In vitro studies in reproductive immunology: 4. Mechanisms of immune response control in human male genital tract.

Fractionation of human seminal plasma by high-speed centrifugation and by gel filtration on Sephadex G-100 produces a high molecular weight component which displays immunosuppressive characteristics. Both materials inhibit mitogen-induced blast transformation of normal human peripheral monocytes, the component isolated by gel filtration being more effective in this regard. Prior treatment with trypsin of the inhibitory material isolated by centrifugation virtually abolishes its inhibitory potency suggesting that an intact protein is essential for biological function. The results also suggest that suppression of the mitogen-induced blast transformation response of cultured monocytes, T- and B-cells can be reversed by the addition of freshly isolated T- or B-cells. The relevance of these experimental observations to problems of human infertility is discussed.