Tolerance exists towards resident intestinal flora but is broken in active inflammatory bowel disease (IBD)

C/EBPβ Deletion Promotes Expansion of Poorly Functional Intestinal Regulatory T Cells

BACKGROUND AND AIMS

Inflammatory Bowel Diseases [IBDs] are chronic intestinal inflammatory conditions in part mediated by CD4+ T cells. Anti-inflammatory Foxp3+ regulatory T cells [Tregs] maintain immune homeostasis and protect against IBD development via multiple mechanisms, including cytokine secretion and cell-cell interaction. CCAAT enhancer binding protein-beta [C/EBPβ] is a stress-responsive transcription factor linked with IBD susceptibility. Whole-body C/EBPβ deficiency induces CD4+ T cell-predominant hyperproliferation, and we hypothesize that this may be due to impaired Treg function.

METHODS

We used the C/EBPβ-/- mice in the CD45RBHigh adoptive transfer model, to assess C/EBPβ-/- CD4+ T cells for their colitiogenic potential, and C/EBPβ-/- CD4+ Foxp3+ Tregs for their ability to inhibit colitis. We assessed Tregs from the C/EBPβ-/- mice for expression of Treg functional genes and proteins.

RESULTS

Naïve C/EBPβ-/- CD4+ T cells are more colitogenic in vivo. The exacerbated colitis does not appear to reflect impaired Treg development, however, as C/EBPβ-/- mice displayed more, rather than fewer intestinal CD4+Foxp3+ Tregs in vivo. Instead, this reflects impaired Treg function as seen by the reduced capacity to suppress T cell proliferation in vitro, along with decreased secretion of the anti-inflammatory cytokine IL-10. These findings were corroborated in vivo by additional adoptive co-transfer studies in which wildtype Tregs prevented colitis but C/EBPβ-/- Tregs did not.

CONCLUSION

C/EBPβ deficiency impairs Treg function and potentiates T cell-mediated colitis. A clearer understanding of the function of this transcription factor may provide a novel therapeutic strategy for IBD.

Microbiome and Allergic Diseases

Allergic diseases, such as respiratory, cutaneous, and food allergy, have dramatically increased in prevalence over the last few decades. Recent research points to a central role of the microbiome, which is highly influenced by multiple environmental and dietary factors. It is well established that the microbiome can modulate the immune response, from cellular development to organ and tissue formation exerting its effects through multiple interactions with both the innate and acquired branches of the immune system. It has been described at some extent changes in environment and nutrition produce dysbiosis in the gut but also in the skin, and lung microbiome, inducing qualitative and quantitative changes in composition and metabolic activity. Here, we review the potential role of the skin, respiratory, and gastrointestinal tract (GIT) microbiomes in allergic diseases. In the GIT, the microbiome has been proven to be important in developing either effector or tolerant responses to different antigens by balancing the activities of Th1 and Th2 cells. In the lung, the microbiome may play a role in driving asthma endotype polarization, by adjusting the balance between Th2 and Th17 patterns. Bacterial dysbiosis is associated with chronic inflammatory disorders of the skin, such as atopic dermatitis and psoriasis. Thus, the microbiome can be considered a therapeutical target for treating inflammatory diseases, such as allergy. Despite some limitations, interventions with probiotics, prebiotics, and/or synbiotics seem promising for the development of a preventive therapy by restoring altered microbiome functionality, or as an adjuvant in specific immunotherapy.

Arabidopsis thaliana and Pseudomonas Pathogens Exhibit Stable Associations over Evolutionary Timescales

Crop disease outbreaks are often associated with clonal expansions of single pathogenic lineages. To determine whether similar boom-and-bust scenarios hold for wild pathosystems, we carried out a multi-year, multi-site survey of Pseudomonas in its natural host Arabidopsis thaliana. The most common Pseudomonas lineage corresponded to a ubiquitous pathogenic clade. Sequencing of 1,524 genomes revealed this lineage to have diversified approximately 300,000 years ago, containing dozens of genetically identifiable pathogenic sublineages. There is differentiation at the level of both gene content and disease phenotype, although the differentiation may not provide fitness advantages to specific sublineages. The coexistence of sublineages indicates that in contrast to crop systems, no single strain has been able to overtake the studied A. thaliana populations in the recent past. Our results suggest that selective pressures acting on a plant pathogen in wild hosts are likely to be much more complex than those in agricultural systems.

Current, experimental, and future treatments in inflammatory bowel disease: a clinical review

Inflammatory bowel diseases (IBDs) may result from dysregulated mucosal immune responses directed toward the resident intestinal microbiota. This review describes the hallmark immunobiology of Crohn's disease and ulcerative colitis as well as therapeutic targets and mechanisms of action for current, experimental, and future treatments in IBD. Conventional therapies include 5-aminosalicylic acid, glucocorticosteroids, thiopurines, and methotrexate. Since 1997, monoclonal antibodies have gained widespread use. These consist of antibodies directed against pro-inflammatory cytokines such as tumor necrosis factor α, interleukin (IL)-12, and IL-23, or anti-homing antibodies directed against α4β7 integrin. Emerging oral therapies include modulators of intracellular signal transduction such as Janus kinase inhibitors. Vitamin D may help to regulate innate and adaptive immune responses. Modulation of the intestinal microbiota, using live microorganisms (probiotics), substrates for the colonic microbiota (prebiotics), or fecal microbiota transplantation (FMT), is in development. Dietary supplements are in widespread use, but providing evidence for their benefit is challenging. Stem cell treatment and nervous stimulation are promising future treatments.

Dietary quercetin ameliorates experimental colitis in mouse by remodeling the function of colonic macrophages via a heme oxygenase-1-dependent pathway

Inflammatory bowel disease (IBD) results from a chronic intestinal inflammation and tissue destruction via an aberrant immune-driven inflammatory response towards an altered gut microbiota. Dietary intervention is becoming an attractive avenue for the therapy of colitis because diet is a key determinant of the mucosal immune response. Quercetin (QCN) is the most common in nature and the major representative of dietary antioxidant flavonoids, which has been demonstrated to influence the progression of colitis. However, the underlying mechanism of QCN on intestinal immunomodulation remains unclear. Here, our study demonstrated dietary QCN could ameliorate experimental colitis in part by modulating the anti-inflammatory effects and bactericidal capacity of macrophages via Heme oxygenase-1 (Hmox1, HO-1) dependent pathway. It suggested that QCN might restore the proper intestinal host-microbe relationship to ameliorate the colitis via rebalancing the pro-inflammatory, anti-inflammatory and bactericidal function of enteric macrophages. Hence, modulating the function of intestinal macrophages with dietary administration of QCN to restore the immunological hemostasis and rebalance the enteric commensal flora is a potential and promising strategy for IBD therapy.

Role of toll-like receptors in inflammatory bowel disease

Inflammatory bowel disease (IBD) is the chronic inflammation of the gastrointestinal tract. Recently, studies of the interplay between the adaptive and innate immune responses have provided a better understanding of the immunopathogenesis of inflammatory disorders such as IBD, as well as identification of novel targets for more potent interventions. Toll-like receptors (TLRs) are a class of proteins that play a significant role in the innate immune system and are involved in inflammatory processes. Activation of TLR signal transduction pathways lead to the induction of numerous genes that function in host defense, including those for inflammatory cytokines, chemokines, and antigen presenting molecules. It was proposed that TLR mutations and dysregulation are major contributing factors to the predisposition and susceptibility to IBD. Thus, modulating TLRs represent an innovative immunotherapeutic approach in IBD therapy. This article outlines the role of TLRs in IBD, focusing on both animal and human studies; the role of TLR-targeted agonists or antagonists as potential therapeutic agents in the different stages of the disease is discussed.

