Immunosuppression by seminal prostaglandins.

In this paper we report studies undertaken to determine the contribution of seminal prostaglandins to some of the known immunosuppressive properties of human seminal plasma. Initial studies revealed that fractions of seminal plasma enriched in E series prostaglandins, obtained by reverse phase chromatography, had a pronounced inhibitory effect on the PHA-induced proliferation of peripheral blood lymphocytes and on the NK-cell-mediated lysis of K562 target cells. Additional investigations revealed that similar inhibitory effects could be achieved with purified PGE2 (10(-6) to 10(-9) M) and 19-OH PGE1 (10(-6) to 10(-7) M), both of which are present in uniquely high concentrations in human seminal plasma. In contrast, 19-OH PGF1 which is found in lower concentrations in semen was slightly stimulatory in proliferative assays and had no effect on NK-cell-mediated cytotoxicity. Removal of the seminal prostaglandins by absorption chromatography resulted in a dramatic decrease in immune suppressive activity. Further studies with fractions obtained by ion-exchange HPLC of desalted seminal plasma indicated that prostaglandins complexed with seminal proteins, and these too were immunosuppressive. The possible relevance of these results to sexually transmitted disease is discussed.