Monoclonal antibody localization of sperm surface antigen secreted by the epididymis of the baboon (Papio cynocephalus)

A monoclonal antibody (BSA6) was generated against an antigenic determinant secreted by the epididymis of the baboon and present on the acrosomal surface of the spermatozoa. This determinant was first secreted by the principal cells of the proximal corpus region, as determined by fluorescent microscopy performed on Bouin-fixed epididymal tissue sections. The secretory product subsequently bound on the lateral acrosomal surfaces in the distal corpus region, but became uniformly distributed over the acrosomal region in the cauda epididymidis. The antigenic determinant had a molecular weight of 82,000 (western blot technique). The testis, caput and other somatic tissues were devoid of the antigen, indicating the restriction of the antigen to spermatozoa and epithelial cells of the corpus epididymidis. Examination of similar tissue from immature baboons indicated that the secretion of this antigen was age-dependent, secretion beginning at about 4 years of age.