Anti-CK-9 antibodies are protein reagents that detect specific antigens. The CK-9 antigen is another term for the human protein keratin 9, encoded by the KRT9 gene. The protein is believed to serve an important special function either in the mature palmar and plantar skin tissue or in the morphogenetic program of the formation of these tissues. Canonically, it has an amino acid length of 623 residues and a mass of 62.1 kilodaltons. and it is reported to be expressed in the terminally differentiated epidermis of palms and soles. The CK-9 protein is a member of the Intermediate filament protein family. Other alias names for CK-9 include EPPK and K9.