F, USP44 knock down in human Tregs. Naïve CD4+ T cells (CD4+CD25-CD45RA+) were isolated from the peripheral blood of healthy donors by FACS, and iTreg were generated after 7 days of in vitro skewing conditions. As in Fig. 3b, shRNA constructs targeting USP44 were delivered by lentivirus. Here human iTregs received either shCK (control), or one of two different shUSP44 constructs. Endogenous FOXP3 and USP44 protein levels were visualized by immunoblot (F) 