(A) Phosphatidylserine molecules on the surface of an apoptotic cell can bind to phosphatidylserine receptors on the surface of a phagocyte and previously it was suggested that this triggered an anti-inflammatory gene response. (B) It was also suggested that the direct apoptotic cell–phagocyte interaction shown in A also results in the release of adenosine by the phagocyte: this adenosine can bind to A2a receptors on the surface of the phagocyte and trigger an anti-inflammatory gene response. (C) Yamaguchi et al. found that the apoptotic cell releases a molecule called adenosine monophosphate (AMP) that is converted to adenosine by a 5′-nucleotidase on the surface of the phagocyte. The adenosine can then trigger an anti-inflammatory gene response by binding to A2a receptors. Enzymes called caspases play a central role in apoptosis in a variety of ways. The action of these caspases is required for the exposure of phosphatidylserine on the surface of the apoptotic cells (A and B); they also activate a channel protein called pannexin-1 to allow the release of AMP (C).