Ontogeny of mouse caudal proteins identified by a monoclonal antibody

A monoclonal antibody (mAb) D2G4 directed to human spermatozoa recognized antigens on the acrosomal region of both human and mouse spermatozoa and reacted with two proteins of molecular weights 45 kd and 26 kd. Immunohistochemical staining with this antibody indicated that only the epithelial cells of the cauda epididymis were stained and not the sections of testis, caput or corpus epididymis. These observations suggest that antigens recognized by D2G4 were acquired by the spermatozoa during their passage through the cauda epididymis and appear to have a role in the maturation of spermatozoa. The ontogeny of these antigens in mice was studied during sexual maturation. These antigens could be detected in cauda epididymis from day 50 onwards by immunohistochemistry. The highest concentration of these antigens was observed in the cauda epididymis of 80-day-old mice. SDS-PAGE analysis indicated that the 26 kd protein recognized by D2G4 was visible from day 50 onwards, confirming the immunohistochemical observations. The plasma testosterone levels showed a significant increase from days 40 to 60 followed by a decrease. The fact that these epididymal proteins appear during sexual maturation and at the time of the testosterone surge indicates that they are androgen dependent.