Autoimmune human sperm antibodies and age in males.

The incidence of autoimmunization to spermatozoa, investigated by means of the Kibrick technique, increased with age in 913 males unselected with regard to fertility. By contrast, the incidence of sperm agglutinin-postive sera decreased with age in 1600 male partners in sterile couples. The increasing incidence of autoimmunization to spermatozoa offers one explanation of the lowering of fertility with increasing age, but sperm antibodies seem to be more important as a cause of sterility at younger ages. The presence of spermatozoa may not be necessary for immunization since sperm agglutinins were found in a 9-year-old boy.