Regulation of murine dendritic cell immune responses by Helicobacter felis antigen

Helicobacter-stimulated IL-10-producing B cells suppress differentiation of lipopolysaccharide/Helicobacter felis-activated stimulatory dendritic cells

Regulatory B cells (Bregs) produce antiinflammatory cytokines and inhibits proinflammatory response. Recently, immunosuppressive roles of Bregs in the effector functions of dendritic cells (DCs) were demonstrated. However, cross talk between Bregs and DCs in Helicobacter infection remains unknown. Here, we showed that direct stimulation of bone marrow-derived DCs (BM-DCs) with Helicobacter felis (H. felis) antigen upregulates their CD86 surface expression and causes the production of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), interleukin-12 (IL-12), and interleukin-10 (IL-10). Furthermore, prestimulation of DCs with supernatants derived from both Helicobacter-stimulated IL-10^– B (Hf_stim-IL-10^– B) or IL-10⁺ B (Hf_stim-IL-10⁺) cells suppresses the secretion of TNF-α and IL-6, but does not affect the expression of CD86 and secretion of IL-12 by lipopolysaccharide (LPS) or H. felis-activated BM-DCs. Remarkably, soluble factors secreted by Hf_stim-IL-10^– B cells, but not by Hf_stim-IL-10⁺ B cells, suppress the secretion of IL-10 by BM-DCs upon subsequent LPS stimulation. In contrast, prestimulation with BM-DCs with supernatants of Hf_stim-IL-10⁺ B cells before H. felis antigen stimulation induces significantly their IL-10 production. Collectively, our data indicated that prestimulation with soluble factors secreted by Hf_stim-IL-10⁺ B cells, DCs exhibit a tolerogenic phenotype in response to LPS or Helicobacter antigen by secreting high levels of IL-10, but decreased levels of IL-6 and TNF-α.

A Novel Gastric Spheroid Co-culture Model Reveals Chemokine-Dependent Recruitment of Human Dendritic Cells to the Gastric Epithelium

BACKGROUND & AIMS

Gastric dendritic cells (DCs) control the adaptive response to infection with Helicobacter pylori, a major risk factor for peptic ulcer disease and gastric cancer. We hypothesize that DC interactions with the gastric epithelium position gastric DCs for uptake of luminal H pylori and promote DC responses to epithelial-derived mediators. The aim of this study was to determine whether the gastric epithelium actively recruits DCs using a novel co-culture model of human gastric epithelial spheroids and monocyte-derived DCs.

METHODS

Spheroid cultures of primary gastric epithelial cells were infected with H pylori by microinjection. Co-cultures were established by adding human monocyte-derived DCs to the spheroid cultures and were analyzed for DC recruitment and antigen uptake by confocal microscopy. Protein array, gene expression polymerase chain reaction array, and chemotaxis assays were used to identify epithelial-derived chemotactic factors that attract DCs. Data from the co-culture model were confirmed using human gastric tissue samples.

RESULTS

Human monocyte-derived DCs co-cultured with gastric spheroids spontaneously migrated to the gastric epithelium, established tight interactions with the epithelial cells, and phagocytosed luminally applied H pylori. DC recruitment was increased upon H pylori infection of the spheroids and involved the activity of multiple chemokines including CXCL1, CXCL16, CXCL17, and CCL20. Enhanced chemokine expression and DC recruitment to the gastric epithelium also was observed in H pylori-infected human gastric tissue samples.

CONCLUSIONS

Our results indicate that the gastric epithelium actively recruits DCs for immunosurveillance and pathogen sampling through chemokine-dependent mechanisms, with increased recruitment upon active H pylori infection.

Differential inflammatory response to Helicobacter pylori infection: etiology and clinical outcomes

The bacterial pathogen Helicobacter pylori commonly colonizes the human gastric mucosa during early childhood and persists throughout life. The organism has evolved multiple mechanisms for evading clearance by the immune system and, despite inducing inflammation in the stomach, the majority of infections are asymptomatic. H. pylori is the leading cause of peptic ulcer disease and gastric cancer. However, disease outcomes are related to the pattern and severity of chronic inflammation in the gastric mucosa, which in turn is influenced by both bacterial and host factors. Despite over 2 decades of intensive research, there remains an incomplete understanding of the circumstances leading to disease development, due to the fascinating complexity of the host-pathogen interactions. There is accumulating data concerning the virulence factors associated with increased risk of disease, and the majority of these have pro-inflammatory activities. Despite this, only a small proportion of those infected with virulent strains develop disease. Several H. pylori virulence factors have multiple effects on different cell types, including the induction of pro- and anti-inflammatory, immune stimulatory, and immune modulatory responses. The expression of multiple virulence factors is also often linked, making it difficult to assess the meaning of their effects in isolation. Overall, H. pylori is thought to usually modulate inflammation and limit acute damage to the mucosa, enabling the bacteria to persist. If this delicate balance is disturbed, disease may then develop.

