Immune sensitization to food, yeast and bacteria in Crohn's disease

Prediction of treatment failure during infliximab induction therapy in inflammatory bowel disease patients based on pharmacokinetic and pharmacodynamic modeling

BACKGROUND

In infliximab (IFX) treatment for Crohn's disease (CD) and ulcerative colitis (UC), it is difficult to predict treatment failure during the induction phase. In the present study for optimal IFX treatment, we attempted to estimate serum IFX concentration and clinical response in individual patients during the induction phase to predict the indication of therapeutic effect and the possibility of treatment failure in the maintenance phase.

METHODS

We estimated pharmacokinetic and pharmacodynamic (PK/PD) parameters and predicted the serum IFX concentration and clinical response using a PK/PD model and Markov chain Monte Carlo Bayesian analysis method during the induction phase. Then, we determined whether the indication of therapeutic effect between predicted and observed clinical response were matched during the maintenance phase.

RESULTS

Data obtained from 15 patients were analyzed. The correlation between predicted and observed values of serum IFX concentration (Pearson product-moment correlation coefficient, 0.700; P < 0.0001, n = 68) and clinical response of CD patients (0.790; P < 0.0001, n = 25) and UC patients (0.702; P = 0.0004, n = 21) were significantly high. The indication of therapeutic effect at the final time point of each patient (from day 115 to day 203) were successfully predicted in 14 of 15 patients (93.3%).

CONCLUSIONS

This study presents prediction of serum IFX concentration and clinical response in individual patients during induction therapy, with presumption of the indication of therapeutic effect and the treatment failure in the maintenance phase. Our results show the possibility of optimizing IFX therapy during the induction phase.

The life and times of yeasts in traditional food fermentations

Yeasts are eukaryotic microorganisms which have a long history in the biotechnology of food production, as they have been used since centuries in bread-making or in the production of alcoholic beverages such as wines or beers. Relative to this importance, a lot of research has been devoted to the study of yeasts involved in making these important products. The role of yeasts in other fermentations in association with other microorganisms - mainly lactic acid bacteria - has been relatively less studied, and often it is not clear if yeasts occurring in such fermentations are contaminants with no role in the fermentation, spoilage microorganisms or whether they actually serve a technological or functional purpose. Some knowledge is available for yeasts used as starter cultures in fermented raw sausages or in the production of acid curd cheeses. This review aimed to summarize the current knowledge on the taxonomy, the presence and potential functional or technological roles of yeasts in traditional fermented plant, dairy, fish and meat fermentations.

Elemental Diet Regulates Intestinal Permeability and Antibody Production in Indomethacin-Induced Intestinal Injury Rats

Crohn's disease is a type of inflammatory bowel disease of unknown etiology. Administration of indomethacin (Indo) to rats induces acute mucosal lesions similar to those observed in Crohn's disease patients, but the damage can be prevented by feeding the animals an elemental diet (ED). In this study, we examined changes in intestinal macroscopic appearance, permeability, and immunoglobulin production after administration of Indo to male Sprague-Dawley rats fed normal lab chow or an ED. Intestinal damage was induced by subcutaneous injection of Indo on two successive days. Mucosal permeability, as measured by urinary excretion of phenolsulfonphthalein, peaked on day 2 after Indo injection, whereas the most severe intestinal damage, as scored by macroscopic inflammatory changes, was observed on day 3. Flow cytometric analysis of mesenteric lymph node cells revealed that the proportion of CD45RA⁺ cells was increased after Indo treatment. Furthermore, in vitro-cultured mesenteric lymph node and spleen lymphocytes from Indo-treated rats produced higher levels of IgA and IgG than did cells from vehicle-treated rats. In contrast, IgG and albumin concentrations in plasma were significantly decreased by Indo administration. Notably, none of the Indo-induced changes was observed in ED-fed rats. These findings suggest that an ED may prevent the appearance of Indo-induced mucosal lesions, at least in part, by modulating intestinal permeability and antibody production.

The Importance and Challenges of Dietary Intervention Trials for Inflammatory Bowel Disease

Inflammatory bowel disease is believed to be caused by a combination of genetic and environmental stimuli such as our diet. Diets high in meat and fats and low in fruits and vegetables have been associated with new-onset inflammatory bowel disease. This has triggered interest in using dietary modification as a treatment. The 3 principle models of dietary intervention are supplementation with selected dietary components, exclusion of selected dietary components, or use of dietary formulas in place of a normal diet. Despite the high level of interest in dietary interventions as a treatment for inflammatory bowel disease, few well-designed clinical trials have been conducted to firmly establish the optimal diet to induce or maintain remission. This may be in part related to the challenges of conducting dietary intervention trials. This review examines these challenges and potential approaches to be used in dietary intervention trials.