Circulating and Tissue-Resident CD4+ T Cells With Reactivity to Intestinal Microbiota Are Abundant in Healthy Individuals and Function Is Altered During Inflammation

BACKGROUND & AIMS

Interactions between commensal microbes and the immune system are tightly regulated and maintain intestinal homeostasis, but little is known about these interactions in humans. We investigated responses of human CD4+ T cells to the intestinal microbiota. We measured the abundance of T cells in circulation and intestinal tissues that respond to intestinal microbes and determined their clonal diversity. We also assessed their functional phenotypes and effects on intestinal resident cell populations, and studied alterations in microbe-reactive T cells in patients with chronic intestinal inflammation.

METHODS

We collected samples of peripheral blood mononuclear cells and intestinal tissues from healthy individuals (controls, n = 13-30) and patients with inflammatory bowel diseases (n = 119; 59 with ulcerative colitis and 60 with Crohn's disease). We used 2 independent assays (CD154 detection and carboxy-fluorescein succinimidyl ester dilution assays) and 9 intestinal bacterial species (Escherichia coli, Lactobacillus acidophilus, Bifidobacterium animalis subsp lactis, Faecalibacterium prausnitzii, Bacteroides vulgatus, Roseburia intestinalis, Ruminococcus obeum, Salmonella typhimurium, and Clostridium difficile) to quantify, expand, and characterize microbe-reactive CD4+ T cells. We sequenced T-cell receptor Vβ genes in expanded microbe-reactive T-cell lines to determine their clonal diversity. We examined the effects of microbe-reactive CD4+ T cells on intestinal stromal and epithelial cell lines. Cytokines, chemokines, and gene expression patterns were measured by flow cytometry and quantitative polymerase chain reaction.

RESULTS

Circulating and gut-resident CD4+ T cells from controls responded to bacteria at frequencies of 40-4000 per million for each bacterial species tested. Microbiota-reactive CD4+ T cells were mainly of a memory phenotype, present in peripheral blood mononuclear cells and intestinal tissue, and had a diverse T-cell receptor Vβ repertoire. These cells were functionally heterogeneous, produced barrier-protective cytokines, and stimulated intestinal stromal and epithelial cells via interleukin 17A, interferon gamma, and tumor necrosis factor. In patients with inflammatory bowel diseases, microbiota-reactive CD4+ T cells were reduced in the blood compared with intestine; T-cell responses that we detected had an increased frequency of interleukin 17A production compared with responses of T cells from blood or intestinal tissues of controls.

CONCLUSIONS

In an analysis of peripheral blood mononuclear cells and intestinal tissues from patients with inflammatory bowel diseases vs controls, we found that reactivity to intestinal bacteria is a normal property of the human CD4+ T-cell repertoire, and does not necessarily indicate disrupted interactions between immune cells and the commensal microbiota. T-cell responses to commensals might support intestinal homeostasis, by producing barrier-protective cytokines and providing a large pool of T cells that react to pathogens.

Ammonia exposure alters the expression of immune-related and antioxidant enzymes-related genes and the gut microbial community of crucian carp (Carassius auratus)

Chronic exposure of ammonia in fish can affect the activities of antioxidant enzymes but few studies investigate the influence of ammonia exposure on the expression of immune-related and antioxidant enzymes-related genes. Also, there is no study demonstrates the effect of ammonia exposure on gut microbial community of fish. In this study, crucian carp (Carassius auratus) were exposed to the ammonia concentrations, 0 (control), 10 mg L^-1 (low) or 50 mg L^-1 (high) for consecutive 30 days at 25 ± 1 °C temperature, respectively, and after that, the fish from all exposure groups were maintained in control conditions for another 15 days. The results showed that low concentration ammonia increased the expression of immune-related genes and antioxidant enzymes-related genes, but high concentration ammonia inhibited the expression of immune-related genes and antioxidant enzymes-related genes. After a 15-day treatment without ammonia, the expression of antioxidant enzymes-related genes and immune-related genes showed no significant changes compared with control. The results of high-throughput sequencing showed that gut microbial communities were significantly differentiated following ammonia exposure. The abundance of Bacteroides and Cetobacterium (two kinds of potential probiotics) increased while fish exposed to 10 mg L^-1 ammonia. The Flavobacterium (a potential fish pathogen) showed increasing trends when the exposure dose reached 50 mg L^-1, while the Bacteroides and Cetobacterium showed almost no abundance. The results also revealed that ammonia exposure concentration or time can alter the intestinal microbial community. In conclusion, ammonia exposure could induce the immune response in crucian carp, and alter the gut microbial community. The results may help us understand the correlations of gut microbial community shift and ammonia exposure and extend our knowledge to comprehend the effects of environmental factors on intestinal microbial community.

Contributions of the intestinal microbiome in lung immunity

The intestine is a critical site of immune cell development that not only controls intestinal immunity but extra-intestinal immunity as well. Recent findings have highlighted important roles for gut microbiota in shaping lung inflammation. Here, we discuss interactions between the microbiota and immune system including T cells, protective effects of microbiota on lung infections, the role of diet in shaping the composition of gut microbiota and susceptibility to asthma, epidemiologic evidence implicating antibiotic use and microbiota in asthma and clinical trials investigating probiotics as potential treatments for atopy and asthma. The systemic effects of gut microbiota are partially attributed to their generating metabolites including short chain fatty acids, which can suppress lung inflammation through the activation of G protein-coupled receptors. Thus, studying the interactions between microbiota and immune cells can lead to the identification of therapeutic targets for chronic lower respiratory diseases.

Streptococcus thermophilus NCIMB 41856 ameliorates signs of colitis in an animal model of inflammatory bowel disease

Treatment of inflammatory bowel disease (IBD) is mainly based on suppression of symptoms, often with numerous side effects. Trials of probiotics in IBD have frequently produced disappointing results. The majority of probiotics are unusual, since they do not require iron for growth, unlike many bacteria resident in the intestine. The IBD intestine is iron-rich due to bleeding and use of oral iron supplements; conventional probiotics would be rapidly outcompeted. We have evaluated an iron-responsive Streptococcus thermophilus strain for its potential to reduce signs of colitis. Efficacy of S. thermophilus was evaluated in the dextran sodium sulphate mouse model of colitis. Treated animals were given 1×108 cfu S. thermophilus per day and clinical observations were taken daily. At termination, gross and histopathological signs of disease, cellular infiltration, location of bacteria, and cytokine expression in the intestine were determined. S. thermophilus delayed onset of colitis and reduced clinical signs of disease, including bodyweight loss and gastrointestinal bleeding. It reduced bacterial translocation into the colonic tissue. Increased numbers of CD8+ intraepithelial lymphocytes were seen in control animals treated with S. thermophilus. S. thermophilus had no effect on gross pathology, histopathology or cytokine production in either colitic or control animals. We propose that S. thermophilus promotes maintenance of mucosal barrier function which reduces bacterial translocation, thereby reducing immune stimulation and associated inflammation. This allows mucosal healing, reducing gastrointestinal bleeding and weight loss. This could be studied as a locally-acting adjunct or alternative to current IBD treatments.

Differing roles for short chain fatty acids and GPR43 agonism in the regulation of intestinal barrier function and immune responses

Inflammatory bowel disease (IBD) is associated with a loss of intestinal barrier function and dysregulated immune responses. It has been shown that short chain fatty acids (SCFAs) are protective in IBD and that GPR43 mediates the protective effects of SCFAs. In this study, we investigated the effects of SCFAs in comparison to highly specific GPR43 agonists on human intestinal epithelial and immune cells. Our results confirm that SCFAs are enhancers of barrier function in intestinal epithelial cells. Additionally, SCFAs also displayed potent immunoregulatory properties based upon the ability to inhibit LPS-induced cytokine production in PBMC, and human T cell proliferation and cytokine production. Unexpectedly, and in contrast to the current belief, specific GPR43 agonists failed to exhibit similar barrier enhancing and anti-inflammatory properties. These findings demonstrate that SCFA possess broad protective functions in IBD and agonizing GPR43 alone is unlikely to be beneficial in patients.

