Abstract
A monoclonal antibody of the IgG class, EGFR1, has been isolated using cells of the epidermoid carcinoma line A431 as immunogen. The A431 antigen recognized by EGFR1 has an apparent molecular weight of approximately 175,000, is a cell‐surface molecule which can be specifically cross‐linked to EGF, exhibits an EGF‐stimulated protein kinase activity, binds to EGFR1 in a number of human cell lines to a degree which parallels EGF binding, and shows EGF‐dependent internalization in A431 cells and human fibroblasts. We therefore conclude that EGFR1 is directed against an antigenic site on the human EGF receptor. EGFR1 is not mitogenic for human fibroblasts and does not inhibit EGF binding under a variety of assay conditions. The characterization of EGFR1 has allowed the unambiguous assignment of the structural gene for the human EGF receptor to chromosome 7. Preliminary results suggest that a convenient method for isolating a range of anti‐EGF receptor monoclonal antibodies can be developed, based on a hybridoma supernatant screening assay in which positive supernatants bind selectively to a human‐mouse cell hybrid containing human chromosome 7.