[Immunologic factors in habitual abortion]

Recent advances in immunology have discovered two immunological factors in part of the patients with habitual first-trimester abortions. Antibody formation against the major histocompatibility antigens (HLA = human leukocyte antigen) which can be demonstrated during normal pregnancy is often not detectable in these patients, sometimes presumably because of compatibility in the HLA antigens between mother and fetus. In a high percentage of these patients immunotherapy by subcutaneous leukocyte injections can lead to antibody formation and successful pregnancy. As another immunological factor, a genetic variant of the complement-inactivating leukocyte differentiation antigen CD46 (= TLX antigen, = membrane cofactor protein) could be identified, which can be seen more frequently in patients with habitual abortions as compared to healthy controls. Both factors seem just to contribute to a predisposition for early-pregnancy abortions rather than to be an absolute barrier, as they can also be seen in normal pregnancy and successful carriages can also occur without any therapy in early-pregnancy aborters with an immunological background.