In CD4+ Tconv, ectopic expression of FOXP3 using retroviral vectors (22, 26, 43) or by HDR of a strong promoter upstream of the FOXP3 coding sequences (19) allowed generation of Treg that suppressed CD4+ Tconv not only in vitro but also inhibited GvHD, colitis or dermatitis in animal models (Table 1). Here, FOXP3 is linked to colitis.