Intraabdominal infections is a life-threatening syndrome with a high incidence and a significant economic burden. The early-stage cytokine storm and the late-stage immunosuppression contribute to the mortality of sepsis. Immune checkpoints expressed on lymphocytes and antigen-presenting cells (APCs) play a crucial role in the pathogenesis of sepsis by regulating immune dysfunction. Specific therapies targeting immune checkpoints have shown great potential in animal and preclinical studies, paving the way for further clinical research. In this study, the significance of serum immune checkpoints - sCD25 (IL-2Ra), 4-1BB, B7.2 (CD86), Free Active TGF-beta1, CTLA-4, PD-L1, PD-1, Tim-3, LAG-3, and Galectin-9 - will be investigated in patients with intraabdominal infection.