Sperm immobilization antibodies in infertile male sera decrease the acrosome reaction: A possible mechanism for immunologic infertility

Objective: To study the effect of sperm-immobilizing antibodies from male sera on spontaneous and A23187-induced acrosome reactions (AR).Design: Swim-up spermatozoa obtained from three fertile donors were incubated with 13 sera with sperm-immobilizing antibodies obtained from infertile men and three control sera obtained from healthy fertile males. Sperm acrosomes were examined by staining with pisum sativum agglutinin labeled with fluorescein isothiocyanate (30 µg/ml; Sigma Chemical Co., St. Louis, MO) as spontaneous and A23187 (used at a final concentration of 10 µM; Sigma Chemical Co.) induced.Results: The incidence of spontaneous AR of spermatozoa incubated with antisperm antibody positive male sera (6.2±0.7) was significantly (P<0.001) lower than that of spermatozoa incubated with control sera (10.7±0.5). And the incidence of A23187-induced and -inducible (incidence of induced minus spontaneous) ARs of spermatozoa incubated with sperm antibody-positive male sera (12.4±1.9 and 6.2±1.9) was significantly lower (P<0.001) than that of spermatozoa incubated with control sera (31.0±0.5 and 20.3±0.9). Sperm-immobilizing antibody-positive sera decreased spontaneous, A23187-induced, and inducible ARs.Conclusions: Sperm-immobilizing antibodies from male sera interfere with fertilization by inhibiting the AR.