INTERFERENCE OF ANTISPERM ANTIBODIES WITH THE INDUCTION OF THE ACROSOME REACTION BY ZONA-PELLUCIDA (ZP) AND ITS RELATIONSHIP WITH THE INHIBITION OF ZP BINDING

Objective: To determine whether antisperm antibodies can interfere wit h the induction of the acrosome reaction (AR) by the zona pellucida (Z P) and whether this interference also can occur in the absence of an i nhibitory effect on ZP binding. Design: Prospective in vitro study. Se tting: A tertiary care center, the Andrologic Clinic, University of L' Aquila. Patient(s): Sera from 12 infertile patients with high titers o f circulating antibodies directed against the sperm head were studied. Intervention: None Main Outcome Measure(s): The effect of antisperm a ntibodies on ZP binding was evaluated by matching antibody-exposed and nonexposed donor sperm suspensions labeled with fluorescein or rhodam ine, respectively, and incubated with the same salt-stored human ZPs. The effect of antibodies on ZP-induced AR was determined by challengin g antibody-exposed and nonexposed donor sperm suspensions with human Z Ps disaggregated with acidic NaH2PO4. Acrosomal status was evaluated u sing fluorescein-labeled Pisum sativum agglutinin and supravital stain Hoechst 33258. In some selected cases, the effect of antisperm antibo dies on the acrosomal status of sperm bound to intact ZP also was eval uated using transmission electron microscopy. Result(s): Five of 12 se ra exhibited an inhibitory effect on ZP binding. An inhibition of AR i nduction by disaggregated ZPs (ranging from 64% to 98%) was produced b y all 5 sera with an inhibitory effect on ZP binding and by 2 of 7 ser a without an inhibitory effect on ZP binding. The different effects of antisperm antibodies on AR induction by disaggregated ZP were confirm ed by comparing with ultrastructural evaluations on the acrosomal stat us of sperm bound to intact ZP. Conclusion(s): Antisperm antibodies ca n interfere with the induction of AR by ZP. This inhibition can occur even in the absence of an inhibitory effect on ZP binding. Neither eff ect may occur. (C) 1997 by American Society for Reproductive Medicine.