The effect of physiological concentrations of placental proteins - trophoblastic beta1-glycoprotein (PSG), human chorionic gonadotropin (hCG) and alpha-fetoprotein (AFP) on the production of interleukin-2 (IL-2) by isolated CD45RA+ and CD45RO+ - cells in an in vitro model has been studied. It was found that at the level of naive T memory cells (CD45RA+) stimulating effect on the production of IL-2 was provided by hCG (10 and 100 IU/ml), and AFP (100 U ml), but not by PSG. Regarding primed memory T cells (CD45RO+), the stimulatory effect showed hCG (10 and 100 IU/ml), and PSG (1 and10 ug/ml), but not AFP. Thus, placental proteins have primarily a stimulating effect on the production of IL-2 memory T-cells.