Lactic acid bacteria strains exert immunostimulatory effect on H. pylori-induced dendritic cells

The aim of this study was to find out if selected lactic acid bacteria (LAB) strains (antagonistic or nonantagonistic against H. pylori in vitro) would differ in their abilities to modulate the DCs maturation profiles reflected by their phenotype and cytokine expression patterns. Methods. Monocyte-derived DCs maturation was elicited by their direct exposure to the LAB strains of L. rhamnosus 900 or L. paracasei 915 (antagonistic and nonantagonistic to H. pylori, resp.), in the presence or absence of H. pylori strain cagA+. The DCs maturation profile was assessed on the basis of surface markers expression and cytokines production. Results. We observed that the LAB strains and the mixtures of LAB with H. pylori are able to induce mature DCs. At the same time, the L. paracasei 915 leads to high IL-10/IL-12p70 cytokine ratio, in contrast to L. rhamnosus 900. Conclusions. This study showed that the analyzed lactobacilli strains are more potent stimulators of DC maturation than H. pylori. Interestingly from the two chosen LAB strains the antagonistic to H. pylori-L. rhamnosus strain 900 has more proinflammatory and probably antibactericidal properties.

The role of spartin and its novel ubiquitin binding region in DALIS occurrence

Troyer syndrome is an autosomal recessive hereditary spastic paraplegia (HSP) caused by frameshift mutations in the SPG20 gene that results in a lack of expression of the truncated protein. Spartin is a multifunctional protein, yet only two conserved domains--a microtubule-interacting and trafficking domain and a plant-related senescence domain involved in cytokinesis and mitochondrial physiology, respectively--have been defined. We have shown that overexpressed spartin binds to the Ile44 hydrophobic pocket of ubiquitin, suggesting spartin might contain a ubiquitin-binding domain. In the present study, we demonstrate that spartin contributes to the formation of dendritic aggresome-like induced structures (DALIS) through a unique ubiquitin-binding region (UBR). Using short hairpin RNA, we knocked down spartin in RAW264.7 cells and found that DALIS frequency decreased; conversely, overexpression of spartin increased the percentage of cells containing DALIS. Using nuclear magnetic resonance spectroscopy, we characterized spartin's UBR and defined the UBR's amino acids that are key for ubiquitin binding. We also found that spartin, via the UBR, binds Lys-63-linked ubiquitin chains but does not bind Lys-48-linked ubiquitin chains. Finally, we demonstrate that spartin's role in DALIS formation depends on key residues within its UBR.

Rapid interaction of Helicobacter pylori with microvilli of the polar human gastric epithelial cell line NCI-N87

Infection with Helicobacter pylori results often in chronic gastritis, gastric ulcers or even gastric tumor development. Little is known about the initial interaction between gastric epithelial cells and H. pylori. The aim of the present study was to analyze the initial host contact to the bacteria. Monolayers of the human gastric epithelial cell line NCI-N87 grown on porous membranes were used and the apical side of the epithelium was exposed to the H. pylori wild-type strain P1 for 1 hr. Many epithelial cells were colonized by bacteria within the period of 60 min. Using scanning electron microscopy we detected that the bacteria were in close contact with the epithelia via microvilli. Further, transmission electron microscopy of the contact sites revealed no difference in the morphology of the microvilli in comparison to those not attached to the bacteria. The present study demonstrates the importance of microvilli on apical epithelial cells during the initial contact of the host by colonizing H. pylori. Anat Rec, 296:1800–1805, 2013. © 2013 The Authors. The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology published by Wiley Periodicals, Inc. on behalf of the American Association of Anatomists.