Dendritic Cell-T-Cell Circuitry in Health and Changes in Inflammatory Bowel Disease and Its Treatment

BACKGROUND

Dendritic, antigen-presenting cells (DCs) determine not only whether lymphocytes produce different types of immune response but also tissue-homing profiles of lymphocytes they stimulate. For example, in health, mucosal DC stimulate T cells focused to home to the mucosa; DC/T-cell circuitry thus targets immune responses to specific tissue locations. Therapies being introduced for inflammatory bowel disease (IBD) include antibodies to gut-homing molecules such as α4β7 (Vedolizumab) used ostensibly to block gut-homing lymphocytes. However, such lymphocytes are dependent on the tissue specificity of DC that stimulated them.

KEY MESSAGES

In health, blood DCs have the potential to home to multiple tissues including gut (α4β7+) and skin (CLA+). DCs have become gut-specific within the intestinal microenvironment stimulated partially by local retinoid to express α4β7 (mucosal homing marker) and/or CCR9 (ileal homing marker) in the absence of skin-specific indicators. They spread veiled extensions, sample their environment, acquire/process antigens, produce cytokines and initiate innate immunity. Myeloid DC also traffic to draining lymph nodes where compartmentalization of adaptive immune responses is determined by DCs from the site of antigen exposure which dictate the homing profiles of lymphocytes they stimulate. In IBD, site and activity of disease are reflected in changes in homing/activation of gut DCs and T-cells they stimulate and also, in greater gut specificity and activation of blood DC. Homing potential of DC can be modulated toward mucosa or skin by vitamins A and D, respectively. Infliximab or interleukin-6 can divert homing profiles toward skin, perhaps predisposing to skin involvement in IBD. Probiotic bacteria or their products can also change homing profiles of gut DC toward skin homing and away from gut.

CONCLUSIONS

In conclusion, development of gut focused inflammation and its treatment relies on changes in DC tissue specificity; therefore, removal or diversion of gut-homing DC as well as T-cells is likely to be critical in prevention of gut-focused inflammation in IBD.

Beta-glucan-depleted, glycopeptide-rich extracts from Brewer's and Baker's yeast (Saccharomyces cerevisiae) lower interferon-gamma production by stimulated human blood cells in vitro

Regulation of the human immune system requires controlled pro- and anti-inflammatory responses for host defence against infection and disease states. Yeasts (Saccharomyces cerevisiae), as used in brewing and baking, are mostly known for ability to stimulate the human immune-system predominantly reflecting the pro-inflammatory cell wall β-glucans. However, in this study, using food-compatible processing methods, glycopeptide-enriched and β-glucan-depleted products were each prepared from Brewer's and Baker's yeasts, which suppressed production of interferon-γ (IFN-γ) in human whole blood cell assay, signifying that anti-inflammatory factors are also present in yeast. Anti-inflammatory bioactivities of products prepared from Brewer's and Baker's yeast were compared with the commercial yeast product, Epicor®. While unfractionated Epicor was inactive, the C18 resin-binding fractions of Brewer's and Baker's yeast products and Epicor dose-dependently lowered IFN-γ, demonstrating that Epicor also contained both pro-inflammatory (β-glucans) and anti-inflammatory components. Anti-inflammatory activity was attributed to C18 resin-binding species glyco-peptides in Epicor and experimental yeast products. This study demonstrated that pro- and anti-inflammatory factors could be resolved and enriched in yeasts by suitable processing, with potential to improve specific activities.

Diet in the pathogenesis and treatment of inflammatory bowel diseases

Some of the most common symptoms of the inflammatory bowel diseases (IBD, which include ulcerative colitis and Crohn's disease) are abdominal pain, diarrhea, and weight loss. It is therefore not surprising that clinicians and patients have wondered whether dietary patterns influence the onset or course of IBD. The question of what to eat is among the most commonly asked by patients, and among the most difficult to answer for clinicians. There are substantial variations in dietary behaviors of patients and recommendations for them, although clinicians do not routinely endorse specific diets for patients with IBD. Dietary clinical trials have been limited by their inability to include a placebo control, contamination of study groups, and inclusion of patients receiving medical therapies. Additional challenges include accuracy of information on dietary intake, complex interactions between foods consumed, and differences in food metabolism among individuals. We review the roles of diet in the etiology and management of IBD based on plausible mechanisms and clinical evidence. Researchers have learned much about the effects of diet on the mucosal immune system, epithelial function, and the intestinal microbiome; these findings could have significant practical implications. Controlled studies of patients receiving enteral nutrition and observations made from patients on exclusion diets have shown that components of whole foods can have deleterious effects for patients with IBD. Additionally, studies in animal models suggested that certain nutrients can reduce intestinal inflammation. In the future, engineered diets that restrict deleterious components but supplement beneficial nutrients could be used to modify the luminal intestinal environment of patients with IBD; these might be used alone or in combination with immunosuppressive agents, or as salvage therapy for patients who do not respond or lose responsiveness to medical therapies. Stricter diets might be required to induce remission, and more sustainable exclusion diets could be used to maintain long-term remission.

