Critical role of IL-2 and TGF-β in generation, function and stabilization of Foxp3+CD4+ Treg

CD4(+)Foxp3(+) Treg consist of two indistinguishable subsets induced in either the thymus or the periphery. In addition to their suppressive activities, IL-6 can convert natural Treg to pro-inflammatory IL-17-producing cells, but those induced with IL-2 and TGF-beta remain Treg. Unlike mouse CD4(+)CD25(-) cells, which rapidly become polyclonal Foxp3(+)CD25(+) Treg when activated appropriately with IL-2 and TGF-beta, human T cells require multiple stimulations to become similar suppressor cells.