PRF1 and Autoimmunity: Tregs primarily function is to maintain immune tolerance and prevent peripheral autoimmunity through the secretion of immunosuppressive cytokines (TGF-β, IL-10, and IL-35), the expression of CTLA4, and competition for IL-2, which inhibits the secretion and proliferation of cytokines (granzymes A and B, perforin, and γ-interferon) from effector T cells to maintain immune tolerance and prevent autoimmunity in the periphery (Figure 3) (123).