Accuracy of computed tomographic features in differentiating intestinal tuberculosis from Crohn's disease: a systematic review with meta-analysis

Abdominal computed tomography (CT) can noninvasively image the entire gastrointestinal tract and assess extraintestinal features that are important in differentiating Crohn's disease (CD) and intestinal tuberculosis (ITB). The present meta-analysis pooled the results of all studies on the role of CT abdomen in differentiating between CD and ITB. We searched PubMed and Embase for all publications in English that analyzed the features differentiating between CD and ITB on abdominal CT. The features included comb sign, necrotic lymph nodes, asymmetric bowel wall thickening, skip lesions, fibrofatty proliferation, mural stratification, ileocaecal area, long segment, and left colonic involvements. Sensitivity, specificity, positive and negative likelihood ratios, and diagnostic odds ratio (DOR) were calculated for all the features. Symmetric receiver operating characteristic curve was plotted for features present in >3 studies. Heterogeneity and publication bias was assessed and sensitivity analysis was performed by excluding studies that compared features on conventional abdominal CT instead of CT enterography (CTE). We included 6 studies (4 CTE, 1 conventional abdominal CT, and 1 CTE+conventional abdominal CT) involving 417 and 195 patients with CD and ITB, respectively. Necrotic lymph nodes had the highest diagnostic accuracy (sensitivity, 23%; specificity, 100%; DOR, 30.2) for ITB diagnosis, and comb sign (sensitivity, 82%; specificity, 81%; DOR, 21.5) followed by skip lesions (sensitivity, 86%; specificity, 74%; DOR, 16.5) had the highest diagnostic accuracy for CD diagnosis. On sensitivity analysis, the diagnostic accuracy of other features excluding asymmetric bowel wall thickening remained similar. Necrotic lymph nodes and comb sign on abdominal CT had the best diagnostic accuracy in differentiating CD and ITB.

Probiotics: The scientific evidence in the context of inflammatory bowel disease

Inflammatory bowel disease (IBD) generally comprises Crohn's disease (CD) and ulcerative colitis (UC), and their main characteristic is the intestinal mucosa inflammation. Although its origin is not yet fully known, there is growing evidence related to genetics, intestinal microbiota composition, and the immune system factors such as precursors for the initiation and progression of intestinal conditions. The use of certain probiotic microorganisms has been touted as a possible and promising therapeutic approach in reducing the risk of inflammatory bowel disease, specifically ulcerative colitis. Several mechanisms have been proposed to explain the benefits of probiotics, indicating that some bacterial strains are able to positively modulate the intestinal microbiota and the immune system, and to produce metabolites with anti-inflammatory properties. The aim of this paper is to bring together the various results and information, based on scientific evidence, that are related to probiotics and inflammatory bowel disease, emphasizing the possible mechanisms involved in this action.

Epithelial-specific Toll-like Receptor (TLR)5 Activation Mediates Barrier Dysfunction in Experimental Ileitis

BACKGROUND

A large body of evidence supports a central role of TLR5 and its natural ligand, flagellin, in Crohn's disease (CD), with the precise mechanism(s) still unresolved.

METHODS

We investigated the role of flagellin/TLR5 in SAMP1/YitFc (SAMP) mice, a spontaneous model of Crohn's disease-like ileitis.

RESULTS

Ileal Tlr5 and serum antiflagellin IgG antibodies were increased in SAMP before the onset of inflammation and during established disease; these trends were abrogated in the absence of colonizing commensal bacteria. Irradiated SAMP receiving either wild-type (AKR) or SAMP bone marrow (BM) developed severe ileitis and displayed increased ileal Tlr5 compared with AKR recipients of either SAMP or AKR bone marrow, neither of which conferred ileitis, suggesting that elevated TLR5 in native SAMP is derived primarily from a nonhematopoietic (e.g., epithelial) source. Indeed, ileal epithelial TLR5 in preinflamed SAMP was increased compared with age-matched AKR and germ-free SAMP. TLR5-specific ex vivo activation of SAMP ileal tissues decreased epithelial barrier resistance, indicative of increased permeability, and was accompanied by altered expression of the tight junction proteins, claudin-3, occludin, and zonula occludens-1.

CONCLUSIONS

Our results provide evidence that aberrant, elevated TLR5 expression is present in the ileal epithelium of SAMP mice, is augmented in the presence of the gut microbiome, and that TLR5 activation in response to bacterial flagellin results in a deficiency to maintain appropriate epithelial barrier integrity. Together, these findings represent a potential mechanistic pathway leading to the exacerbation and perpetuation of chronic gut inflammation in experimental ileitis and possibly, in patients with Crohn's disease.

Development and validation of visceral fat quantification as a surrogate marker for differentiation of Crohn's disease and intestinal tuberculosis

BACKGROUND AND AIM

Crohn's disease (CD) and intestinal tuberculosis (ITB) have close phenotypic resemblance. Mesenteric fat (a component of visceral fat [VF]) hypertrophy and fat wrapping, which is visible radiologically as fibrofatty proliferation, is seen more commonly in CD than in ITB.

AIM

The present study was conducted to study the role of VF in differentiating CD and ITB.

METHODS

Visceral fat area and subcutaneous (SC) fat area were measured on computed tomography in two cohorts (development and validation). VF/SC ratio was also calculated for all patients. In the development cohort, retrospective data collection was carried out for 75 patients with CD and ITB who were on follow-up from January 2012 to November 2014. In the validation cohort, 82 patients were recruited prospectively from December 2014 to December 2015 and were diagnosed as CD or ITB according to standard diagnostic criteria.

RESULTS

Visceral fat area and VF/SC ratio were significantly higher in CD patients (n = 42: development, n = 46: validation) than in ITB patients (n = 33: development, n = 36: validation) in both the development (106.2 ± 63.5 vs 37.3 ± 22, P = <0.001; 1.1 ± 0.57 vs 0.43 ± 0.24, P = <0.001) and validation cohorts (102.2 ± 69.8 vs 55.8 ± 44.9, P = 0.01; 1.2 ± 0.68 vs 0.56 ± 0.33, P = <0.001). A cut-off of 0.63 for VF/SC ratio in the development cohort had a high sensitivity (82%) and specificity (81%) in differentiating CD and ITB. Similar sensitivity (81%) and specificity (78%) were seen when this cut-off was applied in the validation cohort.

CONCLUSION

The VF/SC ratio is a simple, cost-effective, non-invasive and single objective parameter with a good sensitivity and specificity to differentiate CD and ITB.

Immunopathogenesis of Crohn's Disease

This review highlights the huge advances made in the understanding of Crohn's disease in the last 15 years. The pathogenic immune response in the gut wall is a highly polarised T helper cell type 1 response, probably directed against antigens of the commensal flora. There is marked over-expression of pro-inflammatory cytokines such as tumor necrosis factor (TNF)-alpha and increased production of matrix degrading enzymes by fibroblasts and macrophages, which are probably responsible for ulceration and fistula formation. Crohn's disease runs in families and the susceptibility genes identified so far are associated with innate recognition of microbial products (Nod2) or epithelial barrier function (OCTN cation transporter genes and DLG5). Endogenous healing pathways mediated by transforming growth factor (TGF)-beta1 are inhibited because mucosal inflammatory cells express Smad7, the endogenous intracellular inhibitor of TGF-beta signalling. This makes it unlikely that enteral feeds containing TFG-beta are therapeutic by means of direct anti-inflammatory effects, however TGF-beta may still be involved because it is a well known epithelial motogen and may promote mucosal healing, in synergy with changes in mucosal bacterial populations as a result of the change in the diet.

