COMPOSITIONALLY DIFFERENT DESMOSOMES IN THE VARIOUS COMPARTMENTS OF THE HUMAN HAIR FOLLICLE

Hair follicles are complex organs of the skin, in morphological and on togenic continuity with the epidermis. We have examined the location o f desmosomal cadherins and desmosomal plaque proteins in the hair foll icle of adult and fetal human scalp skin by immunohistochemistry and h ave established a localization ''map'' of the hair follicle. Using ant ibodies against the plaque proteins desmoplakin I and II, plakoglobin, and plakophilin 1, we have found that these occur in most, if not all hair follicle desmosomes, whereas plakophilin 2 was absent, except in the basal cells of the outer root sheath, where a weak reactivity was found. By contrast, the desmosomal cadherins were mostly differential ly synthesized, displaying a complicated map. While desmocollin Dsc3 w as detected in all cell types examined,Dsc1 was detected only in the o uter root sheath companion cell layer and the inner root sheath, and D sc2 showed practically a mutually exclusive presence. Desmoglein Dsg2 was observed in basal cells of the outer root sheath as well as in the central cell layers of the subinfundibular outer rood sheath, matrix cells and trichocytes, in partial overlap with the otherwise different immunopositive reactions of Dsg1 and Dsg3. We have also determined wh en these proteins are synthesized during fetal hair follicle developme nt. The differential molecular composition of desmosomes is discussed in relation to possible functional differences between the individual cell types.