IMMUNOSTAINING OF DUCTAL BREAST CARCINOMAS WITH THE MONOCLONAL-ANTIBODY-H

Twenty cases of infiltrating ductal breast carcinomas were stained wit h the mouse monoclonal antibody H, an IgM, in order to estimate the di stribution of the epitope (a carbohydrate moiety) recognized by this a ntibody in the malignant cells. The results showed that in all cases e xamined, the epitope was present in the cytoplasm of the neoplastic ce lls arranged mainly in a diffuse pattern. To identify the polypeptides that carry this epitope, we used extracts from the MCF-7 human breast carcinoma eel line in immunoblotting experiments. In addition to cyto keratin 8 this epitope was also found on five polypeptides originating from Triton X-100-soluble (M(r)x10(-3) of 232, 67, and 37) and from t he Triton X-100-insoluble (M(r)x10(-3) of 51, and 50) fractions, respe ctively. The contribution, if any, of these polypeptides to the staini ng patterns is not known. These data reveal the existence of a common epitope between cytokeratin 8 and other cellular polypeptides. They al so serve as a note of caution in the interpretation of immunohistochem ical staining when anti-cytokeratin antibodies are used.