Dendritic cells (DC) are centrally involved in the initiation and regulation of the adaptive immune response, and different DC can have markedly different (e.g., opposing) function. Acquisition of specific functions is likely to be a result of both nature and nurture, namely differentiation of progenitors into distinct DC subsets as well as the influence of environmental signals. This is not unlike what is seen for T and B cells. This review will focus on the signal transduction pathways that allow an unusually wide range of hematopoietic progenitors to differentiate into DC, the functional characteristics regulated by these pathways, and the ability of pathogens to alter DC function by subverting these pathways during progenitor→DC differentiation.