Major histocompatibility complex antigens, maternal and paternal immune responses, and chronic habitual abortions in humans.

Women with recurrent consecutive spontaneous abortions of unknown etiology compared with those with recurrent spontaneous abortions of known etiology had a significantly increased frequency of sharing HLA antigens at the A, B, and D/DR loci with their spouses. This major histocompatibility complex (MHC) homozygosity was generally associated with female (responder) and male (stimulator) hyporeactivity in mixed lymphocyte culture reactions. The results indicate that MHC homozygosity between spouses is associated with postfertilization pregnancy wastage in humans.