Protein antigens of normal and malignant human cells identified by immunoprecipitation with monoclonal antibodies.

Spleen cells from a mouse immunized with human melanoma cells were fused with mouse myeloma cells, and somatic cell hybrids were grown in selective medium. Eight hybrids, which secreted antibodies to protein antigens of the melanoma cell line, were identified by immunoprecipitation of a 125I-labeled melanoma cell lysate followed by sodium dodecyl sulfate-gel electrophoresis of the immunoprecipitates and autoradiography. Seven of the eight melanoma proteins identified in this way were present at the cell surface. Two of the cell surface proteins, p80 and p97, were not detected in autologous fibroblasts.