Heightened levels of IL-17 have been seen in H. pylori infected gastric mucosa (Luzza et al., 2000; Algood et al., 2007; Caruso et al., 2008; Shi et al., 2010), implicating the role of Th17 cells in the development of H. pylori induced gastritis (Shi et al., 2010). Here, IL17A is linked to gastritis.