Immunologic influences on reproductive biology: sperm gametogenesis and maturation in the male and female genital tracts

Abstract

Many men and women do not experience normal reproductive events but instead experience infertility or reproductive wastage after fertilization which has an immunologic basis. There are several lines of evidence in support of the theory that sperm are antigenically foreign to their host and that the spontaneous formation of antisperm antibodies is a reaction against foreign antigens and does not represent a classical autoimmune phenomenon. Of particular importance is the observation that male animals produce sperm antibodies if systemically inoculated with their own gametes. There are 2 proposed mechanisms for the prevention of an immune response to sperm in all mammalian species tested: sperm maturation occurs in the seminiferous epithelium that establishes an effective compartment shielded from the immune effectors; and barriers created by the tight junctions allow the passage of minute amounts of soluble sperm antigen into the host. Conditions that result in a major disruption of the blood-testis barrier are associated with the formation of sperm antibodies. Once antibodies are present in the systemic circulation the damaged barriers in the testes or other regions of the male genital tract may allow the antibodies access to sperm. Then once complexed with the sperm surface the antibodies can interfere with sperm function. The literature pertaining to passage of spermatozoa through the male genital tract is reviewed focusing on the following: immune protection of sperm during their development; sperm maturation in the efferent ducts of the male genital tract; sperm antibodies; and immunoregulatory factors. The literature pertaining to the passage of spermatozoa through the female genital tract also is reviewed. Attention is directed to the following: the vagina the cervix the uterus the fallopian tube follicular fluid and sperm maturation in the female reproductive tract. To penetrate ova sperm must be altered. Capacitation is the term for this process. Human sperm do not demonstrate obvious morphologic differences between capacitated and noncapacitated sperm but it is unknown whether the 2 sperm populations could be separated by antigenic differences. It is likely that some form of receptor on the sperm surface interacts with the sperms environment to effect capacitation. It also is possible that if an immunoglobulin molecule attached and covered or altered this receptor capacitation might be inhibited. The difficulty in identifying the capacitation process in human sperm has made study of this physiologic event a problem.