Cutting edge: selective usage of chemokine receptors by plasmacytoid dendritic cells

The existence of dendritic cell (DC) subsets is firmly established, but their trafficking properties are virtually unknown. In this study, we show that myeloid (M-DCs) and plasmacytoid (P-DCs) DCs isolated from human blood differ widely in the capacity to migrate to chemotactic stimuli. The pattern of chemokine receptors expressed by blood M-DCs and P-DCs, with the exception of CCR7, is similar. However, most chemokine receptors of P-DCs, in particular those specific for inflammatory chemokines and classical chemotactic agonists, are not functional in circulating cells. Following maturation induced by CD40 ligation, the receptors for inflammatory chemokines are down-regulated, and CCR7 on P-DCs becomes coupled to migration. The drastically impaired capacity of blood P-DCs to migrate in response to inflammatory chemotactic signals contrasts with the response to lymph node-homing chemokines, indicating a propensity to migrate to secondary lymphoid organs rather than to sites of inflammation.