To correlate PLET1 levels in IAV-ARDS BALF with the level of alveolar epithelial injury, we additionally quantified total BALF protein as a measure of alveolar barrier dysfunction in both cohorts (Fig. 7b), and PLET1 concentrations negatively correlated with total BALF protein concentrations (Fig. 7c), indicating that soluble PLET1 was present in BALF of patients with IAV-ARDS and might exert similar barrier-protective functions as observed in mice. This evidence concerns the gene PLET1 and acute respiratory distress syndrome.