Effects of experimentally generated bull antisperm antibodies on in vitro fertilization

To test the hypothesis that bull antisperm antibodies have the capacity to interfere with fertilization, antisperm antibodies were generated in three 13-mo-old Holstein bulls by auto-immunizing each bull with sperm three time s. All bulls produced serum antisperm IgG1 and lgC2 antibodies. No serum an tisperm IgA nor seminal plasma antisperm antibodies of any isotype could be detected by ELISA. Western blots were performed with immunopurified IgG1 a nd IgG2 from pre- and post-immunization sera from one test bull. Both post- immunization IgG1 and lgG2 recognized a 45-kDa sperm antigen. Serum samples from a normal bull stud population tested by, ELISA had significantly high er levels of antisperm antibodies than did heifers. The bull stud serum sam ples giving the highest ELISA values differed from those of the immunized b ulls in that their antisperm antibodies were of the IgM isotype only. Bull sperm were incubated with serum from the immunized and control bulls, then added to bovine oocytes in vitro. Incubation of sperm with post-immuni zation serum reduced in vitro fertilization rates (p < 0.01). This study de monstrated that antisperm IgG1 and IgC2 generated by sperm auto-immunizatio ns reduced fertility in vitro, and therefore naturally occurring antisperm antibodies may affect fertility in bulls.