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MotivationVirtually all biological systems are governed by a set of complex relations between their components. Identification of relations within biological systems involves a rigorous search for patterns among variables/parameters. Two-dimensional (involving two variables) patterns are identified using correlation, covariation, and mutual information approaches. However, these approaches are not suited to identify more complicated multidimensional relations, which simultaneously include 3, 4, and more variables.ResultsWe present a novel pattern-specific method to quantify the strength and estimate the statistical significance of multidimensional Boolean patterns in multiomics data. In contrast with dimensionality reduction and AI solutions, patterns identified by the proposed approach may provide a better background for meaningful mechanistic interpretation of the biological processes. Our preliminary analysis suggests that multidimensional patterns may dominate the landscape of multi-omics data, which is not surprising because complex interactions between components of biological systems are unlikely to be reduced to simple pairwise interactions.

Infection with the Gram-negative, microaerophilic bacterium Helicobacter pylori induces an inflammatory response and oxidative DNA damage in gastric epithelial cells that can lead to gastric cancer (GC). However, the underlying pathogenic mechanism is largely unclear. Here, we report that the suppression of Nei-like DNA glycosylase 2 (NEIL2), a mammalian DNA glycosylase that specifically removes oxidized bases, is one mechanism through which H. pylori infection may fuel the accumulation of DNA damage leading to GC. Using cultured cell lines, gastric biopsy specimens, primary cells, and human enteroid-derived monolayers from healthy human stomach, we show that H. pylori infection greatly reduces NEIL2 expression. The H. pylori infection-induced downregulation of NEIL2 was specific, as Campylobacter jejuni had no such effect. Using gastric organoids isolated from the murine stomach in coculture experiments with live bacteria mimicking the infected stomach lining, we found that H. pylori infection is associated with the production of various inflammatory cytokines. This response was more pronounced in Neil2 knockout (KO) mouse cells than in WT cells, suggesting that NEIL2 suppresses inflammation under physiological conditions. Notably, the H. pylori-infected Neil2-KO murine stomach exhibited more DNA damage than the WT. Furthermore, H. pylori-infected Neil2-KO mice had greater inflammation and more epithelial cell damage. Computational analysis of gene expression profiles of DNA glycosylases in gastric specimens linked the reduced Neil2 level to GC progression. Our results suggest that NEIL2 downregulation is a plausible mechanism by which H. pylori infection impairs DNA damage repair, amplifies the inflammatory response, and initiates GC.

The accumulation of Helicobacter pylori infection-induced oxidative DNA damage in gastric epithelial cells is a risk factor for developing gastric cancer (GC); however, the underlying mechanisms remain poorly understood. Here we report that the suppression of NEIL2, an oxidized base-specific mammalian DNA glycosylase, is one such mechanism via which H. pylori infection may fuel the accumulation of DNA damage during the initiation and progression of GC. Using a combination of cultured cell lines and primary cells, we show that expression of NEIL2 is significantly down-regulated after H. pylori infection; such down-regulation was also seen in human gastric biopsies. The H. pylori infection-induced down-regulation of NEIL2 is specific, as Campylobacter jejuni has no such effect. Using gastric organoids isolated from the murine stomach in co-culture studies with live bacteria mimicking the infected stomach lining, we found that H. pylori infection was associated with IL-8 production; this response was more pronounced in Neil2 knockout (KO) mouse cells compared to wild type (WT) cells, suggesting that NEIL2 suppresses inflammation under physiological conditions. Interestingly, DNA damage was significantly higher in Neil2 KO mice compared to WT mice. H. pylori-infected Neil2 KO mice showed higher inflammation and more epithelial cell damage. Computational analysis of gene expression profiles of repair genes in gastric specimens showed the reduction of Neil2 level is linked to the GC progression. Taken together, our data suggest that down-regulation of NEIL2 is a plausible mechanism by which H. pylori infection derails DNA damage repair, amplifies the inflammatory response and initiates GCs.

Helicobacter pylori is a prevalent human pathogen that successfully establishes chronic infection, which leads to clinically significant gastric diseases including chronic gastritis, peptic ulcer disease (PUD), and gastric cancer (GC). H. pylori is able to produce a persistent infection due in large part to its ability to hijack the host immune response. The host adaptive immune response is activated to strategically and specifically attack pathogens and normally clears them from the infected host. Since B and T lymphocytes are central mediators of adaptive immunity, in this chapter we review their development and the fundamental mechanisms regulating their activation in order to understand how some of the normal processes are subverted by H. pylori. In this review, we place particular emphasis on the CD4(+) T cell responses, their subtypes, and regulatory mechanisms because of the expanding literature in this area related to H. pylori. T lymphocyte differentiation and function are finely orchestrated through a series of cell–cell interactions, which include immune checkpoint receptors. Among the immune checkpoint receptor family, there are some with inhibitory properties that are exploited by tumor cells to facilitate their immune evasion. Gastric epithelial cells (GECs), which act as antigen-presenting cells (APCs) in the gastric mucosa, are induced by H. pylori to express immune checkpoint receptors known to sway T lymphocyte function and thus circumvent effective T effector lymphocyte responses. This chapter reviews these and other mechanisms used by H. pylori to interfere with host immunity in order to persist.

