The B-cell system in inflammatory bowel disease

Secretory immunity is the best-defined part ot the mucosal immune system. This adaptive humoral defense mechanism depends on a fine-tuned cooperation between secretory epithelia and local plasma cells. Such mucosal immunocytes produce preferentially dimers and larger polymers of immunoglobulin A (collectively called pIgA), which contain J chain and therefore can bind to the epithelial secretory component (SC). This transmembrane glycoprotein functions as pIg receptor (pIgR) that also translocates pentameric IgM to the epithelial surface. B cells with a high level of J-chain expression and pIg-pIgR interactions at mucosal effector sites are thus necessary for the generation of secretory antibodies (SIgA and SIgM). Secretory antibodies perform immune exclusion in a first-line defense, thereby counteracting microbial colonization and mucosal penetration of soluble antigens. However, local production of pIgA is significantly down-regulated in inflammatory bowel disease (IBD), as revealed by strikingly decreased J-chain expression. Although the total increase of the immunocyte population in IBD lesions probably compensates for the relatively reduced pIgA production, decreased pIgR/SC expression in regenerating and dysplastic epithelium signifies that the SIgA system is topically deficient. There is, moreover, a significant shift from IgA2 to IgA1 production, the latter subclass being less resistant to proteolytic degradation. These changes--together with activation of mucosal macrophages and a dramatic increase of IgG-producing cells--may reflect local establishment of a second defense line which, however, is unsuccessful in its attempt to eliminate antigens derived from the indigenous microbial flora. Such a 'frustrated' local humoral immune system results in altered immunological homeostasis and jeopardized mucosal integrity. Complement activation observed in relation to epithelium-bound IgG1 in ulcerative colitis indicates, moreover, that the surface epithelium is subjected to immunological attack by an autoimmune reaction. These luminal deposits regularly contain terminal cytotoxic complement, and often also C3b as a sign of persistent activation. Comparison of identical twins, discordant with regard to ulcerative colitis, suggests that the markedly skewed local IgG1 response seen in this IBD entity may be genetically determined. The initial event(s) eliciting B-cell driven immunopathology in IBD remains unknown. Abrogation of oral tolerance to certain antigens from commensal bacteria has been suggested as a putative early mechanism, and lymphoid neogenesis and hyperplasia in the lesions most likely signify massive microbial overstimulation of the local B-cell system. Such ectopic lymphoid microcompartments may contribute substantially to the proinflammatory systemic-type of B-cell responses occurring in established IBD lesions.

Macronutrients and bioactive molecules: is there a specific role in the management of inflammatory bowel disease?

The effect of bioactive nutrient molecules on inflammatory response has an archetype in Inflammatory Bowel Disease. The exacerbated inflammatory response in such conditions can be nutritionally modified by 2 ways: changing the response of the host, or changing the composition of the intestinal ecosystem. Host response can be modified by changing the cell structure and function which is nutrient dependent. Nutrient deprivation will lead to a situation where there is not enough building material for cell replacement and the synthesis of mediators (enzymes, hormones, etc). However, this may occur even in a situation where there is no quantitative nutrient deprivation but only qualitative changes. In Inflammatory Bowel Disease, changes in the sources of some nutrients such as lipids or carbohydrates (CHO) can modify the inflammatory response. Lipids, by changing cell membrane composition, may modify the pattern of eicosanoid synthesis, intracellular signal transmission and activation of nuclear transcription factors, which modify the expression of some genes-that is, changing the host response. On the other hand, certain sources of carbohydrates, by undergoing anaerobic bacterial fermentation, drop the pH in the intestinal lumen favoring the growth of certain strains of bacteria which act favorably in maintaining tolerance in the bowel. In addition, as a consequence of CHO fermentation, short-chain fatty acids are produced which, especially butyrate, may act in 2 ways: by providing energy to the epithelial cells, but also as anti-inflammatory substrate-that is, modifying at least 1 of the mechanisms triggering the inflammatory response enhancement. However, it should not be forgotten that the cellular response to dietary modifications will depend on the individual genome, as has been recently observed. This may explain why some individuals do and others do not show a similar response to dietary interventions.

