Figure 1.
Induction of Regulatory T Cells in Defined MicroenvironnementsIn intestine lamina propria, several subsets of DCs reside and are in close contact with lumen antigen, like gut flora and food-derived antigens. To maintain local homeostasis, these DCs can induce the differentiation of Tr1 cells, TGF-β-secreting T cells, and Foxp3 Treg cells. In particular, CD103+ DCs can induce the neoconversion of Foxp3+ Treg cells via their capacity to release TGF-β and retinoic acid. These de novo-induced Foxp3+ Treg cells express the gut-homing receptors CC-chemokine receptor 9 (CCR9) and α4β7-integrin. In the tumor microenvironment, tumor cells produce suppressive factors that license DCs, myeloid-derived suppressor cells, or tumor-associated macrophages to induce Treg cells. The consequence of this induction is enhanced local immune suppression. In chronic infections, Treg cells can be induced. The consequence of this induction is maintenance of microbial persistence and limitation of collateral tissue damages.