Acidic and Basic Hair/Nail (Hard) Keratins: Their Colocalization in Upper Cortical and Cuticle Cells of the Human Hair Follicle and Their Relationship to Soft Keratins

The study investigated the distribution and expression of various human hair proteins in the hair follicle using mouse monoclonal antibodies. It found that acidic 44K/46K and basic 56-60K keratins co-appeared in upper cortical and cuticle cells, while 10-25K high sulfur proteins were present only in matured cortical cells. Inner root sheath cells did not react with any antibodies, indicating immunological differences from cortex and cuticle filaments. Additionally, the nail plate contained 10-20% soft keratins along with hair keratins. These findings suggested that hair cortex and nail plate precursor cells share a differentiation pathway, with the 44K/46K and 56-60K keratins serving as markers for hair/nail-type epithelial differentiation.