Milk Casein-Based Diet Containing TGF-β Controls the Inflammatory Reaction in the HLA-B27 Transgenic Rat Model

BACKGROUND

A casein-based formula containing TGF-beta has been successfully used in adolescents during acute episodes of Crohn's disease. The role played by this molecule requires confirmation. We have examined the capacity of a TGF-beta containing diet to control the intestinal inflammation in HLA-B27 transgenic rats, and compared its effects with a similar diet devoid of TGF-beta.

METHODS

Three groups of rats were studied. HLA-B27/hbeta2M transgenic rats were fed with a casein-based rat-adapted diet containing TGF-beta or a control casein-based diet without TGF-beta. Fischer control animals were fed the latter. Body weight, dietary intake, tissue weights, fecal samples, leukocyte counts, and acute phase response were analyzed. Intestinal inflammation was assessed by histology, myeloperoxidase, and mRNA expression of cytokines. MUC2 protein expression was assessed by immunohistochemistry. Breakdown of muscle protein was examined.

RESULTS

The test diet improved diarrhea increasing the fecal dry matter and the colonic inflammation as shown by a lower inflammatory score (2.43 +/- 1.13 vs 4.42 +/- 0.53, p < .05), lower mucosal thickness (431.25 +/- 72.29 vs 508.57 +/- 81.32 microm, p = .08) and decreased IFNgamma mRNA expression. MUC2 protein expression was increased in HLA rats fed the TGF-beta diet compared with HLA rats fed the control diet, but restitution to normal pattern was not observed. The test diet also decreased leukocytosis and the acute phase response and improved the muscle catabolic response.

CONCLUSION

The TGF-beta containing diet has a beneficial effect in an animal model of intestinal inflammation. Our observations support a potential role for dietary TGF-beta in the restoration of immune homeostasis.

Antibody repertoire development in fetal and neonatal piglets. XXIV. Hypothesis: The ileal Peyer patches (IPP) are the major source of primary, undiversified IgA antibodies in newborn piglets

The ileal Peyers patches (IPP) of newborn germfree (GF) piglets were isolated into blind loops and the piglets colonized with a defined probiotic microflora. After 5 weeks, IgA levels in the intestinal lavage (IL) of loop piglets remained at GF levels and IgM comprised ∼70% while in controls, IgA levels were elevated 5-fold and comprised ∼70% of total Igs. Loop piglets also had reduced serum IgA levels suggesting the source of serum IgA had been interrupted. The isotype profile for loop contents was intermediate between that in the IL of GF and probiotic controls. Surprisingly, colonization alone did not result in repertoire diversification in the IPP. Rather, colonization promoted pronounced proliferation of fully switched IgA(+)IgM(-) B cells in the IPP that supply early, non-diversified "natural" SIgA antibodies to the gut lumen and a primary IgA response in serum.

Imiquimod-induced CCR9 Ameliorates murine TNBS Colitis

AIMS

To investigate whether Imiquimod (IMQ) as TLR7 ligand protects mice from colonic inflammation and the mechanisms underlying in such immunoregulatory conditions.　METHODS: Murine colitis was induced to Balb/c mice by administration of trinitrobenzene sulfonic acid (TNBS) with or without daily intraperitoneal administration of IMQ.　Colitis was evaluated by body weight decreases and by histological score.　Also colonic mRNA expression was measured by RT-PCR.　To confirm the induction of Regulatory T cells (Tregs) by type-1 IFN from pDCs, we generated mouse bone marrow-derived pDCs and co-cultured these with CD4⁺ T cells isolated from mouse spleen with or without IMQ stimulation.　Cytokine production in the culture supernatant was measured by ELISA and the number of Tregs were analyzed by flow cytometry.　Spleen and mesenteric lymph nodes (MLN) from IMQ-treated mice were collected, and mRNA expressions of cytokine were measured by RT-PCR and cytokine productions were measured by ELISA.　Tregs and chemokine expressions were analyzed in colon of TNBS-induced colitis mouse by immunohistochemistry.　RESULTS: Administration of IMQ significantly suppressed colonic inflammation of TNBS-induced colitis.　In the colons of IMQ-treated mice, mRNA expression of TNF-α was decreased, and strong expressions of IL-6, IFN-β and TGF-β were detected.　IL-10 and TGF-β productions were increased in the supernatant of co-cultured cells stimulated with IMQ, although we were unable to detect Treg differentiaton in IMQ-stimulated co-cultured cells.　In MLN of IMQ-treated mice, strong expressions of TLR7, IFN-β, TGF-β and Foxp3 mRNA were detected.　IL-10 production from MLN cells was also increased in the IMQ-treated group.　Finally, Tregs in the inflamed colon and CCR9 in MLN of IMQ-treated mice were detected.　CONCLUSION: These results suggest that IMQ protects mice from TNBS colitis through induction of CCR9, which regulates accumulation of Tregs in the inflamed colon.

The 100 classic papers in ulcerative colitis: a bibliometric analysis

BACKGROUND

The identification of the top 100 papers in ulcerative colitis (UC) using citation analysis provides a unique insight into the advancement of disease understanding and subsequent treatment innovations that have progressed over time.

METHODS

The Thomson Reuters Web of Knowledge was used to identify the 100 most cited UC manuscripts. Title, first and senior authors, institution and department of first author, journal, country of origin, year and topic of each manuscript were analyzed.

RESULTS

The top 100 manuscripts were published between 1955-2012. Thirty eight percent of the manuscripts originated from the US followed by the UK (26%). Genetics was the topic with the most publications (n = 27), followed by treatment (n = 22) and immunological pathways (n = 17). Truelove had the highest amount of authorships. The institutions with the highest number of publications were St. Mark's, London and the Radcliffe Infirmary.

CONCLUSION

This list of highly cited papers identifies the topics and authors that have made the most impact in the study of UC over the last century. This paper provides a reference of what could be considered as the most influential UC papers and serves as a reference of what comprises a 'highly citable' manuscript for both researchers and clinicians.

TLR signaling at the intestinal epithelial interface

The intestinal epithelium provides a critical interface between lumenal bacteria and the mucosal immune system. Whereas normal commensal flora do not trigger acute inflammation, pathogenic bacteria trigger a potent inflammatory response. Our studies emanate from the hypothesis that the intestinal epithelium is normally hyporesponsive to commensal pathogen-associated molecular patterns (PAMPs) such as LPS. Our data demonstrate that normal human colonic epithelial cells and lamina propria cells express low levels of TLR4 and its co-receptor MD-2. This expression pattern is mirrored by intestinal epithelial cell (IEC) lines. Co-expression of TLR4 and MD-2 is necessary and sufficient for LPS responsiveness in IEC. Moreover, LPS sensing occurs along the basolateral membrane of polarized IEC in culture. Expression of MD-2 is regulated by IFN-γ. Cloning of the MD-2 promoter demonstrates that promoter activity is increased by IFN-γ and blocked by the STAT inhibitor SOCS3. We conclude from our studies that the intestinal epithelium down-regulates expression of TLR4 and MD-2 and is LPS unresponsive. The Th1 cytokine IFN-γ up-regulates expression of MD-2 in a STAT-dependent fashion. The results of our studies have important implications for understanding human inflammatory bowel diseases.

Commensal-Specific CD4(+) Cells From Patients With Crohn's Disease Have a T-Helper 17 Inflammatory Profile

BACKGROUND & AIMS

Crohn's disease (CD) has been associated with an altered immune response to commensal microbiota, mostly based on increased seroreactivity to microbial proteins. Although T cells are believed to contribute to the development of CD, little is known about the antigens involved. We investigated the antigen-specificity of T cells isolated from patients with CD.

METHODS

We isolated peripheral blood mononuclear cells from 65 patients with CD and 45 healthy individuals (controls). We investigated T-cell reactivity to commensal microbial antigens using proliferation assays (based on thymidine incorporation and carboxyfluorescein succinimidyl ester dilution). Gene expression patterns were determined using microarray and real-time polymerase chain reaction analyses. Cytokines, chemokines, and antibodies were measured by enzyme-linked immunosorbent assay, flow cytometry, or multiplex cytokine assays. Intestinal crypts were obtained from surgical resection specimens of 7 individuals without inflammatory bowel disease. We examined the effects of commensal-specific CD4(+) T cells on primary intestinal epithelial cells from these samples.

