EFFECTS OF SPERM-IMMOBILIZING ANTIBODIES ON SPERM ZONA-PELLUCIDA TIGHT-BINDING

Objective: To evaluate the in vitro effects of sperm-immobilizing anti bodies on sperm-zona pellucida (ZP) tight binding. Design: The hemizon a assay (HZA) was used to study the inhibitory effects of infertile wo men's sera with and without sperm-immobilizing antibodies on sperm ZP tight binding. These results were compared with those of monoclonal sp erm-immobilizing antibodies. Setting: The patients were collected from a university hospital infertility clinic. Patients: Sera from 40 infe rtile women (24 with and 16 without sperm-immobilizing antibodies) and 2 postpartum women as control were used. Results: Of 24 patients' ser a with sperm-immobilizing antibodies, 23 (96%) showed significant inhi bitory effect, whereas none of 16 patient's sera without sperm-immobil izing antibodies exhibited any inhibitory effect. However, there was n o correlation between the antibody titers of sperm-immobilizing antibo dy and the hemizona index. Among four monoclonal sperm-immobilizing an tibodies tested, only one showed a significant inhibitory effect on th e sperm-zona tight binding. A human monoclonal antibody derived from a n infertile woman with sperm-immobilizing antibodies, whose serum show ed an inhibitory effect on HZA, did not inhibit the HZA. Conclusions: There are at least two kinds of sperm-immobilizing antibodies, one wit h both activities of sperm immobilization and blocking of sperm-zona t ight binding and another with the former activity alone. The vast majo rity of sperm-immobilizing antibodies reduce zona binding even without the presence of complement.