S100A8 and chronic gastritis: However, until now, the mechanism of H. pylori-associated chronic gastritis remains unclear, and it is believed that the interplays between host and bacterial virulence factors21,27, such as vacA15,28,29, especially a major virulence factor cagA that can be injected into the host cell by Type IV Secretion System (T4SS)30, and that will be phosphorylated after entering the host gastric epithelial cells31, and the following persistent inflammation, are likely the underlying causes.