RESULTS

The bacterial proteins FlaX, A4-fla2, and YidX increased proliferation of CD4(+) T cells isolated from peripheral blood of patients with CD compared with controls. In blood samples from controls, CD4(+) T cells specific for FlaX, A4-fla2, or YidX had a T-helper (Th)1 phenotype; a larger proportion of CD4(+) T cells specific for these proteins in patients with CD had a Th17 phenotype or produced Th1 and Th17 cytokines. When supernatants collected from commensal-specific CD4(+) T cells from patients with CD were applied to healthy intestinal epithelial cells, the epithelial cells increased the expression of the chemokine (C-X-C motif) ligand 1 (CXCL1), CXCL8 and the CC chemokine ligand 20 (CCL20).

CONCLUSIONS

A larger proportion of commensal-specific CD4(+) T cells from patients with CD have a Th17 phenotype or produce Th1 and Th17 cytokines, compared with T cells from controls; this might contribute to intestinal inflammation in patients with CD. These cells might be targeted for treatment of CD. The transcriptional data of commensal-specific CD4(+) T cells from healthy individuals and CD patients have been deposited in the Gene Expression Omnibus at the National Center for Biotechnology Information (accession no: GSE70469).

Adrenal-Derived Hormones Differentially Modulate Intestinal Immunity in Experimental Colitis

The adrenal glands are able to modulate immune responses through neuroimmunoendocrine interactions and cortisol secretion that could suppress exacerbated inflammation such as in inflammatory bowel disease (IBD). Therefore, here we evaluated the role of these glands in experimental colitis induced by 3% dextran sulfate sodium (DSS) in C57BL/6 mice subjected to adrenalectomy, with or without glucocorticoid (GC) replacement. Mice succumbed to colitis without adrenals with a higher clinical score and augmented systemic levels of IL-6 and lower LPS. Furthermore, adrenalectomy negatively modulated systemic regulatory markers. The absence of adrenals resulted in augmented tolerogenic lamina propria dendritic cells but no compensatory local production of corticosterone and decreased mucosal inflammation associated with increased IFN-γ and FasL in the intestine. To clarify the importance of GC in this scenario, GC replacement in adrenalectomized mice restored different markers to the same degree of that observed in DSS group. Finally, this is the first time that adrenal-derived hormones, especially GC, were associated with the differential local modulation of the gut infiltrate, also pointing to a relationship between adrenalectomy and the modulation of systemic regulatory markers. These findings may elucidate some neuroimmunoendocrine mechanisms that dictate colitis outcome.

Enteral feeding reduces metabolic activity of the intestinal microbiome in Crohn's disease: an observational study

BACKGROUND/OBJECTIVES

Enteral feeding will induce remission in as many as 80-90% of compliant patients with active Crohn's disease (CD), but its method of action remains uncertain. This study was designed to examine its effects on the colonic microbiome.

METHODS/SUBJECTS

Healthy volunteers and patients with CD followed a regimen confined to enteral feeds alone for 1 or 2 weeks, respectively. Chemicals excreted on breath or in faeces were characterised at the start and at the end of the feeding period by gas chromatography/mass spectrometry.

RESULTS

One week of feeding in healthy volunteers caused significant changes in stool colour and deterioration in breath odour, together with increased excretion of phenol and indoles on the breath. Feeding for 2 weeks in patients with CD produced significant improvements in symptoms and a decrease in the concentration of C-reactive protein. The faecal concentrations of microbial products, including short-chain fatty acids (SCFAs), and potentially toxic substances, including 1-propanol, 1-butanol and the methyl and ethyl esters of SCFAs, showed significant falls.

CONCLUSIONS

A significant change occurs in the production of microbial metabolites after enteral feeding in both healthy volunteers and patients with CD. Many of those detected in CD are toxic and may feasibly lead to the immunological attack on the gut microbiota, which is characteristic of inflammatory bowel disease. The reduction in the production of such metabolites after enteral feeding may be the reason for its effectiveness in CD.

Intestinal micro-ecology and ulcerative colitis

Ulcerative colitis (UC) is a subtype of inflammatory bowel disease, and its etiology and pathogenesis are not yet clear. UC often shows lesions (mainly ulcer) in the mucosa of the colon, rectum and sigmoid colon, even involving the entire colon. In recent years, with the constant breakthroughs in theoretical research of intestinal microbiology, its use in the diagnosis and treatment of UC has emerged as a new hot spot. Clarification of the classification of intestinal flora and its effect on the intestinal mucosa and intestinal immunity may provide a new avenue for treatment of UC. In this paper, we will review the relationship between intestinal micro-environment and UC.

Influence of environmental factors in the development of inflammatory bowel diseases

Idiopathic inflammatory bowel diseases (IBD), Crohn’s disease (CD) and ulcerative colitis (UC), are multifactorial diseases that are manifested after disruption of a genetic predisposed individual and its intestinal microflora through an environmental stimulus. Urbanization and industrialization are associated with IBD. Epidemiological data, clinical observations and family/immigrants studies indicate the significance of environmental influence in the development of IBD. Some environmental factors have a different effect on the subtypes of IBD. Smoking and appendectomy is negatively associated with UC, but they are aggravating factors for CD. A westernized high fat diet, full of refined carbohydrates is strongly associated with the development of IBD, contrary to a high in fruit, vegetables and polyunsaturated fatty acid-3 diet that is protective against these diseases. High intake of nonsteroidal antiinflammatory drug and oral contraceptive pills as well as the inadequacy of vitamin D leads to an increased risk for IBD and a more malignant course of disease. Moreover, other factors such as air pollution, psychological factors, sleep disturbances and exercise influence the development and the course of IBD. Epigenetic mechanism like DNA methylation, histone modification and altered expression of miRNAS could explain the connection between genes and environmental factors in triggering the development of IBD.

Preventive rather than therapeutic treatment with high fiber diet attenuates clinical and inflammatory markers of acute and chronic DSS-induced colitis in mice

PURPOSE

Inflammatory bowel diseases (IBDs) are chronic inflammatory disorders with important impact on global health. Prebiotic and probiotic strategies are thought to be useful in the context of experimental IBD. Here, we compared the effects of preventive versus therapeutic treatment with a high fiber diet (prebiotic) in combination or not with Bifidobacterium longum (probiotic) in a murine model of chronic colitis.

METHODS

Colitis was induced by adding dextran sulfate sodium (DSS) to drinking water for 6 days (acute colitis) or for 5 cycles of DSS (chronic colitis).

RESULTS

Administration of the high fiber diet protected from acute colitis. Protection was optimal when diet was started 20 days prior to DSS. A 5-day pretreatment with acetate, a short-chain fatty acid, provided partial protection against acute colitis. In chronic colitis, pretreatment with the high fiber diet attenuated clinical and inflammatory parameters of disease. However, when the treatment with the high fiber diet started after disease had been established, overall protection was minimal. Similarly, delayed treatment with acetate or B. longum did not provide any protection even when the probiotic was associated with the high fiber diet.

CONCLUSION

Preventive use of a high fiber diet or acetate clearly protects mice against acute and chronic damage induced by DSS in mice. However, protection is lost when therapies are initiated after disease has been established. These results suggest that any therapy aimed at modifying the gut environment (e.g., prebiotic or probiotic strategies) should be given early in the course of disease.

Seasonal variation in onset and relapse of IBD and a model to predict the frequency of onset, relapse, and severity of IBD based on artificial neural network

BACKGROUND

Previous research has yielded conflicting data as to whether the natural history of inflammatory bowel disease follows a seasonal pattern. The purpose of this study was (1) to determine whether the frequency of onset and relapse of inflammatory bowel disease follows a seasonal pattern and (2) to establish a model to predict the frequency of onset, relapse, and severity of inflammatory bowel disease (IBD) with meteorological data based on artificial neural network (ANN).

