NOS2 and acute respiratory distress syndrome: In a CLP-induced ALI animal model, measurements of Tregs proportions in splenic mononuclear cells and peripheral blood mononuclear cells (PBMC) revealed that treating with luteolin increased the proportion of Tregs and IL-10 expression while reducing the expression of iNOS and increasing the expression of CD206, which promoted M2 macrophage polarization and consequently alleviated lung injury [251].