[Neutrophil: foe or friend?]

Neutrophils are well-recognized phagocytes in the first line of host defense, and are also a major source of pro-inflammatory cytokines, chemokines and lipid mediators, thereby contributing to the onset and early orchestration of the inflammatory response. In contrast, recent studies indicate that neutrophils have tools to limit the magnitude and length of an inflammatory response, and may take part in engaging the resolution process. This article describes endogenous signals that may transform the phenotype of a neutrophil: from a pro-inflammatory cell to one that promotes resolution. Adenosine, an autacoid which can be found at high concentrations in inflammatory sites, inhibits several inflammatory functions of the neutrophil via engagement of the A2A receptor and reshapes the profile of lipid mediators and cytokines released, causing cells to terminate the release of pro-inflammatory signals while progressing toward resolution. These endogenous resolution pathways may represent a key target for better treatments of inflammatory diseases.