Pregnancy and immunity

For mammalian pregnancy to succeed, large physiological adjustments are required in the mother: these changes result from signals passing between the conceptus (especially the trophoblast) and the mother throughout pregnancy. Every system in the body is affected, including the immune system, which is part of a complex signalling system between cells that has developed the ability to recognise self and non-self.

Immune adaptation is not required for the mother to cope with the fetus as an allograft. The lack of HLA antigens on the syncytiotrophoblast and the presence of only the non-classic HLA G antigen on the cytototrophoblast cells precludes the fetal trophoblast from playing any part in currently recognised types of allogeneic immune reactions.1 All these reactions depend on the cellular recognition processes associated with the major histocompatibility complex classes I and II. Not only, therefore, will the maternal immune system fail to be stimulated by allogeneic trophoblast, but allogeneic trophoblast cannot be the target for otherwise armed maternal cytotoxic T cells. Furthermore, according to current understanding …