title: Helicobacter pylori, T cells and cytokines: the "dangerous liaisons".
abstract: Helicobacter pylori infection is the major cause of gastroduodenal pathologies, but only a minority of infected patients develop chronic and life threatening diseases, as peptic ulcer, gastric cancer, B-cell lymphoma, or autoimmune gastritis. The type of host immune response against H. pylori is crucial for the outcome of the infection. A predominant H. pylori-specific Th1 response, characterized by high IFN-gamma, TNF-alpha, and IL-12 production associates with peptic ulcer, whereas combined secretion of both Th1 and Th2 cytokines are present in uncomplicated gastritis. Gastric T cells from MALT lymphoma exhibit abnormal help for autologous B-cell proliferation and reduced perforin- and Fas-Fas ligand-mediated killing of B cells. In H. pylori-infected patients with autoimmune gastritis cytolytic T cells infiltrating the gastric mucosa cross-recognize different epitopes of H. pylori proteins and H+K+ ATPase autoantigen. These data suggest that peptic ulcer can be regarded as a Th1-driven immunopathological response to some H. pylori antigens, whereas deregulated and exhaustive H. pylori-induced T cell-dependent B-cell activation can support the onset of low-grade B-cell lymphoma. Alternatively, H. pylori infection may lead in some individuals to gastric autoimmunity via molecular mimicry.
authors.affiliation: Department of Internal Medicine, University of Florence, Viale Morgagni, 85, 50134 Florence, Italy. delios@unifi.it
authors.forename: Mario Milco
authors.initials: MM
authors.lastname: D'Elios
authors.forename: Amedeo
authors.initials: A
authors.lastname: Amedei
authors.forename: Marisa
authors.initials: M
authors.lastname: Benagiano
authors.forename: Annalisa
authors.initials: A
authors.lastname: Azzurri
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Del Prete
mesh_terms: D001327:Autoimmune Diseases / Q000276:immunology / Q000382:microbiology; D016207:Cytokines / Q000378:metabolism*; D016481:Helicobacter Infections / Q000276:immunology* / Q000382:microbiology / Q000503:physiopathology*; D016480:Helicobacter pylori / Q000276:immunology*; D006801:Humans; D018442:Lymphoma, B-Cell, Marginal Zone / Q000276:immunology / Q000382:microbiology; D010437:Peptic Ulcer / Q000276:immunology / Q000382:microbiology; D013274:Stomach Neoplasms / Q000276:immunology / Q000382:microbiology; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D016207:Cytokines