Cytokines for polarizing T cells into T regulatory cells. T regulatory cells (Tregs) are a subset of T cells that suppress immune function. They are characterized by the expression of CD4, CD25 and Foxp3 and are known to produce immunosuppressive cytokines TGF-β 1 and IL-10. Tregs can be cultured from naive CD4+ T cells by culturing them in the presence of IL-2 and TGF-β 1 with CD3 and CD28 stimulation. In some cases cells are also cultured with neutralizing antibodies to IL-4, IFNγ and IL-12 and/or retinoic acid.