COMPARATIVE IMMUNOREACTIVITY OF MOUSE AND HAMSTER SPERM PROTEINS RECOGNIZED BY AN ANTI-P26H HAMSTER SPERM PROTEIN

The binding of the spermatozoon to the zona pellucida is a species-spe cific phenomenon. We have previously shown that the binding of hamster sperm to the homologous zona pellucida involves a sperm 26-kDa glycop rotein, the P26h, originating in the epididymis. In order to establish to what extent this sperm protein is involved in the species-specific recognition of the egg's extracellular coat, we have compared the inh ibitory properties of anti-P26h antibodies in a sperm-zona pellucida a ssay using hamster and mouse gametes. Anti-P26h IgGs inhibit, in a dos e-dependent manner, gamete interactions in both species, although in a less efficient manner in the mouse than in the hamster. While anti-26 kDa Fab fragments are as efficient as the intact IgG to inhibit hamste r sperm-zona pellucida binding, they have no effect on mouse gamete in teraction. ELISA, Western blot, and immunohistochemical experiments ha ve been performed in order to characterize the mouse antigen(s) recogn ized by the anti-P26h antiserum. ELISA and Western blots showed that t his antiserum recognized two proteins on mouse spermatozoa that are le ss reactive than the hamster P26h. These antigens are localized in the acrosomal region of epididymal spermatozoa of both species. These res ults indicate that the hamster P26H involved in zona pellucida interac tion has certain unique epitopes, while others are common to the sperm of both species. (C) 1995 Wiley-Liss, Inc.