Helicobacter pylori (H. pylori) is a gram-negative bacterium that infects more than 50% of humanity and is associated with gastritis, peptic ulcer and gastric cancer. Although CD4+ T cells are recruited to the gastric mucosa, the host is unable to clear the bacteria. Previously, we demonstrated that H. pylori infection upregulates the expression of the T cell co-inhibitory molecule B7-H1 while simultaneously downregulating the expression of T cell co-stimulatory molecule B7-H2 on gastric epithelial cells (GEC), which together affect the Treg and Th17 cell balance and foster bacterial persistence. Because B7-H3, another member of the B7 family of co-inhibitory receptors, has been found to have important immunoregulatory roles and in cancer, in this study we examined the expression of B7-H3 molecules on GEC and how the expression is regulated by H. pylori during infection. Our study showed that both human and murine GEC constitutively express B7-H3 molecules, but their expression levels increased during H. pylori infection. We further demonstrated that H. pylori uses its type 4 secretion system (T4SS) components CagA and cell wall peptidoglycan (PG) fragment to upregulate B7-H3. Th17 cells and Treg cells which are increased during H. pylori infection also had an effect on B7-H3 induction. The underlying cell signaling pathway involves modulation of p38MAPK pathway. Since B7-H3 were shown to up-regulate Th2 responses, the phenotype of T cell subpopulations in mice infected with H. pylori PMSS1 (contains functional T4SS) or SS1 (cannot deliver CagA into GEC) strains were characterized. A mixed Th1/Th2 response in H. pylori infected mice was observed. Consistent with previous findings, increased Treg cells and decreased Th17 cells in MLN of PMSS1 infected mice compared to SS1 infected mice was observed. Human biopsy samples collected from gastritis biopsies and gastric tumors showed a strong association between increased B7-H3 and Th2 responses in H. pylori strains associated with gastritis. T cell: GEC co-cultures and anti-B7-H3 blocking Ab confirmed that the induction of Th2 is mediated by B7-H3 and associated exclusively with an H. pylori gastritis strain not cancer or ulcer strains. In conclusion, these studies revealed a novel regulatory mechanism employed by H. pylori to influence the type of T cell response that develops within the infected gastric mucosa.

The role of programmed cell death protein 1 (PD-1) and its ligands in the dysregulation of T helper immune responses observed in the inflammatory bowel disease (IBD) is unclear. Recently, a novel concept emerged that CD90Tissues and cells derived from Crohn's disease (CD), ulcerative colitis (UC), and healthy individuals (N) were studiedA significant increase in programmed death-ligand 1 (PD-L1) was observed in the inflamed UC colonic mucosa when compared to the non-inflamed matched tissue samples, CD, and healthy controls. UC-CMFs were among the major populations in the colonic mucosa contributing to the enhanced PD-L1 expression. In contrast, PD-L1 expression was decreased in CD-CMFs. When compared to CD-CMFs and N-CMFs, UC-CMFs demonstrated stronger suppression of IL-2, Th1 transcriptional factor Tbet, and IFN-γ expression by CD3/CD28-activated CD4We present evidence showing that increased PD-L1 expression suppresses Th1 cell activity in UC. In contrast, loss of PD-L1 expression observed in CD contributes to the persistence of the Th1 inflammatory milieu in CD. Our data suggest that dysregulation of the Th1 responses in the inflamed colonic mucosa of IBD patients is promoted by the alterations in PD-L1 expression in the mucosal mesenchymal stromal cell compartment.

Gastric epithelial cells (GECs) are the primary target for Helicobacter pylori infection and may act as APCs regulating local T cell responses. We previously reported that H. pylori infection of GECs induces the expression of the T cell coinhibitory molecule B7-H1 on GECs. This process contributes to the hyporesponsiveness of CD4+ effector T cells and accumulation of regulatory T cells. In the present study, we investigated the impact of H. pylori cytotoxin-associated gene A (CagA) on the modulation of the expression of the T cell costimulator B7-H2 by GECs. B7-H2 is involved in promoting Th17 type responses. H. pylori infection downregulates B7-H2 expression by GECs in a CagA-dependent manner. IFN-γ, which is increased in the H. pylori–infected gastric mucosa, synergizes with H. pylori in downregulating B7-H2 expression by GECs. CagA-mediated modulation of B7-H2 on GECs involves p70 S6 kinase phosphorylation. The CagA-dependent B7-H2 downregulation in GECs correlates with a decrease in Th17 type responses in vitro and in vivo. Furthermore, CagA-dependent modulation of Th17 responses was inversely correlated with the H. pylori colonization levels in vivo. Our data suggest that CagA contributes to the ability of H. pylori to evade Th17-mediated clearance by modulating expression of B7-H2 and, thus, to the establishment of the H. pylori chronic infection.

Gastric epithelial cells (GECs) express the class II major histocompatibility complex (MHC) and costimulatory molecules, enabling them to act as antigen-presenting cells (APCs) and affect local T cell responses. During Helicobacter pylori infection, GECs respond by releasing proinflammatory cytokines and by increasing the surface expression of immunologically relevant receptors, including class II MHC. The CD4 + T cell response during H. pylori infection is skewed toward a Th1 response, but these cells remain hyporesponsive. Activated T cells show decreased proliferation during H. pylori infection, and CD4 + CD25 + FoxP3 + regulatory T cells (Tregs) are present at the site of infection. In this study, we examined the mechanisms surrounding the CD4 + T cell responses during H. pylori infection and found that transforming growth factor β (TGF-β) plays a major role in these responses. GECs produced TGF-β1 and TGF-β2 in response to infection. Activated CD4 + T cells in culture with H. pylori -treated GECs were decreased in proliferation but increased upon neutralization of TGF-β. Naïve CD4 + T cell development into Tregs was also enhanced in the presence of GEC-derived TGF-β. Herein, we demonstrate a role for GEC-produced TGF-β in the inhibition of CD4 + T cell responses seen during H. pylori infection.

