Expression of B7-1 and B7-2 costimulatory molecules by human gastric epithelial cells: potential role in CD4+ T cell activation during Helicobacter pylori infection.

Protective immunity against Helicobacter pylori infection in mice has been associated with a strong Th1 response, involving IL-12 as well as IFN-γ, but recent studies have also demonstrated prominent eosinophilic infiltration, possibly linked to local Th2 activity in the gastric mucosa. In this study we investigated the role of IL-18, because this cytokine has been found to be a coregulator of Th1 development as well as involved in Th2-type responses with local eotaxin production that could influence gastric eosinophilia and resistance to infection. We found that IL-18−/− mice failed to develop protection after oral immunization with H. pylori lysate and cholera toxin adjuvant, indicating an important role of IL-18 in protection. Well-protected C57BL/6 wild-type (WT) mice demonstrated substantial influx of CD4+ T cells and eosinophilic cells in the gastric mucosa, whereas IL-18−/− mice had less gastritis, few CD4+ T cells, and significantly reduced numbers of eosinophilic cells. T cells in well-protected WT mice produced increased levels of IFN-γ and IL-18 to recall Ag. By contrast, unprotected IL-18−/− mice exhibited significantly reduced gastric IFN-γ and specific IgG2a Ab levels. Despite differences in gastric eosinophilic cell infiltration, protected WT and unprotected IL-18−/− mice had comparable levels of local eotaxin, suggesting that IL-18 influences protection via Th1 development and IFN-γ production rather than through promoting local production of eotaxin and eosinophilic cell infiltration.

Section: Discussionmentioning

confidence: 99%

Vaccine-Induced Immunity againstHelicobacter pyloriInfection Is Impaired in IL-18-Deficient Mice

Akhiani

Schön

Lycke

2004

“…The best known function of class II MHC is the presentation of Ags to CD4 ϩ T cells, which are also increased in the infected gastric mucosa (34,35). However, engaged class II MHC may also deliver intracellular signals to the cells which express them.…”

Section: Discussionmentioning

confidence: 99%

Helicobacter pylori Urease Binds to Class II MHC on Gastric Epithelial Cells and Induces Their Apoptosis

Fan

Gunasena

Cheng

et al. 2000

147

Infection by Helicobacter pylori leads to injury of the gastric epithelium and a cellular infiltrate that includes CD4+ T cells. H. pylori binds to class II MHC molecules on gastric epithelial cells and induces their apoptosis. Because urease is an abundant protein expressed by H. pylori, we examined whether it had the ability to bind class II MHC and induce apoptosis in class II MHC-bearing cells. Flow cytometry revealed the binding of PE-conjugated urease to class II MHC+ gastric epithelial cell lines. The binding of urease to human gastric epithelial cells was reduced by anti-class II MHC Abs and by staphylococcal enterotoxin B. The binding of urease to class II MHC was confirmed when urease bound to HLA-DR1-transfected COS-1 (1D12) cells but not to untransfected COS-1 cells. Urease also bound to a panel of B cell lines expressing various class II MHC alleles. Recombinant urease induced apoptosis in gastric epithelial cells that express class II MHC molecules, but not in class II MHC− cells. Also, Fab from anti-class II MHC and not from isotype control Abs blocked the induction of apoptosis by urease in a concentration-dependent manner. The adhesin properties of urease might point to a novel and important role of H. pylori urease in the pathogenesis of H. pylori infection.

“…In addition to their well-characterized contribution to the host response via the secretion of multiple cytokines, GEC may function as APCs due to their constitutive expression of class II MHC molecules, and this expression is increased during H. pylori infection (17). In support of this possibility, previous studies demonstrated CD80 (B7-1) and CD86 (B7-2) in gastric epithelium and up-regulation of CD86 expression following H. pylori infection (17). For efficient T cell activation, T cells require not only the TCR-mediated Ag-specific signal, but also costimulatory signals provided by APCs (18,19).…”

mentioning

confidence: 99%

Expression of B7-H1 on Gastric Epithelial Cells: Its Potential Role in Regulating T Cells during Helicobacter pylori Infection

Das

Suárez

Beswick

et al. 2006

163

144

Helicobacter pylori infection is associated with gastritis, ulcers, and gastric cancer. The infection becomes chronic as the host response is unable to clear it. Gastric epithelial cells (GEC) play an important role during the host response, and their expression of class II MHC and costimulatory molecules such as CD80 and CD86 suggests their role in local Ag presentation. Although T cells are recruited to the infected gastric mucosa, they have been reported to be hyporesponsive. In this study, we detected the expression of B7-H1 (programmed death-1 ligand 1), a member of B7 family of proteins associated with T cell inhibition on GEC. Quantitative real-time RT-PCR revealed that B7-H1 expression increased significantly on GEC after H. pylori infection. Western blot analysis showed that B7-H1 expression was induced by various H. pylori strains and was independent of H. pylori virulence factors such as Cag, VacA, and Urease. The functional role of B7-H1 in the cross talk between GEC and T cells was assessed by coculturing GEC or H. pylori-infected GEC with CD4+ T cells isolated from peripheral blood. Using blocking Abs to B7-H1 revealed that B7-H1 was involved in the suppression of T cell proliferation and IL-2 synthesis, and thus suggested a role for B7-H1 on the epithelium as a contributor in the chronicity of H. pylori infection.