Up-regulation of H3K9 acetylation in Foxp3 promoter CD4⁺CD25⁻ T cells from post septic mice. (A) To determine histone acetylation and methylation status at the promoter region of Foxp3, ChIP assay was performed with 1.5 × 10⁶ FACS-purified CD4⁺CD25⁻ T cells from post septic and sham mice at day 15 after surgery. (B) ChIP assay was performed with 1.5 × 10⁶ FACS-purified CD4⁺CD25⁻ T cells from post septic and sham at day 15 after surgery to determine histone acetylation at H3K9 and H4K12. Numbers above bars indicate the fold change of enrichment after immunoprecipitation (IP) in post septic versus sham mice. Data are representative of 2 independent experiments (average and SEM; n = 4 mice per group). (C) mRNA expression of Kat2a, Kat5, and Kat2b in CD4⁺CD25⁻ T cells from sham and post-CLP groups at day 1, 3, and 15 after surgery. Data from days 1 and 3 are the mean ± SEM from 6 mice in each group (2 spleens pooled at each time point). Data from day 15 are the mean ± SEM from 2 independent experiments (n = 6 for sham, n = 8 for post septic mice). *P ≤ .05, when post septic mice were compared with sham mice.