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

Upon maturation, dendritic cells (DCs) have to adjust their chemokine expre ssion to sequentially attract different leukocyte subsets. We used real-tim e quantitative polymerase chain reaction analysis to study in detail the ex pression of 12 chemokines involved in the recruitment of leukocytes into an d inside secondary lymphoid organs, by DCs in distinct differentiation stag es, both in vitro and in vivo, Monocyte-derived immature DCs expressed high levels of DC chemokine 1 (DC-CK1), EBI1-Ligand chemokine (ELC), macrophage -derived chemokine (MDC), macrophage-inflammatory protein (MIP)-1 alpha, an d thymus and activation-regulated chemokine (TARC), Upon maturation, DCs up -regulated the expression of DC-CK1 (60-fold), ELC (7-fold), and TARC (10-f old). Activation of DCs by CD40 Ligand further upregulated the expression o f ELC (25-fold). We found that freshly isolated blood DCs expressed only lo w levels of interleukin-8, lymphotactin, and MIP-1 alpha. It is interesting that the chemokine profile expressed by activated CD11c(-) lymphoid-like a s well as CD11c(+) myeloid blood DCs mimics that of monocyte-derived DCs, A dditionally, purified Langerhans cells that had migrated out of the epiderm is expressed a similar chemokine pattern, These data indicate that differen t DC subsets in vitro and in vivo can express the same chemokines to attrac t leukocytes.