METHOD

Patients with diagnosis of ulcerative colitis (UC) or Crohn's disease (CD) between 2003 and 2011 were investigated according to the occurrence of onset and flares of symptoms. The expected onset or relapse was calculated on a monthly basis over the study period. For artificial neural network (ANN), patients from 2003 to 2010 were assigned as training cohort and patients in 2011 were assigned as validation cohort. Mean square error (MSE) and mean absolute percentage error (MAPE) were used to evaluate the predictive accuracy.

RESULTS

We found no seasonal pattern of onset (P = 0.248) and relapse (P = 0.394) among UC patients. But, the onset (P = 0.015) and relapse (P = 0.004) of CD were associated with seasonal pattern, with a peak in July and August. ANN had average accuracy to predict the frequency of onset (MSE = 0.076, MAPE = 37.58%) and severity of IBD (MSE = 0.065, MAPE = 42.15%) but high accuracy in predicting the frequency of relapse of IBD (MSE = 0.009, MAPE = 17.1%).

CONCLUSION

The frequency of onset and relapse in IBD showed seasonality only in CD, with a peak in July and August, but not in UC. ANN may have its value in predicting the frequency of relapse among patients with IBD.

Microbial Population Differentials between Mucosal and Submucosal Intestinal Tissues in Advanced Crohn's Disease of the Ileum

Since Crohn's disease is a transmural disease, we hypothesized that examination of deep submucosal tissues directly involved in the inflammatory disease process may provide unique insights into bacterial populations transgressing intestinal barriers and bacterial populations more representative of the causes and agents of the disease. We performed deep 16s microbiota sequencing on isolated ilea mucosal and submucosal tissues on 20 patients with Crohn's disease and 15 non-inflammatory bowel disease controls with a depth of coverage averaging 81,500 sequences in each of the 70 DNA samples yielding an overall resolution down to 0.0001% of the bacterial population. Of the 4,802,328 total sequences generated, 98.9% or 4,749,183 sequences aligned with the Kingdom Bacteria that clustered into 8545 unique sequences with <3% divergence or operational taxonomic units enabling the identification of 401 genera and 698 tentative bacterial species. There were significant differences in all taxonomic levels between the submucosal microbiota in Crohn's disease compared to controls, including organisms of the Order Desulfovibrionales that were present within the submucosal tissues of most Crohn's disease patients but absent in the control group. A variety of organisms of the Phylum Firmicutes were increased in the subjacent submucosa as compared to the parallel mucosal tissue including Ruminococcus spp., Oscillospira spp., Pseudobutyrivibrio spp., and Tumebacillus spp. In addition, Propionibacterium spp. and Cloacibacterium spp. were increased as well as large increases in Proteobacteria including Parasutterella spp. and Methylobacterium spp. This is the first study to examine the microbial populations within submucosal tissues of patients with Crohn's disease and to compare microbial communities found deep within the submucosal tissues with those present on mucosal surfaces. Our data demonstrate the existence of a distinct submucosal microbiome and ecosystem that is not well reflected in the mucosa and/or downstream fecal material.

Gut microbes, immunity, and spondyloarthritis

The last decade has witnessed an explosion of studies evaluating the impact of the human microbiota on a variety of disease states. The microbiota can impact diseases in multiple ways, including through abnormalities in the diversity and contents of the microbiota, as well as by acting as targets of immunologic dysregulation. Herein, evidence that the microbiota in spondyloarthritis is both altered and abnormally targeted by the immune system will be presented.

Isolation and cytokine analysis of lamina propria lymphocytes from mucosal biopsies of the human colon

Much of our understanding of gut-microbial interactions has come from mouse models. Intestinal immunity is complex and a combination of host genetics and environmental factors play a significant role in regulating intestinal immunity. Due to this complexity, no mouse model to date gives a complete and accurate representation of human intestinal diseases, such as inflammatory bowel diseases. However, intestinal tissue from patients undergoing bowel resection reflects a condition of severe disease that has failed treatment; hence a more dynamic perspective of varying inflammatory states in IBD could be obtained through the analyses of pinch biopsy material. Here we describe our protocol for analyzing mucosal pinch biopsies collected predominantly during colonoscopies. We have optimized flow cytometry panels to analyze up to 8 cytokines produced by CD4+ and CD8+ cells, as well as for characterizing nuclear proteins and transcription factors such as Ki67 and Foxp3. Furthermore, we have optimized approaches to analyze the production of cytokines, including TGF-beta from direct ex vivo cultures of pinch biopsies and LPMCs isolated from biopsies. These approaches are part of our workflow to try and understand the role of the gut microbiota in complex and dynamic human intestinal diseases.

Antigen administration by continuous feeding enhances oral tolerance and leads to long-lasting effects

The ability to avoid inflammatory responses to dietary components and microbiota antigens in the gut mucosa is achieved by a mechanism termed oral tolerance. This phenomenon is crucial to maintain the physiological immune activity in the gut and to prevent inflammatory disorders such as food allergy and inflammatory bowel diseases. Moreover, orally administered antigens induce regulatory cells that control systemic inflammatory responses as well. Given its specific, systemic and long-lasting effects, oral tolerance represents a promising approach for immunotherapies that aim to modulate inflammatory and autoimmune diseases. However, there are different protocols of feeding for induction of oral tolerance, and they have an impact in tolerance efficiency and length. Herein, we present and discuss different experimental feeding protocols and how they influence the outcome of oral administration of antigens.

Mucosal Immune Development in Early Life: Setting the Stage

Our environment poses a constant threat to our health. To survive, all organisms must be able to discriminate between good (food ingredients and microbes that help digest our food) and bad (pathogenic microbes, viruses and toxins). In vertebrates, discrimination between beneficial and harmful antigens mainly occurs at the mucosal surfaces of the respiratory, digestive, urinary and genital tract. Here, an extensive network of cells and organs form the basis of what we have come to know as the mucosal immune system. The mucosal immune system is composed of a single epithelial cell layer protected by a mucus layer. Different immune cells monitor the baso-lateral side of the epithelial cells and dispersed secondary lymphoid organs, such as Peyer’s patches and isolated lymphoid follicles are equipped with immune cells able to mount appropriate and specific responses. This review will focus on the current knowledge on host, dietary and bacterial-derived factors that shape the mucosal immune system before and after birth. We will discuss current knowledge on fetal immunity (both responsiveness and lymphoid organ development) as well as the impact of diet and microbial colonization on neonatal immunity and disease susceptibility. Lastly, inflammatory bowel disease will be discussed as an example of how the composition of the microbiota might predispose to disease later in life. A fundamental understanding of the mechanisms involved in mucosal immune development and tolerance will aid nutritional intervention strategies to improve health in neonatal and adult life.

The involvement of gut microbiota in inflammatory bowel disease pathogenesis: potential for therapy

Over the past recent years, a great number of studies have been directed toward the evaluation of the human host-gut microbiota interaction, with the goal to progress the understanding of the etiology of several complex diseases. Alterations in the intestinal microbiota associated with inflammatory bowel disease are well supported by literature data and have been widely accepted by the research community. The concomitant implementation of high-throughput sequencing techniques to analyze and characterize the composition of the intestinal microbiota has reinforced the view that inflammatory bowel disease results from altered interactions between gut microbes and the mucosal immune system and has raised the possibility that some form of modulation of the intestinal microbiota may constitute a potential therapeutic basis for the disease. The aim of this review is to describe the changes of gut microbiota in inflammatory bowel disease, focusing the attention on its involvement in the pathogenesis of the disease, and to review and discuss the therapeutic potential to modify the intestinal microbial population with antibiotics, probiotics, prebiotics, synbiotics and fecal microbiota transplantation.