Helicobacter pylori (Hp) bacteria successfully establishes chronic infection leading to chronic gastritis, peptic ulcer disease (PUD), and gastric cancer (GC). Since we have previously shown that Hp hijacks expression of checkpoint immunoregulators (i.e., PD-L1), we hypothesized that strains from different gastric pathologies differ in their ability to evade the host response. We used human gastric organoids (hGOs), which recapitulate polarized epithelium, gastric gland and pit cell markers observed in the stomach. We cultured hGOs in transwell inserts which were exposed to Hp on the apical surface and cultured with naïve T cells on the basolateral side of polarized epithelial cells, thereby reproducing the interactions observed in vivo. After 7 days of culture, we recovered all cells and evaluated levels of PD-L1, B7-H3, B7-H4, and CTLA4; and in CD4+ T cells markers of Th1, Th2, Th17 and Treg. Infection of hGOs with Hp strains isolated from cases of gastritis, PUD or GC, all led to increased expression of negative immune checkpoint regulators, predominantly PD-L1, which binds PD-1 on T cells and promotes loss of effector functions, apoptosis, and reduced T cell-target cell contact. Interestingly, PUD strains are the stronger inducers of PD-L1 and GC strains were the lowest inducers of Th1 cells (Tbet+, IFNγ+), which suggest that different strains differ in their orchestration of the host response, which may contribute to the type of pathology elicited. Our data suggest that this co-culture system to evaluate expression of immune checkpoint regulators and CD4+ T cell differentiation in the context of strains comparison may provide insights in differential expression of candidate biomarkers of disease and future therapies.

Comparative voltammetric studies were performed between high purity pyrite mineral (98.86%) and arsenopyrite mineral (content of 85.96% arsenopyrite, FeAsS; 11.84% pyrite, FeS2; 0.98% galena, PbS; 0.06% chalcopyrite, CuFeS2) in order to analyze the galvanic effect on the electrochemical reactivity of two different mineralogical phases when these are associated in the same mineral, using carbon paste electrodes (CPE) in 0.1 M NaNO3 (pH 6.5) as electrolyte. Theoretical studies were performed for a more detailed analysis on the total energy and energy relative of a total optimization of the species involved in the pyrite and arsenopyrite oxidation as pure mineral. The results indicate that the electrochemical reactivity of pyrite in the arsenopyrite mineral was delayed and displaced to more positive potentials with respect to the high purity pyrite mineral electrochemical response, due to a galvanic effect. On the other hand, the voltammetric studies showed the oxidation stages of arsenopyrite mineral, indic...

Helicobacter pylori is one of the most common human pathogens and is associated with chronic gastritis, peptic ulcers and gastric carcinoma. H. pylori establishes a persistent infection, suggesting that the host response is ineffective in clearing the infection. H. pylori employs multiple mechanisms to undermine host responses. For example, CD4+ T cells are recruited to the gastric mucosa of infected individuals, but these cells are predominantly T helper 1 (TH1) cells, which do not provide protection from the extracellular pathogen. H. pylori neutrophil-activating protein (HP-NAP) promotes the TH1 polarized response. HP-NAP induces macrophages and dendritic cells to produce IL-12 and IL-23, which could explain the effect on T cells. These properties of HP-NAP make it a potential immunotherapeutic tool to redirect harmful TH2 cell responses, as seen in atopic allergy, to TH1 cell responses and also in IL-12 induction in cancer therapy.

During Helicobacter pylori infection, T cells are recruited to the gastric mucosa, but the host T-cell response is not sufficient to clear the infection. Some of the recruited T cells respond in a polarized manner to a Th1 response, while others become anergic. We have previously shown that T-cell anergy may be induced during infection by the interaction of T cells with B7-H1, which is up-regulated on the gastric epithelium during H. pylori infection. Recently, regulatory T (Treg) cells with a CD4 + CD25 high FoxP3 + phenotype were found at an increased frequency in the gastric mucosa of biopsy specimens from H. pylori -infected patients. While Treg cells are important in maintaining tolerance, they can also suppress immune responses during infection. In this study, we examined the induction of the Treg phenotype when naïve T cells were incubated with gastric epithelial cells exposed to H. pylori . The frequency of this phenotype was markedly decreased when B7-H1 was blocked with monoclonal antibodies or its expression was blocked with small interfering RNA. The functional role of these Treg cells was assessed in proliferation assays when the cells were cocultured with activated T cells, which effectively decreased proliferation of the cells.

Following adhesion of Helicobacter pylori to gastric epithelial cells, intracellular signaling leads to cytokine production, which causes H. pylori-related gastric injury. Two adjacent homologous genes (alpA and alpB), which encode H. pylori outer membrane proteins, are thought to be associated with adhesion and cytokine induction. We co-cultured gastric epithelial cells with wild type H. pylori strains and their corresponding alpA/alpB-deleted mutants (DeltaalpAB). Results were confirmed by complementation. Flow cytometry confirmed that AlpAB was involved in cellular adhesion. Deletion of alpAB reduced interleukin (IL)-6 induction in gastric epithelial cells. Deletion of alpAB reduced IL-8 induction with East Asian but not with Western strains. All AlpAB-positive strains tested activated the extracellular signal-regulated kinase, c-Fos, and cAMP-responsive element-binding protein. Activation of the Jun-N-terminal kinase, c-Jun, and NF-kappaB was exclusive to AlpAB from East Asian strains. DeltaalpAB mutants poorly colonized the stomachs of C57BL/6 mice and were associated with lower mucosal levels of KC and IL-6. Our results suggest that AlpAB may induce gastric injury by mediating adherence to gastric epithelial cells and by modulating proinflammatory intracellular signaling cascades. Known geographical differences in H. pylori-related clinical outcomes may relate to differential effects of East Asian and Western types of AlpAB on NF-kappaB-related proinflammatory signaling pathways.

