Langerhans Cells – The Macrophage in Dendritic Cell Clothing

Our assumptions on the identity and functions of Langerhans cells (LCs) of the epidermis have undergone considerable changes. Once thought to be prototypic representatives of the dendritic cell (DC) lineage, they are now considered to be a specialized subset of tissue-resident macrophages. Despite this, LCs display a remarkable mixture of properties. Like many tissue macrophages, they self-maintain locally. However, unlike tissue macrophages and similar to DCs, they homeostatically migrate to lymph nodes and present antigen to antigen-specific T cells. Current evidence indicates that the immune responses initiated by LCs are complex and dependent on antigenic properties and localization of the stimulus. This complexity is reflected in the recently demonstrated roles of LCs in type 17, regulatory, and humoral immune responses.