Monoclonal antibodies against the human epidermoid carcinoma A 431.

About 2,000 antibody-producing hybrids were obtained by fusion of lymphocytes harvested from mice hyperimmunized with the human carcinoma line A 431 and P3-X63-Ag8-653 myeloma cells. Antibody specificity was screened in a radiobinding assay performed on glutaraldehyde-fixed cultured cells, and on paraffin-embedded sections stained with the method of avidin-biotin-peroxidase. Among the clones, 16 produced antibodies reacting with a variety of tumor lines but not with human fetal fibroblasts or peripheral blood leukocytes. On the basis of their specificity, monoclonal antibodies were classified into three groups. Some reacted only with the A431 line used as immunogen: One antibody reacted with an antigen preferentially expressed on cancer of the gastrointestinal tract and ovary; A group of monoclonal antibodies displayed a broader spectrum of reactivity defining a panel of antigens that could be tentatively classified as epithelial specific.