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 normal control group (Con group: 4.5 ± 0.7%, ALI 24 h group: 2.2 ± 0.1%, P = 0.0029, Fig. 5).