Controversies in reproductive immunology.

Nine areas of current controversy in the field of immunology of reproduction have been selected for discussion: (1) do antisperm antibodies cause infertility; (2) does cell mediated immunity cause infertility; (3) do antibodies cause spontaneous abortion; (4) is abortion due to rejection of the "fetal allograft"; (5) is altered antigen expression crucial for survival of the "fetal allograft"; (6) is abortion mediated by graft rejection mechanisms; (7) does locoregional suppression prevent abortion; (8) does immunization to prevent abortion and promote pregnancy act via immunotropism and cytokine cross-talk; (9) do immune responses prevent spontaneous abortion in humans? The reasons for debate and uncertainty are reviewed and current data considered in an attempt to arrive at the most likely answer to each question. Directions for future research are proposed where appropriate.