The effect of human chorionic gonadotropin and placental lactogen on lymphocyte transformation in vitro

Crude preparations of human chorionic gonadotropin (hCG) inhibited phytohemagglutinin (PHA) and allogeneic cell (MLC) lymphocyte stimulation of human peripheral blood lymphocytes (PBL) in vitro as measured by [3H]thymidine incorporation, whereas purified hCG was not inhibitory except at very high concentrations. Sephadex G-100 chromatography of crude hCG showed that the inhibitory effect on PHA lymphocyte stimulation eluted in those fractions after hormonally active hCG. In addition, purified human placental lactogen (hPL) did not inhibit lymphocyte transformation except at very high concentrations. These data suggest that the immunosuppressive activities found in crude preparations are not due to the hormones but to contaminating material.