Figure 3. IL-33 increases Tregs that are required for protective functions of IL-33 after ALI.

(A and B) Flow cytometric assessment of CD45⁺CD3⁺CD4⁺CD25⁺ cells isolated from enzymatically digested WT B6 and B6 Il33^–/– mouse lung tissue at day 8 after bleomycin revealed that delivery of IL-33 increased ST2⁺ Tregs in damaged Il33^–/– lung tissue. Data depicted in B are the mean ± SD and are representative of 2 independent experiments, with 4–5 mice per group in each experiment. (C) Survival of B6 Foxp3^DTR mice injected i.t. with bleomycin alone or with rIL-33 (1 μg i.t.) in the presence of Tregs or following their deletion with diphtheria toxin (15 μg/kg on day –3, –2, and –1, and every other day starting from day 1). Depicted data represent 1 experiment with 6–7 mice per group. P values were determined by 1-way ANOVA followed by Tukey’s multiple comparisons test (B) or log-rank test (C). *P < 0.05; **P < 0.01; ***P < 0.001. NS, not significant.