Figure 1 (a–c).

Proposed role of extracellular ATP in the regulation of DC trafficking. Due to cell death, the extracellular space surrounding sites of tissue injury is characterised by increased ATP concentration. Circulating DCs might follow the ATP gradient to traffic to perilesional area where an antigen encounter is more likely to occur (a) and where ATP might reach concentrations in the micromolar range. P2Y₁₁ activation transiently inhibits DCs migration, prolonging their persistence at the site of antigen encounter (b). At later stages, due to the action of ecto-nucleotidases, extracellular ATP levels drop down, and the chemokines CCR7 and CXCR4 are upregulated by P2Y₁₁ signaling. This sets DCs for efficient migration from peripheral tissues toward regional lymph nodes (c).