Immunology and immunopathology of the male genital tract - Control and impairment of immune privilege in the testis and in semen

It has long been known that the testis is an immunologically privileged sit e in the body, and that human seminal plasma possesses a generalized immuno suppressive activity. Multiple factors participate in the establishment of immunotolerance in the testis: the blood-tubular barrier; the local product ion of immunosuppressive molecules by Sertoli cells; and the Fas system as regulator of immunological homeostasis in both physiological and pathologic al conditions. Cytokine-induced up-regulation of Fas as well as of integrin ligands, which are known to be specific binding molecules for lymphocytes on the Sertoli cell surface, indicates that the 'nursing' cells of seminife rous epithelium might be important in the impairment of immune privilege, c ausing autoimmune orchitis. In addition, the soluble form of Fas-ligand pro tein present in the seminal plasma of infertile patients might suggest a ro le for this immunomodulatory protein in male infertility. Finally, an under standing of the mechanisms underlying immune privilege in the testis and in semen might help to clarify how cells expressing 'non-self' antigens (such as male gametes) can escape the immune system in both the male and female genital tracts.