Identification of an Anti-Human Osteogenic Sarcoma Monoclonal-Antibody-Defined Antigen on Mitogen-Stimulated Peripheral Blood Mononuclear Cells

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Abstract
An anti-human osteogenic sarcoma monoclonal antibody (mouse IgG2b) termed 791T/36 exerted complement-dependent cytotoxicity against phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear (PBMN) cells. This reaction was examined by flow cytofluorimetry using indirect membrane immunofluorescence to detect cell-bound antibody and by measurement of the binding of fluorescein-isothiocyanate-conjugated 791T/36 antibody to cells. The antibody reacted strongly with peripheral blood blast cells induced by PHA; there was negligible reactivity with resting lymphocytes. Maximum binding was observed after 3 days culture with PHA coinciding with maximum DNA synthesis; this represented of the order of 2 .times. 105 antibody molecules bound per cell. After cell surface radioiodination of PHA-stimulated PBMN cells, detergent lysis and immunoprecipitation of antigen with 791T/36 antibody and Sepharose-protein A the apparent MW of this antigen was determined to be 72,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This is identical to that of the 791T/36-defined antigen expressd on various osteogenic sarcoma cell lines; by the criterion the antigen is distinguishable from other cell surface markers of activated human lymphocytes.