Effects of sperm-immobilizing antibodies on sperm-zona pellucida tight binding.

ABSTRACT

OBJECTIVE: To evaluate the in vitro effects of sperm-immobilizing antibodies on sperm-zona pellucida (ZP) tight binding. DESIGN: The hemizona assay (HZA) was used to study the inhibitory effects of infertile women's sera with and without sperm-immobilizing antibodies on sperm ZP tight binding. These results were compared with those of monoclonal sperm-immobilizing antibodies. SETTING: The patients were collected from a university hospital infertility clinic. PATIENTS Sera from 40 infertile women (24 with and 16 without sperm-immobilizing antibodies) and 2 postpartum women as control were used. RESULTS: Of 24 patients' sera with sperm-immobilizing antibodies, 23 (96%) showed significant inhibitory effect, whereas none of 16 patient's sera without sperm-immobilizing antibodies exhibited any inhibitory effect. However, there was no correlation between the antibody titers of sperm-immobilizing antibody and the hemizona index. Among four monoclonal sperm-immobilizing antibodies tested, only one showed a significant inhibitory effect on the sperm-zona tight binding. A human monoclonal antibody derived from an infertile woman with sperm-immobilizing antibodies, whose serum showed an inhibitory effect on HZA, did not inhibit the HZA. CONCLUSIONS: There are at least two kinds of sperm-immobilizing antibodies, one with both activities of sperm immobilization and blocking of sperm-zona tight binding and another with the former activity alone. The vast majority of sperm-immobilizing antibodies reduce zona binding even without the presence of complement.