Epidermal DR+T6- dendritic cells in inflammatory skin diseases.

T lymphocyte and dendritic cell subpopulations were counted in three biopsies each of endogenous eczema and pityriasis rosea and two of lichen planus and compared with previous findings in psoriatic lesions. In common with psoriasis, proportionately more CD4 T cells than CD8 T cells were DR+ in both epidermis and dermis of all lesions. In addition, total numbers of epidermal dendritic cells were significantly increased in endogenous eczema and pityriasis rosea, and variably in lichen planus lesions. Interestingly, a DR+T6- subpopulation of dendritic cells was present in varying proportions in all three skin lesion types. Electron microscopy of DR+T6- dendritic cells from psoriatic lesions, using an immunogold staining technique, showed the cells to be of the Langerhans' cell lineage. DR+T6- dendritic cells are a subpopulation of Langerhans' cells which are not specific to psoriasis, but present in the lesions of other benign, inflammatory skin conditions in which CD4 T cells are preferentially activated.