Tregs can also be induced in vitro (induced Tregs, iTregs) from CD4+CD25- T cells following stimulation with IL-2 and transforming growth factor-β (TGF-β).[25] Those iTregs are unstable and can convert back into non-suppressive T effector cells, particularly in the presence of a proinflammatory microenvironment.[26] Therefore, although easy to expand in vitro in numbers large enough for the transfusion into SLE patients,[27] iTregs are not considered an optimal choice for long-term maintenance of immune cell homeostasis driven by stable Tregs. Here, CD4 is linked to systemic lupus erythematosus.