IRAK-M expression limits dendritic cell activation and proinflammatory cytokine production in response to Helicobacter pylori

Helicobacter pylori (H. pylori) infects the gastric mucosa and persists for the life of the host. Bacterial persistence may be due to the induction of regulatory T cells (T_regs) whichmay have protective effects against other diseases such as asthma. It has been shown that H. pylori modulates the T cell response through dendritic cell reprogramming but the molecular pathways involved are relatively unknown. The goal of this study was to identify critical elements of dendritic cell (DC) activation and evaluate potential influence on immune activation. Microarray analysis was used to demonstrate limited gene expression changes in H. pylori stimulated bone marrow derived DCs (BMDCs) compared to the BMDCs stimulated with E. coli. IRAK-M, a negative regulator of TLR signaling, was upregulated and we selectedit for investigation of its role in modulating the DC and T cell responses. IRAK-M^−/− and wild type BMDC were compared for their response to H. pylori. Cells lacking IRAK-M produced significantly greater amounts of proinflammatory MIP-2 and reduced amounts of immunomodulatory IL-10 than wild type BMDC. IRAK-M^−/− cells also demonstrated increased MHC II expression upon activation. However, IRAK-M^−/− BMDCs were comparable to wild type BMDCs in inducing T-helper 17 (T_H17) and T_reg responses as demonstrated in vitro using BMDC CD4+ T cells co-culture assays,and in vivo though the adoptive transfer of CD4⁺ FoxP3-GFP T cells into H. pylori infected IRAK-M^−/− mice. These results suggest that H. pylori infection leads to the upregulation of anti-inflammatory molecules like IRAK-M and that IRAK-M has a direct impact on innate functions in DCs such as cytokine and costimulation molecule upregulation but may not affect T cell skewing.

Helicobacter pylori induces in-vivo expansion of human regulatory T cells through stimulating interleukin-1β production by dendritic cells

Helicobacter pylori is one of the most common infections in the world. Despite inciting inflammation, immunological clearance of the pathogen is often incomplete. CD4(+) CD25(hi) forkhead box protein 3 (FoxP3(+)) regulatory T cells (T(regs)) are potent suppressors of different types of immune responses and have been implicated in limiting inflammatory responses to H. pylori. Investigating the influence of H. pylori on T(reg) function and proliferation, we found that H. pylori-stimulated dendritic cells (DCs) induced proliferation in T(regs) and impaired their suppressive capability. This effect was mediated by interleukin (IL)-1β produced by H. pylori-stimulated DCs. These data correlated with in-vivo observations in which H. pylori(+) gastric mucosa contained more T(regs) in active cell division than uninfected stomachs. Inciting local proliferation of T(regs) and inhibiting their suppressive function may represent a mechanism for the chronic gastritis and carcinogenesis attributable to H. pylori.

Lack of genetic influence on the innate inflammatory response to helicobacter infection of the gastric mucosa

Helicobacter pylori (H. pylori) is a bacterial pathogen that resides at the gastric mucosa and has a world-wide prevalence of over 50%. Infection usually lasts for the life of the host, and although all infected individuals will develop histologic gastritis only a subset will develop symptomatic gastritis, peptic ulcer disease, gastric MALT lymphoma, or gastric adenocarcinoma. The bacterial and host factors that determine clinical outcome and influence the development of widely varying diseases have not been elucidated. We compared disease in Helicobacter-infected severe combined immunodeficient (SCID) mice on different genetic backgrounds with their corresponding immunocompetent partners to determine if the genetics of the host significantly impacts the innate inflammatory outcome, independent of variations in bacterial virulence factors. BALB/c SCID and C57BL/6 SCID mice developed equivalent histologic gastritis by 8 weeks of infection. Immunocompetent BALB/c mice and C57BL/6 mice developed significantly lower or higher degrees of inflammation respectively. Innate inflammation in immunodeficient mice on the C57BL/6 background remained low even in the absence of the regulatory cytokine IL-10. These results demonstrate that adaptive immunity is not required for the generation of low level inflammation in response to Helicobacter infection and that the degree of inflammation is consistent among different genetic backgrounds. Additionally, this inflammation is limited even in the absence of regulatory T cells.

Deficiency of claudin-18 causes paracellular H+ leakage, up-regulation of interleukin-1β, and atrophic gastritis in mice

BACKGROUND & AIMS

Although defects in tight junction (TJ) epithelial paracellular barrier function are believed to be a primary cause of inflammation, the mechanisms responsible remain largely unknown.

