CD4 and acute respiratory distress syndrome: The prevalence of Treg (CD4+ CD25+ Foxp3+/CD4+ T cells) in lung was markedly lower in ALI 24 h group than that in ALI 6 h group (ALI 6 h group: 3.0 ± 0.2%, ALI 24 h group: 2.2 ± 0.1%, P = 0.0075, Fig. 5).