Standard versus rapid food reintroduction after exclusive enteral nutritional therapy in paediatric Crohn's disease

BACKGROUND

In paediatric Crohn's disease (PCD), 6-8 weeks of exclusive enteral nutrition (EEN) is effective in 60-80% cases. EEN is followed by gradual food reintroduction over variable (1-5 weeks) periods. Currently, there is no recommended duration or method for food reintroduction. The rationale for slow reintroduction is unclear and may be because of concerns about food intolerance or to maintain longer remission.

AIMS

The aims of this study were as follows: to compare relapse rates following standard and rapid reintroduction of food after EEN in PCD and to determine the duration of maintained remission in two groups of PCD patients.

MATERIALS AND METHODS

Two groups with PCD were compared: group A received standard food reintroduction over 5 weeks and group B received rapid reintroduction over 3 days. Data were collected over two consecutive time periods: group A (2005-2009) and group B (2009-2011). Only patients with a new diagnosis of PCD were included. Those with strictures and those on steroids or biologicals during EEN were excluded. The minimum duration of follow-up was 1 year.

RESULTS

Group A included 20 patients and group B included 19 patients. In these groups, EEN led to clinical remission in 80% of the patients in group A and in 76% of the patients in group B. At 6 months, one-third of the patients from each group had developed relapse and a year after EEN, 50% of the patients in group A and 47% of the patients in group B developed relapse. Time to first relapse was 188 days (group A) and 136 days (group B). None of these results were statistically significant.

CONCLUSION

In PCD, rapid food reintroduction following 6-week EEN is safe and equally effective as longer food reintroduction. We propose that a rapid food reintroduction schedule be recommended as the most tolerable approach for food reintroduction. Relapse rate and duration of remission are uninfluenced by the type of food reintroduction.

Candidate genes involved in beneficial or adverse responses to commonly eaten brassica vegetables in a New Zealand Crohn's disease cohort

Crohn’s disease (CD) is one of the two manifestations of inflammatory bowel disease. Particular foods are thought with CD to exacerbate their illness. Vegetables, especially Brassicaceae, are often shunned by people with CD because of the negative effects they are alleged to have on their symptoms. Brassicaceae supply key nutrients which are necessary to meet recommended daily intakes. We sought to identify the candidate genes involved in the beneficial or adverse effects of Brassicaceae most commonly eaten, as reported by the New Zealand adults from the “Genes and Diet in Inflammatory Bowel disease Study” based in Auckland. An analysis of associations between the single nucleotide polymorphisms (SNPs) and the beneficial or adverse effects of the ten most commonly eaten Brassicaceae was carried out. A total of 37 SNPs were significantly associated with beneficial effects (p = 0.00097 to 0.0497) and 64 SNPs were identified with adverse effects (p = 0.0000751 to 0.049). After correcting for multiple testing, rs7515322 (DIO1) and rs9469220 (HLA) remained significant. Our findings show that the tolerance of some varieties of Brassicaceae may be shown by analysis of a person’s genotype.

Lost therapeutic potential of monocyte-derived dendritic cells through lost tissue homing: stable restoration of gut specificity with retinoic acid

Human monocyte-derived dendritic cells (DC) (MoDC) are utilized for immunotherapy. However, in-vitro immunological effects are often not mirrored in vivo. We studied the tissue-homing potential of MoDC. Circulating monocytes and DC expressed different tissue-homing markers and, during in-vitro development of MoDC, homing marker expression was lost resulting in a 'homeless' phenotype. Retinoic acid (RA) induced gut-homing markers (β7 and CCR9) and a regulatory phenotype and function [decreased human leucocyte antigen D-related (HLA-DR) and increased ILT3 and fluorescein isothiocyanate (FITC-dextran uptake) in MoDC]. RA-MoDC were less stimulatory and primed conditioned T cells with a gut-homing profile (β7(+)CLA(-)). Unlike the normal intestinal microenvironment, that from inflamed colon of ulcerative colitis (UC) patients did not induce regulatory properties in MoDC. However, RA-MoDC maintained their regulatory gut-specific properties even in the presence of UC microenvironment. Therefore, MoDC may be ineffectual for immunotherapy because they lack tissue-homing and tissue-imprinting specificity. However, MoDC rehabilitation with gut-homing potential by RA could be useful in promoting immunotherapy in pathologies such as UC.

