Disorders of Macrophages And Dendritic Cells

Abstract

The mononuclear phagocytic system consists of dendritic cells (DCs) and monocytes/macrophages, historically referred to as histiocytes. The macrophages exhibit varying degrees of phagocytic activity. DCs typically have dendritic morphology. Their phagocytic activity is limited. Instead, they play a key role in antigen presentation to lymphocytes. The various populations of macrophages and DCs (such as Langerhans cells [LCs] and dermal dendrocytes) are usually distinguished based on characteristic morphology and patterns of expression of specific cell surface and intracellular markers. Abnormal accumulation and behavior of these cells may lead to the development of a spectrum of diseases collectively known as the histiocytoses. Clinically, histiocytic disorders comprise a wide variety of conditions that affect both children and adults and range from benign skin lesions to rapidly progressive life-threatening systemic disorders. LCs play a pivotal role in the development of Langerhans cell histiocytosis, dermal dendrocytes are the predominant cell population in the lesions of juvenile xanthogranuloma, and macrophages are central to the pathogenesis of hemophagocytic lymphohistiocytosis and related disorders. This review contains 5 figures, 3 tables, and 77 references. Key words: dendritic cells, dermal dendrocytes, hemophagocytic lymphohistiocytosis, histiocytes, juvenile xanthogranuloma, Langerhans cell histiocytosis, Langerhans cells, macrophage activation syndrome, macrophages