Extraintestinal manifestations of inflammatory bowel disease and intestinal tuberculosis: Frequency and relation with disease phenotype

BACKGROUND

Extraintestinal manifestations (EIMs) in inflammatory bowel disease (IBD) including ulcerative colitis (UC) and Crohn's disease (CD), as well as intestinal tuberculosis (ITB) from Asia, are underreported. We, therefore, describe the prevalence of EIMs in Indian IBD and ITB patients and study their relationship with disease extent and severity in IBD.

METHODS

This retrospective single-center study included all IBD and ITB patients evaluated from January 2005 to July 2012. Disease profile and frequencies of arthropathies (peripheral and central) and ocular (episcleritis, iritis/uveitis), oral (aphthous stomatitis), skin (erythema nodosum, pyoderma gangrenosum, psoriasis), hepatobiliary (primary sclerosing cholangitis), and thromboembolic manifestations were analyzed.

RESULTS

Of 1,652 patients (1146 UC, 303 CD, 203 ITB), frequency of any EIM was 33.2 %, 38.3 %, and 14.3 % in UC, CD, and ITB patients, respectively. Thromboembolism was more common among UC patients with pancolitis than proctitis (p < 0.001) and left-sided colitis (p = 0.02). Primary sclerosing cholangitis was seen in 0.4 % UC patients. Steroid-dependent UC patients had higher frequency of any EIM, peripheral arthropathy, or thromboembolism than patients with no or infrequent steroid requirement (p < 0.05). Peripheral arthropathy (p = 0.02), erythema nodosum (p = 0.01), and aphthous stomatitis (p = 0.004) were more common with CD than with UC patients. Patients with colonic CD had higher frequency of peripheral arthropathy, any EIM, and multiple EIMs than ileal or ileocolonic disease (p < 0.05). Relative to ITB, CD patients had higher frequencies of peripheral arthropathy (p < 0.001), aphthous stomatitis (p = 0.01), any EIM (p < 0.001), and multiple EIMs (p < 0.001).

CONCLUSIONS

In Indian IBD and ITB patients, EIMs appear to be related to disease severity in UC and disease location in CD and are significantly more common in CD than in ITB. Overall prevalence of EIMs in these patients is similar to that of the West.

T lymphocytes control microbial composition by regulating the abundance of Vibrio in the zebrafish gut

Dysbiosis of the intestinal microbial community is considered a risk factor for development of chronic intestinal inflammation as well as other diseases such as diabetes, obesity and even cancer. Study of the innate and adaptive immune pathways controlling bacterial colonization has however proven difficult in rodents, considering the extensive cross-talk between bacteria and innate and adaptive immunity. Here, we used the zebrafish to study innate and adaptive immune processes controlling the microbial community. Zebrafish lack a functional adaptive immune system in the first weeks of life, enabling study of the innate immune system in the absence of adaptive immunity. We show that in wild type zebrafish, the initial lack of adaptive immunity associates with overgrowth of Vibrio species (a group encompassing fish and human pathogens), which is overcome upon adaptive immune development. In Rag1-deficient zebrafish (lacking adaptive immunity) Vibrio abundance remains high, suggesting that adaptive immune processes indeed control Vibrio species. Using cell transfer experiments, we confirm that adoptive transfer of T lymphocytes, but not B lymphocytes into Rag1-deficient recipients suppresses outgrowth of Vibrio. In addition, ex vivo exposure of intestinal T lymphocytes to Rag1-deficient microbiota results in increased interferon-gamma expression by these T lymphocytes, compared to exposure to wild type microbiota. In conclusion, we show that T lymphocytes control microbial composition by effectively suppressing the outgrowth of Vibrio species in the zebrafish intestine.

Inflammatory bowel disease: the classic gastrointestinal autoimmune disease

Inflammatory bowel disease (IBD) is an idiopathic disease thought to be caused by a dysregulated immune response to host intestinal microflora. The role of genetic factors is indicated by familial clustering of cases and higher incidence in monozygotic twins. An interaction between genetic and environmental factors is thought to play a role in the pathogenesis of these disorders. Changes in diet, antibiotic use and intestinal colonization have likely contributed to increased prevalence of inflammatory bowel disease in the past century. Environmental factors or infections are thought to alter the barrier function of the epithelium, leading to loss of immune tolerance to intestinal antigens. This loss of tolerance activates dendritic cells, triggering their transport to mesenteric lymph nodes, where they promote differentiation of naïve T cells to TH-1, TH-2, TH-17 cells or T regulatory cells. Production of proinflammatory cytokines and chemokines then follows. Circulating effector and regulatory cells enter the intestine through a highly selective mechanism that involves interaction with the vascular endothelium, diapedesis through the vessel wall and migration to the lamina propria. There are several genes implicated in IBD. Mutations in certain genes can cause defective down regulation of the innate immune response, ineffective clearance of intracellular bacteria and proliferation of both luminal and mucosal-adherent commensal bacteria. IBD is a chronic relapsing inflammatory condition that is immune mediated. Results from research in animal models, human genetics, basic science and clinical trials provide evidence that it is heterogeneous, characterized by various genetic abnormalities, leading to a dysregulated and overly aggressive T cell response to commensal enteric bacteria. Different genetic abnormalities can be characterized as causing defects in mucosal barrier function, immunoregulation or bacterial clearance. Advances in our understanding of the interplay between components of innate and adaptive immune response will be central to future progress.

Systems biology approaches for inflammatory bowel disease: emphasis on gut microbial metabolism

Although the prevalence of main idiopathic forms of inflammatory bowel disease (IBD) has risen considerably over the last decades, their clinical features do not allow accurate prediction of prognosis, likelihood of disease progression, or response to specific therapy. Through a better understanding of the molecular pathways involved in IBD and the promise of more targeted therapies, the personalized approach to the management of IBD shows potential. To achieve this, there remains a significant need to better understand the disease process at cellular and molecular levels for any given individual with IBD. The complexity of biological functional networks behind the etiology of IBD highlights the need for their comprehensive analysis. In this, omics technologies can generate a systemic view of IBD pathogenesis on which to base novel, multiple pathway-integrated therapies. Omics sciences have just started to contribute here by generating gene, protein expression, metabolite data at global level and large scale, and more recently by offering new opportunities to explore gut functional ecology. In particular, there is much expectation regarding the putative role of the gut microbiome in IBD. No doubt it will provide additional insights and lead to the development of alternative, hopefully better, diagnostic, prognostic, and monitoring tools in the management of IBD. This review discusses perspectives of relevance to clinical translation with emphasis on gut microbial metabolic activities.

FOXP3+ regulatory T-cell counts correlate with histological response in Crohn's colitis treated with infliximab

Crohn's disease is a chronic inflammatory bowel disease of unknown aetiology. Mucosal inflammatory dysregulation is likely important, with increased production of pro-inflammatory cytokines, including tumour necrosis factor alpha (TNFα). The chimeric monoclonal antibody, infliximab, inhibits TNFα and promotes intestinal mucosal healing. Despite this, many patients still require surgical intervention. Patients who have undergone colonic resection post-infliximab therapy, show markedly variable morphological response to treatment. FOXP3+ CD4+ regulatory T-cells have been shown to have a protective role in autoimmune/inflammatory diseases and their sequestration to the bowel is found in those treated with infliximab. We examined the immunohistochemical profile of lymphoid aggregates in tissue sections from post-infliximab Crohn's colitis resection specimens, classified as morphological responders or non-responders, defined in relation to the absence/presence of mucosal ulceration and active inflammation, and a control group. Results indicated no significant diffences in CD68-positive cell counts but increased FOXP3-positive (P = 0.02) and CD4-positive (P = 0.05) cell counts in responders versus non-responders. Untreated control scores were similar to non-responders. Although based on small study numbers, our results suggest an association between upregulation of FOXP3+/CD4+ regulatory T-cells and morphological response to infliximab therapy. This represents a possible quantitative methodology for monitoring therapeutic response to infliximab therapy, based on immunohistochemical evaluation of endoscopic biopsy specimens.