Dietary beliefs and behavior among inflammatory bowel disease patients

BACKGROUND

We investigated dietary beliefs and behavior in a large population of adult inflammatory bowel disease (IBD) patients and evaluated their impact on patients' social life.

METHODS

A questionnaire of 14 items was administered to all consecutive IBD patients followed at the Nancy University Hospital Department of Gastroenterology from February to July 2011.

RESULTS

A total of 244 patients participated in the survey; 15.6% (n = 38) of patients believed that diet could initiate the disease, while 57.8% (n = 141) believed that food can play a role in causing a relapse. Forty percent (107/244) of patients identified food as a risk factor for relapse. Seventy-three percent of respondents reported having already received nutritional advice. The majority of respondents (47.5%, n = 116) reported that the disease had changed the pleasure of eating. Only one-quarter of patients had a normal diet in case of relapse. Almost two out of three patients (66.8%, n = 163) reported not eating certain foods they usually like to eat in order to prevent a relapse. Dietary beliefs and behavior had an impact on their social life for one-fifth of patients. Excluding food was associated with refusing outdoor dining for fear of causing relapse (P = 0.006) and not sharing the same menu as the other members of the family living under the same roof (P = 0.002).

CONCLUSIONS

The majority of IBD patients are avoiding certain foods. Dietary beliefs and behavior have a strong impact on their social life.

Role of diet in the management of inflammatory bowel disease

Many studies have looked at connections between diet, etiology, signs and symptoms associated with inflammatory bowel disease (IBD). Although these connections are apparent to clinicians, they are difficult to prove qualitatively or quantitatively. Enteral feeding and polymeric diets are equally effective at bringing about remission in Crohn’s disease (CD). Parenteral feeding is also effective, although none of these methods is as effective as corticosteroid therapy. However, enteral feeding is preferred in the pediatric population because linear growth is more adequately maintained via this route. Exclusion diets in patients brought into remission using an elemental diet have been shown to maintain remission for longer periods. Studies that aim to isolate culpable food groups have shown that individuals react differently on exposure to or exclusion of various foods. The commonly identified food sensitivities are cereals, milk, eggs, vegetables and citrus fruits. Studies that have looked at gut mucosal antigen behavior have shown higher rectal blood flow, in response to specific food antigens, in those with CD over healthy subjects. Exclusion of sugar shows little evidence of amelioration in CD. Omega 3 fatty acids show promise in the treatment of IBD but await larger randomized controlled trials. Patients frequently notice that specific foods cause aggravation of their symptoms. Whilst it has been difficult to pinpoint specific foods, with advances in the laboratory tests and food supplements available, the aim is to prolong remission in these patients using dietary measures, and reduce the need for pharmacotherapy and surgical intervention.

Serologic investigations in children with inflammatory bowel disease and food allergy

The aim of the study was the evaluation of frequency and titre of IgA ASCA and IgG ASCA and p-ANCA, c-ANCA in children with IBD and occurrence of ASCA antibodies in relation to coexistence of FA. Patients and methods. The study comprised 95 children at the ages of 2 to 18 years. The diagnosis of IBD was established on the basis of Porto criteria. Tests of blood serum were performed in all children: IgA and IgG ASCA, p-ANCA, c-ANCA using ELISA method. Results. IgE-dependent FA was found in 32.5% children with UC and in 21% with CD. We did not observe any relation between the occurrence of FA and the frequency and ASCA titre. p-ANCA were significantly more frequent in the group of children with UC. The occurrence of ASCA antibodies was observed in 73.7% of children with CD, 17.5% with UC and almost 30% with allergic colitis. Conclusions. Patients with CD and the presence of ASCA revealed a significantly more frequent localization of lesions within the small bowel and a tendency towards older age. We observed a connection between the occurrence of antibodies and the examined mutations of gene NOD2/CARD15.

Early-life exposures associated with antibiotic use and risk of subsequent Crohn's disease

OBJECTIVE

An inappropriate immune response to normal bowel flora is implicated in the etiology of Crohn's disease. Tolerance to bowel flora develops in infancy, so factors disrupting normal patterns of bowel colonization may increase the risk of Crohn's disease. The aim of this study was to test the hypothesis that antibiotic therapy between birth and age 5 years may disrupt the pattern of bowel colonization and increase the risk of Crohn's disease.

MATERIAL AND METHODS

Some 1098 patients with Crohn's disease and 6550 controls matched by delivery unit, year of birth, sex, and born between 1973 and 1997 were identified through the Swedish population registers. Seven inpatient diagnoses between birth and age 5 years associated with antibiotic therapy were identified by prospectively recorded data.

