Effect of seminal plasma and its fractions on in vitro blastogenic response to mitogen

Five fractions of human seminal plasma were isolated on Sephadex G-100 column. The in vitro effect of whole human seminal plasma and its fractions on the lymphocyte transformation induced by phytomitogen was studied. A significant inhibition of lymphocyte response to mitogen was observed with whole seminal plasma fractions I and III at a concentration of 100-200 micrograms/ml. However fraction II stimulates the in vitro human lymphocyte transformation induced by phytomitogen at a concentration of 200 micrograms/ml. Maximum amount of inhibition by whole seminal plasma and its fractions I and III was achieved by preexposure of lymphocytes to these antigens. Pre-exposure of lymphocytes to these antigens, followed by washing, does not result in suppression of lymphocyte response to mitogen. These observations suggest that the antigens of the whole seminal plasma or of fractions I, III, and II act by simple competition with mitogen for the receptor sites on the lymphocyte membrane. Therefore, the human seminal plasma may play an immunoregulatory role against the auto- or isosensitization towards spermatozoal antigens.