H. pylori infection has close associations with the development of peptic ulcer diseases as well as gastric cancer, gastric adenoma, and gastric MALT lymphoma. The association of the host genetics with the susceptibility to various gastroduodenal disorders has been intensively investigated in the pathogenesis of peptic ulcer and gastric cancer by H. pylori infection .

In chronic active gastritis induced by H. pylori infection, activated neutrophils and mononuclear cells produce several pro-inflammatory and anti-inflammatory cytokines. In fact, levels of pro-inflammatory and anti-inflammatory cytokines are elevated in gastric mucosa infected with H. pylori.

Cytokine polymorphisms are associated with various inflammatory and autoimmune diseases. Recently, cytokine polymorphisms are considered to play an important role in the pathogenesis of peptic ulcer and gastric cancer. However, the roles of the IL-10 polymorphisms on the pathogenesis of H. pylori-related gastric cancer and peptic ulcer have not been fully elucidated.It is unclear whether pro-inflammatory and anti-inflammatory cytokines polymorphisms were associated with pathogenesis of peptic ulcer and gastric cancer in Japan. Then, we intended to clarify the association between polymorphisms of IL-10 and the susceptibility to gastric cancer, gastric ulcer and duodenal ulcer in Japan, and to detect the individuals who have higher risks for gastrointestinal disease development.