To evaluate the possible biological effects of IL-33 in H. pylori-associated immunopathogenesis in vivo, we compared the levels of IL-33 expression in gastric mucosa with different severity of gastritis, and found that the expression of IL-33 was positively correlated with the severity of gastritis (Fig. 4a), and a positive correlation between IL-33 and TNF-α was observed (Fig. 4b). This evidence concerns the gene TNF and gastritis.