Immunobiology of pregnancy: evidence for a fetal immune response against the mother.

In a study of 11 pregnancy sera, four retroplacental sera were found to contain antibodies directed against the current pregnancy. In two cases, cord sera were also positive. Surprisingly, the first serum contained antibodies apparently directed against the mother but not the father, thus suggesting an immune response of the fetus. Interestingly, the second was also positive despite the fact that it was a primigravida.