We co-cultured the human gastric cancer cell line AGS with H. pylori exposed to IFN-γ; both phosphorylated CagA and nonphosphorylated CagA in AGS cells were downregulated by IFN-γ, and the proportion of cells with the ‘hummingbird’ phenotype was also decreased. Thus, IFN-γ can help control H. pylori infection indirectly through the virulence factor CagA. Helicobacter pylori is one of the most frequently seen pathogens in gastric mucosa and colonizes the stomachs of more than half of the world’s population selleck today (Suerbaum & Josenhans, 2007). The main consequences include chronic gastritis, stomach and duodenal ulcers, gastric carcinoma and mucosa-associated lymphoid

tissue lymphoma. Gastric carcinoma is the fourth most common of all cancers. Helicobacter

selleck products pylori was classified as a class I carcinogenic factor by the World Health Organization in 1994. Helicobacter pylori has a cytotoxin-associated gene (Cag) pathogenicity island, a 40-kb DNA that encodes a type IV secretion system (T4SS). This T4SS can inject a virulence factor such as CagA protein into the host cells (Covacci & Rappuoli, 2000) and augment the gastric carcinoma risk (Franco et al., 2008). CagA protein is one of the most important virulent factors in H. pylori, and its expression is regulated by many environmental factors, including iron (Ernst et al., 2005), acid (Karita et al., 1996; Merrell et al., 2003; Shao et al., 2008b), sodium chloride (Loh et al., 2007; Gancz

et al., 2008), bile (Shao et al., 2008a) and nitric oxide (Qu et al., 2009). Interleukin-1b (IL-1b) (Porat et al., 1991), tumor necrosis factor-α (TNF-α; Luo et al., 1993), IL-2 and granulocyte-macrophage colony-stimulating factor (Denis et al., 1991) can affect the growth and virulence properties of a Resveratrol virulent strain of Escherichia coli, and interferon-γ (IFN-γ) can upregulate the main virulence of Pseudomonas aeruginosa (Wu et al., 2005). However, no study has investigated IFN-γ altering the properties of H. pylori, or more particularly, the effect on the virulence protein CagA. IFN-γ is a proinflammatory cytokine secreted predominantly by CD4+CD25− effector T-helper cells in response to many stimuli, including endotoxin and Gram-negative bacteria. Clinical samples show a significantly higher level of IFN-γ in H. pylori-infected human gastric mucosa than in uninfected mucosa (Shimizu et al., 2004; Pellicanòet al., 2007), as do animal models (Cinque et al., 2006; Sayi et al., 2009). In addition, peripheral blood mononuclear cells produced IFN-γ when exposed to an H. pylori component (Meyer et al., 2000). IFN-γ was produced by natural killer cells in response to an H. pylori component (Yun et al., 2005). Although Shimizu et al. (2004) found no significant correlation between IFN-γ levels and inflammatory cell infiltrations in children with H.