[Immune tolerance of mother against fetus and placenta].

A review is presented outlining the actual knowledge of immunological mechanisms of pregnancy which seem to play a role in the tolerance of the fetal allograft. During the pregnancy two immunocompetent organisms coexist for a certain time. The fetal survival is possible by several mechanisms and conditions including the lack of direct blood and lymphatic connections between mother and fetus or placenta, the specific function of trophoblast which regulates the transfer of factors and cells and the exposure to maternal and fetal antigens, the effect of specific and nonspecific suppressive factors, the enhancement, the histoincompatibility and the changes of general immunoregulation.