking the production of pro-inflammatory cytokines and LPS-induced lethality. Herein we investigated the immunomodulatory activities of these substances in lymphocyte proliferation and cytokine production and in transplantation. The addition of physalins B, F or G to concanavalin A-activated splenocyte cultures induced a concentration-dependent inhibition of proliferation. Physalin B also inhibited IL-2 production by Con A-activated spleen cells. The addition of 2 Ag/ml physalin B to mixed lymphocyte reaction (MLR) caused a 100% inhibition of proliferation. More importantly, treatment of mice with physalin B, F or G prevented the rejection of allogeneic heterotopic heart transplant. Our results demonstrate the suppressive activity of physalins B, F and G in lymphocyte function and indicate the potential use of physalins as immunosuppressive agents for treatments of pathologies in which inhibition of immune responses is desired.