RESULTS

Of the seven diagnoses, only pneumonia and otitis media were sufficiently common for use in the analyses. Pneumonia and otitis media were not independent of each other in their association with Crohn's disease and the more important association was with pneumonia. Pneumonia by age 5 years was statistically significantly associated with both pediatric- and adult Crohn's disease, with odds ratios (and 95% CI) of 2.74 (1.04-7.21) and 4.94 (1.83-13.23), respectively. Pneumonia after age 5 years was not statistically significantly associated with Crohn's disease.

CONCLUSIONS

Pneumonia prior to age 5 years, but not later, was associated with subsequent Crohn's disease and this may represent either susceptibility or causation. The results are consistent with early exposures influencing immune function, such as through disruption of bowel colonization, and thus increasing the risk of Crohn's disease.

IgG antibodies against common gut bacteria are more diagnostic for Crohn's disease than IgG against mannan or flagellin

INTRODUCTION

Antibodies to baker's yeast (mannan) have been widely used to aid in diagnosis of Crohn's disease. Recently, there has been interest in antibodies against a flagellin from Clostridium coccoides subphylum. We hypothesized that reactivity with these antigens is a surrogate marker for a generalized increased IgG response against intestinal microbiota in Crohn's disease.

METHODS

We compared the diagnostic utility of IgG antibodies against flagellin and mannan with two complex surface antigen preparations, one derived from B. vulgatus (Bv), the other from over 20 common mucosa-associated microbiota, a multibacterial membrane preparation (MBP). IgG antibodies were measured in sera from two age- and sex-matched populations: 120 Crohn's patients (CD) and 160 gastroenterology controls (CON) comprising 40 ulcerative colitis (UC) and 120 non-IBD patients.

RESULTS

IgG was elevated against all antigen preparations in Crohn's but statistical analysis of receiver operator characteristic (ROC) plots showed that IgG against the complex antigen preparations MBP and Bv had better diagnostic accuracy to distinguish the two populations (CD and CON) than IgG against mannan (P < or = 0.01) or flagellin (P < or = 0.04). Concentrations of antibody reactive with distinct individual antigens correlated weakly.

DISCUSSION

The findings support our hypothesis that measurement of IgG reactivity against individual antigens gives an indication of a generalized increased IgG response against individual intestinal microbiota in Crohn's, rather than measuring specific immune responses important for pathogenesis. The data are consistent with either a mucosal defect that facilitates increased exposure to microbial antigens or an altered immune response, both of which could occur due to known genetic and molecular defects in Crohn's disease.

Resistin-like molecule beta (RELMbeta/FIZZ2) is highly expressed in the ileum of SAMP1/YitFc mice and is associated with initiation of ileitis

SAMP1/Fc mice develop spontaneous ileitis that shares many features with human Crohn's disease. One of the earliest features of ileitis in SAMP1/Fc mice is an increase in the number of ileal goblet and intermediate cells. Resistin-like molecule beta (RELMbeta) is a goblet cell-specific, cysteine-rich peptide previously shown to function as part of the innate immune response. In this study, we examined the role of expression of RELMbeta in the initiation of ileal inflammation in SAMP1/Fc mice. RELMbeta was highly induced in the ilea of SAMP1/Fc mice beginning at age 5 wk, coincident with the histological appearance of inflammation. RELMbeta was found in ileal goblet cells and some intermediate and Paneth cells. Surprisingly, RELMbeta mRNA levels were significantly increased in the ilea of 80% of germ-free SAMP1/Fc mice examined compared with specific pathogen-free AKR control mice of similar age. Ileitis was observed in germfree SAMP1/Fc mice, although it was attenuated relative to specific pathogen-free SAMP1/Fc mice. These data suggest that neither the early induction of RELMbeta expression nor ileal inflammation requires the presence of viable intestinal flora. Neither was the induction of RELMbeta dependent on the major Th1 or Th2 cytokines. However, RELMbeta stimulated naive bone marrow-derived macrophages to secrete significant amounts of TNF-alpha, IL-6, and RANTES. Our data suggest that RELMbeta is involved in the initiation of ileitis in SAMP1/Fc mice and may act through the induction of proinflammatory cytokines from resident immune cells within the mucosa.

Serologic markers in inflammatory bowel disease: tools for better diagnosis and disease stratification

In the last decade, new serologic markers have been identified, and attempts to delineate their potential roles in inflammatory bowel disease diagnosis, determination of prognosis and identification of apparently healthy subjects at risk have significantly increased our knowledge. In this review, the major serologic markers will be described, focusing on their common features as a group. It is predicted that within the next 5 years, panels of antibodies will prove to have a significant impact on disease diagnosis and stratification, as well as on the identification of populations at risk and the prediction of response to treatment. Thus, it is expected that they will become useful clinical tools that will enable an improved, 'tailored' approach to inflammatory bowel disease patients.

