The effect of native alpha-fetoprotein (AFP) on the conversion of naive T-helpers to central memory T-cells (TCM) and effector subpopulations of the preterm differentiated (TEM) and terminal-differentiated (TEMRA) memory T cells was studied. It was found that AFP prevented the conversion of naive T-helpers into effector subpopulations of memory T cells (TEM and TEMRA) while reducing the total production of IL-4 and IFN-γ by the populations under study. The obtained data reveal a new role of AFP in the formation of immune tolerance during pregnancy.