The H-Y response in mid-gestation and long after delivery in mice primed before pregnancy.

The mechanisms underlying maternal tolerance of the semi-allogeneic fetus are not completely understood. The maternal immune system's response to the male antigen, H-Y is an example of the conflicting evidence that both supports and refutes the idea that the immune system in pregnant females is fundamentally different from that in non-pregnant females. Although multiple pregnancies may inactivate H-Y specific T cells, the immune system of the pregnant female can also generate a cytotoxic response to this antigen. To help understand this apparent conflict, we immunized female mice against H-Y with male spleen cells before pregnancy and examined the subsequent anti H-Y response during mid-pregnancy. The pregnant mice studied were able to mount cytotoxic immune responses to H-Y that were equivalent to those generated in their non-pregnant counterparts. Moreover the experience of pregnancy did not impair the ability to maintain immunologic memory to H-Y. The data support the idea that pregnancy does not violate general rules of antigen specific immunity, even if the antigen is expressed on the fetus.