Table 2.
Treg-mediated suppressive mechanisms
| Moleculesa | Ligands | Function |
|---|---|---|
| Contact-dependent suppression | ||
| CTLA-4 | B7-1/B7-2 | Blockade of B7–CD28 costimulatory signals by binding to B7 with greater avidity Inhibition of maturation of antigen-presenting cells (APCs) by physical transfer of B7 on/ in Tregs or transmitting reverse signals to induce IDO in APCs |
| ? | ? | Rendering self-antigen-specific CD8+ T cells to a stable anergic state expressing CCR7 and CTLA-4 |
| CD39, CD73 | A2A
receptor |
Conversion of ATP, an inflammatory molecule and a danger signal, to inhibitory adenosine by CD39/CD73 |
| Granzyme, perforin | Not applicable | Direct cytotoxicity against effector cells |
| Cytokine-mediated suppression | ||
| CD25 (IL-2 receptor α-chain) | IL-2 | Inhibition of differentiation to effector cells by consuming IL-2 |
| TGF-β, IL-10,IL-35 | Not applicable | Inhibition of effector T cells, macrophages, cancer-associated fibroblasts, etc. |
aThe major mechanisms are mediated by CTLA-4 and by CD25.