research K25 (K25irs1), K26 (K25irs2), K27 (K25irs3), and K28 (K25irs4) Represent the Type I Inner Root Sheath Keratins of the Human Hair Follicle
K25, K27, and K28 are found in all inner root sheath layers of hair, while K26 is only in the cuticle.
