FOXP3 and leukemia: As shown in Figure 4A, co-culture with IFN-γ-activated AML blasts resulted into an increase of FoxP3-expressing bona fide Treg cells, when compared with cultures maintained in the absence of leukemia blasts or with those nurtured with a polyclonal stimulus, such as PHA, and IL-2, a Treg growth factor [28].