METHODS

We generated knockout mice of stomach-type claudin-18, a major component of TJs in the stomach.

RESULTS

Cldn18(-/-) mice were afflicted with atrophic gastritis that started on postnatal day 3. This coincided with a decrease in intragastric pH due to H(+) secretion from parietal cells and concomitant up-regulation of the cytokines, interleukin-1β, cyclooxygenase-2, and KC, resulting in spasmolytic polypeptide-expressing metaplasia (SPEM). Oral administration of hydrochloric acid on postnatal day 1 induced the expression of these cytokines in Cldn18(-/-) infant stomach, but not in Cldn18(+/+) mice. A paracellular H(+) leak in Cldn18(-/-) stomach was detected by electrophysiology and H(+) titration, and freeze-fracture electron microscopy showed structural defects in the TJs, in which the tightly packed claudin-18 (stomach-type)-based TJ strands were lost, leaving a loose meshwork of strands consisting of other claudin species.

CONCLUSIONS

These findings provide evidence that claudin-18 normally forms a paracellular barrier against H(+) in the stomach and that its deficiency causes paracellular H(+) leak, a persistent up-regulation of proinflammatory cytokines, chronic recruitment of neutrophils, and the subsequent development of SPEM in atrophic gastritis.

Enhanced antitumor effects of a dendritic cell vaccine transfected with gastric cancer cell total RNA carrying the 4-1BBL gene in vitro

T cell-mediated antitumor immunity is a cellular immune response that requires two signals. The dendritic cell (DC) has been considered as the most efficient antigen-presenting cell (APC). It plays essential roles in the induction, regulation and maintenance of antitumor immunity in humans. The 4-1BB/4-1BB ligand (4-1BBL) pathway plays crucial roles in immune response, tumor immunity and autoimmune diseases through transduction of T cell co-stimulatory signals. The aim of this study was to generate the preparation protocol for a DC vaccine transfected with gastric cancer cell total ribonucleic acid (RNA) carrying the 4-1 BBL gene in vitro and to investigate its antitumor effects in murine forestomach carcinoma (MFC). The vaccine was prepared by transfecting MFC total RNAs carrying the 4-1BBL gene into the DCs that were isolated from 615 mouse bones. The T cell proliferation rate in the MFC/4-1BBL/DC group was higher than that in the DC group. The tumor cell kill rate in the MFC/4-1BBL/DC group was higher than that in the DC group. ELISA analysis showed that IL-12 and IFN-γ in the MFC/4-1BBL/DC group were more highly expressed compared to the other group. Collectively, our data demonstrate that the DC vaccine transfected with gastric cancer cell total RNA carrying the 4-1BBL gene has a stronger ability to kill gastric cancer cells through promoting T cell proliferation and enhancing the ability of cytotoxic T lymphocytes (CTLs) to kill gastric carcinoma cells and to secrete IL-12 and IFN-γ. Our results provide an effective therapeutic strategy for treating gastric cancer using a DC vaccine.

TLR2-dependent modulation of dendritic cells by LT-IIa-B5, a novel mucosal adjuvant derived from a type II heat-labile enterotoxin

A host of human pathogens invades the body at mucosal surfaces. Yet, strong, protective mucosal immune responses directed against those pathogens routinely cannot be induced without the use of adjuvants. Although the strongest mucosal adjuvants are members of the family of HLTs, the inherent toxicities of HLT holotoxins preclude their clinical use. Herein, it is shown that LT-IIa-B(5) enhances mucosal immune responses by modulating activities of DCs. i.n. immunization of mice with OVA in the presence of LT-IIa-B(5) recruited DCs to the NALT and significantly increased uptake of OVA by those DCs. Furthermore, LT-IIa-B(5) increased expression of CCR7 by DCs, which mediated enhanced migration of the cells from the NALT to the draining CLNs. LT-IIa-B(5) also enhanced maturation of DCs, as revealed by increased surface expression of CD40, CD80, and CD86. Ag-specific CD4(+) T cell proliferation was augmented in the CLNs of mice that had received i.n. LT-IIa-B(5). Finally, when used as an i.n. adjuvant, LT-IIa-B(5) dramatically increased the levels of OVA-specific salivary IgA and OVA-specific serum IgG. Strikingly, each of the activities induced by LT-IIa-B(5) was strictly TLR2-dependent. The data strongly suggest that the immunomodulatory properties of LT-IIa-B(5) depend on the productive modulation of mucosal DCs. Notably, this is the first report for any HLT to demonstrate in vivo the elicitation of strong, TLR2-dependent modulatory effects on DCs with respect to adjuvanticity.

