IMMUNOCHEMICAL CHARACTERIZATION AND ANTIFERTILITY EFFECT OF AN ANDROGEN-INDEPENDENT ANTIGEN OF SPERMATOZOA IDENTIFIED BY A MONOCLONAL-ANTIBODY (D(7)G(3))

Monoclonal antibody, (mAb) D(7)G(3), directed to human spermatozoa and cross-reactive with mouse and rat spermatozoa was found to be a sperm agglutinating antibody. It reacted with antigen present on the post a crosomal region of human spermatozoa and acrosomal region of mouse spe rmatozoa. The antigen reacting with mAb D(7)G(3) was localized in mous e testicular germ cells and Sertoli cells. It was also localized in th e epithelium and spermatozoa of the caput, corpus and cauda epididymid es. In addition, the antigen was detected in the epithelial cells and secretions of the prostate and seminal vesicle. The mAb D(7)G(3) react ed with a band of molecular mass 16 kDa in testicular and epididymal s perm and protein preparations of ventral prostate. In the seminal vesi cle, an additional band of molecular mass 36 kDa was also identified. The effect of castration on the expression of proteins was studied in the rat. Immunohistochemical localization and Western blotting experim ents showed that the antigens identified by the mAb D(7)G(3) was detec table in the epididymis, ventral prostate and seminal vesicle after tw o weeks of castration. In the seminal vesicle, three additional bands were identified by mAb D(7)G(3) following castration. The expression o f this antigen throughout spermatogenesis and sperm maturation indicat ed that it may have an important biological function. A polyclonal ant iserum directed to the 16 kDa mouse epididymal sperm protein was raise d in rabbits. Passive immunization of female mice with this antibody c aused a significant reduction in fertility only if administered 24 hou rs prior to mating, indicating that the antibody inhibited a pre-ferti lization event by inhibiting sperm function.