The role of chemokines in the regulation of dendritic cell trafficking.

The immunobiology of dendritic cells (DC) involves localization in tissues and trafficking via the lymph or blood to lymphoid organs. Appropriate assays representative of different steps of DC trafficking (e.g., reverse transmigration) provide the tools to dissect the migratory properties of these cells. Chemokines have emerged as important regulators of DC migration. DC are both the target and the source of chemokines. DC express receptors for and respond to a set of chemoattractants that overlap with, but are distinct from, those active on other leukocytes. Differential expression of the CCR6 receptor reveals heterogeneity among DC populations. Functional maturation is associated with loss of responsiveness to chemokines present at sites of inflammation and acquisition of a receptor repertoire that renders these cells responsive to signals that guide their localization in lymphoid organs. A better understanding of the molecular basis of DC trafficking may provide molecular and conceptual tools to direct and modulate DC traffic as a strategy to up-regulate and orient specific immunity.