ENTPD1 and infection: Intracellular ATP can be released to become extracellular ATP—a “danger” molecule released from damaged/stressed host cells or upon infection by pathogens [27]—that undergoes ATP hydrolysis mainly by the host surface enzymes, CD39 (ectonucleoside triphosphate diphosphohydrolase-1; ENTPD1) and CD73 (ecto-5′-nucleotidase; NT5E).