T cells of the human intestinal lamina propria are high producers of interleukin-10

The Production and Function of Endogenous Interleukin-10 in Intestinal Epithelial Cells and Gut Homeostasis

The healthy gut is achieved and maintained through a balanced relationship between the mucosal immune system, microbial communities resident in the lumen, and the intestinal epithelium. The intestinal epithelium plays an exceptionally important role in harmonizing the interaction between the host immunity and the luminal residents, as this selectively permeable barrier separates but also allows interchange between the 2 environments. Interleukin (IL)-10 has been well established to play an important role in maintaining gut homeostasis by imparting diverse effects on a variety of cell types in this relationship. In the intestine, the source and the target of IL-10 include leukocytes and epithelial cells. Given that both the epithelium and IL-10 are essential players in supporting homeostasis, we discuss the relationship between these 2 factors, focusing on epithelial sources of IL-10 and the effects of IL-10 on the intestinal epithelium. Insight into this relationship reveals an important aspect of the innate immune function of intestinal epithelial cells.

A Review of Inflammatory Bowel Disease: A Model of Microbial, Immune and Neuropsychological Integration

Objective: Inflammatory bowel diseases (IBDs) are complex chronic inflammatory disorders of the gastro-intestinal (GI) tract with uncertain etiology. IBDs comprise two idiopathic disorders: Crohn's disease (CD) and ulcerative colitis (UC). The aetiology, severity and progression of such disorders are still poorly understood but thought to be influenced by multiple factors (including genetic, environmental, immunological, physiological, psychological factors and gut microbiome) and their interactions. The overarching aim of this review is to evaluate the extent and nature of the interrelationship between these factors with the disease course. A broader conceptual and longitudinal framework of possible neuro-visceral integration, core microbiome analysis and immune modulation assessment may be useful in accurately documenting and characterizing the nature and temporal continuity of crosstalk between these factors and the role of their interaction (s) in IBD disease activity. Characterization of these interactions holds the promise of identifying novel diagnostic, interventions, and therapeutic strategies. Material and Methods: A search of published literature was conducted by exploring PubMed, EMBASE, MEDLINE, Medline Plus, CDSR library databases. Following search terms relating to key question were set for the search included: "Inflammatory bowel diseases," "gut microbiota," "psychological distress and IBD," "autonomic reactivity and IBD," "immune modulation," "chronic inflammation," "gut inflammation," "enteric nervous system," "gut nervous system," "Crohn's disease," "Ulcerative colitis", "depression and IBD", "anxiety and IBD", "quality of life in IBD patients," "relapse in IBDs," "remission in IBDs," "IBD disease activity," "brain-gut-axis," "microbial signature in IBD," "validated questionnaires in IBD," "IBD activity indices," "IBD aetiology," "IBDs and stress," "epidemiology of IBDs", "autonomic nervous system and gut inflammation", "IBD and environment," "genetics of IBDs," "pathways of immune response in IBDs," "sleep disturbances in IBD," "hypothalamic-pituitary-adrenal axis (HPA)," "sympatho-adrenal axis," "CNS and its control of gut function" "mucosal immune response," "commensal and pathogenic bacteria in the gut," "innate and adaptive immunity." Studies evaluating any possible associations between gut microbiome, psychological state, immune modulation, and autonomic function with IBDs were identified. Commonly cited published literatures with high quality research methodology/results and additional articles from bibliographies of recovered papers were examined and included where relevant. Results: Although there is a substantial literature identifying major contributing factors with IBD, there has been little attempt to integrate some factors over time and assess their interplay and relationship with IBD disease activity. Such contributing factors include genetic and environmental factors, gut microbiota composition and function, physiological factors, psychological state and gut immune response. Interdependences are evident across psychological and biological factors and IBD disease activity. Although from the available evidence, it is implausible that a single explanatory model could elucidate the interplay between such factors and the disease course as well as the sequence of the effect during the pathophysiology of IBD. Conclusion: Longitudinal monitoring of IBD patients and integrating data related to the contributing/risk factors including psychological state, physiological conditions, inflammatory/immune modulations, and microbiome composition/function, could help to explain how major factors associate and interrelate leading to exacerbation of symptoms and disease activity. Identifying the temporal trajectory of biological and psychosocial disturbances may also help to assess their effects and interdependence on individuals' disease status. Moreover, this allows greater insight into understanding the temporal progressions of subclinical events as potential ground for disease severity in IBD. Furthermore, understanding the interaction between these risk factors may help better interventions in controlling the disease, reducing the costs related to disease management, further implications for clinical practice and research approaches in addition to improving patients' mental health and quality of life.

Microbes, microglia, and pain

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Explore the connection between the gut microbiome and microglia in chronic pain.

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Discuss mechanisms by which gut bacteria might influence microglia to contribute to chronic pain.

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Highlight gaps in knowledge and discuss future directions for the field.

Globally, it is estimated that one in five people suffer from chronic pain, with prevalence increasing with age. The pathophysiology of chronic pain encompasses complex sensory, immune, and inflammatory interactions within both the central and peripheral nervous systems. Microglia, the resident macrophages of the central nervous system (CNS), are critically involved in the initiation and persistence of chronic pain. Microglia respond to local signals from the CNS but are also modulated by signals from the gastrointestinal tract. Emerging data from preclinical and clinical studies suggest that communication between the gut microbiome, the community of bacteria residing within the gut, and microglia is involved in producing chronic pain. Targeted strategies that manipulate or restore the gut microbiome have been shown to reduce microglial activation and alleviate symptoms associated with inflammation. These data indicate that manipulations of the gut microbiome in chronic pain patients might be a viable strategy in improving pain outcomes. Herein, we discuss the evidence for a connection between microglia and the gut microbiome and explore the mechanisms by which commensal bacteria might influence microglial reactivity to drive chronic pain.

Translational Chemistry Meets Gluten-Related Disorders

Gluten‐related disorders are a complex group of diseases that involve the activation of the immune system triggered by the ingestion of gluten. Among these, celiac disease, with a prevalence of 1 %, is the most investigated, but recently, a new pathology, named nonceliac gluten sensitivity, was reported with a general prevalence of 7 %. Finally, there other less‐prevalent gluten‐related diseases such as wheat allergy, gluten ataxia, and dermatitis herpetiformis (with an overall prevalence of less than 0.1 %). As mentioned, the common molecular trigger is gluten, a complex mixture of storage proteins present in wheat, barley, and a variety of oats that are not fully degraded by humans. The most‐studied protein related to disease is gliadin, present in wheat, which possesses in its sequence many pathological fragments. Despite a lot of effort to treat these disorders, the only effective method is a long‐life gluten‐free diet. This Review summarizes the actual knowledge of gluten‐related disorders from a translational chemistry point of view. We discuss what is currently known from the literature about the interaction of gluten with the gut and the critical host responses it evokes and, finally, connect them to our current and novel molecular understanding of the supramolecular organization of gliadin and the 33‐mer gliadin peptide fragment under physiological conditions.

The IBD interactome: an integrated view of aetiology, pathogenesis and therapy

Crohn's disease and ulcerative colitis are prototypical complex diseases characterized by chronic and heterogeneous manifestations, induced by interacting environmental, genomic, microbial and immunological factors. These interactions result in an overwhelming complexity that cannot be tackled by studying the totality of each pathological component (an '-ome') in isolation without consideration of the interaction among all relevant -omes that yield an overall 'network effect'. The outcome of this effect is the 'IBD interactome', defined as a disease network in which dysregulation of individual -omes causes intestinal inflammation mediated by dysfunctional molecular modules. To define the IBD interactome, new concepts and tools are needed to implement a systems approach; an unbiased data-driven integration strategy that reveals key players of the system, pinpoints the central drivers of inflammation and enables development of targeted therapies. Powerful bioinformatics tools able to query and integrate multiple -omes are available, enabling the integration of genomic, epigenomic, transcriptomic, proteomic, metabolomic and microbiome information to build a comprehensive molecular map of IBD. This approach will enable identification of IBD molecular subtypes, correlations with clinical phenotypes and elucidation of the central hubs of the IBD interactome that will aid discovery of compounds that can specifically target the hubs that control the disease.

