A fresh morphological and functional look at dermal dendritic cells.

During the past decade, a group of cells located in the dermis and possessing a dendritic morphology have emerged from obscurity and become recognized as important members of the "dermal immune system". This group of cells is characterized by a considerable degree of immunophenotypic and functional heterogeneity. In this review, the salient features of these dermal dendritic cells are put into a dermatopathology perspective, with particular emphasis on a broad group of inflammatory and neoplastic skin diseases. There appear to be multiple subsets of dermal dendritic cells, and 17 different conditions linked to active participation of these newly recognized cells. Exactly how these different subsets of dermal dendritic cells interact amongst each other, as well as with adjacent cells such as T-lymphocytes, endothelial cells, fibroblasts, and keratinocytes in these different diseases is unclear at this time. However, isolation techniques and monoclonal antibodies capable of distinguishing these subsets, as well as functional assays, are currently available and will permit definitive conclusions to be drawn regarding their pathophysiological significance. It is highly likely that, as more data is gathered, dermal dendritic cells will be the focus of further investigative activity by dermatopathologists for the next decade, and well past the year 2000.