Immunohistochemical localization of the MHS-5 antigen in principal cells of human seminal vesicle epithelium.

The location of the antigen recognized by monoclonal antibody MHS-5 in the human reproductive tract was examined by means of enzyme-linked immunosorbant assay (ELISA) and indirect immunohistochemistry employing the strepavidin-biotin-complex method. Homogenates of male reproductive tract tissues and other human organs assayed by ELISA demonstrated immunoreactivity of the MHS-5 monoclonal antibody specifically with human seminal vesicle extracts. Varying ratios of seminal protein and monoclonal antibody ascites were tested to determine the amount of antigen necessary to completely absorb the antibody in the ELISA assay. This ratio was subsequently used to obtain the absorbed negative control for histochemical localization studies. By light microscope examination of seminal vesicle tissue in paraffin section, the MHS-5 antigen was localized in principal cells of the seminal vesicle epithelium. Epididymal sperm, obtained from patients at orchiectomy and vasovasostomy were found to lack the MHS-5 antigen. Following incubation with seminal protein or fluid obtained from the lumen of the human seminal vesicle, epididymal sperm reacted with the MHS-5 antibody on ELISA. These findings indicate that the MHS-5 antigen, a novel protein previously shown to be a unique marker for human semen, is a secretory product of the human seminal vesicle epithelium and may be reconstituted on the surface of epididymal spermatozoa.