Immunoglobulin-Fc binding factor in human male reproductive organs

Human seminal plasma, testis, seminal vesicle, epididymis, and prostate contain a component with an estimated Mr of 20 kD that binds human immunoglobulin-Fc. The factor did not bind goat-IgG-Fc, immunoglobulins of human, rat, mouse, goat, horse, or rabbit sera and did not interact with antibodies raised against Fc gamma receptors. The present findings show that this Fc binding factor in seminal plasma is a secretory product of the testis and accessory sex organs. It binds human Ig-Fc but does not meet the criteria of an Fc receptor. Additional IgG-Fc binding proteins with estimated Mr of 90, 88, and 86 kD were detected in the prostate, testis, and seminal vesicle, respectively.