Effect of monoclonal antisperm antibodies on the penetration rates of human spermatozoa in zona-pellucida-free hamster oocytes.

The penetration rate of human spermatozoa in zona pellucida-free hamster oocytes was reduced by four monoclonal antisperm antibodies (A-24, B-20, III3 and VII-5) of six tested. The other two (VI-1 and VI-16) left the penetration rates virtually unchanged. The extent of the penetration rate reduction depended on the concentrations of antibodies A-24, B-20, III-3 and VII-5; if undiluted, they produced a significant reduction in the penetration rates; the largest average reduction was almost 50% with undiluted antibody A-24. Decreasing concentrations of the monoclonal antisperm antibodies resulted in significantly smaller reductions in the sperm penetration rates. The reason for the reduced penetration rates observed might have been a blockage of receptors on the sperm surface by the antibodies. That can inhibit enzyme reactions of the spermatozoa or interfere with the interaction between oocyte and spermatozoon membranes. Only antibody III-3 caused agglutination of human spermatozoa in the micro sperm agglutination and immobilization tests. Therefore, the agglutination or immobilization of spermatozoa might not be responsible for the reduced penetration rates after the addition of monoclonal antibodies, in contrast to findings with polyclonal antibodies.