Sperm-bound antisperm antibodies prevent capacitation of bovine spermatozoa

Abstract It was hypothesized here that sperm-bound antisperm antibodies (ASAs) impair the ability of bovine spermatozoa to undergo capacitation, bind to the zona pellucida, and complete the acrosome reaction. The effect of ASA binding on these functions was evaluated in frozen/thawed spermatozoa from four bulls before and after induction of ASAs. Ejaculates were divided into ASA negative ( R 2  = −0.48) but not IgG binding. Sperm binding to the zona pellucida was lower in IgA-positive (six spermatozoa/oocyte; 3–10 spermatozoa/oocyte) than IgA-negative ejaculates (seven spermatozoa/oocyte; 4–13 spermatozoa/oocyte) (P = 0.019). Zona binding was negatively correlated with the percentage of IgA-bound spermatozoa (P = 0.04; R 2 = −0.24) but not IgG-bound spermatozoa. The percentage of acrosome-reacted spermatozoa was higher in calcium ionophore A23187-treated than control aliquots in both ASA-negative and ASA-positive ejaculates (P