Human primary gastric dendritic cells induce a Th1 response to H. pylori

Adaptive CD4 T-cell responses are important in the pathogenesis of chronic Helicobacter pylori gastritis. However, the gastric antigen-presenting cells that induce these responses have not yet been identified. Here we show that dendritic cells (DCs) are present in the gastric mucosa of healthy subjects and are more prevalent and more activated in the gastric mucosa of H. pylori-infected subjects. H. pylori induced gastric DCs isolated from noninfected subjects to express increased levels of CD11c, CD86 and CD83, and to secrete proinflammatory cytokines, particularly interleukin (IL)-6 and IL-8. Importantly, gastric DCs pulsed with live H. pylori, but not control DCs, mediated T-cell secretion of interferon-gamma. The ability of H. pylori to induce gastric DC maturation and stimulate gastric DC activation of Th1 cells implicates gastric DCs as initiators of the immune response to H. pylori.

Enhanced antigen uptake by dendritic cells induced by the B pentamer of the type II heat-labile enterotoxin LT-IIa requires engagement of TLR2

The potent mucosal adjuvant properties of the type II heat-labile enterotoxin LT-IIa of Escherichia coli are dependent upon binding of the B pentamer of the enterotoxin (LT-IIa-B(5)) to ganglioside receptors on immunocompetent cells. To evaluate the immunomodulatory activities of LT-IIa-B(5), in vitro experiments employing bone marrow-derived dendritic cells (BMDC) were performed. Uptake of OVA-FITC, a model antigen (Ag), was enhanced by treatment of BMDC with LT-IIa-B5, but not by treatment of cells with the B pentamer of cholera toxin (CTB). Expression of co-stimulatory molecules (CD40, CD80, CD86, and MHC-II) and cytokines (IL-12p40, TNF-alpha, and IFN-gamma) was increased in BMDC treated with LT-IIa-B(5). The capacity of LT-IIa-B(5) to enhance Ag uptake and to induce expression of co-stimulatory receptors and cytokines by BMDC was dependent upon expression of TLR2 by the cell. Increased Ag uptake induced by LT-IIa-B(5) was correlated with increased Ag-specific proliferation of CD4(+) T cells in an in vitro syngeneic DO11.10 CD4(+) T cell proliferation assay. These experiments confirm that LT-IIa-B(5) exhibits potent immunomodulatory properties which may be exploitable as a non-toxic mucosal adjuvant.

Helicobacter pylori immune escape is mediated by dendritic cell-induced Treg skewing and Th17 suppression in mice

BACKGROUND & AIMS

Helicobacter pylori infection increases gastric regulatory T cell (Treg) response, which may contribute to H pylori immune escape. We hypothesize that H pylori directs Treg skewing by way of dendritic cells (DCs) and thus inhibits interleukin-17(+) helper T cells (Th17) immunity.

METHODS

Two-photon microscopy was used to locate DCs in gastric lamina propria of mice. The induction of Th17 and Treg responses by bacteria-pulsed murine bone marrow-derived DCs was analyzed by cytokine production and stimulation of T-cell proliferation. The effect of VacA, CagA, transforming growth factor-beta (TGF-beta), and IL-10 on Th17/Treg balance was assessed. The in vivo significance of Tregs on the H pylori-specific Th17 response and H pylori density was determined by using anti-CD25 neutralizing antibodies to deplete Tregs in mice.

RESULTS

We showed that mucosal CD11c(+) DCs are located near the surface of normal gastric epithelium, and their number increased after H pylori infection. Study of the direct interaction of DCs with H pylori showed a Treg-skewed response. The Treg skewing was independent of H pylori VacA and CagA and dependent on TGF-beta and IL-10. In vivo Treg skewing by adoptive transfer of H pylori-pulsed DCs reduces the ratio of gastric IL-17/Foxp3 mRNA expressions. The depletion of CD25(+) Tregs results in early reduction of H pylori density, which is correlated with enhanced peripheral H pylori-specific Th17, but not Th1, response.

CONCLUSIONS

Overall, our study indicates that H pylori alters the DC-polarized Th17/Treg balance toward a Treg-biased response, which suppresses the effective induction of H pylori-specific Th17 immunity.

