Ultrastructural Localization of Hair Keratins in Human Scalp Hair Shafts as Revealed by Rapid-Freezing Immunocytochemistry

The study utilized rapid-freezing immunocytochemistry to investigate the ultrastructural localization of hair keratins in human scalp hair shafts. This method, which involved rapid-freezing, freeze-substitution in acetone without chemical fixatives, and immunogold staining, preserved both the fine structure and antigenicity of hair keratins. The findings revealed that in the cortex, hair keratins were mainly located on the macrofibrils, while in the cuticle, they were primarily in the endocuticle, which lacked the fibrous structure of macrofibrils. This technique was deemed effective for examining the macromolecular architecture of fully keratinized human hair tissue.