Keratins are a large family of proteins that form the intermediate filament cytoskeleton of epithelial cells, which are classified into two major sequence types. Type I keratins are a group of acidic intermediate filament proteins, including K9-K23, and the hair keratins Ha1-Ha8. Type II keratins are the basic or neutral courterparts to the acidic type I keratins, including K1-K8, and the hair keratins, Hb1-Hb6. Keratin-1 is type II keratin. It is a specific marker for terminal differentiation in mammalian epidermis. It is specifically expressed in the spinous and granular layers of the epidermis with family member KRT10 and mutations in these genes have been associated with bullous congenital ichthyosiform erythroderma. This antibody is specifically against ketatin I.