A role for extracellular ATP in humanised mice is indirectly evidenced by the blockade of CD39 (ectonucleoside triphosphate diphosphohydrolase-1) and CD73 (5′-nucleotidase), which increases extracellular ATP, and was shown to worsen GVHD [138]. The gene discussed is NT5E; the disease is graft versus host disease.