Normal Pregnancy and Parturition in Rats with Acquired Immunological Tolerance to their Mates

Abstract

FOR the period of gestation, the mammalian embryo exists as a successful homograft to its mother. However, once born, the recent foetus and its mother will both reject transplants made from the other. Indeed, tissue of the embryo transplanted from the uterus to another location in the mother during pregnancy is promptly rejected¹. Since allogeneic grafts are rejected from the lumen of the uterus², and since trophoblastie tissue is not immunologically rejected from extra-uterine sites³, attention has shifted from the antigenic character of the foetus to that of the foetal placenta (for review see Bardawil and Toy⁴, and Schlesinger⁵). Increasing evidence is accumulating that the tissue of the embryo, though immunologically vulnerable, is not rejected because it is protected from the mother's immunological defences by the foetal placenta, which is not antigenic^5,6.