The human gastrointestinal mucosa is exposed to a diverse normal microflora and dietary Ags and is a common site of entry for pathogens. The mucosal immune system must respond to these diverse signals with either the initiation of immunity or tolerance. APCs are important accessory cells that modulate T cell responses which initiate and maintain adaptive immunity. The ability of APCs to communicate with CD4+ T cells is largely dependent on the expression of class II MHC molecules by the APCs. Using immunohistochemistry, confocal microscopy, and flow cytometry, we demonstrate that α-smooth muscle actin+, CD90+ subepithelial myofibroblasts (stromal cells) constitutively express class II MHC molecules in normal colonic mucosa and that they are distinct from professional APCs such as macrophages and dendritic cells. Primary isolates of human colonic myofibroblasts (CMFs) cultured in vitro were able to stimulate allogeneic CD4+ T cell proliferation. This process was dependent on class II MHC and CD80/86 costimulatory molecule expression by the myofibroblasts. We also demonstrate that CMFs, engineered to express a specific DR4 allele, can process and present human serum albumin to a human serum albumin-specific and DR4 allele-restricted T cell hybridoma. These studies characterize a novel cell phenotype which, due to its strategic location and class II MHC expression, may be involved in capture of Ags that cross the epithelial barrier and present them to lamina propria CD4+ T cells. Thus, human CMFs may be important in regulating local immunity in the colon.

The pathogenesis associated withHelicobacter pyloriinfection is the result of both bacterial factors and the host response. We have previously shown thatH. pyloribinds to CD74 on gastric epithelial cells. In this study, we sought to identify the bacterial protein responsible for this interaction.H. pyloriurease from a pool of bacterial surface proteins was found to coprecipitate with CD74. To determine how urease binds to CD74, we used recombinant urease A and B subunits. Recombinant urease B was found to bind directly to CD74 in immunoprecipitation and flow cytometry studies. By utilizing both recombinant urease subunits and urease B knockout bacteria, the urease B-CD74 interaction was shown to induce NF-κB activation and interleukin-8 (IL-8) production. This response was decreased by blocking CD74 with monoclonal antibodies. Further confirmation of the interaction of urease B with CD74 was obtained using a fibroblast cell line transfected with CD74 that also responded with NF-κB activation and IL-8 production. The binding of theH. pyloriurease B subunit to CD74 expressed on gastric epithelial cells presents a novel insight into a previously unrecognizedH. pyloriinteraction that may contribute to the proinflammatory immune response seen during infection.

CD74, or the class II MHC-associated invariant chain, is best known for the regulation of Ag presentation. However, recent studies have suggested other important roles for this protein in inflammation and cancer studies. We have shown that CD74 is expressed on the surface of gastric cells, and Helicobacter pylori can use this receptor as a point of attachment to gastric epithelial cells, which lead to IL-8 production. This study investigates the ability of H. pylori to up-regulate one of its receptors in vivo and with a variety of gastric epithelial cell lines during infection with H. pylori. CD74 expression was increased dramatically on gastric biopsies from H. pylori-positive patients and gastric cell lines exposed to the bacteria. Gastric cells exposed to H. pylori-conditioned medium revealed that the host cell response was responsible for the up-regulation of CD74. IL-8 was found to up-regulate CD74 cell surface expression because blocking IL-8Rs or neutralizing IL-8 with Abs counteracted the increased expression of CD74 observed during infection with H. pylori. These studies demonstrate how H. pylori up-regulates one of its own receptors via an autocrine mechanism involving one of the products induced from host cells.

CD74 is known as the major histocompatibility complex (MHC) class II-associated invariant chain (Ii) that regulates the cell biology and functions of MHC class II molecules. Class II MHC and Ii expression was believed to be restricted to classical antigen-presenting cells (APC); however, during inflammation, other cell types, including mucosal epithelial cells, have also been reported to express class II MHC molecules. Given the importance of Ii in the biology of class II MHC, we sought to examine the expression of Ii by gastric epithelial cells (GEC) to determine whether class II MHC molecules in these nonconventional APC cells were under the control of Ii and to further support the role that these cells may play in local immune and inflammatory responses during Helicobacter pylori infection. Thus we examined the expression of Ii on GEC from human biopsy samples and then confirmed this observation using independent methods on several GEC lines. The mRNA for Ii was detected by RT-PCR, and the various protein isoforms were also detected. Interestingly, these cells have a high level expression of surface Ii, which is polarized to the apical surface. These studies are the first to demonstrate the constitutive expression of Ii by human GEC.

Helicobacter pylori infects approximately half of the world's population and the bacterium is associated with gastric cancer and peptic and duodenal ulcers. In this study, Surface Enhanced Laser Desorption /Ionization time-of-flight mass spectrometry (SELDI-TOF-MS) was used to identify the biomarkers from H. pylori infected gastric epithelial cells (GEC) to understand key mechanisms associated with pathogenesis. Using different chip surfaces, differential protein expression profile of GEC was obtained and several upregulated or downregulated biomarkers were detected on GEC, following H. pylori infection. Four different H. pylori infected GECs were compared based on their expression of MHC class II, a receptor reported to trigger apoptosis. One biomarker was identified in H. pylori infected GEC as Annexin A2 (Annexin II) from the flow through of the anion-exchange resin. The increased expression of Annexin II in GEC following H. pylori infection was further confirmed by Western Blot analyses and indicates its involvement in H. pylori pathogenesis.

