Figure 1

The role of transforming growth factor-β (TGF-β) in the differentiation pathway of CD8⁺ regulatory T cells. In response to antigen stimulation, the combination of IL-2 produced by CD4⁺ cells and the active form of TGF-β produced by natural killer (NK) cells or macrophages (not shown) induce CD8⁺ cells to lose their cytotoxic potential and become regulatory, TGF-β-producing, Th3-like cells. IL-2 also enhances the extracellular conversion of TGF-β from the latent to the biologically active form.