Trophic effects of first-trimester human trophoblasts and human chorionic gonadotropin on lymphocyte proliferation

We examined the effects of pure first-trimester human trophoblast cells grown in long-term cultures or their secreted products on the proliferation of human peripheral blood lymphocytes cultured alone, under allogeneic stimulation, or in the presence of concanavalin A. Both trophoblasts and their culture supernatants stimulated lymphocyte proliferation. Culture supernatant had a moderate enhancing effect on lymphocyte mitogenesis in mixed lymphocyte cultures and in the presence of concanavalin A. Anti-human chorionic gonadotropin antibody suppressed the proliferative effect of trophoblast cells and their supernatants in the above experiments in a dose-dependent manner. At physiologic concentrations, both pure and impure forms of human chorionic gonadotropin enhanced (in a dose-dependent manner) proliferation of lymphocytes cultured alone (peak stimulation index, 6 to 7.8 at approximately 7 IU/ml). At higher concentrations (20 to 400 IU/ml) the proliferative effect was abolished. Trophoblast culture supernatant induced the expression of interleukin-2 receptors on lymphocytes after 48 hours of incubation. The supernatant also stimulated proliferation of human colon carcinoma cells. Thus trophoblast or trophoblast-derived human chorionic gonadotropin has a lymphocytotrophic function that may have implications for fetal survival.