HLA sharing and spontaneous abortion in humans.

Twenty-one Caucasian couples with two or more idiopathic fetal losses and with either no live-born children or with only one live-born child were typed for HLA-A, B, and DR antigens, and mixed lymphocyte responses of the maternal lymphocytes to stimulation by paternal lymphocytes were studied. The mixed lymphocyte response results showed that women who experienced habitual fetal loss had normal immune responses, thereby lending less credence to the idea that a defective immunologic response is involved in problem pregnancies. The data were pooled and analyzed with those of similar reports, and there was a strong indication that aborting couples shared a greater portion of the chromosome that contains the major histocompatibility complex (MHC) than would be expected in random matings.