Pregnancy outcome in human couples with recurrent spontaneous abortions: HLA antigen profiles; HLA antigen sharing; female serum MLR blocking factors; and paternal leukocyte immunization.

Critical features of the trophoblast for immune protection in the mother are: (1) its resistance to cytotoxic lymphocytes and antibodies; (2) it forms a physical barrier to immune effector cells, but not antibody, from reaching the fetus; (3) it signals the migration of suppressor and other functionally hyporesponsive lymphocytes into the uterine decidua and uterine lymphatics; (4) it promotes the production of maternal serum MLR (mixed lymphocyte reaction) blocking antibody with paternal antigen specificity. Some of these immunological features are lacking in women with recurrent abortions of immune etiology. Eleven women who aborted an additional time after immunization with paternal leukocytes were compared with 14 women who delivered infants at term post-immunization. It was found that those who aborted: (1) had HLA antigen profiles that did not differ significantly from those of control fertile couples or from observed antigen frequencies in North American Caucasians; (2) shared more HLA A, B, D/DR, and MT antigens with their spouses than controls; (3) were not more hyporesponsive in MLR to paternal antigens pre- and post-immunization when compared to controls; (4) failed to develop female serum MLR blocking factors post-immunization; (5) failed to develop humoral alloantibodies to B-cell alloantigens; (5) had lymphocytes in the uterine decidua mantling the conceptus and in the uterine lymphatics that were reactive/cytotoxic to paternal stimulating alloantigens. These results are in sharp contrast to the immunodynamics of peripheral blood leukocytes and decidual leukocytes to paternal alloantigens in women who delivered infants at term post-immunization.