Class II major histocompatibility complex (MHC) expression is a hallmark of antigen presenting cells (APC). Human gastric epithelial cells (GEC) express class II MHC and this expression increases during infection with Helicobacter pylori as does the number of CD4 T cells found adjacent or in between epithelial cells. These observations suggested that human GEC act as APCs. To characterize and compare class II MHC complexes with those present in conventional APC, immunoprecipitated class II MHC from GEC and B cells, as prototypic APC, were separated by two-dimensional electrophoresis. Although the composition of class II MHC from both cell phenotypes was similar, their electrophoretic mobility differed. Methodical elimination of carbohydrates, either enzymatically with endoglycosidase-H or blocking with tunicamycin, revealed that the deviations were due to differences in glycosylation in both cell phenotypes. When deglycosylated class II MHC α chains, β chains, and the invariant chain from both cell phenotypes were mixed and run in the same gel, the core proteins had identical migration patterns. Because differences in glycosylation of class II MHC proteins may affect peptide selection and/or recognition by T cells, the noted differences in glycosylation of class II MHC expressed by GEC could be important in considering their potential role as APC locally.

The gastrointestinal epithelium has cells with features that make them a powerful line of defense in innate mucosal immunity. Features that allow gastrointestinal epithelial cells to contribute in innate defense include cell barrier integrity, cell turnover, autophagy, and innate immune responses. Helicobacter pylori (H. pylori) is a spiral shape gram negative bacterium that selectively colonizes the gastric epithelium of more than half of the world's population. The infection invariably becomes persistent due to highly specialized mechanisms that facilitate H. pylori's avoidance of this initial line of host defense as well as adaptive immune mechanisms. The host response is thus unsuccessful in clearing the infection and as a result becomes established as a persistent infection promoting chronic inflammation. In some individuals the associated inflammation contributes to ulcerogenesis or neoplasia. H. pylori has an array of different strategies to interact intimately with epithelial cells and manipulate their cellular processes and functions. Among the multiple aspects that H. pylori affects in gastric epithelial cells are their distribution of epithelial junctions, DNA damage, apoptosis, proliferation, stimulation of cytokine production, and cell transformation. Some of these processes are initiated as a result of the activation of signaling mechanisms activated on binding of H. pylori to cell surface receptors or via soluble virulence factors that gain access to the epithelium. The multiple responses by the epithelium to the infection contribute to pathogenesis associated with H. pylori.

During Helicobacter pylori (H. pylori) infection CD4+ T cells in the gastric lamina propria are hyporesponsive and polarized by Th1/Th17 cell responses controlled by Treg cells. We have previously shown that H. pylori upregulates B7-H1 expression on GEC, which, in turn, suppress T cell proliferation, effector function, and induce Treg cells in vitro. In this study, we investigated the underlying mechanisms and the functional relevance of B7-H1 induction by H. pylori infection to chronic infection. Using H. pylori wild type (WT), cag pathogenicity island (cag PAI-) and cagA - isogenic mutant strains we demonstrated that H. pylori requires its type 4 secretion system (T4SS) as well as its effector protein CagA and peptidoglycan (PG) fragments for B7-H1 upregulation on GEC. Our study also showed that H. pylori uses the p38 MAPK pathway to upregulate B7-H1 expression in GEC. In vivo confirmation was obtained when infection of C57BL/6 mice with H. pylori PMSS1 strain, which has a functional T4SS delivery system, but not with H. pylori SS1 strain lacking a functional T4SS, led to a strong upregulation of B7-H1 expression in the gastric mucosa, increased bacterial load, induction of Treg cells in the stomach, increased IL-10 in the serum. Interestingly, B7-H1-/- mice showed less Treg cells and reduced bacterial loads after infection. These studies demonstrate how H. pylori T4SS components activate the p38 MAPK pathway, upregulate B7-H1 expression by GEC, and cause Treg cell induction; thus, contribute to establishing a persistent infection characteristic of H. pylori.

Signaling via programmed death ligand-1 (PD-L1) and PD-L2 is crucial for maintaining peripheral tolerance. CD90+ myofibroblasts/fibroblasts (CMFs) are major programmed cell death-1 (PD-1) ligand–expressing cells in normal human colonic mucosa. CMFs suppress activated CD4+ T cell proliferation via PD-1 ligands. It is not known whether signaling through TLRs contribute to the regulation PD-1 ligands on CMFs upon colonic mucosal tolerance. In this study, we demonstrated that stimulation of TLR4 on human CMFs upregulates PD-L1, but not PD-L2, and reinforces CMF-mediated suppression of CD4+ T cell proliferation and IFN-γ production. TLR4-mediated upregulation of PD-L1 on CMFs involved NF-κB pathways and was JAK2 and MyD88 dependent. MyD88-dependent stimulation of TLR1/2 and TLR5 also upregulated PD-L1 expression on CMFs in culture. PD-L1 expression was drastically decreased in vivo in the colonic mucosa of mice devoid of MyD88. Induction of MyD88 deficiency in CMFs in fibroblast-specific MyD88 conditional knockout mice resulted in a strong increase in a mucosal IFN-γ expression concomitantly with the abrogation of PD-L1 expression in CMFs under homeostasis and epithelial injury induced by dextran sodium sulfate. Together, these data suggest that MyD88-dependent TLR stimulation of CMFs in the normal colonic mucosa may reinforce these cells’ anti-inflammatory capacity and thus contribute to the maintenance of mucosal tolerance.

Helicobacter pylori (H. pylori) is perhaps the most ubiquitous and successful human pathogen, since it colonizes the stomach of more than half of humankind. Infection with this bacterium is commonly acquired during childhood. Once infected, people carry the bacteria for decades or even for life, if not treated. Persistent infection with this pathogen causes gastritis, peptic ulcer disease and is also strongly associated with the development of gastric cancer. Despite induction of innate and adaptive immune responses in the infected individual, the host is unable to clear the bacteria. One widely accepted hallmark of H. pylori is that it successfully and stealthily evades host defense mechanisms. Though the gastric mucosa is well protected against infection, H. pylori is able to reside under the mucus, attach to gastric epithelial cells and cause persistent infection by evading immune responses mediated by host. In this review, we discuss how H. pylori avoids innate and acquired immune response elements, uses gastric epithelial cells as mediators to manipulate host T cell responses and uses virulence factors to avoid adaptive immune responses by T cells to establish a persistent infection. We also discuss in this review how the genetic diversity of this pathogen helps for its survival.