Oral administration of synthetic porcine beta-defensin-2 improves growth performance and cecal microbial flora and down-regulates the expression of intestinal toll-like receptor-4 and inflammatory cytokines in weaned piglets challenged with enterotoxigenic Escherichia coli

Synthetic porcine beta-defensin-2 (pBD-2) was tested as an alternative to antimicrobial growth-promoters in pig production. Thirty 21-day weaned piglets were challenged with enterotoxigenic Escherichia coli, and orally dosed with either sterile water (CON), pBD-2 (BD) or neomycin sulphate (NS) twice daily for 21 days. pBD-2 and NS led to higher growth performance, jejunum villus height and increased expression of insulin-like growth factor-I compared with the CON group (P < 0.05). Hemolytic E. coli scores from rectal swabs, and copy numbers of E. coli, Bacteroides fragilis and Streptococcus in the cecal digesta of the BD- or NS-treated piglets were lower than those in the CON group (P < 0.05). Messenger RNA levels of toll-like receptor 4, tumor necrosis factor-α, interleukin (IL)-1β, and IL-8 in the jejunum mucosa of the BD and NS groups were lower than those in the CON group (P < 0.05). Copy numbers of Lactobacilli and Bifidobacteria in the cecal digesta of the BD group were higher than those of the CON and NS groups (P < 0.05). Therefore, pBD-2 has antimicrobial activity in piglets, and it can improve growth performance, reduce inflammatory cytokine expression and affect intestinal morphological indices in the same way as probiotics. © 2015 Japanese Society of Animal Science.

Grape seed extract supplementation attenuates the heat stress-induced responses of jejunum epithelial cells in Simmental × Qinchuan steers

Grape seed extract (GSE), a rich source of polyphenols, is reported to possess antioxidant, anti-inflammatory and immunomodulatory properties. The objective of the present study was to determine whether GSE could attenuate the heat stress-induced responses of jejunum epithelial cells (JEC) in cattle. The JEC of a steer (Simmental × Qinchuan) were exposed to heat stress for 2 h in the absence (0 μg/ml) or presence (10, 20, 40 and 80 μg/ml) of GSE in the culture medium. When cultured at 40°C, JEC supplemented with GSE exhibited increased glutathione peroxidase activity (P= 0·04), viability (P= 0·004), and mRNA expression of epidermal growth factor (EGF; P= 0·03) and EGF receptor (EGFR; P = 0·01). Under the same conditions, the cells exhibited decreased mRNA expression of IL-8 (P= 0·01) and TNF-α (P= 0·03) and decreased protein concentrations of IL-1β (P= 0·02), Toll-like receptor 4 (TLR4; P= 0·04) and heat shock protein 70 (HSP70; P< 0·001). When cultured at 43°C, JEC supplemented with GSE exhibited increased catalase activity (P= 0·04), viability (P< 0·001), and mRNA expression of EGF (P< 0·001) and EGFR (P< 0·001) and decreased protein concentrations of IL-1β (P< 0·001), TLR4 (P= 0·03) and HSP70 (P< 0·001), as well as mRNA expression of IL-8 (P< 0·001), TLR4 (P= 0·002) and TNF-α (P< 0·001). Temperature × GSE concentration interactions were also observed for the concentrations of IL-1β (P< 0·001), IL-8 (P< 0·001), TNF-α (P= 0·01) and HSP70 (P= 0·04) and viability (P< 0·001) of JEC. The results of the present study indicate that GSE can attenuate the responses of JEC induced by heat stress within a certain range of temperatures.

Age-associated remodeling of the intestinal epithelial barrier

Disorders of the gastrointestinal tract are common in the elderly people; however, the precise trait(s) of aging that contribute to the vulnerability of the gastrointestinal tract are poorly understood. Recent evidence suggests that patients with gastrointestinal disorders have increased intestinal permeability. Here, we address the hypothesis that disruption of the intestinal barrier is associated with aging. Our results demonstrated that permeability was significantly higher in colonic biopsies collected from old baboons compared with young baboons. Additionally, colonic tissue from the older animals had decreased zonula occluden-1, occludin, and junctional adhesion molecule-A tight junction protein expression and increased claudin-2 expression. Upregulation of miR-29a and inflammatory cytokines IFN-γ, IL-6, and IL-1β was also found in colonic biopsies from old baboons relative to young baboons. These results show for the first time that a pivotal contributing factor to geriatric vulnerability to gastrointestinal dysfunction may be increased colonic permeability via age-associated remodeling of intestinal epithelial tight junction proteins.

The role of phosphoinositide 3-kinase signaling in intestinal inflammation

The phosphatidylinositol 3-kinase signaling pathway plays a central role in regulating the host inflammatory response. The net effect can either be pro- or anti-inflammatory depending on the system and cellular context studied. This paper focuses on phosphatidylinositol 3-kinase signaling in innate and adaptive immune cells of the intestinal mucosa. The role of phosphatidylinositol 3-kinase signaling in mouse models of inflammatory bowel disease is also discussed. With the development of new isoform specific inhibitors, we are beginning to understand the specific role of this complex pathway, in particular the role of the γ isoform in intestinal inflammation. Continued research on this complex pathway will enhance our understanding of its role and provide rationale for the design of new approaches to intervention in chronic inflammatory conditions such as inflammatory bowel disease.

Human mucosal CD4+ T cells but not blood CD4+ T cells respond vigorously towards CD28 engagement

Human lamina propria T lymphocytes (LPT) possess functional properties profoundly different from those of peripheral blood T lymphocytes (PBT). While they are characterized by a low proliferative response to T cell receptor (TCR)/CD3 stimulation in vitro their responsiveness to activation through the 'co-stimulatory' CD2-receptor is enhanced when compared to PBT. In this study, we demonstrate that engagement of another co-stimulatory receptor on both LPT and PBT, namely CD28, by a single monoclonal antibody (mAb), respectively, strongly activates the former but not the latter through a PI3-kinase dependent signalling pathway leading to the production of inflammatory cytokines such as interleukin (IL)-2, tumour necrosis factor (TNF)-α, interferon (IFN)-γ and granulocyte-macrophage colony-stimulating factor (GM-CSF). In addition to the high sensitivity of LPT to CD2 stimulation, this finding supports the notion that 'non-specific/innate' mechanisms to activate T lymphocytes play a predominant role vis-à-vis'TCR driven/adaptive' responses in the intestinal mucosa. Furthermore, it suggests that results from preclinical tests for therapeutic antibodies performed with human blood derived T cells are probably insufficient to predict reactivities of tissue-resident immune cells, which--given their quantitative predominance--may critically determine the in-vivo response to such compounds.

Enhanced IL-10 production by CD4+ T cells primed in IL-15Rα-deficient mice

In this study, we investigated the functional outcomes of CD4(+) T cells primed in the absence of IL-15 transpresentation. Compared with their WT counterparts primed in WT mice, IL-15Rα KO CD4(+) T cells primed in KO mice were found to exclusively overproduce IL-10 upon in vitro restimulation(.) The comparable expression of IL-4 and Foxp3 in CD4(+) T cells primed in the WT and IL-15Rα KO mice indicated that this was neither due to T(H) 2- nor Treg cell-differentiation. IL-10 overproduction was also observed when OVA-specific TCR transgenic CD4(+) T (OT-II) cells were primed in KO mice, excluding an intrinsic deficiency of KO CD4(+) T cells. To investigate the WT and KO microenvironment, DCs from both WT and IL-15Rα KO mice were compared. DCs from both backgrounds were indistinguishable in their steady-state survival and in their expression of MHC class II and costimulatory molecules CD80, CD86, and CD40. However, IL-15Rα KO DCs primed OT-II cells in vitro to produce higher levels of IL-10 upon their restimulation. Additionally, IL-15Rα KO DCs produced significantly more IL-10 upon activation, and IL-10 neutralization during DC-mediated in vitro priming abolished IL-10 overproduction by CD4(+) T cells. Thus, IL-15Rα KO DCs provide an IL-10-enriched environment that preferentially primes CD4(+) T cells for more IL-10 production, highlighting a regulatory role for IL-15 transpresentation in CD4(+) T-cell priming.

