INDUCTION OF THE HUMAN SPERM ACROSOME REACTION WITH MANNOSE-CONTAINING NEOGLYCOPROTEIN LIGANDS

In the interest of classifying cases of male factor infertility, we ha ve paid particular attention to the sugar ligand binding properties of the human sperm surface and the functional capacity of the acrosome f or exocytosis-key parameters for assessing sperm fertilizing ability. Zona recognition and binding involve the interactions of sperm surface mannose receptors (lectins) with mannose ligands on the zona pellucid a. Sperm surface mannose lectins can be visualized by their ability to bind a synthetic model zona ligand, fluorescein isothiocyanate (FITC) -conjugated mannosylated bovine serum albumin (BSA) (Man-FITC-BSA). We now report that Man-FITC-BSA biologically also mimics the effects of solubilized authentic human zonae, in that binding of Man-FITC-BSA res ults in a time-dependent receptor aggregation and the induction of acr osome exocytosis in capacitated sperm populations from fertile donors. In our assay, the addition of mM amounts of mannose monosaccharide to Man-FITC-BSA increases the number of polyvalent mannose ligands bound by individual spermatozoa and increases the rate of the acrosome reac tions induced by Man-FITC-BSA, thereby increasing specimen processing efficiency. We conclude that exposure of human spermatozoa to polyvale nt mannose ligands + D-mannose monosaccharide offers a new, convenient and readily available system to study sperm capacity for induced acro some loss.