REGULATORY T CELLS AND EFFECTOR T CELLS METABOLISM: Tregs are a subset of CD4+ T cells that play a vital role in maintaining immunological homeostasis, preventing autoimmunity, and graft rejection due to their potent immunosuppressive and reparative activities [40-44]. To accomplish these multiple roles in control of the disproportionate inflammatory response and tissue injury Treg cells express various effector molecules for their activation and stability [45]. Tregs have two main subsets, thymus-derived natural Treg (nTreg) and peripherally (induced) derived Treg (iTreg) cells. iTregs are generated at peripheral sites from naïve T cells after TCR stimulation in the presence of TGF‐β, or they can arise from conventional effector T cells [46].