The immune response to coitus and conception

It is well recognized that cells or tissues exchanged between genetically dissimilar members of the same species will be destroyed by a specific immune response. This process of destruction is initiated by the expression of histocompatibility antigens on the surface of the donor cells which provoke a reaction by the immune system of the recipient. Successful reproduction even through a fundamental process is thought to expose the female to significant antigenic challenge. Numerous hypotheses have been proposed to account for the survival of the semiallogeneic conceptus, although the immunological consequences of coitus are frequently ignored. The possible immunosuppressive role of seminal plasma in normal reproduction is clearly of great clinical importance. Its exclusion from the in vitro fertilization techniques of human reproduction may partially account for the high failure rates associated with this form of assisted reproduction. Its presence in the normal ejaculate may explain the vulnerability of the female reproductive tract to virally inducted neoplasms and be a relevant factor in the etiology of the acquired immune deficiency syndrome.