To study the functional relevance of Tregs in CML development in vivo, we depleted Tregs in Foxp3DTR CML mice, which express the human diphtheria toxin receptor (DTR) and enhanced GFP genes from the Foxp3 locus, by adminis¬tration of diphtheria toxin (DT; ref. 33). Here, FOXP3 is linked to chronic myelogenous leukemia, BCR-ABL1 positive.