Dendritic cells and monocyte-derived cells: Two complementary and integrated functional systems.

Dendritic cells (DC) are professional antigen sensing and presenting cells that link innate and adaptive immunity. Within the DC population multiple subpopulations exist, each possessing distinct phenotypic and functional properties, together forming a complex cellular network capable of integrating multiple environmental signals and determining immunity or tolerance. Inflammatory monocyte-derived DC are considered a subtype of DC generated upon inflammation. However, we now know that rather than being a bona fide DC subtype, these monocyte-derived cells (MC) more likely represent a distinct type of highly plastic cell that is able to acquire a multitude of functional capabilities, some of which are shared with DC. In this review, we will first discuss the latest developments in our understanding of the organization of the DC and MC networks in both mouse and human and of the functional specializations of their subpopulations. Finally, we will discuss how DC and MC form two complementary and integrated functional systems.