and murine dermis contain dendritic cells. Isolation by means of a novel method and phenotypical and functional characterization

Dendritic cells (DC) comprise a system of cells in lymphoid and nonlymphoid organs that are specialized to present anti-gens and to initiate primary T cell responses. The Langerhans cell of the epidermis is used as a prototype for studies ofDC in the skin. We have characterized a population of DC in human dermis, one of the first examples of these cells in nonlymphoid organs other than epidermis. To identify their distinct functions and phenotype, we relied upon the preparation ofenriched popu-lations that emigrate from organ explants of dermis. The der-mal cells have the following key features of mature DC: (a) sheet-like processes, or veils, that are constantly moving; (b) very high levels of surface MHC products; (c) absence of markers for macrophages, lymphocytes, and endothelium; (d) substantial expression of adhesion/costimulatory molecules such as CD11 /CD18, CD54(ICAM-1), B7/BB1, CD40; and (e) powerful stimulatory function for resting T cells. Dermal DC are fully comparable to epidermis-derived DC, except for the lack of Birbeck granules, lower levels of CD1a, and higher levels of CD36. DC were also detected in explants of mouse dermis. We conclude that cutaneous DC include both epider-mal and dermal components, and suggest that other human nonlymphoid tissues may also serve as sources of typical im