Association of deficiency for mannan-binding lectin with anti-mannan antibodies in Crohn's disease: a family study

BACKGROUND

Antibodies against mannan, a component of the yeast Saccharomyces cerevisiae cell wall, are more frequently found in Crohn's disease (CD) patients with low levels of mannan-binding lectin (MBL). MBL concentration depends on genetic polymorphisms. The aim of this study was to evaluate whether low MBL is related to ASCA production in healthy family members of CD patients.

METHODS

ASCA and MBL concentrations in sera from patients (n=52), and their 158 healthy relatives were measured by enzyme-linked immunosorbent assay (ELISA). Genetic MBL variants were determined by DNA sequencing.

RESULTS

Thirty-five (67%) patients were ASCA-positive. Twenty-six (74%) of the 35 ASCA-positive patients had low MBL levels (<500 ng/mL), whereas only 4 (24%) of the 17 ASCA-negative patients had low values for MBL (P=0.001). ASCA were found in 38 (24%) family members. Twenty-three (50%) of 46 family members with low values for MBL were ASCA-positive compared to 15 (13%) of 112 family members with normal values for MBL (P<0.0001). ASCA were found in 33 of 104 (32%) family members of ASCA-positive patients and in 5 family members (9%) of ASCA-negative patients (P=0.002). Relatives with mutations leading to MBL deficiency had significantly more frequent ASCA than relatives without these mutations (P=0.018).

CONCLUSIONS

MBL deficiency is associated with ASCA positivity not only in patients with CD, but also in their relatives. An impaired innate immune system defined by low MBL serum concentrations may lead to an increased reactivity of the specific immune system to mannan antigens, and therefore facilitate the generation of ASCA.

Gastrointestinal allergy in adults

The prevalence of food allergy reaches 3% in the adult population. Chronic gastrointestinal allergy is a rare entity: 4.2% of food allergies in adults, and represents 3.2% of all intestinal disorders. Non-specific symptoms are the rule but eosinophilic gastrointestinal disorders are the subject of much interest. Endoscopy and biopsies of the gastrointestinal tract help the differential diagnoses. Food allergy is suspected from the patient's history leading to skin tests and laboratory tests identifying a sensitization but allergy is only confirmed by standardized challenges or eviction diets over a sufficiently long period. New types of investigations coupling oral challenges to foods to gastroenterological techniques should be studied further.

The influence of microbial metabolites on human intestinal epithelial cells and macrophages in vitro

Microbial metabolites may influence the metabolic integrity of intestinal epithelial cells and induce mucosal immune responses. Therefore, we investigated the effects of the microbial metabolites butyrate, iso-valerate, and ammonium on Caco-2 cells and macrophages. Barrier functioning was determined by measuring transepithelial electrical resistance and basolateral recoveries of metabolites. The barrier function of Caco-2 cells remained intact after exposures. Basolateral recoveries ranged from 6.2% to 15.2%. Tumour necrosis factor-alpha and interleukin-10 were measured to determine immune reactions. The Caco-2 cells did not secrete both cytokines. Physiological concentrations of butyrate and iso-valerate stimulated the secretion of tumour necrosis factor-alpha and suppressed the secretion of interleukin-10 by macrophages that are not protected by an epithelial barrier. In contrast, ammonium concentrations as high as those produced by microbiotas of IBD patients suppressed the release of both cytokines when the barrier function is impaired.

Chronic inflammatory disorders of the gastrointestinal tract of companion animals

In the inflammatory bowel diseases (IBD) that affect dogs and cats there appears to be dysregulation of normal mucosal immunity, characterised by polyclonal lymphocytic infiltrates which are presumably specific for luminal antigens. There is an absence of a classical polarisation of either T-helper (Th) 1 or Th2 cytokine responses, although increased expression of mRNA for interleukin (IL) 2 and IL-12p40 and a shift towards mucosal immunoglobulin (Ig) G production are consistent findings, whilst variable responses are seen in tumour necrosis factor-alpha (TNF-alpha), IL-1, IL-4, IL-6, and interferon-gamma (IFN-gamma). Increased mucosal permeability and deranged intestinal motility are common sequelae. Despite obvious similarities with Crohn's disease and ulcerative colitis in humans, important differences exist. Of these, the diffuse superficial nature but with no Th1 or Th2 bias, and the prevalence of proximal small intestinal disease are notable. Potential hypotheses for these disparities include specific differences in the types or locations of agonistic gut flora, diffuse abnormalities in microbial-host interactions, a greater importance of diet, or anatomical or cellular differences in mucosal immune responses. Although specific pathogens and genetic susceptibilities may be involved, quantitative or qualitative changes in the normal flora or abnormal responses to a normal flora are more likely to be involved in the immunopathogenesis. Dietary influences include a large source of antigen, promotion of abnormal microbial growth through Maillard compounds within canned diets, and specific macro- and micronutrient deficiencies. Although dependent on a histopathological diagnosis, limitations of biopsies procured endoscopically, lack of histopathological standardisation and difficulty distinguishing inflammation from neoplasia remain significant problems. Clinician-pathologist dialogue, immunohistochemistry, cytokine profiling and lymphocyte clonality assessment may lead to more accurate diagnoses, a deeper understanding of the immunopathogenesis, and ultimately to new therapies or prevention of disease induction.

