The alloantibody response in the allogeneically pregnant rat. VI. Detection in maternal serum of specific antigen-antibody complexes.

We have examined prepartum and postpartum sera from allogeneically pregnant rats for the presence of paternal antigen using a mAb sandwich assay. Paternal class I antigen, RT1Aa, was frequently detected in postpartum and prepartum rat sera. Postpartum sera from high responders also include anti-RT1Aa alloantibodies, some of which were complexed with the RT1Aa antigen. Although the concentration of antigen is low, the high uterine blood flow causes the amount of class I antigen entering the pregnant female to be in the low microgram per day range. Such an amount could have immunoregulatory significance.