CD4 and acute respiratory distress syndrome: The prevalence of Th1 (CD4+ IFN-γ+/CD4+ T cells) in peripheral blood was markedly lower in ALI 24 h group than that in ALI 6 h group (ALI 6 h group: 1.6 ± 0.15%, ALI 24 h group: 0.8 ± 0.15%, P = 0.003, Supplementary Fig. S1).