IMMUNOSUPPRESSIVE ACTIVITIES IN THE SEMINAL PLASMA OF INFERTILE MEN -RELATIONSHIP TO SPERM ANTIBODIES AND AUTOIMMUNITY

Semen samples from infertile men were assessed for sperm autoimmunity by direct immunobead assay for immunoglobulin (Ig)A and IgG sperm anti bodies and mucus penetration test. Immunosuppressive activity in semin al plasma was measured by an in-vitro bioassay employing dose-dependen t inhibition of phytohaemagglutinin-induced activation of rat thymocyt es, in the presence or absence of hydroxylamine (0.1 mM), an inhibitor of polyamine oxidation. All seminal plasma samples, regardless of aut oimmune status, caused inhibition of T-lymphocyte activation, and hydr oxylamine reduced this bioactivity by similar to 50%. Dialysis (<3500 molecular weight) also significantly reduced seminal plasma bioactivit y, both in the presence and absence of hydroxylamine. In the presence of hydroxylamine, there was a negative correlation between IgA, but no t IgG, antibody concentrations and lymphosuppressive activity in semin al plasma. Antibody-positive samples displaying impaired sperm functio n, as indicated by the mucus penetration test, had reduced activity co mpared with other samples. In contrast, there was no relationship betw een sperm autoimmunity and lymphosuppressive activity assayed in the a bsence of hydroxylamine. The data indicate that T-lymphocyte inhibitio n by human seminal plasma is due to multiple factors, and reduced amou nts of these factors may contribute to the development and/or persiste nce of sperm autoimmunity in infertile men; however, differences in po lyamine substrates available for oxidation in semen do not appear to b e a major contributing factor.