Fetal and oncofetal antigens - regulators of immune reactions.

This paper proposes the hypothesis that cells which express fetal antigen activate a variety of suppressor mechanisms and thus induce a state of immunological tolerance. Clinical and experimental evidence is cited which supports the hypothesis and indicates that foreign antigens, expressed in association with fetal antigen, are actively tolerated. Thus the fetus, which bears foreign histocompatibility antigens and neoplastic tumours which re-express fetal antigens, fail to evoke appropriate immunological rejection responses, but rather induce a state of active tolerance.