To maintain the immune system's homeostasis, multiple control systems are essential for managing infections, inhibiting tumor growth, preventing inflammation, and avoiding autoimmune diseases. T cells are known to be critical in this regulatory process. Specifically, Th3 cells primarily secrete TGF-? along with varying levels of IL-4 and IL-10. Natural regulatory T cells and Tr1 cells can suppress cytokine production in vitro through CD4+/CD25- T cells or antigen-specific Th1 or Th2 cells.