, 2004a). Recently, Vermoote et al. (2011) reported significant histone deacetylase activity differences between H. suis and H. pylori genomes. These studies comparing H. pylori and several H. suis strains can help to elucidate the pathogenesis of gastric disorders induced by H. suis. It was revealed that IL-4 is not essential for the induction of lymphoid follicle formation caused by H. suis infection (Fig. 7), although the mRNA levels of Th2 cytokines were slightly enhanced in the stomachs of the infected C57BL/6J WT mice (Fig. 5). In another study, gastric lymphoid follicles progressed toward a severe MALT lymphoma-like appearance, including

the presence of lymphoepithelial lesions (Nakamura et al., 2007). Regarding animal models of the pathogenesis of MALT lymphoma induced by bacterial infection, Fukui et al. (2004) reported that MALT lymphoma like-lesions develop after H. pylori infection in neonatally thymectomized BALB/c mice, which are a Th2-dominant strain, but not in C57BL/6J mice. In patients with gastric DAPT datasheet MALT lymphoma, it is disputed whether the Th1 or the Th2 response is predominant. Notably high levels of Th1 cytokines and relatively low levels of Th2 cytokines were seen in tumor-infiltrating T cells from two patients with MALT lymphoma in vitro (Hauer et al., 1997). On the contrary, Th2 cytokines in combination with costimulatory

molecules are essential for the progression of MALT lymphoma cells (Greiner et al., 1997; Knorr et al., 1999). Therefore, the Th1/2 paradigm alone is supposed to be insufficient to account for the immune response during the development of gastric MALT lymphoma. Further investigation, for example, of Th17 and Treg responses, is required to elucidate the immune response behind the progression of gastric lymphoma. In conclusion, IFN-γ, a Th1 cytokine, is deeply involved in the pathogenesis

of gastric lymphoid follicle formation induced by H. suis infection. The aggregation of B cells was aided Reverse transcriptase by CD4-positive T cells and DC. This work was supported, in part, by grants for the Global COE Program, Global Center of Excellence for Education and Research on Signal Transduction Medicine in the Coming Generation (T.A. and M.Y.), Scientific Research in Priority Areas ‘Genome’ (T.A. and M.Y.), and Grant-in-Aid for Scientific Research on Innovative Areas (T.A.) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan, and for the COE research support program from Hyogo prefecture (T.A.). This work was also supported by Grant-in-Aid for Young Scientists (I.M.), Mitsubishi Pharma Research Foundation (M.Y.), and a grant for the Education Program for Specialized Clinicians of the Support Program for Improving Graduate School Education from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (T.M.).