Immunohistochemical Study on Keratin Expression in Rat Hair Tissues Using Anti-Hair Keratin Monoclonal Antibodies

The study investigated keratin expression in developing rat hair tissues using monoclonal antibodies HKN-2, 4, 5, and 6. These antibodies were applied to skin specimens from rats at various developmental stages. HKN-2 showed reactivity with developing cells in the medulla, cortex, hair cuticle, and root sheaths, while HKN-4 reacted broadly with all skin epithelial cells. HKN-5 and 6 were specific to hair tissues but did not react before the anagen phase. The findings suggested that hair germ cells differ from epidermal basal cells in keratin expression, and hair-specific keratins are produced after morphological differentiation. The innermost cell layer of the outer root sheath may have distinct characteristics since hair generation.