Immunochemical characterization of a tumor-associated antigen defined by a monoclonal antibody.

A murine monoclonal antibody of the subclass IgG2b, designated MAb JSI, was produced utilizing standard hybridoma technology. Female BALB/c mice were immunized with a fetal antigen that had been partially purified from the spent serum-free culture media of a human melanoma cell line. Utilizing MAb JSI, the antigen was isolated from serum of melanoma patients by affinity chromatography utilizing an acid elution and studied following exposure to trypsin, protease, and heat in an enzyme-linked immunosorbent assay (ELISA). The antigenic activity was destroyed following treatment with trypsin and protease as well as by exposure to heat (100 degrees C). By immunoperoxidase staining, MAb JSI reacted with melanoma, carcinoma, and sarcoma cell lines, but not with cell lines derived from normal skin or lungs. Affinity-isolated antigen was subjected to polyacrylamide gel electrophoresis and stained with Coomassie blue. Under dissociating conditions, a band in the 31,000 to 42,700 Da range was identified that was shown to be reactive with MAb JSI in ELISA. The antigenic determinant defined by MAb JSI appears to be a protein, with expression on a number of malignant tissues.