Human dendritic cells: potent antigen-presenting cells at the crossroads of innate and adaptive immunity.

Dendritic cells (DCs) are specialized, bone marrow-derived leukocytes that are critical to the development of immunity. Investigators have emphasized the role of DCs in initiating adaptive or acquired MHC-restricted, Ag-specific T cell responses. More recent evidence supports important roles for DCs in the onset of innate immunity and peripheral tolerance. Progress in the generation of DCs from defined hemopoietic precursors in vitro has revealed the heterogeneity of these APCs and their attendant divisions of labor. This review will address these developments in an attempt to integrate the activities of different DCs in coordinating innate and adaptive immunity.