Fig. 1. Helicobacter pylori products appear to be involved in virulence. There are bacterial virulence factors such as adhesins (AlpA/B, BabA, HopQ and SabA), urease, catalase, neutrophil-activating protein (NAP), adhesin, heat shock proteins (HSP60), outer membrane proteins (OipA), glutamyltranspeptidase (γ-GTP), lipopolysaccharide (LPS), cytotoxin-associated gene pathogenecity island (cagPAI) and vacuolating cytotoxin (VacA). The cagPAI-encoded proteins serve as building blocks of a type IV secretion apparatus, which forms a syringe-like structure capable of penetrating gastric epithelial cells and facilitating the translocation of CagA. CagA is encoded by cagA gene is a marker for the presence of the 40 kb-long genomic cagPAI and contributes to the inflammatory response by initiating a signal transduction cascade, resulting in interleukin (IL) 8 production. LPS can also induce enhanced production of various proinflammatory cytokines. NAP plays a role as a chemoattractant for neutrophils. VacA causes cellular disorder and inhibition of T-cell activation along with γ-GTP. Urease exerts strong activity to generate ammonia from urea, then producing monochloramine, a harmful bioactive molecule against the epithelium. Additional enzyme products including mucinase, phospholipase, lipase and protease damage mucus layer covering the gastric epithelium.