MONOCLONAL-ANTIBODIES TO A HUMAN-PROSTATE ANTIGEN

Abstract

Three monoclonal antibodies reactive with a purified extractable MW 24,000 prostate antigen (PA) were prepared by fusing splenocytes of BALB/c mice preimmunized with purified PA with the NS1 mouse myeloma cell line. The 3 antibodies were all of the IgG-1 subclass. The antibodies defined 2 non-cross-blocking unique determinants on PA; each present as 1 site per molecule. IF3 defined one antigenic site and 2G7 and 1C5 defined another antigenic determinant. All of the antibodies reacted with PA in a solid-phase radioimmunoassay and immunoprecipitated 125I-labeled PA. Absorption and sandwich radioimmunoassays showed PA in prostate tissues but not in tonsil, liver or kidney. Immunoperoxidase staining of formalin-fixed paraffin-embedded sections of benign prostatic hyperplasia and prostatic carcinoma revealed strong prostate epithelial reactivity. None of the antibodies showed reactivity with prostate membrane preparations. A sandwich radioimmunoassay used 2G7 as a plate coat. 125I-labeled IF3 was used to detect 5 ng PA/ml in sera of patients with prostate cancer. These results confirm previous observations regarding the specificity of PA and shed new evidence for its intracellular localization. [These results are discussed with reference to serum assays for following cancer treatment, and section staining diagnosis of metastatic adenocarcinoma and immunotherapy.].