| Sumari: | Dendritic cells (DCs) are crucial participants in maintaining immune surveillance of the periphery and initiating primary immune responses within the draining lymph nodes. The afferent lymphatic vessels provide a conduit for this essential trafficking and, as this review will describe, play an active role in regulating DC migration. Afferent lymphatic capillaries support constitutive trafficking of DCs from resting, non-inflamed tissue, to maintain tolerance against self-antigen and to provide immune surveillance. Following exposure to pathogens or pro-inflammatory cytokines, DCs mature from phagocytes to professional antigen-presenting cells, whilst the lymphatic endothelium adopts an activated phenotype to support the ensuing increase in leukocyte trafficking. The lymphatic endothelial-derived chemokine CCL21 plays a well-characterized role in directing migration of CCR7+ DC in both resting and acute inflammatory conditions. However, efficient trafficking of DCs from inflamed tissue also demands additional chemokine-receptor pairs. Thus, entry of DCs to activated lymphatic vessels is an intricately regulated multi-step process involving numerous chemokines and adhesion molecules.
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