Monoclonal antibodies to membrane antigens of human small cell carcinoma of the lung were produced by fusion of P3X63/Ag8U1 mouse myeloma cells with spleen cells from BALB/c mice immunized against the intact cells of the small cell carcinomas grown in BALB/c nude mice. The hybrids were screened for antibody production using intact cells in a solid-phase radioimmunoassay or in a membrane fluorescence with a fluorescence-activated cell sorter. Four monoclonal antibodies were chosen that demonstrated reactivities with human small cell carcinoma of the lung and not with apparently normal diploid fibroblasts or lymphoblastoid cells. The antibodies designated as TFS-1 and TFS-2 rather demonstrated “pancarcinoma” reactivity, showing binding to the other types of lung cancer (adenocarcinoma, squamous cell carcinoma, and large cell carcinoma) and carcinomas derived from other organs, such as colon, pancreas, or stomach. The monoclonal antibodies TFS-3 and TFS-4 preferentially bound to small cell carcinoma cells and neuroblastoma cells, but not to non-small cell carcinomas (adenocarcinoma, squamous cell, or large cell). Especially, TFS-4 did not bind to a variety of other normal or malignant cells. Immunoprecipitation of the antigens by monoclonal antibodies and sodium dodecyl sulfate:polyacrylamide gel electrophoresis revealed that they had different molecular weights.

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This work was supported in part by grants from the Japanese Ministry of Education, Science and Culture, and from the Japanese Ministry of Health and Welfare.

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