Induction of Maturation and Cytokine Release of Human Dendritic Cells byHelicobacter pylori

Abstract

Helicobacter pylori causes a persistent infection in the human stomach, which can result in chronic gastritis and peptic ulcer disease. Despite an intensive proinflammatory response, the immune system is not able to clear the organism. However, the immune escape mechanisms of this common bacterium are not well understood. We investigated the interaction between H. pylori and human dendritic cells. Dendritic cells (DCs) are potent antigen-presenting cells and important mediators between the innate and acquired immune system. Stimulation of DCs with different concentrations of H. pylori for 8, 24, 48, and 72 h resulted in dose-dependent interleukin-6 (IL-6), IL-8, IL-10 and IL-12 production. Lipopolysaccharide (LPS) from Escherichia coli, a known DC maturation agent, was used as a positive control. The cytokine release after stimulation with LPS was comparable to that induced by H. pylori except for IL-12. After LPS stimulation IL-12 was only moderately released compared to the large amounts of IL-12 induced by H. pylori. We further investigated the potential of H. pylori to induce maturation of DCs. Fluorescence-activated cell sorting analysis of cell surface expression of maturation marker molecules such as CD80, CD83, CD86, and HLA-DR revealed equal upregulation after stimulation with H. pylori or LPS. We found no significant differences between H. pylori seropositive and seronegative donors of DCs with regard to cytokine release and upregulation of surface molecules. These data clearly demonstrate that H. pylori induces a strong activation and maturation of human immature DCs.Helicobacter pylori is a gastric pathogenic gram-negative bacterium that colonizes the gastric mucus layer but does not invade the mucosal epithelium. This bacterial colonization leads to a cellular infiltrate of polymorphonuclear leukocytes, an acute immune response, followed by the migration of macrophages, lymphocytes, and plasma cells in the gastric mucosa, resulting in chronic gastritis. This chronic inflammation does not necessarily produce symptoms but does increase the risk of developing peptic ulcer disease, adenocarcinoma of the distal stomach (antrum and fundus), and primary non-Hodgkin's lymphoma of the stomach (MALTomas) (8,42,43).Although H. pylori induces an immune response involving both the innate and the acquired immune systems, the host is unable to clear the organism from the mucosa, resulting in lifelong infection. This inability to eliminate the bacterium may be due to immune-evasive strategies. Possible mechanisms were investigated, with emphasis on the acquired immune response. Several studies have shown inhibitory effects of H. pylori on cell proliferation (11, 24-26, 60), and the induction of H. pylori-specific regulatory T cells that actively suppress T-cell response have been described (31).Recent studies have investigated possible impairment of antigen presentation. VacA, an H. pylori virulence factor, was reported to interfere with proteolytic processing of tetanus toxoid and was shown to inhibit the Ii-depen...

Vector-Encoded Helicobacter pylori Neutrophil-Activating Protein Promotes Maturation of Dendritic Cells with Th1 Polarization and Improved Migration

“…4). This is different to stimulation with the whole H. pylori bacteria, where also IL-6 and IL-10 secretion is present (26). The presence of IL-12 in tumor stroma restores the function of dysfunctional myeloid-derived cells such as macrophages, DCs, and myeloid-derived suppressor (39)(40)(41).…”

“…Depending on the maturation signal received by the DCs, they can promote effector T cell responses with polarized cytokine secretion pattern like cytokine-polarized Th1, Th2, Th9, Th17, or regulatory T cell responses (23,24), which is very essential for successful outcome of vaccination or Ag-specific immunotherapy. H. pylori bacteria and its virulence factors such as cytotoxin-associated gene A (CagA) induce a semimatured tolerogenic DC phenotype secreting cytokines, including IL-6, IL-10, IL-8, and IL-12 (25,26). However, the role of HP-NAP alone on DC maturation and subsequent activation of the immune system have not been completely studied.…”

Impact of Helicobacter pylori Virulence Factors and Compounds on Activation and Maturation of Human Dendritic Cells

“…Several studies have focused on the interaction between H. pylori and the innate immune system (12,22,41), showing H. pylori-induced cytokine production by antigen-presenting cells. Our group and others (24,33) have demonstrated activation and maturation of human DCs by H. pylori. Furthermore, DCs pulsed with H. pylori were shown to induce NK cell activation, as well as Th1 effector responses (24).…”

“…Monocytes were isolated by leukapheresis of healthy donors, subsequent Ficoll-Hypaque density gradient centrifugation, and countercurrent elutriation with a J6 M-E centrifuge (Beckman, Munich, Germany) as previously described (33,34). Monocytes were Ͼ90% pure, as determined by flow cytometry (data not shown).…”

“…The detailed experimental procedures were described previously (33). In brief, cells were harvested after 7 days and washed twice with 10 ml of phosphatebuffered saline (PBS).…”