Helicobacter pylori infection is linked to chronic gastritis, peptic ulcer and gastric carcinoma. During H. pylori infection, class II MHC expression by the gastric epithelium increases, as does the number of local CD4(+) T cells, which appear to be important in the associated pathogenesis. These observations suggested that the epithelium might present antigens to T cells. Thus, we sought to determine whether gastric epithelial cells process antigens to establish their function as local antigen presenting cells (APC). We examined a panel of gastric epithelial cell lines for expression of the antigen processing cathepsins B (CB), L (CL), S (CS), and D (CD). The mRNA for these enzymes were detected by RT-PCR and the enzymes in the gastric epithelial cells were identified by various independent methods. We corroborated the expression of CB and CD on gastric epithelial cells from human biopsy samples. The functions of these proteases were confirmed by assessing their ability to digest ovalbumin, a conventional dietary antigen, and proteins from H. pylori. In summary, multiple lines of evidence suggest gastric epithelial cells process antigens for presentation to CD4(+) T cells. To our knowledge, these are the first studies to document the antigen processing capacity of human gastric epithelial cells.

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.

Helicobacter pylori infection is associated with gastric epithelial damage, including apoptosis, ulceration, and cancer. Although bacterial factors and the host response are believed to contribute to gastric disease, no receptor has been identified that explains how the bacteria attach and signal the host cell to undergo apoptosis. Using H. pylori as “bait” to capture receptor proteins in solubilized membranes of gastric epithelial cells, class II major histocompatibility complex (MHC) molecules were identified as a possible receptor. Signaling through class II MHC molecules leading to the induction of apoptosis was confirmed using cross-linking IgM antibodies to surface class II MHC molecules. Moreover, binding of H. pylori and the induction of apoptosis were inhibited by antibodies recognizing class II MHC. Since type 1 T helper cells are present during infection and produce interferon (IFN)-γ, which increases class II MHC expression, gastric epithelial cell lines were exposed to H. pylori in the presence or absence of IFN-γ. IFN-γ increased the attachment of the bacteria as well as the induction of apoptosis in gastric epithelial cells. In contrast to MHC II–negative cell lines, H. pylori induced apoptosis in cells expressing class II MHC molecules constitutively or after gene transfection. These data describe a novel receptor for H. pylori and provide a mechanism by which bacteria and the host response interact in the pathogenesis of gastric epithelial cell damage.

The invariant chain (Ii) due to its intimate association with major histocompatibility complex (MHC) α and β chains is a determining element in the development of immune responses. Ii plays a major role in the assembly, the intracellular transport and peptide selection by class II MHC. A segment of Ii designated as CLIP (class II–associated Ii peptide) binds into the antigen binding site of class II MHC molecules until class II MHC reach intracellular compartments that contain peptides from internalized antigens. This association limits the self endogenous peptides that can bind to class II MHC molecules. The removal of CLIP from class II MHC catalyzes the binding of antigenic peptides and their subsequent cell surface expression. An isoform of Ii, known as chondroitin sulfate–modified Ii (IiCS), that is surface–expressed enhances T cell activation while acting as a coreceptor for CD44. The expression of class II MHC molecules by mucosal epithelial cells has generated interest in the role that these cells may have in mucosal immunity. Since in classical antigen–presenting cells (APC) the biology of class II MHC is regulated by Ii, it is necessary to bring into perspective the known functions of Ii in conventional APC to understand the role that Ii may play in mucosal epithelial cells as potential regulators of local immune responses.

Fetal swallowing of amniotic fluid, which contains numerous cytokines and growth factors, plays a key role in gut mucosal development. Preterm birth interrupts this exposure to amniotic fluid-borne growth factors, possibly contributing to the increased risk of necrotizing enterocolitis (NEC) in premature infants. We hypothesized that supplementation of formula feeds with amniotic fluid can provide amniotic fluid-borne growth factors and prevent experimental NEC in rat pups. We compared NEC-like injury in rat pups fed with infant formula vs. formula supplemented either with 30% amniotic fluid or recombinant hepatocyte growth factor (HGF). Cytokines/growth factors in amniotic fluid were measured by immunoassays. Amniotic fluid and HGF effects on enterocyte migration, proliferation, and survival were measured in cultured IEC6 intestinal epithelial cells. Finally, we used an antibody array to investigate receptor tyrosine kinase (RTK) activation and immunoblots to measure phosphoinositide 3-kinase (PI3K) signaling. Amniotic fluid supplementation in oral feeds protected rat pups against NEC-like injury. HGF was the most abundant growth factor in rat amniotic fluid in our panel of analytes. Amniotic fluid increased cell migration, proliferation, and cell survival in vitro. These effects were reproduced by HGF and blocked by anti-HGF antibody or a PI3K inhibitor. HGF transactivated several RTKs in IEC6 cells, indicating that its effects extended to multiple signaling pathways. Finally, similar to amniotic fluid, recombinant HGF also reduced the frequency and severity of NEC-like injury in rat pups. Amniotic fluid supplementation protects rat pups against experimental NEC, which is mediated, at least in part, by HGF.