Bovine milk as a source of functional oligosaccharides for improving human health

Human milk oligosaccharides are complex sugars that function as selective growth substrates for specific beneficial bacteria in the gastrointestinal system. Bovine milk is a potentially excellent source of commercially viable analogs of these unique molecules. However, bovine milk has a much lower concentration of these oligosaccharides than human milk, and the majority of the molecules are simpler in structure than those found in human milk. Specific structural characteristics of milk-derived oligosaccharides are crucial to their ability to selectively enrich beneficial bacteria while inhibiting or being less than ideal substrates for undesirable and pathogenic bacteria. Thus, if bovine milk products are to provide human milk-like benefits, it is important to identify specific dairy streams that can be processed commercially and cost-effectively and that can yield specific oligosaccharide compositions that will be beneficial as new food ingredients or supplements to improve human health. Whey streams have the potential to be commercially viable sources of complex oligosaccharides that have the structural resemblance and diversity of the bioactive oligosaccharides in human milk. With further refinements to dairy stream processing techniques and functional testing to identify streams that are particularly suitable for enriching beneficial intestinal bacteria, the future of oligosaccharides isolated from dairy streams as a food category with substantiated health claims is promising.

Prebiotic oligosaccharides: in vitro evidence for gastrointestinal epithelial transfer and immunomodulatory properties

Prebiotic oligosaccharides are present in breast milk and evidence is pointing toward immunomodulatory properties of the acidic fraction. Recently, prebiotic supplements of infant formula [short-chain galacto (scGOS)-, long-chain fructo (lcFOS)-oligosaccharides] showed preventive effects on atopic disease development. We aimed to define the direct immunologic effects of these oligosaccharides and of human (aHMOS) and cows' milk (aCMOS) acidic oligosaccharides and to investigate the systemic uptake of prebiotic supplements of infant formula and a specific pectin-derived acidic oligosaccharide hydrolysate (pAOS) in vitro. After assurance of LPS-free conditions (limulus assay, toll like receptor-2, -4 transfected human embryonic kidney-cells), in vitro-transfer through a CaCo-2 cell monolayer was measured using high-pH anion exchange chromatography with pulsed amperometric detection. Direct effects on proliferation, cytokine-induction of cord blood mononuclear cells and modulation of allergen-specific CD4+ T-cell cytokine profiles from allergic and non-allergic individuals were investigated. Transfer of scGOS/lcFOS and pAOS in-vitro was detected with a rate of transfer of 4-14%, depending on the molecular size and structure. AHMOS induced IFN-γ and IL-10 but not the Th-2 cytokine IL-13 at physiologic concentrations (10-100 μg/ml) in cord blood, whereas aCMOS did not induce any of these cytokines. AHMOS significantly suppressed Th-2 type cytokine-production by Ara h1-specific CD4+ T cells (CFSE(low) CD3(+) CD4(+) cells) from peanut allergic patients. In conclusion, human milk-derived acidic oligosaccharides may modulate postnatal allergen-specific immune responses by the suppression of Th-2-type responses in atopy-prone individuals. Moreover, there is in vitro evidence for epithelial transport of prebiotic oligosaccharides.

Effects of spray-dried animal plasma on serous and intestinal redox status and cytokines of neonatal piglets

The study investigated the effects of dietary supplementation with spray-dried animal plasma (SDAP) on growth performance, intestinal morphology, as well as serum and intestinal cytokines and antioxidant indicators of artificially reared neonatal piglets. Three diets, 1) control (a fish meal basal diet), 2) SDAP (containing 10% SDAP), and 3) autoclaved SDAP (auSDAP; containing 10% auSDAP), were fed to 36 weaned piglets (3 d old), which were randomly allotted to 3 groups. At 21 d of age, blood and intestinal mucosal samples were collected from all piglets after they were slaughtered. Compared with the control, both SDAP and auSDAP improved ADFI and duodenal villus height of piglets (P < 0.05), whereas SDAP increased ADG and duodenal villus height to crypt depth ratio (P < 0.05). Piglets fed SDAP and auSDAP had reduced malondialdehyde (MDA) content in mucosa (P < 0.05). The concentration of serum MDA was decreased and mucosal catalase (CAT) activities were increased in piglets fed SDAP diet than those fed the control diet (P < 0.05). In the mucosa, both SDAP and auSDAP decreased tumor necrosis factor α, IL-6, transforming growth factor β, and soluble IL-2 receptor contents (P < 0.05). Mucosal IL-1β was decreased in SDAP compared with auSDAP and control groups (P < 0.05). The SDAP and control groups had increased mucosal IL-2 compared with auSDAP group (P < 0.05). The cytokines in serum were not affected by SDAP and auSDAP. The results indicate that both SDAP and auSDAP improved the growth performance of neonatal piglets, whereas the SDAP had a greater effect. The benefits of SDAP probably resulted from the promotion of the intestinal development, which were accompanied by the increased antioxidant capacity and the decreased production of inflammatory factors in the intestinal mucosa.

Transgenic plant-based oral vaccines

Oral vaccines offer significant advantages over needle-based vaccines for achieving universal childhood vaccination goals. The expression of vaccine antigens in transgenic plants has the potential to provide a convenient, safe approach for oral vaccination and thus a feasible alternative to traditional parenteral vaccines. Many developments in the field have ushered in improvements such as enhanced protein antigen expression for the use of plants as factories for vaccine production, and facilitated studies pertaining to immunogenicity of candidate vaccines. Oral delivery of plant-based vaccines offers the benefit of antigen protection within the harsh intestinal environment. Within the gut, mucosal immune cells are poised to respond to pathogens, but can also be exploited to elicit protective immune responses to oral vaccines. Inclusion of mucosal adjuvants during immunization with the vaccine antigen has been an important step towards the success of plant-based vaccines. This review discusses the mechanisms that control mucosal immune responses and highlights some of the studies and the results achieved following immunization with transgenic plants.

CD46-induced immunomodulatory CD4+ T cells express the adhesion molecule and chemokine receptor pattern of intestinal T cells

Tissue homing of activated T cells is typically mediated through their specific integrin and chemokine receptor repertoire. Activation of human primary CD4(+) T cells in the presence of CD46 cross-linking induces the development of a distinct immunomodulatory T cell population characterized by high IL-10/granzyme B production. How these regulatory T cells (Tregs) migrate/home to specific tissue sites is not understood. In this study, we determined the adhesion protein and chemokine receptor expression pattern on human CD3/CD46-activated peripheral blood CD4(+) T cells. CD3/CD46-activated, but not CD3/CD28-activated, T cells up-regulate the integrin alpha(4)beta(7). The interaction of alpha(4)beta(7) with its ligand mucosal addressin cell adhesion molecule 1 (MAdCAM-1) mediates homing or retention of T cells to the intestine. CD3/CD46-activated Tregs adhere to/roll on MAdCAM-1-expressing HeLa cells, similar to T cells isolated from the human lamina propria (LP). This interaction is inhibited by silencing MAdCAM-1 expression in HeLa cells or by the addition of blocking Abs to beta(7). CD46 activation of T cells also induced the expression of the surface-bound cytokine LIGHT and the chemokine receptor CCR9, both marker constitutively expressed by gut LP-resident T cells. In addition, we found that approximately 10% of the CD4(+) T lymphocytes isolated from the LP of patients undergoing bariatric surgery contain T cells that spontaneously secrete a cytokine pattern consistent with that from CD46-activated T cells. These data suggest that CD46-induced Tregs might play a role in intestinal immune homeostasis where they could dampen unwanted effector T cell responses through local IL-10/granzyme B production.

