[Selection and characterization of human acrosome-reacted sperm: application to subzonal insemination].

Acrosome reacted spermatozoa were selected with immunobeads coated with an antibody directed against the inner acrosomal membrane (GB24) and then detached immunologically using an anti-Fab'2 antibody. Using this method, we have shown that acrosome reaction occurs in the most morphologically normal spermatozoa and is followed by a loss in motility and a decrease in longevity. Moreover, when injected in the perivitelline space of hamster oocytes, the selected spermatozoa had a higher fertilization rate than unselected spermatozoa, confirming that acrosome reaction is necessary for the fusion with the oocyte plasma membrane and that the selection method does not alter the fertilizing ability of the spermatozoa. Therefore, this method represents a new way for understanding the sperm functions.