Localization of S100A2, S100A4, S100A6, S100A7, and S100P in the human hair follicle.

The hair follicle is a highly differentiated structure. In this study, we examined immunohistological localization of S100A2, S100A4, S100A6, S100A7, and S100P using specific monoclonal antibodies. S100A2 was strongly expressed in the entire outer-root sheath (ORS), but more weakly in cuticle and medulla in the bulb. S100A6, S100A7, and S100P were expressed in the innermost cells of ORS. The cuticular area was weakly positive for S100A2, S100A6, S100A7, and S100P. S100A4 was expressed in dendritic Langerhans cells and melanocytes. Sebaceous cells were variably immunopositive for S100A2, S100A6, and S100A7. A subset of dermal papilla cells expressed S100A4 and S100A6. None of the antibodies labeled the inner-root sheath. The distinct spatiostructural distributions of the S100 family proteins suggest that each protein is differentially involved in the physiological function of normal hair follicles.