Massive interleukin-12-induced interferon-gamma production by interleukin-15-stimulated lamina propria lymphocytes followed by down-regulation of the interleukin-12 receptor

The intestinal mucosal immune response must differentiate between harmless foreign antigens and pathogens, a distinction that may depend upon changes in the cytokine milieu. A key cytokine in the adaptive immune response is interleukin-12 (IL-12), secreted by antigen-presenting cells (APC) immediately after encounter with a pathogen. IL-12 is important in the priming and polarization of naïve T cells. Here, we show that IL-12 and IL-15 direct human intestinal lamina propria lymphocytes (LPL) in the absence of T-cell receptor engagement to secrete extremely high amounts of interferon-gamma (IFN-gamma), greater than with any other stimulus. The functional synergy of IL-12 with IL-15 surprisingly operates independently of signal transducer and activator of transcription 1 (STAT1), STAT3, STAT4, or STAT5 phosphorylation and occurs during transcription. Four-colour immunofluorescence showed that IL-12 receptor beta1 is found on the CD4+ T cells expressing intracytoplasmic IFN-gamma. Importantly, IL-12 receptors beta1 and beta2 are not up-regulated by IL-12, unlike findings using antigen-specific T cells, and are lost over time. This study demonstrates the early and massive IFN-gamma response of LPL to IL-12 and IL-15, providing the tools to deal with a pathogen. The down-regulation of IL-12 receptors may curtail any excess damaging inflammation.

Mucosal IL-10 and TGF-beta play crucial roles in preventing LPS-driven, IFN-gamma-mediated epithelial damage in human colon explants

IL-10 is an immunomodulatory cytokine that plays an obligate role in preventing spontaneous enterocolitis in mice. However, little is known about IL-10 function in the human intestinal mucosa. We showed here that IL-10 was constitutively expressed and secreted by the human normal colonic mucosa, including epithelial cells. Depletion of IL-10 in mucosal explants induced both downregulation of the IL-10-inducible, immunosuppressive gene BCL3 and upregulation of IFN-gamma, TNF-alpha, and IL-17. Interestingly, TGF-beta blockade also strongly induced IFN-gamma production. In addition, the high levels of IFN-gamma produced upon IL-10 depletion were responsible for surface epithelium damage and crypt loss, mainly by apoptosis. Polymyxin B, used as a scavenger of endogenous LPS, abolished both IFN-gamma production and epithelial barrier disruption. Finally, adding a commensal bacteria strain to mucosa explant cultures depleted of both IL-10 and LPS reproduced the ability of endogenous LPS to induce IFN-gamma secretion. These findings demonstrate that IL-10 ablation leads to an endogenous IFN-gamma-mediated inflammatory response via LPS from commensal bacteria in the human colonic mucosa. We also found that both IL-10 and TGF-beta play crucial roles in maintaining human colonic mucosa homeostasis.

Up-regulation of the phosphoinositide 3-kinase pathway in human lamina propria T lymphocytes

Human intestinal lamina propria T lymphocytes (LPT), when investigated ex vivo, exhibit functional properties profoundly different from those of peripheral blood T lymphocytes (PBT). One prominent feature represents their enhanced sensitivity to CD2 stimulation when compared to PBT. Given that LPT are hyporesponsive to T cell receptor (TCR)/CD3 stimulation, an alternative activation mode, as mimicked by CD2 triggering in vitro, may be functional in mucosal inflammation in vivo. This study provides insight into signalling events associated with the high CD2 responsiveness of LPT. When compared to PBT, LPT show an increased activation of the phosphoinositide 3/protein kinase B/glycogen synthase kinase 3beta (PI3-kinase/AKT/GSK-3beta) pathway in response to CD2 stimulation. Evidence is provided that up-regulation of this pathway contributes to the enhanced CD2-induced cytokine production in LPT. Given the importance of TCR-independent stimulation for the initiation of intestinal immune responses analysis of signalling pathways induced by 'co-stimulatory' receptors may provide valuable information for therapeutic drug design.

Azathioprine in inflammatory bowel disease: improved molecular insights and resulting clinical implications

Azathioprine and 6-mercaptopurine represent important first-line immunosuppressive drugs in the treatment of inflammatory bowel disease. Owing to 45 years of clinical experience with thiopurines in inflammatory bowel disease, there currently exist strong data from numerous clinical trials and meta-analyses, which clearly document the therapeutic efficacy of azathioprine and 6-mercaptopurine in the treatment of inflammatory bowel disease. However, the exact molecular mechanism of action of these drugs was insufficiently understood for a long time. During the last few years, important new insights into the intracellular effects of azathioprine have been gained and thiopurines have been identified as strong inducers of T-cell apoptosis. This article aims to summarize traditional and current concepts of azathioprine-mediated effects and endeavors to discuss the resulting clinical implications.

1,25-dihydroxyvitamin D3 and dexamethasone increase interleukin-10 production in CD4+ T cells from patients with Crohn's disease

BACKGROUND AND AIM

In Crohn's disease (CD), epidemiological data and animal studies suggest that vitamin D (vitD) has protective immune-modulating properties. 1,25-dihydroxyvitamin D3 and dexamethasone (DEX) induce interleukin (IL)-10 productions in healthy controls (HC) T cells. We studied if 1,25-dihydroxyvitamin D3 with and without DEX could induce IL-10 production, downregulate pro-inflammatory Interferon (IFN)-gamma and Tumor Necrosis Factor (TNF)-alpha production, and influence cell kinetics in peripheral CD4+ T cells from CD patients.

METHODS

CD4+ T cells were separated from peripheral blood from CD patients and HC. Cells were activated by anti-CD3 and anti-CD28 in the presence of 1,25-dihydroxyvitamin D3 and/or DEX. Cytokine levels, proliferation, and apoptosis were measured following 7 days of culture.

RESULTS

In T cells from CD patients, 1,25-dihydroxyvitamin D3 and DEX increased IL-10 production from a median of 0.08 ng/ml to 0.2 ng/ml (p<0.01) and downregulated IFN-gamma production from 8.3 ng/ml to 3.1 ng/ml (p<0.01). The induced IL-10 increase in cultures from HC (0.2 ng/ml to 1.0 ng/ml, p<0.01) was significantly higher than in CD patients (p<0.05). In CD cultures, the IL-4 production increased from 0.3 ng/ml to 0.5 ng/ml (p<0.01) and IL-6 production from 2.5 ng/ml to 6.1 ng/ml (p<0.05). Similar changes in cytokine levels were observed with 1,25-dihydroxyvitamin D3 independently of DEX. In addition, 1,25-dihydroxyvitamin D3 and DEX decreased proliferation and reduced viability of T cells.

CONCLUSION

We found that 1,25-dihydroxyvitamin D3 with and without DEX stimulation increased IL-10 and reduced IFN-gamma production. These findings suggest that vitD may play a therapeutic role in CD.

Mucosal dendritic cells

The internal surfaces of the human body are covered by distinct types of epithelial cells and mucus-secreting cells. The mucosal surfaces serve many vital functions, such as respiration (nasal passage and lung), absorption (gastrointestinal tract), excretion (lung, urinary tract, large intestine), and reproduction (reproductive tract). In performing these functions, the host is inevitably exposed to environmental antigens, food particles, commensal flora, and pathogens. Mucosal surfaces contain specialized dendritic cells (DCs) capable of sensing these external stimuli and mounting appropriate local responses depending on the nature of the elements they encounter. In the absence of pathogens, mucosal DCs either ignore the antigen or induce regulatory responses. Upon recognition of microorganisms that invade the mucosal barrier, mucosal DCs mount robust protective immunity. This review highlights progress in our understanding of how mucosal DCs process external information and direct appropriate responses by mobilizing various cells of the innate and adaptive immune systems to achieve homeostasis and protection.

