In this issue, Seiffert et al. show that adenosine triphosphate enhances the production of inflammatory mediators by human dermal endothelial cells. However, a growing literature shows that adenosine triphosphate exerts anti-inflammatory effects, partly by inducing a semi-maturation of dendritic cells associated with immune tolerance. These discrepancies can be reconciled knowing that extracellular nucleotides constitute danger signals that are released in response to both external aggression (chemical, microbial) and excess inflammation.