This review explores the regulation of regulatory T cells (Tregs) by cytokine signaling and co-stimulatory molecules. Tregs are essential for maintaining immune homeostasis and preventing excessive immune responses. Key cytokines involved in Treg regulation include TGF-β, IL-2, IL-10, and IL-35, which promote Treg differentiation and enhance their immunosuppressive functions. Conversely, IL-6 and TNF-α can impair Treg suppressive functions or drive their reprogramming into effector T cells. The B7 family of co-stimulatory molecules, including CTLA-4 and PD-1, plays a crucial role in regulating Treg differentiation, function, and survival. Treg dysfunction contributes to autoimmune diseases, and Treg-based immunotherapy shows potential for treating autoimmune diseases, transplant rejection, and cancer. The review highlights the importance of understanding Treg regulation by cytokines and co-stimulatory molecules for developing new therapeutic strategies. Key findings include the role of TGF-β in Treg development, the importance of IL-2 in Treg survival and function, the anti-inflammatory effects of IL-10, and the role of IL-35 in promoting Treg function. Inhibitory cytokines like IL-6 and TNF-α can disrupt Treg function, while co-stimulatory molecules such as CTLA-4 and PD-1 regulate Treg activity. Treg-based immunotherapy is a promising approach for treating various diseases, including autoimmune disorders, transplant rejection, and cancer. The review emphasizes the need for further research to fully understand the complex interactions between Tregs, cytokines, and co-stimulatory molecules to develop effective therapeutic strategies.This review explores the regulation of regulatory T cells (Tregs) by cytokine signaling and co-stimulatory molecules. Tregs are essential for maintaining immune homeostasis and preventing excessive immune responses. Key cytokines involved in Treg regulation include TGF-β, IL-2, IL-10, and IL-35, which promote Treg differentiation and enhance their immunosuppressive functions. Conversely, IL-6 and TNF-α can impair Treg suppressive functions or drive their reprogramming into effector T cells. The B7 family of co-stimulatory molecules, including CTLA-4 and PD-1, plays a crucial role in regulating Treg differentiation, function, and survival. Treg dysfunction contributes to autoimmune diseases, and Treg-based immunotherapy shows potential for treating autoimmune diseases, transplant rejection, and cancer. The review highlights the importance of understanding Treg regulation by cytokines and co-stimulatory molecules for developing new therapeutic strategies. Key findings include the role of TGF-β in Treg development, the importance of IL-2 in Treg survival and function, the anti-inflammatory effects of IL-10, and the role of IL-35 in promoting Treg function. Inhibitory cytokines like IL-6 and TNF-α can disrupt Treg function, while co-stimulatory molecules such as CTLA-4 and PD-1 regulate Treg activity. Treg-based immunotherapy is a promising approach for treating various diseases, including autoimmune disorders, transplant rejection, and cancer. The review emphasizes the need for further research to fully understand the complex interactions between Tregs, cytokines, and co-stimulatory molecules to develop effective therapeutic strategies.