Colonic Crohn's disease in children does not respond well to treatment with enteral nutrition if the ileum is not involved

Data supporting a response to treatment with exclusive enteral nutrition in pediatric colonic Crohn's disease are few. We examined clinical and biochemical responses of ileal, colonic, and ileocolonic Crohn's disease and assessed the endoscopic and histological colonic mucosal response in the colonic and ileocolonic groups. We prospectively enrolled 65 children (age: 8-17 years) with acute intestinal Crohn's disease (Pediatric Crohn's Disease Activity Index [PCDAI] >20). After ileocolonoscopy, gastroscopy, and a barium meal and follow-through, they were distributed into three groups (ileal, n = 12, ileocolonic, n = 39; and colonic, n = 14). All patients received exclusive polymeric feed as treatment, with a repeat endoscopy at completion of treatment. At enrollment the ileal group had significantly less severe disease (P = 0.05) compared to the colonic and ileocolonic groups. However, the colonic disease group showed the least fall in PCDAI scores at completion of treatment with enteral nutrition (P = 0.03), with the lowest remission rate (50%, vs 82.1% in the ileocolonic and 91.7% in the ileal group [chi2 test, P = 0.021]). Endoscopic and histologic colonic mucosal assessment showed a post-treatment improvement in the ileocolonic (P < or = 0.01) but not in the colonic disease group (P = ns). Children with disease in the colon respond better to enteral nutrition if the ileum is also involved. This may be due to different underlying inflammatory mechanisms. Detailed pretreatment assessment in studies of Crohn's disease according to disease distribution with appropriate individualized tailoring of treatment may be important in this regard.

Genetic variants of the mannan-binding lectin are associated with immune reactivity to mannans in Crohn's disease

BACKGROUND & AIMS

Some patients with Crohn's disease (CD) develop antibodies against mannan, a component of the yeast Saccharomyces cerevisiae cell wall. Mannan-binding lectin (MBL), a component of the innate immune system, can bind to S. cerevisiae . MBL concentration depends on genetic polymorphisms. The aim of this study was to evaluate whether low MBL contributes to anti-S. cerevisiae antibody (ASCA) production.

METHODS

ASCA and MBL concentrations in sera from patients with CD (n = 74), ulcerative colitis (UC) (n = 22), and healthy controls (n = 32) were measured by an enzyme-linked immunosorbent assay (ELISA). Genetic MBL variants were determined from 58 CD patients, 18 UC patients, and 47 controls by DNA sequencing. Lymphocytes were tested for proliferative response after stimulation with mannan.

RESULTS

ASCA were found in 47% of the patients with CD and in 0% of the controls. More ASCA-positive patients (52%) had low serum MBL concentrations compared with ASCA-negative patients (4%) (P < 0.0001). T-cell proliferation in response to mannan stimulation was observed in ASCA-positive patients and could be inhibited by the addition of MBL. These patients had significantly lower MBL serum concentrations than patients whose lymphocytes did not proliferate on mannan stimulation (P < 0.0001). Homozygous or compound heterozygous MBL mutations in the exon 1 and promoter occurred in 12 patients with cellular or humoral immune reactivity to mannan as compared with only 1 nonreactive patient (P < 0.0001).

CONCLUSIONS

A subgroup of CD patients is characterized by ASCA positivity, T-cell proliferation on mannan stimulation, and mutations in the MBL gene that result in MBL deficiency. Thus, we propose that enhanced mannan exposure stimulates specific immune responses in a subgroup of CD patients with genetically determined low MBL concentrations. This enhanced exposure contributes to the generation of ASCA.