Helicobacter pylori stimulates dendritic cells to induce interleukin-17 expression from CD4+ T lymphocytes

Helicobacter pylori is a human gastroduodenal pathogen that leads to active chronic inflammation characterized by T-cell responses biased toward a Th1 phenotype. It has been accepted that H. pylori infection induces a Th17 response. At mucosal sites, dendritic cells (DCs) have the capacity to induce effector T cells. Here, we evaluate the role of DCs in the H. pylori-induced interleukin-17 (IL-17) response. Immunohistochemistry and immunofluorescence were performed on human gastric mucosal biopsy samples and showed that myeloid DCs in H. pylori-infected patients colocalized with IL-23- and that IL-17-producing lymphocytes were present in H. pylori-infected antral biopsy samples. In parallel, human monocyte-derived DCs stimulated in vitro with live H. pylori cells produced significant levels of IL-23 in the absence of IL-12 release. The subsequent incubation of H. pylori-infected DCs with autologous CD4(+) T cells led to gamma interferon (IFN-gamma) and IL-17 expression. The inhibition of IL-1 and, to a lesser extent, IL-23 inhibited IL-17 production by T cells. Finally, isogenic H. pylori mutant strains not expressing major virulence factors were less effective in inducing IL-1 and IL-23 release by DCs and IL-17 release by T cells than parental strains. Altogether, we can conclude that DCs are potent inducers of IL-23/IL-17 expression following H. pylori stimulation. IL-1/IL-23 as well as H. pylori virulence factors seem to play an important role in mediating this response.

Inverse relationship between dendritic cell CCR9 expression and maturation state

CCR9 has been identified on T cells as a chemokine receptor that directs these cells to migrate to the intestine. CCR9 has also been reported on different cell types in the intestine, thymus, liver and peripheral blood. Little is reported concerning the presence of or functional implications of this chemokine receptor on myeloid dendritic cells (DC). In the host, DC encounter a multiplicity of antigenic stimuli to which they mount immune responses. In addition to intracellular and functional changes on sensing antigen, maturation of DC is typically reflected in the up-regulation of costimulatory molecules on DC. However, alterations in other surface markers may also be an indicator of DC activation. Using bone marrow-propagated DC these studies investigated cellular maturation in the presence of microbial stimuli and analyzed the relationship of CCR9 expression with DC maturation. Fractionation of DC into CCR9(high) and CCR9(low)subsets revealed a distinct ability of each subset to induce division in naïve CD4(+) T cells. Our results suggest that DC expressing high levels of CCR9 are less activated/mature than DC expressing low levels of CCR9.

Helicobacter pylori as a vaccine delivery system

For more than 10 years a vaccine against Helicobacter pylori has been the elusive goal of many investigators. The need for a vaccine was highlighted when eradication attempts in developing countries were foiled by reinfection rates of 15-30% per annum. In addition, physicians in developed countries were concerned that attempts at total eradication of H. pylori would result in widespread macrolide resistance in both H. pylori and other important pathogens. Although attempts to produce vaccines against H. pylori have failed in their ultimate goal, considerable knowledge has been developed on the pathogenesis and immunology of Helicobacter infections. In this article we describe an alternative use for this new knowledge, i.e. a plan to use live Helicobacter species to deliver vaccines against other organisms. Because of its intimate attachment to the gastric mucosa and long-term residence there, H. pylori might succeed as an antigen delivery system, a goal which has eluded most other strategies of nonparenteral vaccination.

Helicobacter pylori inflammation, immunity, and vaccines

Helicobacter pylori infects almost 50% of the world population and is the major cause of gastroduodenal diseases. H. pylori colonizes the gastric mucosa, activates Toll-like and Nod-like receptors, and usually elicits a T helper 1 (Th1) type of immune response, fully polarized in peptic ulcer patients. Among several bacterial factors, the neutrophil-activating protein represents a key factor driving Th1 inflammation. A complex and fascinating balance between H. pylori and host factors takes part in the gastric niche and allows the majority of infected individuals to be without any symptom during their entire life. Novel insights into the innate and adaptive responses against H. pylori, dealing with regulatory T cells and cytokines, CTLA-4 molecule, cholesterol glucosylation, and immune evasion have been elucidated during the past year and are discussed for the development of an effective vaccine.