Osteopontin, a protein with cytokine-like properties, is associated with inflammation in Crohn's disease

In Crohn's disease (CD) mucosal T-cells produce increased interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) levels and TNF-alpha antibody treatment [Infliximab (Ifx)] is effective. Osteopontin (OPN), a glycoprotein stimulating activated T-lymphocytes, may be involved in the disturbed immune-regulation but also in normal immune-homeostasis and mucosal repair, since it is expressed in many tissues and present in human milk. This study investigates plasma-OPN levels in CD patients during Ifx treatment and the in vitro effect of OPN on intestinal T cells. Thirty-seven CD patients received three Ifx doses at week 0, 2 and 6. Blood samples, colonic biopsies and clinical scores were obtained before treatment and at week 8, 26 and 52. In-vivo activated T-cell cultures were established from colonic biopsies in the presence of interleukin (IL)-2 and IL-4. The in vitro effect of OPN stimulation on T-cell IFN-gamma, TNF-alpha, and IL-10 production was measured. Plasma-OPN was increased in active CD (increased CRP-level) compared with quiescent disease (P = 0.02) and declined after three Ifx doses (P = 0.04). It was inversely correlated with in vitro T-cell IL-10 production. OPN increased CD69 and CD25 expression and enhanced T-cell IFN-gamma and TNF-alpha production in a dose-dependent fashion with higher levels in CD than in healthy controls (HC), but induced a concomitant higher IL-10 production in HC than CD. In conclusion, plasma-OPN levels are related to CD inflammation. In vitro, OPN-stimulated IL-10 production increases less in T-cell cultures from CD patients than from HC, indicating that IL-10 deficiency may be involved in the defect immune-regulation in CD, even after OPN stimulation.

Crohn's disease intestinal CD4+ T cells have impaired interleukin-10 production which is not restored by probiotic bacteria

OBJECTIVE

Crohn's disease (CD) has been associated with low mucosal interleukin (IL)-10 production, but the mechanism behind this deficiency remains unclear. The aim of this study was to investigate IL-10 and interferon (IFN)-gamma production in intestinal CD4+ T cells from CD patients and healthy volunteers (HV) and to examine how this was affected by bacterial products and the presence or absence of autologous dendritic cells.

MATERIAL AND METHODS

We cultured intestinal CD4+ T cells from CD patients (n=9) and HV (n=6) and differentiated dendritic cells from their peripheral monocytes. Intestinal T cells were stimulated with Lactobacillus strains or autologous intestinal bacteria in the presence or absence of dendritic cells. IL-10 and IFN-gamma were measured on day 4.

RESULTS

When there were autologous dendritic cells present, CD intestinal T cells produced high levels of IFN-gamma (mean 6.4 ng/ml+/-standard error of the mean 1.1 ng/ml) but low levels of IL-10 (0.7 ng/ml+/-0.1 ng/ml). In contrast, HV intestinal T cells produced less IFN-gamma (3.9 ng/ml+/-0.8 ng/ml, p=0.06) and more IL-10 (4.6 ng/ml+/-0.9 ng/ml, p=0.0001) than CD intestinal T cells. Co-culture with Lactobacilli failed to revert this imbalance in CD, but tended to do so in HV. When there were no dendritic cells, CD intestinal T cells responded to autologous bacteria with an increased IFN-gamma production (2.3+/-1.3 ng/ml) compared with HV intestinal T cells (0.3+/-0.2 ng/ml).

CONCLUSIONS

Crohn's disease intestinal CD4+ T cells display a pro-inflammatory cytokine profile with impaired production of the regulatory cytokine IL-10. Tolerogenic bacteria (Lactobacilli) failed to restore this regulatory defect.

Expression of interleukin-10 in intestinal lymphocytes detected by an interleukin-10 reporter knockin tiger mouse

To identify interleukin-10 (IL-10)-producing cells in vivo, we generated a knockin mouse where an internal ribosome entry site (IRES) green fluorescence protein (GFP) element was inserted immediately before the polyadenylation site of the IL-10 gene. GFP fluorescence in cells from these mice was found to correlate positively with IL-10 protein expression. With this model, we found that after multiple T cell receptor (TCR) stimulations, strong expression of IL-10 was produced specifically by intraepithelial lymphocytes (IEL) in the small intestine and colonic lamina propria lymphocytes (cLPL). We found that anti-CD3 treatment induces T regulatory cell 1 (Tr1)-like cells in small intestinal IEL (sIEL) and led to the accumulation of naturally occurring regulatory T (nTreg) cells in colonic LPL (cLPL). These findings highlight the intestine as a unique site for induction of IL-10-producing T cells, which play a critical role in the regulation of inflammation in the gut.

From immunogenic mechanisms to novel therapeutic approaches in inflammatory bowel disease

Crohn's disease (CD) and ulcerative colitis (UC) are the two most common forms of chronic inflammatory bowel disease (IBD). The etiology of IBD is still unclear and should be considered as multi-factorial according to recent studies. Genetic factors seem to play a pathogenetic role as well as environmental, infectious and immulogical factors. Substantial progress, however, has been made in the understanding of the pathogenesis of IBD during the past years persuing the view, that IBD could result from disturbances of the intestinal barrier and a pathologic activation of the intestinal immune response towards luminal, bacterial antigens. This paradigm has led to the identification of key players of the intestinal immune system, which represent promising targets for novel therapeutic approaches. The objective of this chapter is to provide an overview over recent advances in the elucidation of the intestinal immune system in IBD and novel therapeutic approaches that have been derived from these results. Molecular biological techniques have revealed, that many of the established conventional antiinflammatory drugs such as salicylic acids, steroids or immunuosuppressants act at the same molecules that are the target for modern biologicals, i.e., the cytokine TNF or the transcription factor NFkappaB. This chapter, however, focusses on novel experimental approaches such as recombinant antiinflammatory cytokines, neutralizing antibodies or antisense oligonucleotides.

Complement-induced regulatory T cells suppress T-cell responses but allow for dendritic-cell maturation

Concurrent activation of the T-cell receptor (TCR) and complement regulator CD46 on human CD4+ T lymphocytes induces Tr1-like regulatory T cells that suppress through IL-10 secretion bystander T-cell proliferation. Here we show that, despite their IL-10 production, CD46-induced T-regulatory T cells (Tregs) do not suppress the activation/maturation of dendritic cells (DCs). DC maturation by complement/CD46-induced Tregs is mediated through simultaneous secretion of GM-CSF and soluble CD40L, factors favoring DC differentiation and reversing inhibitory effects of IL-10. Thus, CD46-induced Tregs produce a distinct cytokine profile that inhibits T-cell responses but leaves DC activation unimpaired. Such "DC-sparing" Tregs could be desirable at host/environment interfaces such as the gastrointestinal tract where their specific cytokine profile provides a mechanism that ensures unresponsiveness to commensal bacteria while maintaining reactivity to invading pathogens.

The gut: beyond immunology

The immune system is characterized by the ability to distinguish self from non-self. The intestinal immune system bears this latter property but, furthermore, it must discriminate among nutritious and beneficial substances from toxic or harmful ones. Considering that the gut has to be colonized by commensal bacteria participating in digestion as well as in the control of pathogen microorganisms, it is not surprising that mucosal surfaces are the largest and probably the most exquisitely specialized immune system's compartment. This means that not only innate and adaptive immunity are present, but further, particular structures, cells, and mechanisms such as physical barrriers, epithelia, Peyer's patches, M cells among others, which together are involved in the dynamic control of the homeostasis between gut and its flora. The present review deals with some popular conceptions about the digestive system with particular emphasis on the gut's immunology.

Activation antigens on colonic T cells in inflammatory bowel disease: effects of IL-10

Activated T cells that express activation antigens are termed nonprofessional antigen-presenting cells (T-APCs). This study evaluates the ability of lamina propria lymphocytes (LPLs) in inflammatory bowel disease (IBD) to become T-APCs. LPLs were stained by two-colour immunofluorescence to determine the expression of activation antigens on T cells. Those from actively inflamed IBD mucosa expressed greater amounts of MHC class II (DR) and CD86 than did LPL T cells from disease controls or normal individuals. After culture in IL-2 with or without IL-10, the ability of the T-APCs from IBD colon to stimulate allogeneic peripheral blood T cell proliferation was measured. The T-APCs from IBD stimulated an allogeneic mixed lymphocyte reaction, particularly through their expression of DR and CD86, as demonstrated by antibody blocking. Normal LPLs acquired these properties only if repeatedly stimulated with allogeneic peripheral blood lymphocytes (PBLs) used as cell lines in the presence of IL-2. Addition of IL-10 reduced expression of activation antigens and the stimulatory ability of LPLs from either IBD patients or from these cell lines. In summary, LPLs from active IBD, but not from disease controls, express activation antigens that stimulate naïve T cells, a process that is reduced by IL-10. This may contribute to perpetuation of the inflammation.

