MOLECULAR NATURE OF A SPERM ACROSOMAL ANTIGEN RECOGNIZED BY HS-13 MONOCLONAL-ANTIBODY

Among the numerous monoclonal antibodies generated against human sperm antigens, HS-13 monoclonal antibody was shown to react with an intra- acrosomal antigen from human, mouse and rat. In this study, HS-13 was used as the affinity ligand for the purification of the cognate antige n from human sperm by immunoaffinity chromatography. The purified cogn ate antigen from human sperm, designated as HSAg-13, was found to be a protein with a molecular weight of approximately 80 kDa on SDS-PAGE i n the presence of reducing reagents. This monoclonal antibody was used as the probe to study the tissue distributions and developmental expr ession of the cognate antigen from human, mouse and rat by immunohisto chemical assays. It was concluded that the antigen recognized by HS-13 antibody is highly sperm specific and found only in sperm and mature testis, but not in any other somatic tissues examined in human and mou se. The antigen was shown to be expressed at the postmeiotic stages of spermatogenesis in mouse and rat. By using indirect immunofluorescent staining assay, HS-13 was shown to react only with the methanol-fixed acrosome-intact sperm but not with the live sperm. Following calcium ionophore A23187 treatment, acrosome-reacted sperm showed either negat ive staining or residual staining in the equatorial region, suggesting the intra-acrosomal location of HSAg-13. The spontaneous acrosome rea ction following overnight incubation in BWW medium resulted in a stati stically significant decrease of antibody-stained human sperm. In view of excellent correlations for the scoring of acrosome-intact sperm wi th that of fluorescence-labeled Pistum sativum agglutinin (PSA) probe, HS-13 monoclonal antibody can be routinely used for monitoring sperm capacitation and acrosome reaction. (C) 1997 Elsevier Science Ireland Ltd.