Fig. 1

Underlying mechanisms of Treg-mediated immunosuppression. From left to right: 1 Secretion of immunosuppressive cytokines, such as TGF-β, IL-10, and IL-35. 2 Suppression of Teff activity via adenosine-A2AR signaling. 3 Granzyme B/perforin-dependent cytolysis of target cells via direct cell–cell contact. 4 “IL-2 sink.” 5 Inhibition of antigen-presenting cell maturation by selectively expressing cell surface suppressor receptors, such as CTLA-4, PD-1, TIGIT, LAG-3, and TIM-3, the receptors of which are CD80/86, PD-L1, CD155, MHC-II, and Gal-9. A2AR A2A receptor, APC antigen-presenting cell, TIGIT T cell immunoreceptor with immunoglobulin and ITIM domains, LAG-3 lymphocyte activation gene 3, TIM-3 T cell immunoglobulin mucin-domain-containing-3, Gal-9 Galectin-9