Background: The development of accurate classification models depends upon the methods used to identify the most relevant variables. The aim of this article is to evaluate variable selection methods to identify important variables in predicting a binary response using nonlinear statistical models. Our goals in model selection include producing non-overfitting stable models that are interpretable, that generate accurate predictions and have minimum bias. This work was motivated by data on clinical and laboratory features of Helicobacter pylori infections obtained from 60 individuals enrolled in a prospective observational study. Results: We carried out a comprehensive performance comparison of several nonlinear classification models over the H. pylori data set. We compared variable selection results by Multivariate Adaptive Regression Splines (MARS), Logistic Regression with regularization, Generalized Additive Models (GAMs) and Bayesian Variable Selection in GAMs. We found that the MARS model approach has the highest predictive power because the nonlinearity assumptions of candidate predictors are strongly satisfied, a finding demonstrated via deviance chisquare testing procedures in GAMs. Conclusions: Our results suggest that the physiological free amino acids citrulline, histidine, lysine and arginine are the major features for predicting H. pylori peptic ulcer disease on the basis of amino acid profiling.

The role for Helicobacter pylori in the pathogenesis of disease provides the conundrum that only a subset of subjects infected with H. pylori will ever develop peptic ulcer or gastric cancer. Thus, variation in strain as well as environmental or host factors converge in the gastroduodenal milieu and control the final outcome of infection. The host immune and inflammatory response is emerging as an important element in the pathogenesis of these gastric diseases. The ideal host response provides protection to clear an infection without causing excessive amounts of inflammation that could compromise the integrity and function of host cells. This review will cover four main questions: (1) What are the mucosal immune/inflammatory responses that confer protection without damaging the host? (2) How do the gastric immune responses during infection with H. pylori differ from this ideal scenario? (3) Do these responses contribute to autoimmune-mediated damage to gastric tissue? (4) Can immunomodulation through vaccination enhance protective, nondestructive responses that prevent or treat infection or, at least, attenuate inflammation?

Stromal cells, such as myofibroblasts and fibroblasts, represent a significant fraction of MHC class II-positive cells in the normal human colonic lamina propria, suggesting they may play an important role in CD4(+) T cell regulation in a tolerogenic environment. The aim of this study was to examine whether human colonic myofibroblasts (CMFs) phenotypically and functionally resemble conventional antigen-presenting cells (APCs). Our results support the hypothesis that intestinal myofibroblasts are a novel, nonprofessional APC phenotype important in modulating mucosal T cell responses. Given their strategic location, we propose that intestinal myofibroblasts play a critical role in mediating tolerance to luminal antigens.

The identification of Helicobacter pylori in the pathogenesis of chronic gastritis, peptic ulcer, and gastric cancer has provided an enormous advance in clinical gastroenterology. Epidemiologic studies show that many of the more severe clinical manifestations of H. pylori infection occur in a minority of the infected population. Thus, the interaction among the organism, environmental factors, and the host response contributes to the various forms of disease. This review considers the most recent literature in the context of the hypothesis that gastric diseases associated with H. pylori infection result from a failure in the host's ability to develop an appropriate mucosal immune response to this luminal antigen. A better understanding of the immunopathogenesis of this process will provide a more informed approach for the development of therapeutic intervention through mucosal immunization.

Respective subsets of human invariant chain (Ii), as identified with antibodies to two different epitopes, were characterized as a function of their associations with major histocompatibility complex (MHC) class II alpha,beta chains and intracellular processing. E1 antiserum to Ii(183-193) and VIC-Y1 monoclonal antibody to an N-terminal determinant identified Ii(E1) and Ii(VIC) populations, respectively. Ii proteins comprise several species which have been defined with either genomic or post-translational processes: Ii itself; IpN and IpO, which represent the glycosylated forms on asparagine or threonine/serine, respectively; gamma 2 and gamma 3, which originate from an alternative initiation site for transcription; and p41, which has a 64-amino-acid insert which originated from an additional exon placed after the sixth exon of Ii. Immunoprecipitates of detergent-solubilized protein complexes from [35S]methionine-labeled Raji cells showed that Ii(E1) consisted of Ii, p41, IpN, and immature alpha chain, while Ii(VIC) consisted of Ii, processed Ii with N- and O-linked glycosylation (IpN,IpO), p41, and associated MHC class II alpha,beta chains. In the MHC class II-deficient P3HR-1 cells, Ii(E1) and Ii(VIC) were virtually identical. Ii(E1) was resistant to cathepsin B digestion while Ii(VIC) was sensitive. In pulse-chase radiolabeling experiments with brefeldin A (BFA)-treated cells, Ii(VIC) progressively became resistant to endoglycosidase H (endo H) and had a longer half-life than that in cells not treated with BFA, but Ii(E1) remained susceptible to endo H and its half-life was unaffected by BFA. Since BFA redistributes Golgi enzymes to the endoplasmic reticulum, this observation suggests that Ii(E1) is protected from processing enzymes while Ii(VIC) is not. These studies define association of Ii with MHC class II molecules when certain epitopes on Ii are exposed or not. These differences relate to intracellular transport of Ii and to its release for the binding of antigenic peptides.

A staged pattern of cathepsin B cleavage of MHC class II alpha, beta-bound invariant (Ii) chain and release of fragments was defined. Charge-loss mutations in the Ii chain were created in three clusters of cathepsin B putative cleavage sites R78K80K83K86, K137K143, and R151K154. Products of HLA-DR1 alpha, beta and wild type (WT) or mutant Ii genes, co-transfected into COS1 cells, were cleaved by cathepsin B and immunoprecipitated by antibodies either to MHC class II chains or to different Ii epitopes. In WT Ii, cathepsin B digestion generated two forms of p21 Ii fragments: a p21 recognized by anti-C-terminus antibodies and a p21 recognized by an antibody to a determinant near the N-terminus. C-terminal p21 was released from MHC class II alpha, beta chains upon its formation while N-terminal p21 remained associated with MHC class II alpha, beta chains. Mutations at K137K143 inhibited the generation of N-terminal p21 by cathepsin B. Mutation at R78K80K83K86 led to an accumulation of MHC class II-bound N-terminal p21 without the appearance of MHC class II-bound p14, p10, and p6 fragments after cathepsin B digestion. These results indicate that cathepsin B cleaves wild type Ii first about K137K143 to produce a MHC class II-associated N-terminal p21, which is then cleaved about R78K80K83K86 to generate p14, p10 and finally p6 which still associates with MHC class II alpha, beta chains. This pattern of staged cleavage and release of Ii might be related to a concerted mechanism regulating the binding of antigenic peptides to MHC class II molecules.

