Two mouse monoclonal antibodies (MoAbs), B10 and 1H5, were generated by fusing mouse myeloma NS-1 cells with spleen cells from a BALB/c mouse immunized with Ueda-1 cells derived from human squamous cell carcinoma (SCC) of the floor of the mouth. Immunohistochemical analysis revealed that these MoAbs recognize the filamentous components of cytoplasm which were protein in nature. While the pattern of antigen distribution in various cell lines was not cell-type specific, reactivity of these antibodies with tissue sections was informative. MoAb 1H5 was preferentially reactive with well-differentiated squamous cell carcinoma, however, reaction with adenocarcinoma was observed infrequently. This antibody also preferentially reacted with the spinous layer of normal stratified squamous epithelium. MoAb B10, however, was reactive with nonepithelial tissues as well as with epithelial ones, and its level of binding bore no relationship to the grade of histologic malignancy. SDS-PAGE and Western blotting analysis, using cytokeratin extracts of Ueda-1 cells and human epidermis, demonstrated that MoAb B10 reacted with a wide range of keratin proteins of 65-67K, 58K, 56.5K, 56K, 52K, 50K, 48K, 45K, 40K, 38K, 36K, and 34K molecular weight (MW), while MoAb 1H5 reacted with keratin proteins of 65-67K, 58K, 56.5K, 56K, 52K, 48K, and 34K MW. These results suggest that MoAb 1H5 may recognize keratin subfamilies related to squamous differentiation, whereas MoAb B10 recognizes a wide range of keratin proteins, and may even react with other kinds of intermediate filament proteins (IFPs).
