Effect on sperm-immobilizing antibodies on the spontaneous and calcium-ionophore (A23187)-induced acrosome reaction.

Objective ― To study the effect of sperm-immobilizing antibodies on spontaneous and A23187-induced acrosome reactions. Material and Methods ― Swim-up spermatozoa obtained from a fertile donor were incubated with 16 sera containing sperm-immobilizing antibodies obtained from infertile women and 3 control sera obtained from healthy females. The acrosome loss, either occurring spontaneously or induced by 10-μM A23187, were examined by staining the sperm with Pisum sativum agglutinin labeled with fluorescein isothiocyanate. Results ― The incidence of the spontaneous acrosome reaction of spermatozoa incubated with anti-sperm antibodies (6.25 ± 1.4%) was significantly (P <.001) lower than that of the spermatozoa incubated with control sera (12 ± 0.8%). The incidence of A23187-induced and inducible (incidence of induced minus spontaneous) acrosome reactions of spermatozoa incubated with sera positive for sperm antibodies (10.4 ± 1.3% and 4.2 ± 1.5%) was also significantly lower (P <.001) than that of spermatozoa incubated with control sera (30.7 ± 0.5% and 18.7 ± 1.2%). Conclusion ― Sperm-immobilizing antibodies interfere with fertilization by inhibiting the acrosome reaction.