Langerhans cells and extra-epidermal dendritic cells. An investigation in laboratory animals and man with immunomorphological methods.

S-100 protein was demonstrated in the cytoplasm of dendritic cells (DCs) in normal and pathologic lymphoid tissues and epidermis in man and several other species. The presence of S-100 protein served to distinguish these cells from other mononuclear cells, most importantly from those of macrophage/histiocyte lineage. Fractionation procedures to isolate and enrich suspensions of DCs were coupled with immunocytochemical techniques to identify S-100-positive cells. Langerhans cells in the epidermis and in aural cholesteatomata and nodal, splenic, and thymic interdigitating cells were S-100-positive. Lymph node and splenic follicular dendritic cells (except in rats) were negative, indicating that this DC may be a separate cell type.