Organization of the monocyte/macrophage system of normal human skin.

Monocytes and macrophages are known to be important for a variety of functions; however, whereas epidermal Langerhans cells have been studied in great detail, few data are available for the dermal monocyte/macrophage system. Therefore we investigated the density, distribution, and phenotype of dermal macrophages in normal human skin using a panel of monoclonal antibodies for single and double labeling. We demonstrate here that within normal human dermis macrophages reside with a remarkable density. Principally, these cells exhibit the phenotype of the phagocytic macrophage system (CD11c+, KiM8+), whereas members of the immune phagocyte system (CD11c+, KiM8-) are absent from normal dermis with the exception of a few Langerhans cells in the papillary body. Within the dermal phagocytic macrophage system we uncover an unexpected phenotypical and morphologic heterogeneity, which correlates with the tissue localization. This study provides a basis for investigating the participation and change of the dermal macrophage system in cutaneous disorders.