Potential role of thioredoxin in immune responses in intestinal lamina propria T lymphocytes

Thioredoxin (TRX) is a ubiquitous oxidoreductase with strong co-cytokine, chemoattractant and anti-apoptotic activities. TRX expression was found to be particularly elevated in the intestinal mucosa, where its physiologic function is entirely unknown. Here, we demonstrate a high level of TRX expression in lamina propria T cells (LP-T) as opposed to autologous peripheral blood T lymphocytes (PB-T). Addition of recombinant human TRX (rhTRX) to PB-T enhances TRX gene expression. This autoregulation involves the calcineurin signaling pathway, as rhTRX antagonizes the cyclosporine A (CsA)- and tacrolimus-mediated suppression of TRX gene expression. Similarly, rhTRX reverses the suppression of IL-2 mRNA production by CsA and enhances cytokine production preferentially in prestimulated cells. The differential TRX expression in LP-T versus PB-T may thus contribute to the high-level, CsA-resistant IL-2 production characteristic for CD2-stimulated LP-T. Inversely, inactivation of TRX in LP-T through inhibition of TRX reductase abolishes cytokine gene expression. TRX may play a key role in the specialized intestinal microenvironment in amplifying immediate immune responses of LP-T whenever appropriate costimulation of LP-T is provided.

Signal transducers and activators of transcription 3 signaling pathway: an essential mediator of inflammatory bowel disease and other forms of intestinal inflammation

Crohn's disease (CD) and ulcerative colitis (UC), the two major forms of chronic inflammatory bowel disease (IBD), are characterized by mucosal immune cell activation that is driven by a cytokine imbalance. Several cytokines involved in IBD act through the activation of the signal transducers and activators of transcription (STAT) family. We investigated the activation of STAT3 in the mucosa of CD and UC patients, and evaluated whether this event is specific for IBD patients. Using immunofluorescence and immunoblotting, total and phosphorylated STAT3 levels were assessed in biopsy specimens, isolated lamina propria mononuclear cells, and peripheral blood mononuclear cells from patients with CD, UC, other forms of intestinal inflammation, and control subjects. Immunoblotting revealed phosphorylated STAT3 in mucosal biopsy specimens from patients with CD, UC, celiac disease, and acute self-limited colitis, but not in the normal mucosa of control subjects. In IBD patients, STAT3 activation was confined to actively inflamed areas. Accordingly, activated STAT3 was detected in isolated lamina propria mononuclear cells from inflamed IBD tissues, but not in peripheral blood mononuclear cells from control subjects or IBD patients. Immunofluorescence demonstrated that the sources of activated STAT3 were macrophages and T lymphocytes, but not neutrophils. STAT3 activation also was detected in T cells infiltrating the duodenal mucosa of celiac disease patients. We conclude that STAT3 signaling occurs in both CD and UC, where it is strictly confined to areas of active inflammation and is limited to infiltrating macrophages and T cells. The occurrence of STAT3 signaling in other acute and chronic intestinal inflammatory conditions suggests that, rather than a specific feature of IBD, it represents a fundamental signaling pathway that is shared by multiple forms of gut inflammation.

Recombinant human interleukin 10 suppresses gliadin dependent T cell activation in ex vivo cultured coeliac intestinal mucosa

BACKGROUND

Enteropathy in coeliac disease (CD) is sustained by a gliadin specific Th1 response. Interleukin (IL)-10 can downregulate Th1 immune responses.

AIM

We investigated the ability of recombinant human (rh) IL-10 to suppress gliadin induced Th1 response.

PATIENTS AND METHODS

IL-10 RNA transcripts were analysed by competitive reverse transcription-polymerase chain reaction in duodenal biopsies from untreated and treated CD patients, non-coeliac enteropathies (NCE), and controls. CD biopsies were cultured with a peptic-tryptic digest of gliadin with or without rhIL-10. The proportion of CD80+ and CD25+ cells in the lamina propria, epithelial expression of Fas, intraepithelial infiltration of CD3+ cells, as well as cytokine synthesis (interferon gamma (IFN-gamma) and IL-2) were measured. Short term T cell lines (TCLs) obtained from treated CD biopsies cultured with gliadin with or without rhIL-10 were analysed by ELISPOT for gliadin specific production of IFN-gamma.

RESULTS

In untreated CD and NCE, IL-10 RNA transcripts were significantly upregulated. In ex vivo organ cultures, rhIL-10 downregulated gliadin induced cytokine synthesis, inhibited intraepithelial migration of CD3+ cells, and reduced the proportion of lamina propria CD25+ and CD80+ cells whereas it did not interfere with epithelial Fas expression. In short term TCLs, rhIL-10 abrogated the IFN-gamma response to gliadin.

CONCLUSIONS

rhIL-10 suppresses gliadin specific T cell activation. It may interfere with the antigen presenting capacity of lamina propria mononuclear cells as it reduces the expression of CD80. Interestingly, rhIL-10 also induces a long term hyporesponsiveness of gliadin specific mucosal T cells. These results offer new perspectives for therapeutic strategies in coeliac patients based on immune modulation by IL-10.

Recombinant human interleukin 10 suppresses gliadin dependent T cell activation in ex vivo cultured coeliac intestinal mucosa

BACKGROUND

Enteropathy in coeliac disease (CD) is sustained by a gliadin specific Th1 response. Interleukin (IL)-10 can downregulate Th1 immune responses.

AIM

We investigated the ability of recombinant human (rh) IL-10 to suppress gliadin induced Th1 response.

PATIENTS AND METHODS

IL-10 RNA transcripts were analysed by competitive reverse transcription-polymerase chain reaction in duodenal biopsies from untreated and treated CD patients, non-coeliac enteropathies (NCE), and controls. CD biopsies were cultured with a peptic-tryptic digest of gliadin with or without rhIL-10. The proportion of CD80+ and CD25+ cells in the lamina propria, epithelial expression of Fas, intraepithelial infiltration of CD3+ cells, as well as cytokine synthesis (interferon gamma (IFN-gamma) and IL-2) were measured. Short term T cell lines (TCLs) obtained from treated CD biopsies cultured with gliadin with or without rhIL-10 were analysed by ELISPOT for gliadin specific production of IFN-gamma.

RESULTS

In untreated CD and NCE, IL-10 RNA transcripts were significantly upregulated. In ex vivo organ cultures, rhIL-10 downregulated gliadin induced cytokine synthesis, inhibited intraepithelial migration of CD3+ cells, and reduced the proportion of lamina propria CD25+ and CD80+ cells whereas it did not interfere with epithelial Fas expression. In short term TCLs, rhIL-10 abrogated the IFN-gamma response to gliadin.

CONCLUSIONS

rhIL-10 suppresses gliadin specific T cell activation. It may interfere with the antigen presenting capacity of lamina propria mononuclear cells as it reduces the expression of CD80. Interestingly, rhIL-10 also induces a long term hyporesponsiveness of gliadin specific mucosal T cells. These results offer new perspectives for therapeutic strategies in coeliac patients based on immune modulation by IL-10.

Current concept of pathophysiological understanding and natural course of ulcerative colitis

INTRODUCTION

According to the current paradigm both ulcerative colitis (UC) and Crohn's disease (CD) result from a complex interplay of genetic susceptibility factors, environmental factors, alterations of the physiological intestinal flora and a defective regulation of the intestinal immune system.

