Relative immunosuppressive activity of human seminal prostaglandins

Human seminal plasma contains uniquely high concentrations of prostaglandins of the E series which are believed to contribute to its immunosuppressive effects in vivo. In order to obtain further insight into their activity we have compared the immunosuppressive properties in vitro of PGE1, PGE2 and 19-OH PGE using three immunological systems known to be modulated by prostaglandins, namely, mitogen induced lymphocyte proliferation, IL-2 and transferrin receptor expression and NK-cell mediated cytotoxicity. These studies revealed that PGE1 and PGE2 exerted a greater immunosuppressive effect than 19-OH PGE, but considerably higher levels of 19-OH PGE in semen might contribute the majority of immunosuppressive activity in vivo. Our studies also show that the lower stability of 19-OH PGE in culture media may be responsible for its lower immunosuppressive effect observed in vitro.