Disrupted regulatory T cell homeostasis in inflammatory bowel diseases

Figure 1 Regulatory T cells control immune responses through a large panel of suppressive mechanisms. In order to control Teff functions, regulatory T cells (Tregs) can use diverse immunosuppressive strategies: A: Treg suppression can be mediated through the inhibitory cytokines IL-10, IL-35, and TGF-β; B: Tregs can modulate DC maturation or function through the interaction of CTLA-4, LAG-3 and Nrp1 expressed by Tregs and the CD80/86 costimulatory molecules, MHC class II and Sema4a expressed by DC, respectively leading to IDO production and preventing DC maturation and Teff activation; C: Tregs can disrupt metabolic functions through the expression of the ectoenzymes CD39/73 allowing adenosine generation, or by IL-2 deprivation; D: Tregs can also induce direct killing of Teff through the production of granzyme B (GZB) or via the interaction between Gal-9 expressed by Tregs and Tim-3 expressed by Teff.