CD4 and acute respiratory distress syndrome: As shown in Fig. 4, the prevalence of Th17 (CD4+ IL-17A+/CD4+ T cells) in peripheral blood was higher in ALI 6 h group than that in normal control group (Con group: 0.9 ± 0.06%, ALI 6 h group: 1.2 ± 0.25%, P = 0.07, Fig. 4).