Fig. 2: Administration of sPD-L1 attenuated inflammatory lung injury and improved survival rate in mice with direct ARDS.

A Time course of protein concentration in bronchoalveolar lavage fluid (BALF) of ARDS mice (n = 5/each group). B Time course of cell counts in BALF of ARDS mice (n = 5/each group). C Time course of PD-1 expression in CD45 + lung cells of ARDS mice (n = 5/each group). D PD-1 expression in CD45 + lung cells of ARDS mice at different time points post-infection (n = 5/each group). E Schematic depicting experiment workflow: The mice were intratracheal injected with PAO1(2 × 10⁶ CFU/mL, 50 µL/mouse) to establish the ARDS model, 6 h later the mice were randomly divided into two groups. The mice in sPD-L1 group were intravenous injected with 20 µg/100 µl sPD-L1 protein while those in PBS group were administrated with 100 μL PBS. The mortality was monitored for 7 days and. Every 24 h the mice were administrated with another dose of sPD-L1 or PBS. F Kaplan–Meier plot of survival rate of ARDS mice (n = 23/group) *P < 0.05 by log-rank test. G To detect the lung injury after administration of sPD-L1/PBS, mice were sacrificed at 12-h post infection (6-h post administration of sPD-L1/PBS). Protein concentration in BALF of Sham mice, IgG/PBS-treated ARDS mice, and sPD-L1-treated ARDS mice (n = 10–11/each group). H Cell counts of BALF of Sham mice, IgG/PBS-treated ARDS mice, and sPD-L1-treated ARDS mice (n = 10–11/each group). I Wet to dry ratio of the left lung in Sham mice, IgG/PBS-treated ARDS mice, and sPD-L1-treated ARDS mice (n = 10–11/each group). J HE staining of the left lung in control, IgG/PBS-treated ARDS mice, and sPD-L1-treated ARDS mice (n = 10–11/each group) The experiments have been repeated for at least three times. Each value represents the mean ± SEM of three independent experiments. *P < 0.05, **P < 0.01, ***P < 0.001, analyzed by t test.