DISCUSSION

The objective of this review is to give an overview of these factors and mechanisms, including genetic, environmental and microbial factors, with special alterations of relevant cellular components of the intestinal immune system such as T cells, macrophages and epithelial cells will then be addressed. In addition, the most relevant animal model systems that have contributed to our current pathogenetic understanding will be introduced. Clinically, the natural course of UC with special reference to the risk of colorectal cancer will be addressed.

CONCLUSION

The elucidation of pathomechanisms at the level of the intestinal immune system provides the potential for novel, effective treatment strategies. Best surgical management of patients with UC, however, still remains a challenge.

Over-expression of interleukin 10 in mucosal T cells of patients with active ulcerative colitis

Ulcerative colitis (UC), a chronic inflammatory bowel disease, exhibits pronounced increase of T lymphocytes in the inflamed mucosa. To understand the role of intestinal T lymphocytes in the pathogenesis of UC their cytokine production in the mucosa was analysed. Intestinal T lymphocytes of UC, Crohn's disease and control patients were analysed for cytokine mRNA levels by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) directly after isolation without in vitro stimulation. Frequencies of cytokine positive cells were determined in UC and control colon by immunomorphometry. T lymphocytes in normal colon expressed interleukin (IL)-2, interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha and transforming growth factor (TGF)-beta1, but not IL-4, IL-5 or IL-10. In UC, a highly significant increase in IL-10 mRNA levels in T lymphocytes and an increased frequency of IL-10 positive cells was seen in colon. IL-10 mRNA levels were also elevated in T lymphocytes of the non-inflamed ileum and correlated with disease activity at both locations. CD4+ T lymphocytes were the major source of IL-10 mRNA. IL-2, IFN-gamma and TNF-alpha mRNA levels were decreased in colonic T lymphocytes, and virtually no IL-2, IFN-gamma, TNF-alpha or TGF-beta positive cells were detected in basal lymphoid aggregates. However, scattered IL-10 positive cells were found here. Lamina propria outside the aggregates contained IL-10-, IFN-gamma, TNF-alpha and TGF-beta but not IL-2 positive cells. T cells of UC patients did not express IL-4 or IL-5. Taken, together the data suggest a generalized activation of IL-10 producing CD4+ T cells along the intestine of UC patients. The local environment seems to determine the biological consequences of elevated IL-10.

Fas is not essential for lamina propria T lymphocyte homeostasis

IL-2 receptor alpha-deficient (IL2Ralpha-/-) mice spontaneously accumulate vast numbers of intestinal lamina propria (LP) T cells and develop bowel inflammation. The accumulation of T cells in IL2Ralpha-/- mice is thought to result, in part, from defective Fas-induced cell death. To understand the role of cell proliferation and death in regulating LP T cells in IL2Ralpha-/- mice, we have directly examined the proliferation and Fas sensitivity of wild-type, lpr/lpr, and IL2Ralpha-/- LP T cells. In wild-type mice, 5'-bromodeoxyuridine (BrdU) labeling and Fas susceptibility are greatest in CD44Hi LP T cells. Fas-deficient lpr/lpr mice have normal total numbers of LP T cells, despite an increased proportion of BrdU+ T cells. By contrast, IL2Ralpha-/- mice possess increased total numbers of LP T cells, despite normal proportions of BrdU+ LP T cells. Finally, wild-type and IL2Ralpha-/- LP T cells are equivalently Fas sensitive. These results demonstrate that LP T cells proliferate and are Fas-sensitive cells. IL2Ralpha-/- mice accumulate a large number of these Fas-sensitive LP T cells and clearly differ from Fas-deficient lpr/lpr mice in this regard. Thus our studies reveal that Fas is dispensable for LP T cell homeostasis and suggest that the intestinal inflammation observed in IL2Ralpha-/- mice is independent of defective Fas-induced cell death.

CC chemokine receptor 9 expression defines a subset of peripheral blood lymphocytes with mucosal T cell phenotype and Th1 or T-regulatory 1 cytokine profile

The chemokine receptor CCR9 is expressed on most small intestinal lamina propria and intraepithelial lymphocytes and on a small subset of peripheral blood lymphocytes. CCR9-expressing lymphocytes may play an important role in small bowel immunity and inflammation. We studied the phenotype and functional characteristics of CCR9(+) lymphocytes in blood from normal donors. A subset of CCR9(+) T cells have a phenotype of activated cells and constitutively express the costimulatory molecules CD40L and OX-40. In contrast to CCR9(-), CCR9(+)CD4(+) peripheral blood T cells proliferate to anti-CD3 or anti-CD2 stimulation and produce high levels of IFN-gamma and IL-10. IL-10-producing cells were exclusively detected within the CCR9(+) subset of CD4(+) T cells by intracellular staining and were distinct from IL-2- and IFN-gamma-producing cells. Moreover, memory CCR9(+)CD4(+) lymphocytes respond to CD2 stimulation with proliferation and IFN-gamma/IL-10 production, whereas memory CCR9(-)CD4(+) cells were unresponsive. In addition, memory CCR9(+)CD4(+) T cells support Ig production by cocultured CD19(+) B cells in the absence of prior T cell activation or addition of exogenous cytokines. Our data show that the memory subset of circulating CCR9(+)CD4(+) T cells has characteristics of mucosal T lymphocytes and contains cells with either Th1 or T-regulatory 1 cytokine profiles. Studies on the cytokine profile and Ag specificity of this cell subset could provide important insight into small intestinal immune-mediated diseases and oral tolerance in humans.

Helicobacter pylori modulation of gastric and duodenal mucosal T cell cytokine secretions in children compared with adults

BACKGROUND

In contrast to adults, ulcers are un-common in Helicobacter pylori-infected children. Since immunological determinants influence the outcome of H. pylori infection, we have investigated mucosal T cell responses in H. pylori-infected children and compared them with those of adults and negative controls.

MATERIAL AND METHODS

Mucosal biopsies were obtained from 43 patients undergoing an upper GI endoscopy for dyspeptic symptoms. The concentrations of released cytokines and the density of CD3+, CD25+ and CD69+cells were evaluated by flow cytometry, and the numbers of cytokine-secreting cells were measured by ELISPOT.

RESULTS

The numbers of isolated antral CD3+ lymphocytes were only significantly raised in infected adults compared with noninfected controls (p < 0.05), whereas the proportion of CD3+ cells expressing activation markers (CD25 or CD69) remained low. In the stomach, IFN-gamma concentrations increased in infected children and infected adults compared with controls (p < 0.05), but IFN-gamma concentrations were tenfold lower in children than in adults (p < 0.01). IL-2, IL-4, IL-10 and TNF-alpha concentrations were similar in infected and in uninfected children and adults. In contrast, in the duodenum, IFN-gamma, as well as IL-4 and IL-10 concentrations were only increased in infected children compared with controls (p < 0.05). The concentrations of these cytokines were similar in both groups of adults who, however, like children, displayed a higher number of duodenal IL-4-secreting cells compared to controls (p < 0.05).

CONCLUSION

These results suggest that IFN-gamma secretion in the stomach of H. pylori-infected patients is lower in children than in adults. This could protect children from development of severe gastro-duodenal diseases such as ulcer disease. In addition, infected patients are characterised by a dysregulation of the mucosal cytokine secretion at distance from the infection site.

Anatomical basis of tolerance and immunity to intestinal antigens

The intestinal immune system has to discriminate between harmful and beneficial antigens. Although strong protective immunity is essential to prevent invasion by pathogens, equivalent responses against dietary proteins or commensal bacteria can lead to chronic disease. These responses are normally prevented by a complex interplay of regulatory mechanisms. This article reviews the unique aspects of the local microenvironment of the intestinal immune system and discuss how these promote the development of regulatory responses that ensure the maintenance of homeostasis in the gut.

Response, relapse and mucosal immune regulation after infliximab treatment in fistulating Crohn's disease

BACKGROUND

Infliximab reduces mucosal inflammation in some, but not all, patients with Crohn's disease.

AIM

To monitor clinical data and changes in mucosal cytokine levels after infliximab treatment to identify differences between responders and non-responders.

