Keratin expression in the normal nail unit: markers of regional differentiation

Differentiation within the nail unit was examined using a range of antikera tin monoclonal antibodies including the recently described antibody LHTric- 1, specific to the acidic hair-type keratin Hal, keratinocytes of the nail matrix, nail bed and the digit pulp were characterized by different pattern s of keratin expression, Nail matrix was the sole site of expression of Hal , which colocalized in suprabasal matrix epidermis with epidermal keratins K1 and K10, Small amounts of K17 were found at the apex of the matrix in so me cases. K6 and K16 were found where the epidermal surface folds forwards to become the ventral aspect of the proximal nail fold. The nail bed was di stinguished by the absence of hair-type keratin Hal and the absence of mark ers of cornified epidermis and mucosal differentiation K1/K10 and K4/K13, r espectively, while K6, K16 and K17 were detected. The basal keratin conform ation marker, LH6, was expressed suprabasally throughout the nail bed. This complement of keratins exists in the nail bed in the absence of notable pr oliferative activity, and suggests a state of minimally developed different iation which may be afforded by the physical or biological properties of th e overlying nail, Keratins, K6, K16 and K17 were all found in the digit pul p in limited amounts, possibly in association with the epidermal component of the eccrine duct, The simple epithelial keratins, K7, K8 and K18, were f ound in small amounts in the specimens from younger individuals, mainly in epibasal cells of the apex of the matrix and in putative Merkel cells.