Anti-HA1 antibodies enable researchers to detect and measure the HA1 antigen in biological samples. This target is a reported synonym of the KRT31 gene, which encodes keratin 31. This protein is known to function in epidermis development and epithelial cell differentiation, among other biological roles. The human version of HA1 has a canonical amino acid length of 416 residues and a protein mass of 47.2 kilodaltons. It is reported to be notably expressed in the hair. HA1 is a member of the Intermediate filament protein family.