Detection using antisperm monoclonal antibodies of shared epitopes expressed by human spermatozoa and oocytes

Objective: To determine whether human spermatozoa and oocytes share common antigenic epitopes, supporting the hypothesis that their cross- linking by antisperm antibodies present in the clinical sera of infertile couples could promote sperm adhesion to the oolemma. Design: Human and hamster eggs were studied for the presence of antigens recognized by a panel of World Health Organization Task Force monoclonal antibodies (mAbs) originally raised against human spermatozoa. A new technique was devised, using frozen sections of paraformaldehyde-fixed individual human and hamster eggs, to screen rapidly antisperm mAbs for egg reactivity. Living zona-free human and hamster eggs then were exposed to Covaspheres (Duke Scientific, Palo Alto, CA) coupled with these mAbs to document the presence of reactive epitopes on the oolemma. Setting: Academic research environment. Main Outcome Measure(s): Indirect immunofluorescence and Covasphere rosetting. Result(s): Eleven of 37 antisperm mAbs tested reacted with fixed hamster eggs and 10 reacted with human eggs. Five of 6 mAbs reactive with both fixed eggs also reacted with the oolemma of living, zona-free eggs. Conclusion(s): Common antigenic epitopes, some of which are shared with somatic tissues, exist on the oolemma of human eggs and on the plasma membrane of human spermatozoa.