Among the others, IL-1 has been shown to be

a key cytokine in initiating and amplifying the inflammatory responses against H. pylori [37-39]. Very recently, IL-1β present in the gastric mucosa has been shown to play an important role in H. pylori-induced epigenetic changes linking inflammation to carcinogenesis [40]. Finally, H. pylori virulence and IL-1B genes contribute to peptic ulcers and intestinal metaplasia [41]. Elevation of Tregs at the site of infection and H. pylori-specific Tregs in the circulation [20, 21] has been suggested as a mechanism of pathogen persistence, on the assumption that Tregs are differentiated cells with professional suppressive function. In this study we show for the first time that H. pylori interacts with human Tregs indirectly via DCs and modifies their function. Our data show that H. pylori-treated DCs stimulate Treg proliferation, diminish their suppressive Nivolumab supplier Erlotinib datasheet function and that DC-derived IL-1β drives this process. Biopsy data from in-vivo H. pylori-infected antrum corroborated these findings, showing that a significant portion of Tregs found in infected gastric biopsies are actively undergoing mitosis. The persistence of H. pylori in the gastric mucosa may allow continual restimulation of the Treg population. This restimulation may allow for expansion of the Treg population beyond the 3-day peak observed in vitro. In this model it is not the presence of Tregs that promote the

L-gulonolactone oxidase persistence of infection, but rather the persistence of infection that expands the Treg population in an attempt to limit the damage caused by a prolonged and excessive inflammatory response. Demonstrations that suppressive function of Tregs can be undermined by pathogens have been shown previously in the context of L. major and H. hepaticus infections, limiting inflammation while hindering pathogen clearance [18, 19]. Although pathogens can influence Treg function directly, such as through engagement of TLR-2, -4 and -8 [42-44], we found that H. pylori had no direct effect on Tregs and that the changes induced in Treg behaviour could be explained by cytokine production from DCs. We have found that IL-1β plays a central role in mediating the effects of H. pylori on Tregs. This is of particular interest, as virulent strains of H. pylori expressing cagPAI are associated with elevated levels of IL-1β [13, 45]. As a result, the influence of H. pylori DCs on Tregs may be enhanced by the local microenvironment. In addition, IL-1β has a significant inhibitory effect on gastric acid production [46], which encourages H. pylori colonization to spread and downstream pathological events (gastritis and gastric cancer). As IL-1β appears to have a central role in H. pylori biology and its mechanisms of immune evasion and chronic inflammation, it may be revealing to study the relationship between polymorphisms in IL-1β and interactions between H.