Review article: the role of nutrition in the treatment of inflammatory bowel disease

Nutrients may be involved in the modulation of the immune response through at least three different mechanisms. First, the intestinal ecosystem plays a pivotal role in the pathogenesis of inflammatory bowel disease, triggering the uncontrolled inflammatory response in genetically predisposed individuals. Nutrients, together with bacteria, are major components of, and can therefore influence, the intestinal environment. Second, as components of cell membranes, nutrients can mediate the expression of proteins involved in the immune response, such as cytokines, adhesion molecules and nitric oxide synthase. The composition of lipids in the cell membrane is modified by dietary changes and can influence cellular responses. Indeed, various epidemiological, experimental and clinical data suggest that the immune response may be sensitive to changes in dietary composition. Finally, suboptimal levels of micronutrients are often found in both children and adults with inflammatory bowel disease, although, with the exception of iron and folate, it is unusual to discover symptoms attributable to these deficits. However, subclinical deficits may have a pathophysiological significance, as they may favour the self-perpetuation of the disease (due to defects in the mechanisms of tissue repair), cause defective defence against damage produced by oxygen free radicals and facilitate lipid peroxidation. These events can occur even in clinically inactive or mildly active disease, as well as in the development of dysplasia in the intestinal mucosa. Some dietary manipulations have been attempted as primary treatment for rheumatoid arthritis, and specially formulated diets for enteral nutrition have proved to be an effective treatment for Crohn's disease. Most trials, although lacking sufficient patient numbers, have demonstrated a role for dietary manipulation as primary therapy for inflammatory disease. Dietary lipids are one of the most active nutritional substrates modulating the immune response. Recently, it has been demonstrated that lipids may be a key factor explaining the therapeutic effect of clinical nutrition in Crohn's disease.

Immune sensitization to yeast antigens in ASCA-positive patients with Crohn's disease

BACKGROUND

Alimentary antigens may play a role in the perpetuation of inflammation in Crohn's disease (CD). Yeast antigens are widespread components of food. A proportion of CD patients develop antibodies against the yeast Saccharomyces cerevisiae (ASCA), but little is known about the cellular immune reactivity against food antigens in antibody-positive and -negative patients.

METHODS

Lymphocytes from patients with CD, ulcerative colitis, and healthy controls were tested for their proliferative response after stimulation with the yeast antigen mannan and ovalbumin. The cellular phenotypes and activation markers were analyzed via FACS. Cytokine concentrations and antibody titers were determined by ELISA.

RESULTS

Only lymphocytes of ASCA-positive patients with CD proliferated after stimulation with mannan. These lymphocytes expressed increased activation markers (CD25, CD69). Activation of T cells was mediated by antigen-presenting cells and was associated with increased tumor necrosis factor-alpha (TNF-alpha) levels. The immune reactivity to ovalbumin was predominantly found in CD patients. It was weaker compared with mannan, independent of ASCA status, and also present in healthy controls.

CONCLUSIONS

A disturbed humoral and cellular response to the yeast antigen mannan is specifically seen in a subgroup of CD patients. This phenomenon may be due to a loss of tolerance toward yeast and is possibly genetically determined.

Nutrition and inflammatory bowel disease: its relation to pathophysiology, outcome and therapy

Nutritional deficiencies are frequent in patients with ulcerative colitis and Crohn's disease, and negatively influence the outcome of the disease. Growth retardation, osteopenia and thromboembolic phenomena are some of the inflammatory bowel disease complications in which nutritional deficits are involved. Moreover, nutrients can play a role in the pathogenesis of the disease and, in some cases, can be a primary therapeutic tool. Enteral nutrition has proven to play a therapeutic role in Crohn's disease. The nutrient(s) responsible for this effect are not well identified but dietary fat appears to be a major factor. In ulcerative colitis, unabsorbable carbohydrates can modulate the intestinal microbial environment, thus contributing to improve colonic inflammation.

Gut mucosal response to food antigens in Crohn's disease

BACKGROUND

Food antigens may contribute to gut inflammation in Crohn's disease.

AIM

To assess in vivo sensitization to food antigens, ascertain whether sensitivity is gut specific, assess food sensitization in vitro, and correlate in vivo changes with histological and blood changes.

METHODS

Skin testing and rectal exposure to six food antigens (cereal, cabbage, citrus, milk, yeast and peanut) and control saline were assessed double-blind by immediate and 3.5-h laser Doppler blood flowmetry, and rectal biopsies were taken. Peripheral blood lymphocyte proliferation was measured in response to the same antigens.

RESULTS

Ten patients with Crohn's disease and 10 healthy controls were studied. Blood flow increased in 24 of 60 antigen sites in Crohn's disease patients and six of 60 antigen sites in controls (P < 0.0001) after 3.5 h. The Crohn's disease group demonstrated higher rectal blood flow than controls in response to all food antigens, and this was significantly different for the responses to yeast (P = 0.036) and citrus fruits (P = 0.038). Lymphocyte proliferation occurred in 32 of 60 tests in Crohn's disease patients and eight of 60 tests in controls (P < 0.0001). There were no skin responses. Submucosal oedema corresponded to increased mucosal flow.

CONCLUSIONS

Crohn's disease patients demonstrate in vivo and in vitro sensitization to food antigens, which is gut specific. Mucosal flowmetry allows the identification of sensitization to gut antigens.