Monoclonal antibodies to human cytokeratins: application to various epithelial and mesothelial cells

Immunohistological analysis of human tissue using monoclonal antibodies against cytokeratins, which are confined to cells of epithelial origin, is a valuable technique. Using human epidermal keratins as antigen, we prepared monoclonal antibodies against cytokeratins (ZK1, ZK7, ZK61 and ZK99) and against a desmosomal protein (ZK31). Immunohistochemical staining of human skin sections using these antibodies showed a specific reaction with the epidermis: ZK1 stained the entire epidermis, ZK7 only the basal layer, ZK61 and ZK99 the suprabasal layers, and ZK31 the cellular interfaces. In order to test for antibody specificity, immunoblots with human epidermal and amnion epithelial cytokeratin polypeptides, as well as immunofluorescence microscopy of simple epithelia (glandular and simple columnar epithelia) were performed. ZK1, ZK61 and ZK99 reacted preferentially with cytokeratin polypeptides of stratified squamous epithelia and ZK7 recognized cytokeratins of stratified and simple epithelia. When the ZK antibodies were tested on mesothelial cells in pleural effusions, only ZK7 reacted with these cells. Biochemical analysis of cytokeratin accumulation in cells of primary and long-term cultures indicated that the cytokeratin pattern of mesothelial cells was quite unstable, while that of amnion epithelial cells showed only minor quantitative changes. The use of these antibodies to determine the epithelial origin of cells present in pleural effusions is proposed.