Fig. 4.

Survival curves. a Cox regression analysis survival curves showed that septic patients with the percentage of PD-L1⁺ NK cells  ≥ 5.58% had higher mortality at 28 days (HR 10.128 (1.372–74.772), χ² = 10.999; p = 0.001) as compared to patients with lower levels. b Septic patients with the predicted probability of the SOFA+NK PD-L1 model  ≥ 0.1241 had higher mortality at 28 days (HR 13.730 (3.241–58.158), χ² = 24.907; p < 0.001) as compared to those with lower levels. SOFA, sepsis-related organ failure assessment; NK PD-L1, the percentage of PD-L1⁺ NK cells; HR, hazard ratio