Abstract
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.