Biochemical and epitope analysis of the 17-1A membrane antigen

The antigen recognized by the monoclonal anti-colon carcinoma antibody 17-1A was found to be a 37 kD glycoprotein in three human colon carcinoma cell lines. The 17-1A antigen (17-1A Ag) contains asparagine-linked carbohydrates as determined by inhibition of glycosylation with tunicamycin. After reduction of 17-1A precipitates with 2-mercaptoethanol two bands of 33 and 40 kD were obtained from the cell lines DLD-1 and HT-29, but only one band from cell line WiDr. Four new MAbs generated against fresh colon carcinoma tissue were shown to be directed against the 17-1A Ag by immunoprecipitation and Western blotting. Two of these MAbs appear to define a novel epitope on the 17-1A Ag as judged from cross-blocking experiments and idiotype expression. Immunohistochemical analysis revealed that the 17-1A Ag is distinctly expressed on a variety of normal and malignant epithelial tissues.