Clinical significance of changes of Treg and Th17 cells in patients with ulcerative colitis

AIM: To investigate the proportions of regulatory T (Treg) cells and T helper 17 (Th17) cells in peripheral blood and inflamed mucosa of patients with ulcerative colitis (UC) before and after treatment, and clarify the role of imbalance of the Treg/Th17 axis in the development of UC.

METHODS: Fifteen healthy control subjects and forty-five active UC patients were enrolled in the current study from May 2012 to December 2013. The proportions of Treg cells and Th17 cells in peripheral blood was determined by flow cytometry before and 4 wk after treatment. Foxp3⁺ or interleukin-17 (IL-17⁺) cells in inflamed mucosa were detected by immunohistochemistry. Analysis of variance was used to compare the differences between groups.

RESULTS: The proportion of Treg cells significantly increased in the mucosa of patients with active UC, but decreased in peripheral blood compared with controls (P < 0.01). The proportion of Th17 cells significantly increased in peripheral blood and inflamed mucosa of patients with active UC compared with controls (P < 0.01). At remission stage, the proportion of Th17 cells decreased, but was still higher than that in controls (P < 0.01).

CONCLUSION: The imbalance of Treg/Th17 cells is involved in the pathogenesis of UC, and it is a potential therapeutic target for UC.

A brave new world: the lung microbiota in an era of change

The development of culture-independent techniques has revolutionized our understanding of how our human cells interact with the even greater number of microbial inhabitants of our bodies. As part of this revolution, data are increasingly challenging the old dogma that in health, the lung mucosa is sterile. To understand how the lung microbiome may play a role in human health, we identified five major questions for lung microbiome research: (1) Is the lung sterile? (2) Is there a unique core microbiome in the lung? (3) How dynamic are the microbial populations? (4) How do pulmonary immune responses affect microbiome composition? and (5) Are the lungs influenced by the intestinal immune responses to the gut microbiome? From birth, we are exposed to continuous microbial challenges that shape our microbiome. In our changing environment, perturbation of the gut microbiome affects both human health and disease. With widespread antibiotic use, the ancient microbes that formerly resided within us are being lost, for example, Helicobacter pylori in the stomach. Animal models show that antibiotic exposure in early life has developmental consequences. Considering the potential effects of this altered microbiome on pulmonary responses will be critical for future investigations.

Penta-O-galloyl-β-D-glucose ameliorates inflammation by inhibiting MyD88/NF-κB and MyD88/MAPK signalling pathways

BACKGROUND AND PURPOSE

The gallnut of Rhus chinensis MILL and its main constituent penta-O-galloyl-β-D-glucose (PGG) inhibited NF-κB activation in LPS-stimulated peritoneal and colonic macrophages. Here we have investigated PGG mechanisms underlying anti-inflammatory effects of PGG in vitro and in vivo.

EXPERIMENTAL APPROACH

Male C57BL/6 mice (18-22 g, 6 weeks old) were used to prepare peritoneal and colonic macrophages and for the induction of colitis by intrarectal administration of 2,3,4-trinitrobenzene sulphonic acid (TNBS). A range of inflammatory markers and transcription factors were evaluated by elisa, immunoblotting, flow cytometry and confocal microscopy.

KEY RESULTS

Expression of Toll-like receptor (TLR)-4 or Lipopolysaccharide (LPS) binding to TLR-4 in LPS-stimulated peritoneal macrophages was not affected by PGG. However PGG inhibited binding of an anti-MyD88 antibody to peritoneal macrophages, but did not reduce binding of anti-IL-1 receptor-associated kinase (IRAK1) and IRAK4 antibodies to the macrophages with or without transfection with MyD88 siRNA. PGG potently reduced the activation of IRAK1, NF-κB, and MAPKs in LPS- or pepetidoglycan-stimulated peritoneal and colonic macrophages. PGG suppressed IL-1β, TNF-α and IL-6 in LPS-stimulated peritoneal macrophages, while increasing expression of the anti-inflammatorycytokine IL-10. Oral administration of PGG inhibited colon shortening and myeloperoxidase activity in mice with TNBS-induced colitis, along with reducing NF-κB activation and IL-1β, TNF-α, and IL-6 levels, whereas it increased IL-10.

CONCLUSIONS AND IMPLICATIONS

PGG reduced activation of NF-κB and MAPK signalling pathways by directly interacting with the MyD88 adaptor protein. PGG may ameliorate inflammatory diseases such as colitis.

Intestinal antigen-presenting cells in mucosal immune homeostasis: Crosstalk between dendritic cells, macrophages and B-cells

The intestinal immune system maintains a delicate balance between immunogenicity against invading pathogens and tolerance of the commensal microbiota. Inflammatory bowel disease (IBD) involves a breakdown in tolerance towards the microbiota. Dendritic cells (DC), macrophages (MΦ) and B-cells are known as professional antigen-presenting cells (APC) due to their specialization in presenting processed antigen to T-cells, and in turn shaping types of T-cell responses generated. Intestinal DC are migratory cells, unique in their ability to generate primary T-cell responses in mesenteric lymph nodes or Peyer’s patches, whilst MΦ and B-cells contribute to polarization and differentiation of secondary T-cell responses in the gut lamina propria. The antigen-sampling function of gut DC and MΦ enables them to sample bacterial antigens from the gut lumen to determine types of T-cell responses generated. The primary function of intestinal B-cells involves their secretion of large amounts of immunoglobulin A, which in turn contributes to epithelial barrier function and limits immune responses towards to microbiota. Here, we review the role of all three types of APC in intestinal immunity, both in the steady state and in inflammation, and how these cells interact with one another, as well as with the intestinal microenvironment, to shape mucosal immune responses. We describe mechanisms of maintaining intestinal immune tolerance in the steady state but also inappropriate responses of APC to components of the gut microbiota that contribute to pathology in IBD.

Early mucosal sensing of SIV infection by paneth cells induces IL-1β production and initiates gut epithelial disruption

HIV causes rapid CD4+ T cell depletion in the gut mucosa, resulting in immune deficiency and defects in the intestinal epithelial barrier. Breakdown in gut barrier integrity is linked to chronic inflammation and disease progression. However, the early effects of HIV on the gut epithelium, prior to the CD4+ T cell depletion, are not known. Further, the impact of early viral infection on mucosal responses to pathogenic and commensal microbes has not been investigated. We utilized the SIV model of AIDS to assess the earliest host-virus interactions and mechanisms of inflammation and dysfunction in the gut, prior to CD4+ T cell depletion. An intestinal loop model was used to interrogate the effects of SIV infection on gut mucosal immune sensing and response to pathogens and commensal bacteria in vivo. At 2.5 days post-SIV infection, low viral loads were detected in peripheral blood and gut mucosa without CD4+ T cell loss. However, immunohistological analysis revealed the disruption of the gut epithelium manifested by decreased expression and mislocalization of tight junction proteins. Correlating with epithelial disruption was a significant induction of IL-1β expression by Paneth cells, which were in close proximity to SIV-infected cells in the intestinal crypts. The IL-1β response preceded the induction of the antiviral interferon response. Despite the disruption of the gut epithelium, no aberrant responses to pathogenic or commensal bacteria were observed. In fact, inoculation of commensal Lactobacillus plantarum in intestinal loops led to rapid anti-inflammatory response and epithelial tight junction repair in SIV infected macaques. Thus, intestinal Paneth cells are the earliest responders to viral infection and induce gut inflammation through IL-1β signaling. Reversal of the IL-1β induced gut epithelial damage by Lactobacillus plantarum suggests synergistic host-commensal interactions during early viral infection and identify these mechanisms as potential targets for therapeutic intervention.