CD39

null CD39, the ectonucleoside triphosphate diphosphohydrolase-1 (ENTPD1), is a two-transmembrane ectoenzyme that sequentially hydrolyzes extracellular ATP and ADP to AMP, which CD73 then converts to adenosine. Positioned at the head of the adenosinergic pathway, CD39 terminates purinergic danger signaling, inhibits platelet recruitment and feeds immunosuppressive adenosine generation. It is constitutively expressed on vascular endothelium and natural regulatory T cells, and inducibly on tumor-infiltrating lymphocytes and myeloid cells. Blocking CD39 is pursued to reinstate ATP-driven antitumor immunity, while soluble CD39 fusion proteins are explored for thrombosis and inflammation control.