Figure 6. IL-33 and STAT6 increase Treg cell population after sepsis.

(a–c) Spleen cells from BALB/c, Il1rl1^−/− or Stat6^−/− mice undergoing CLP and antibiotic treatment were collected 15 days after CLP. Frequency and number of ST2⁺Foxp3⁺CD4⁺ and Foxp3⁺CD4⁺ lymphocytes were analysed by FACS (n≥4 mice per group). (d) C57BL/6 J macrophages from BMDM were cultured for 2 days with M-CSF (M0) or IL-4, IL-13 and IL-33 (M2). Naive CD4⁺ T cells (CD4⁺CD25⁻ T cells) were then cultured for 4 days with M0 or M2 in the presence of IL-2 and anti-CD3 antibody. Percentage of CD4⁺Foxp3⁺ lymphocytes was analysed by FACS (pooled from five mice and pooled from five well per group). (e,f) M0 or M2 macrophages were adoptively transferred (4 × 10⁶ cells, i.v., on day 3 after CLP) into Stat6^−/− sepsis-surviving mice. The surviving mice were either killed or challenged with L. pneumophila on day 15 after CLP. (e) Representative FACS plots, frequency and number of Foxp3⁺ CD4⁺ T cells (n=3 mice per group). (f) Survival curves of mice after L. pneumophila challenge (n=5 mice per group). *P<0.05, **P<0.01 and ***P<0.001 (two-tailed unpaired Student's t-test in a–c,e, Mantel–Cox log-rank test in f). Data are representative of one (f), two (a,e) or four (b,d) independent experiments (mean±s.e.m. in a–c,e).