Gamma seminoprotein (γSm), a glycoprotein isolated from human seminal plasma with a molecular weight of 29,000 and possibly a serine protease, has been demonstrated to be one of the prostate organ-sepecific antigens. We established a murine monoclonal antibody (MoAb) to γ-Sm in order to prove the presence and localization of this protein in the prostate. The hybrid clones were obtained by fusing mouse SP2/O-Ag-14 myeloma cells with splenocytes from Balb/c mouse immunized with the major fractions of γ-Sm. The enzyme-linked immunosorbent assay was done for antibody screening. After cloning twice in soft agarose, the stable clone, termed 43-21-1-1, was finally chosen. This MoAb, IgG1(κ), recognized γ-Sm specifically, which was verified by an immunoblotting assay. The specificity of the MoAb was further evaluated by immunohistochemical study by the avidin-biotin complex method. Periodate-lysine-paraformaldehyde-fixed surgical specimens, including the prostate associated with fibromuscular hyperplasia, seminal vesicles, bladder, testis and epididymis, were examined. Formaldehyde (10%)-fixed surgical specimens from patients with adenocarcinoma of the prostate and primary transitional cell carcinoma arising from the periurethral prostatic ducts were also examined. Positive reactions of γ-Sm were recognized only in the cytoplasm of prostatic glandular epithelial cells and along the luminal surface. Fibrous and muscular tissues always gaven negative staining. Neither nonprostatic tissues nor transitional cell carcinoma of the prostate were stained positively for γ-Sm. These results show that this MoAb (43-21-1-1) is quite specific to γ-Sm and may be useful for the immunohistochemical study with prostatic tissue.
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