Characterization of sperm antigens reacting with human antisperm antibodies

Antibodies reacting with human spermatozoa have been detected by various immunological techniques in the sera of subfertile men. Different patterns of sperm agglutination are observed with different sera, either head-to-head, tail-to-tail, or tail-tip-to-tail-tip. Differences have been detected between the clinically relevant antibodies in spontaneously infertile males and the less important antibodies in males who have undergone reversal of vasectomy. It has been suggested that the variations in agglutination patterns are due either to different classes of antibody or to binding of antibody to different antigens. In the present study immunoblotting techniques were used to characterize the reactivity of solubilized sperm proteins with serum samples exhibiting different modes of sperm agglutination. This involved the electrophoretic transfer of proteins from SDS gels to nitrocellulose sheets followed by overlay with serum antibody. Using these techniques we have attempted to characterize the antigens of spermatozoa which react with sera from both spontaneously infertile and vasovasostomized men. The results showed that although antisperm antibodies bind to discrete and sperm-associated antigens, there is no substantial difference between the antigenic patterns observed with antibodies producing different types of sperm agglutination. Neither the antigens detected, nor the intensity of reaction showed significant differences although there was a tendency for head-to-head agglutinating antibodies to react more strongly with the higher molecular weight antigens. Moreover, although with sequential serum samples the patterns of agglutination may change, the antigenic pattern remains unchanged.