ENTPD1 and graft versus host disease: The GMSCs were treated with POM-1 or isotype control for 4 h prior to injection into the GVHD Model I. We observed that the protective effect of GMSCs in acute GVHD was substantially reduced following treatment with POM-1 in vitro (Fig. 5a, b), suggesting that CD39 plays an important role in this process.