The binding of a T cell-presented peptide to MHC class II alpha,beta chains occurs as a concurrent process with the release of the associated invariant chain (Ii) by cathepsin B. Ii was digested by cathepsin B from solubilized, MHC class II alpha,beta,Ii complexes in the presence of N-hydroxysuccinimidyl-4-azidobenzoate-conjugated, 125I-labeled, influenza virus matrix (18-29) peptide. The peptide was crosslinked where it became bound. This HLA-DR1-restricted peptide bound about three times more efficiently to class II alpha,beta chains of DR1-positive B cells when present during cathepsin B digestion of Ii than when added afterward, also at pH 5.0. Binding was competed by similarly DR-restricted peptides. Cathepsin D cleaved Ii but did not enhance peptide binding. However, a trace level of cathepsin D, added to the assay for peptide binding in the presence of cathepsin B, further enhanced peptide binding about three times. These experiments support an hypothesis for the staged release of Ii fragments by cathepsin D and cathepsin B, catalyzing at one point the insertion of a peptide into the antigen binding site formed by class II alpha and beta chains.

Staphylococcus aureus (S. aureus) is a Gram positive bacterium that is carried by about one third of the general population and is responsible for common and serious diseases. These diseases include food poisoning and toxic shock syndrome, which are caused by exotoxins produced by S. aureus. Of the more than 20 Staphylococcal enterotoxins, SEA and SEB are the best characterized and are also regarded as superantigens because of their ability to bind to class II MHC molecules on antigen presenting cells and stimulate large populations of T cells that share variable regions on the b chain of the T cell receptor. The result of this massive T cell activation is a cytokine bolus leading to an acute toxic shock. These proteins are highly resistant to denaturation, which allows them to remain intact in contaminated food and trigger disease outbreaks. A recognized problem is the emergence of multi-drug resistant strains of S. aureus and these are a concern in the clinical setting as they are a common cause of antibiotic-associated diarrhea in hospitalized patients. In this review, we provide an overview of the current understanding of these proteins.

We seek to identify consensus sequences in digested fragments of antigenic proteins regulating selection and major histocompatibility complex (MHC)-restricted presentation to T cells of epitopes within those fragments. One such pattern, of recurrent, hydrophobic sidechains forming a longitudinal hydrophobic strip when a sequence is coiled as an alpha-helix, is found in or near most T cell-presented epitopes. Such recurrent hydrophobicity may lead to protease-protected coiling of the fragment against endosomal membranes and transfer to MHC molecules. This concept leads to better identification of T cell-presented sequences and possible to engineering of T cell-presented vaccines to affect their potency and MHC restriction.

The aim of the study is to identify the barriers associated with breastfeeding in mothers of Puerto Rican children with Down.A non-probabilistic sample (n = 26) of mothers was used in the study. The sample was obtained in an institution in Puerto Rico specializing in care of infants with Down Syndrome [IDS]. A self-administered questionnaire was used consisting of six sections. Descriptive statistics were used for data analysis.The majority of interviewed mothers (80.8%) had 70.0% or higher correct answers regarding the benefits of breastfeeding. 84.6% of the mothers who decided not to breastfeed or who discontinued breastfeeding reported as the main reason that the baby presented sucking problems and 50.0% of the participants were not allowed to have their baby with them during their stay in the hospital. 84.3% of the participants indicated having breastfed their IDS and 61.5% stated that they would not breastfeed in public places.Active support, instruction, and collaboration among members of the health care team are essential for breastfeeding success.

CD74 is a protein whose initial role in antigen presentation was recognized two decades ago. Recent studies have revealed that it has additional functions as a receptor for macrophage migration inhibitory factor and as a receptor for an important human pathogen, Helicobacter pylori (H pylori). The role of CD74 as a receptor is important because after binding of migration inhibitory factor or H pylori, NF-kappaB and Erk1/2 activation occurs, along with the induction of proinflammatory cytokine secretion. This review provides an up-to-date account of the functions of CD74 and how it might be involved in inflammation and cancer within the gastrointestinal tract.

Helix formation in folding proteins is stabilized by binding of recurrent hydrophobic side chains in one longitudinal quadrant against the locally most hydrophobic region of the protein. To test this hypothesis, we fitted sequences of 247 alpha-helices of 55 proteins to the circular (infinite) template (symbol; see text) to maximize the strip-of-helix hydrophobicity index (the mean hydrophobicity of residues in (symbol; see text) positions). These template-predicted configurations closely matched crystallographic structures in 87% of four- or five-turn helices compared. We determined the longitudinal quadrant distributions of amino acids in the template-fitted, sheet projections of alpha-helices with respect to the best longitudinal, hydrophobic strip on each helix and to the N and C termini, interiors, and entire helices. Amino acids Leu, Ile, Val, and Phe were concentrated in one longitudinal quadrant (p less than 0.001). Lys, Arg, Asp, and Glu were not in the quadrant of Leu, Ile, Val, and Phe (p less than 0.001). Significant quadrant distributions for other amino acids and for termini of the helices were also found.