Phenotypic Heterogeneity of the Dermal Monocyte/Macrophage System

This chapter focuses on the immunophenotypical analysis of the sub-populations. It highlights the impact of this approach for routine dermatopathology as well as for the general understanding of the pathogenesis of certain dermatoses. The chapter utilizes the characteristics of this cell type as “coordinates” to define the members of the dermal monocyte/macrophage system. It provides evidence that the cells of the monocyte/macrophage system located within the human dermis reveal an unexpected heterogeneity. The initial point of view of macrophages being little more than “big eaters” has long been replaced by a more differentiated concept. Identification of monocytes or macrophages is possible by enzyme cytochemical methods as well as immunohistochemical procedures using antibodies. Analysis of cells belonging to the monocyte/macrophage lineage is complicated by the finding that these cells also express markers previously regarded as T cell specific. Inflammatory dermatoses revealed a modest increast in the number of FXIIIa + cells in and around areas showing a dermal inflammatory infiltrate.