CAR-3, a monoclonal antibody-defined antigen expressed on human carcinomas.

Several monoclonal antibodies were raised against the human epidermoid carcinoma line A 431. The antibody produced by clone AR-3, when tested in enzyme-linked immunosorbent assay, was found to react with the cell line used as immunogen, the human gastric carcinoma line KATO III, the colon carcinoma line HT29, and the ovarian carcinoma line SW626. This monoclonal antibody was found unreactive when tested on human peripheral blood leukocytes or on a number of normal or neoplastic cell lines. The antibody precipitated a high-molecular-weight glycosylated component. When tested on paraffin sections by the avidin:biotin: peroxidase method, the AR-3 antibody stained pancreatic (6:7), gastric (11:14), ovarian (5:6), colon (4:8), endometrial (4:6), and cervical (4:7) carcinomas. A small minority of carcinomas of other organs was also stained. Sarcomas, lymphomas, and other tumors of nonepithelial origin were constantly negative. Staining of some normal epithelial cells was also observed. Among the fetal tissue tested, the antibody reacted with pancreatic ducts and the small intestine. The antibody recognized metastatic carcinoma cells in peritoneal effusions. On the basis of its tissue distribution, the antigenic determinant defined by the AR-3 monoclonal antibody was called CAR-3. The monoclonal AR-3 did not cross-react with partially purified preparations of carcinoembryonic antigen, gastrointestinal carcinoma antigen, or the human milk fat globule antigen. The AR-3 MAb appear, thus, to broaden the number of available reagents for histopathological diagnosis of carcinomas.