It seems that H. pylori induces a regulatory T cell response, possibly contributing to its commensal coexistence with the human host, and that chronic gastritis and peptic ulcer disease occur when this regulatory response is inadequate.18 A similar effect was also seen in our study on THP-1 cells stimulated with H. pylori. Inhibited action of cathepsin X led to profoundly lower levels of IL-10 in the supernatant of THP-1 cells. This evidence concerns the gene IL10 and chronic gastritis.