Effect of antisperm antibodies present in human follicular fluid upon the acrosome reaction and sperm-zona pellucida interaction.

PROBLEM: To determine the ability of IgGs isolated from follicular fluids (hFFIgGs) to induce the acrosome reaction (AR) in human spermatozoa and to inhibit sperm-zona pellucida (ZP) interaction. METHOD OF STUDY: Incubation of capacitated spermatozoa with hFFIgGs (n = 40) and assessment of their effect on the AR or hemizona (HZ) assay in a condition that allows sperm-ZP interaction, avoiding acrosomal exocytosis. RESULTS: hFFIgGs from different women varied in their ability of inducing the AR. Those hFFIgGs with the highest AR-inducing capacity evoked the exocytotic response in most of the different sperm donors tested [high Induction Frequency (IF)]. Some of these antibodies were also able of inhibiting sperm binding to ZP [low HZ Index (HZI)]. A significant correlation was found between the IF and the HZI for each hFFIgG. CONCLUSIONS: Human follicular fluid contains antibodies capable of inducing the AR and inhibiting sperm-ZP binding, suggesting that they could be directed towards ZP receptors. hFFIgGs would constitute a tool for the identification of sperm entities involved in fertilization.