Selection and characterization of human acrosome reacted spermatozoa

In order to study the characteristics of human acrosome reacted spermatozoa, we developed a method to select them. Spermatozoa, obtained from 20 fertile volunteers, were selected by using GB24 antibody fixed on magnetic immunobeads, after acrosome reaction induced by 50% follicular fluid. Bead-bound spermatozoa were then detached using sheep anti-mouse IGG F(ab')2 antibody. This method allowed recovery of 170 +/- 48 x 10(3) spermatozoa (n = 20), free of GB24 antibody, as assessed by incubation with FITC-rabbit anti-mouse antibody. The percentage of acrosome reacted spermatozoa in the selected population was 88 +/- 3% versus 32 +/- 6% in the whole sperm population. Concerning sperm morphology, the percentage of head abnormalities was lowered (15 +/- 3% versus 20 +/- 3%). The motility of selected spermatozoa was dramatically reduced (7 +/- 3% versus 53 +/- 7% in the whole population) despite no difference in viability (84 +/- 3% versus 80 +/- 4%). However, the viability after an 18 h incubation was very low (1 +/- 0.5% versus 46 +/- 5%). These results show that acrosome reaction occurs in the most morphologically normal spermatozoa and is followed by a loss in motility and a decrease in longevity.