IDENTIFICATION OF HUMAN SPERM ANTIGEN RECOGNIZED BY SERUM OF AN IMMUNOINFERTILE WOMAN - A CANDIDATE FOR IMMUNOCONTRACEPTION

PROBLEM: It has been well documented that antisperm antibodies can be causative factors of infertility. In this study we have identified an antigen on human sperm surface using serum of an immunoinfertile woman ; it is thus a candidate for immunocontraception. METHOD: Thirty-three women of reproductive age who were infertile were screened for presen ce of antisperm antibodies by indirect immunofluorescence and agglutin ation assay. The serum of one such woman, SU-4, reacted with her husba nd's as well as normal donor sperm and recognized a band of apparent m olecular weight of 71-kDa on Western blot. Anti-71-kDa antiserum was r aised in rabbit by eluting 71-kDa protein and was characterized by agg lutination test, immunofluorescence assay, transmission electron micro scopy, flow cytometry, and sperm-egg interaction in mouse system. RESU LTS: Interestingly, sera raised in rabbit against 71-kDa antigen, was identified by immunoinfertile serum of SU-4, revealed similar results of localization of human acrosome. Anti-71-kDa antibodies showed cross -reactivity with other species of sperm, demonstrated inhibition of sp erm attachment to oocytes in an in vitro mouse system, and revealed su rface binding of human live sperm by flow cytometry. Transmission elec tron microscopy documented the presence of 71-kDa antigen in the acros omal compartment. CONCLUSION: This study has put in evidence an antige n of apparent molecular weight of 71-kDa in all donor sperm tested in this study. The presence of this antigen on the sperm of several speci es will enable us to determine the efficacy of this antigen in control ling fertility in vivo in both rodents and primates. This antigen may be a candidate for immunocontraception.