Dendritic cells (DCs) are potent antigen-presenting cells (1 ) with wide tissue distribution. They are classified based primarily on their localization: as Langerhans cells when present in the epidermis and as dermal DCs when found in the dermis. DCs exhibit several common features: an irregular shape with elongated dendritic processes, a distinctive cell-surface phenotype, low buoyant density, active motility, and the ability to stimulate vigorous proliferation of unprimed T-cells. DCs are able to ingest, process, and present antigen in the context of major histocompatibility complex (MHC) molecules. However, because of their high expression of MHC class I and II, as well as costimulatory molecules and adhesion molecules, DCs have the ability to induce primary T-cell-dependent immune responses in vivo and in vitro. This outstanding feature gives DCs a central role in controlling adaptive T-cell-based immunity.