CTLA4 and Sepsis: In the development of sepsis, Tregs can mainly inhibit the activation of T lymphocytes, especially CD4+ T lymphocytes through various suppressive mechanisms, including suppression by inhibitory cytokines and cell-to-cell contact (such as CTLA-4 and membrane associated TGF-β), inhibition of cytolysis (especially granzymes), down-regulation of metabolic disruption, and suppression of maturation and function of antigen presenting cells15, 16, 21, 26.