Antispermatozoal effects of human seminal plasma--an immunologic phenomenon.

Semen samples were obtained from seven men who had self-agglutination of spermatozoa, and a spermatozoal antibody in the immunoglobulin G (IgG) fraction of their blood. The seminal plasma of these men produced spermatozoal immobilization and agglutination when added to normal semen from healthy men. Analysis of the seminal plasma samples showed that they contained IgA and complements C-3 and C-4, whereas only 1 of 10 samples from normal men contained IgA, and none had complements C-3 and C-4. The IgG levels of the seminal plasma from the study group were higher than those of the controls. It is suggested that the mechanism of spermagglutination is one of autooimmunization in which the main antibody is IgA from the genital tract, augmented by a circulating antibody from the IgG fraction of the blood.