[An immunohistochemical study on cell differentiation in the outer root sheath of the normal human anagen hair follicles with antikeratin monoclonal antibodies].

The expressions of several cytokeratins (CKs) in the outer root sheath (ORS) of the human anagen hair follicles were immunohistochemically studied using 11 antikeratin monoclonal antibodies (MoAbs) and 10 specimens from scalp. CKs 1, 10, 11, which are markers for differentiating keratinocytes, were exclusively found in the intermediate cells and the granular cells at the infundibulum. In cytokeratin expression, a distinct linear demarcation between the infundibulum and the isthmus was observed. Trichilemmal keratinization appeared to go in an inner-upward direction toward the hair canal. CK 19, a marker of undifferentiated stem cells, was found in outermost cells of the ORS at the isthmus and in some cells of the lower ORS. CK 16, a marker of hyperproliferative keratin, was detected in the outermost cells of the infundibulum and all the cells of the ORS below the isthmus. Therefore, the keratinocytes at the infundibulum may show a differentiation similar to that of the interfollicular epidermal keratinocytes. The ORS cells below the isthmus seem to move up to inner-upward direction along the hair axis with differentiation.