METHODS

Twenty-six patients with fistulating Crohn's disease received three infliximab infusions at weeks 0, 2 and 6. Follow-up was for 1 year and included clinical examination, colonoscopy, ano-rectal ultrasound and magnetic resonance imaging. Biopsies were taken at weeks 0, 8, 26 and 52. Cell cultures were established and analysed for tumour necrosis factor-alpha, interferon-gamma and interleukin-10 levels, and related to clinical status and fistula healing.

RESULTS

Eleven of 15 patients (73%) with active disease (Crohn's disease activity index > 150) obtained remission (Crohn's disease activity index < 150) at 8 weeks. In in vitro cell cultures, there was reduced tumour necrosis factor-alpha and interleukin-10 production at week 26, with the latter persistent throughout the study period. When the disease deteriorated or relapsed, there was increased interferon-gamma production in in vitro cell cultures. Fistula healing was associated with reduced production of interferon-gamma, tumour necrosis factor-alpha and interleukin-10.

CONCLUSIONS

Infliximab down-regulates mucosal immune activation in Crohn's disease. Monitoring of mucosal cytokine levels after infliximab treatment by whole biopsy cultures may be useful as interleukin-10, tumour necrosis factor-alpha and interferon-gamma production are different in responders and at relapse.

Expression of the EP4 prostaglandin E2 receptor subtype with rat dextran sodium sulphate colitis: colitis suppression by a selective agonist, ONO-AE1-329

Expression of the EP4 receptor, a prostaglandin (PG)E2 receptor subtype, as well as disease suppression by the administration of a selective EP4 agonist (ONO-AE1-329) was investigated in the colorectal mucosa of rats with dextran sodium sulphate (DSS)-induced colitis. Rats were given drinking water containing 3% DSS for 2 weeks. Expression of EP4 receptor mRNA was barely detectable under normal conditions according to reverse transcription-polymerase chain reaction (RT-PCR). By 1 week after the initial administration of DSS, the receptor mRNA was strongly expressed. After ONO-AE1-329 was administered intracolonically to rats with DSS colitis for 7 consecutive days, erosion and ulceration decreased. Peripheral white blood cell (WBC) counts became less elevated. Interleukin (IL)-1beta and growth-regulated gene product/cytokine-induced neutrophil chemoattractant (GRO/CINC-1) concentrations in colorectal mucosa were lower than in colitis control group (IL-1beta: 12.8 +/- 4.6 and 30.8 +/- 6.2 microg/mg protein, P < 0.05; GRO/CINC-1: 15.5 +/- 3.0 and 39.2 +/- 5.4 microg/mg protein, P < 0.05), and the expression of the corresponding cytokine mRNA was strongly suppressed. IL-10 concentration was higher than in control group (14.5 +/- 1.7 and 7.9 +/- 1.2 microg/mg, P < 0.05), and the mRNA was more strongly expressed. These results suggest that the EP4 receptor is important in colonic inflammation, and that PGE2 suppresses DSS colitis at least partly via the EP4 receptor and the above cytokine changes. Intracolonic administration of selective EP4 agonist might have therapeutic applicability in inflammatory bowel disease such as ulcerative colitis.

Human milk-specific mucosal lymphocytes of the gastrointestinal tract display a TH2 cytokine profile

BACKGROUND

A number of gastrointestinal disorders, including allergic eosinophilic gastroenteritis and food protein-induced enteropathy, have been associated with milk hypersensitivity. The immunologic reactions appear to involve T cells that are activated by specific food proteins.

OBJECTIVE

The present study was performed to examine the cytokine profiles of milk-specific lymphocytes from the duodenal lamina propria from children with milk-induced gastrointestinal diseases.

METHODS

Duodenal biopsy specimens obtained from 10 patients with allergic eosinophilic gastroenteritis, food protein-induced enteropathy, or both and 12 control subjects were mechanically minced and cultured with either mitogens (i.e., polyclonal T-cell expansion) or milk proteins (i.e., milkspecific T-cell expansion). By using flow cytometry, expanded T cells were phenotyped with anti-CD4, anti-CD8, anti-IL-4, anti-IL-5, and anti-IFN-gamma mAbs. The milk specificity of the lines was evaluated by means of the lymphocyte proliferation assay. In addition, the release of T(H)1, T(H)2, and T(H)3 cytokines was determined after restimulation.

RESULTS

In patients and control subjects polyclonal expansion of mucosal lymphocytes resulted in predominantly T(H)1 cells. Milk-specific mucosal T-cell lines could be established in 60% of the patients but in none of the control subjects. In contrast to the polyclonal expansion of T cells, the milk-specific expansion of mucosal T cells showed a clear T(H)2 cytokine profile. On restimulation with milk protein, these cells showed a high proliferative response. They released T(H)2 cytokines, predominately IL-13, but failed to release T(H)3 cytokines important in the development of oral tolerance.

CONCLUSION

The release of T(H)2 cytokines after stimulation of milk-specific mucosal T cells may play a pathogenic role in the inflammatory changes seen in milk-induced gastrointestinal disorders.

Lamina propria CD4+ T lymphocytes synergize with murine intestinal epithelial cells to enhance proinflammatory response against an intracellular pathogen

Acute and lethal ileitis can be elicited in certain strains of inbred mice after oral infection with the intracellular protozoan parasite Toxoplasma gondii. The development of this inflammatory process is dependent upon the induction of a robust Th1 response, including overproduction of IFN-gamma, TNF-alpha, and NO, as has been reported in other experimental models of human inflammatory bowel disease. In this study we have investigated the role of CD4(+) T cells from the lamina propria (LP) in the early inflammatory events after T. gondii infection using isolated and primary cultured intestinal cells from infected mice and immortalized mouse mIC(cl2) intestinal epithelial cells. Primed LP CD4(+) T cells isolated from parasite-infected mice produce substantial quantities of both IFN-gamma and TNF-alpha. IFN-gamma- and TNF-alpha-producing LP CD4(+) T cells synergize with infected mIC(cl2) and enhance the production of several inflammatory chemokines including macrophage-inflammatory protein-2, monocyte chemoattractant protein-1, monocyte chemoattractant protein-3, macrophage-inflammatory protein-1alphabeta, and IFN-gamma-inducible protein-10. Furthermore, primed LP CD4(+) T cells cocultured with infected mIC(cl2) inhibited replication of the parasite in the intestinal epithelial cells. Thus, LP CD4(+) T cells can interact with parasite-infected intestinal epithelial cells and alter the expression of several proinflammatory products that have been associated with the development of intestinal inflammation. The interaction between these two components of the gut mucosal compartment (CD4(+) T cells and enterocytes) may play a role in the immunopathogenesis of this pathogen-driven experimental inflammatory bowel disease model.

Regulation of mucosal immune responses in effector sites

In human disease and rodent models, immune responses in the intestinal mucosa can be damaging. Damage is characterised by villus atrophy, crypt hyperplasia and reduced ability to digest and absorb nutrients. In normal individuals active responses to harmless environmental antigens associated with food and commensal bacteria are controlled by the development of immunological tolerance. Similar pathological changes occur in piglets weaned early from their mothers. Active immune responses to food antigens are observed in these piglets, and we and others have hypothesised that the changes occur as a result of transient allergic immune responses to novel food or bacteria antigens. The normal mechanism for producing tolerance to food antigens may operate at induction (Peyer's patches and mesenteric lymph nodes) or at the effector stage (intestinal lamina propria). In our piglet studies immunological tolerance occurs despite the initial active response. Together with evidence from rodents, this observation suggests that active responses are likely to be controlled at the effector stage, within the intestinal lamina propria. Support for this mechanism comes from the observation that human and pig intestinal T-cells are susceptible to apoptosis, and that this process is accelerated by antigen. We suggest that the role of the normal mature intestinal lamina propria is a balance between immunological effector and regulatory function. In neonatal animals this balance develops slowly and is dependant on contact with antigen. Immunological insults such as weaning may tip the balance of the developing mucosal immune system into excessive effector or regulatory function resulting in transient or chronic allergy or disease susceptibility.