Intermediate filaments (IF) are a subset of cytoskeletal proteins which function to give overall structural integrity to the plasma membrane as well as organize cells into specific tissues. IF proteins can be divided into six major types based upon the similarity in sequence. Type I and II IF proteins are designated keratins based upon whether they are acidic (I) or basic (II) and are characterized by their remarkable biochemical diversity. A subgroup of keratins, designated cytokeratins, are represented in epithelial tissues by at least 20 different polypeptides, designated 1 to 20. The various epithelia in the human body usually express cytokeratins which are not only characteristic of the type of epithelium, but also related to the degree of maturation or differentiation within an epithelium. Cytokeratin 5 has a molecular weight of approximately 58 kDa (NCBI Accession number P13647) while cytokeratin 8 is approximately 53 kDa (NCBI Accession number P05787). We observe cytokeratin 5 to migrate at approximately 54 kDa and cytokeratin 8 at approximately 52 kDa.
The antibody recognizes cytokeratins 5 and 8 from human, mouse, rat, hamster, rabbit, canine, and swine. The antibody stains all epithelial tissue; it does not stain non-epithelial tissue. The human lung cancer cell line (MR21) was used as the immunogen.