Immunology of spermatozoa and cervical mucus

Auto-immunization of the male and iso-immunization of the female with spermatozoal or testicular material can lead to a significant impairment of fertility. Interference of sperm antibodies with reproductive processes may occur by impairment of sperm migration through cervix, uterus and tubes and by blocking adherence of spermatozoa to the surface of the zona pellucida of the oocyte. A very important point to consider in this context is the immunological situation in the female genital tract which is a target organ for sex hormones. Observations in human and subhuman primates as well as in other mammalian species have shown that the levels of immunoglobulins and specific antibodies in secretions of the different compartments of the female reproductive tract are low compared to the serum in general and show typical cyclic changes under the influence of oestrogens and progesterone. Antibody levels appear to be especially low during the preovulatory period in cervical mucus and--according to observations in primates--in tubal fluid. Complement is present in borderline concentrations or not detectable. Data on levels of immunoglobulins or specific antibodies in endometrial fluid are scarce. However, their presence has been demonstrated. There are indications that a secretory immune system may be operational mainly in the cervical compartment of the female genital tract. Serum antibody levels do not reflect properly the immunological situation in secretions of the genital tract in most instances. This may be different in the male. Demonstrations of sperm antibodies in serum or even in genital secretions are not necessarily indicative of permanent sterility; the chances of conception may, however, be reduced. Antibody specificity, immunoglobulin class and quantitative relationships between spermatozoa and antibodies and hormonal influences have to be taken into consideration. Immunity to spermatozoa does not seem to be an all-or-nothing phenomenon and should be considered a relative rather than absolute cause of infertility.