The fetus as an allograft: a longitudinal study of normal human pregnancies studied with mixed lymphocyte cultures between mother-father and mother-child.

A longitudinal investigation of the mixed lymphocyte culture (MLC) response during pregnancy between mother and father, between mother and child, and between the mother and an indifferent lymphocyte pool has been carried out, using starting values before pregnancy and a cryobiological freezing system that allows in vitro playback of the immunological course of pregnancy. Lymphocyte and serum samples from twenty-two pregnant women taken before and during pregnancy, at delivery, and after delivery were used. The study shows that the mother reacts during the course of pregnancy with an increasing MLC response to the father, which is replaced at delivery by a decrease in response and a subsequent increase after delivery. It is also shown that the mother reacts to the child in a similar manner at about half the level of reaction to the father. The mother also reacts similarly to a pool of indifferent lymphocytes. The MLC reactions mentioned are affected by both non-pregnant and pregnant serum, leading to a moderation of the MLC reaction in relation to that carried out in neutral AB serum. In addition, there seems to be cooperation between cellular and humoral factors, since the MLC reaction to the child carried out in relevant autologous serum seems to show a decreasing response during the course of pregnancy, in accordance with increasing tolerance of the fetal allograft.