Increased production of antibodies to spermatozoa and seminal fluid in rabbits used as semen donors.

Sera of 20 male rabbits that were used as frequent donors of semen and age-matched normal male and female rabbit controls were examined by an enzyme-linked immunosorbent assay (ELISA), with sperm and seminal fluid as antigens. Five of the 20 semen donors developed an especially high humoral response to seminal fluid and spermatozoa, similar to that observed in some female breeders. The antibodies increased gradually during the 9 months of semen collection. The specificity of the antibodies was demonstrated by total or partial absorption with seminal fluid or spermatozoa. The antibodies were virtually all IgM and were directed against the acrosomal cap region of the spermatozoa, but variable fluorescence was also observed in the postnuclear region and tail.