Figure 1.

This figure represents some of the main regulatory mechanisms of Regulatory T-cells (Tregs). Firstly, through the use of CD39 and CD73 Treg’s convert ATP to adenosine which through A2aR signaling can inhibit the effects of CD8+ and CD4+ T-cells (18, 19). Next Tregs down regulate effector mechanisms by consuming cytokines such as IL-2. Tregs can also directly induce apoptosis by expressing Fas and Fas-L interaction and can modulate immune checkpoints by utilizing the LAG-3 and MHC II pathway. All three of these signaling pathways also induce apoptosis through the secretion of granzymes and perforins (20). Next Tregs can use cytotoxic T‐lymphocyte antigen‐4 (CTLA‐4) to impair modulate the maturation and function of antigen presenting cells (21). Lastly, they can secrete inhibitory cytokines such as TGF-β, IL-10, and IL-35.