Quantitative analysis of chemokine expression by dendritic cell subsets in vitro and in vivo

Upon maturation, dendritic cells (DCs) have to adjust their chemokineexpression to sequentially attract different leukocyte subsets. We usedreal‐time quantitative polymerase chain reaction analysis to study indetail the expression of 12 chemokines involved in the recruitment ofleukocytes into and inside secondary lymphoid organs, by DCs indistinct differentiation stages, both in vitro and in vivo. Monocyte‐derived immature DCs expressed high levels of DCchemokine 1 (DC‐CK1), EBI1‐ligand chemokine (ELC), macrophage‐derivedchemokine (MDC), macrophage‐inflammatory protein (MIP)‐1α, and thymusand activation‐regulated chemokine (TARC). Upon maturation, DCsup‐regulated the expression of DC‐CK1 (60‐fold), ELC (7‐fold), and TARC(10‐fold). Activation of DCs by CD40 ligand further up‐regulated theexpression of ELC (25‐fold). We found that freshly isolated blood DCsexpressed only low levels of interleukin‐8, lymphotactin, and MIP‐1α. It is interesting that the chemokine profile expressed by activatedCD11c− lymphoid‐like as well as CD11c+ myeloidblood DCs mimics that of monocyte‐derived DCs. Additionally, purifiedLangerhans cells that had migrated out of the epidermis expressed asimilar chemokine pattern. These data indicate that different DCsubsets in vitro and in vivo can express the same chemokines to attractleukocytes.