IL-33 is highly expressed in TNBS-induced colitis. Colonic tissue samples were collected from mice on d 4 after instillation with TNBS or 50% ethanol. (A) Expression of IL-33, IFN-γ and IL-17 proteins in total tissue extracts was assessed by immunoblot. f-IL-33 and c-IL-33 mean precursor of and mature IL-33, respectively. (B) The mRNA expression of IL-33in colonic tissue was analyzed. Data from one representative out of three experiments indicate mean ± SD (n = 5-8/group); #p < 0.01. (C) The colonic tissue sections from the two groups (TNBS and ethanol treatment) were stained with hematoxylin and eosin. (D) The production of IL-33 in colonic tissue was detected by immunohistochemistry (red arrows). (E) The colonic tissue sections from TNBS-treated mice were costained by IL-33 (green) and F4/80 (red) antibody. Colocalization is indicated as yellow (white arrows). (F) IL-33 mRNA and protein expression in peritoneal macrophage and the RAW 264.7 cell line was assessed by RT-PCR and immunoblot. Data shown are representative of three independent experiments.