Figure 2.

Transforming growth factor-β (TGF-β) regulates the production of extracellular adenosine. Extracellular ATP released from infections and necrotic cell death is potently inflammatory. Regulatory T (Treg) cells constitutively express the two ectoenzymes CD39 and CD73 that can convert ATP, via AMP into adenosine, thereby converting an inflammatory stimulus into an anti-inflammatory one. TGF-β is, however, able to induce the expression of both CD39 and CD73 on the majority of activated T cells, as well as on other cell types such as macrophages and dendritic cells, thereby providing a mechanism to dramatically amplify the anti-inflammatory action of these two enzymes.