This MAb recognizes a protein of 56kDa, identified as cytokeratin 6A (KRT6A). In humans, multiple isoforms of Cytokeratin 6 (6A-6F), encoded by several highly homologous genes, have distinct tissue expression patterns. Cytokeratin 6A is the dominant form in epithelial tissue. Cytokeratin 6 and 16 are expressed in keratinocytes, which are undergoing rapid turnover in the suprabasal region (also known as hyper-proliferation-related keratins). Cytokeratin 6 is found in hair follicles, suprabasal cells of a variety of internal stratified epithelia, in epidermis, in both normal and hyper-proliferative situations. Epidermal injury results in activation of keratinocytes, which express KRT6 and KRT16. KRT6 is strongly expressed in about 75% of head and neck squamous cell carcinomas.