IL22 and gastritis: Through H&E staining, ELISA, qRT‐PCR, and flow cytometry analysis, it was demonstrated that patients with H. pylori infection have more severe tissue damage and higher inflammation levels in gastric mucosal and serum, and proved that number of Treg and Th22 cells were raised in H. pylori‐infected patients, and the mRNA levels of their marker gene IL‐22 and Foxp3 were closely related with the degree of H. pylori infection and the severity of gastritis.