For example, CD39 and CD73 expressed in regulatory T cells (Tregs) convert extracellular ATP to adenosine, which suppresses the function of T effector cells.205 The recent finding that CD39 knockout mice possess enhanced immunity due to increased extracellular ATP and decreased adenosine, thus producing more CD8+ T in their spleen to resist bacterial infection further corroborates this model.221 Given the vital role of extracellular ATP in the onset of immune response, a long-standing question is that how ATP is released from the cells under infectious lesions or tissue-damaging conditions. This evidence concerns the gene ENTPD1 and bacterial infectious disease.