PDCD1 and Sepsis: This was based on the following findings and arguments: (1) the percentage of PD-1+NK cells of sepsis patients who died within 28 days was significantly higher than that of those who survived, (2) multivariate cox regression analysis showed that the percentage of PD-1+ NK cells and SOFA score were independent risk factors for 28-day mortality, (3) the AUC of predicting the 28-day mortality was non-inferior to the ordinary inflammatory biomarkers.