Langerhans and Dermal Dendritic Cells
As part of the first line of defense against exogenous pathogens, the skin houses a number of highly specialized dendritic cell (DC) subsets. Following antigen recognition, skin-localized DCs migrate to skin-draining lymph nodes where they induce an immune response or promote tolerance. The epidermis hosts a network of specialized migratory dendritic cells known as Langerhans cells. Unlike most DCs, which originate from bone marrow-localized precursors, Langerhans cells originate from yolk sac progenitors or fetal liver-derived monocytes. Langerhans cells function similarly in human and mouse and can be identified by the presence of Langerin/CD207-containing Birbeck granules. Both human and mouse Langerhans cells express MHC class II, E-Cadherin, EpCAM/TROP1, Integrin alpha X/CD11c, and Langerin/CD207. In addition, human Langerhans cells express CD1a and may express Integrin alpha M/CD11b, while mouse Langerhans cells express Integrin alpha M/CD11b, DEC-205/CD205, and F4/80. Two subsets of human dermal-localized DC subsets (DDCs) have also been characterized and are defined by the presence or absence of CD1a and CD14.