ENTPD1 and multiple sclerosis: Reduced percentages of Foxp3+CD39+ Treg have been described in PBMC of patients with multiple sclerosis compared to healthy donors [18], [19], and the CD39+ cells that were present had impaired ATP-hydrolysing capacity [19], providing evidence for a link between CD39 expression on Treg cells and a function in regulating inflammation through controlling extracellular ATP levels.