Probiotics: a practical review of their role in specific clinical scenarios

The use of probiotics (live viable microbial organisms) in the treatment of specific diseases has evolved into an extremely valuable option yet to be optimally used in clinical medicine. Probiotics have been shown to have immunomodulating properties and enhance the mucosal barrier. This review will briefly discuss the use of probiotics in inflammatory bowel disease, pancreatitis, liver transplantation, and various uses in diarrhea. When using probiotics, one must be cautious of the sometime overzealous claims that are commonly made when dealing with medical foods. As we begin to appreciate the degree of complexity that our indigenous microbial population has on health, it is only then that we can begin to understand the importance in disease. In the arena of probiotics, numerous fundamental questions remain unanswered.

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.

Experimental models of inflammatory bowel disease reveal innate, adaptive, and regulatory mechanisms of host dialogue with the microbiota

There are now many experimental models of inflammatory bowel disease (IBD), most of which are due to induced mutations in mice that result in an impaired homeostasis with the intestinal microbiota. These models can be clustered into several broad categories that, in turn, define the crucial cellular and molecular mechanisms of host microbial interactions in the intestine. The first of these components is innate immunity defined broadly to include both myeloid and epithelial cell mechanisms. A second component is the effector response of the adaptive immune system, which, in most instances, comprises the CD4+ T cell and its relevant cytokines. The third component is regulation, which can involve multiple cell types, but again particularly involves CD4+ T cells. Severe impairment of a single component can result in disease, but many models demonstrate milder defects in more than one component. The same is true for both spontaneous models of IBD, C3H/HeJBir and SAMPI/Yit mice. The thesis is advanced that 'multiple hits' or defects in these interacting components is required for IBD to occur in both mouse and human.

Involvement of intestinal dendritic cells in oral tolerance, immunity to pathogens, and inflammatory bowel disease

Dendritic cells (DCs) are composed of a family of cells, now recognized to be essential for innate and acquired immunity. DCs at mucosal surfaces have a particular capacity to induce the differentiation of regulatory T cells producing interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) in the steady state (non-infected, non-immunized), yet they retain the capacity to induce effector T cells in response to invasive pathogens. This decision between the induction of active immunity and tolerance will depend on the subpopulation of DC involved and the surface receptors engaged during DC activation and T-cell priming. The local microenvironment will likely play an important role both in defining the DC phenotype and in providing direct signals to responding T cells. Furthermore, DCs in organized mucosal lymphoid tissues preferentially induce the expression of CCR9 and alpha4beta7 on T cells, which results in T-cell homing to the intestinal lamina propria. Finally, DCs may play an important role in the maintenance of abnormal intestinal inflammation either by driving pathogenic T-cell responses in mesenteric lymph nodes or by acting to expand or maintain pathogenic T cells locally at sites of inflammation. In this review, a brief discussion of general issues of DC biology that are pertinent to mucosal immunity is followed by a more in-depth discussion of the phenotype and function of DC populations in the intestine.

Progress in inflammatory bowel disease

During the past 20 years, advances have been made in Crohn's disease and chronic ulcerative colitis. Despite impressive progress, it is still necessary to call these diseases 'idiopathic', as the details of their etiology remain obscure. Four areas will be reviewed in this article: genetics; intestinal inflammation; the relationship between the gut flora and the mucosa; and medical therapy.

Novel approaches to the nutritional management of the allergic infant

The increased prevalence of atopic diseases, i.e. atopic eczema, allergic rhinitis and asthma, has been described as the epidemic of the 21st century in Western societies. New approaches in the fight against allergic diseases are clearly called for, the target being the persistence of the allergic responder pattern beyond infancy. The advantage afforded by elimination diets lies in the silencing of specific allergic inflammation induced by an offending food. Novel nutritional approaches, beyond the treatment of food allergies, have recently attracted research interest subsequent to the identification of the immunomodulatory potential of specific dietary compounds. Dietary lipids as immunomodulators may prevent allergic sensitization by down-regulating inflammatory response whilst protecting the epithelial barrier. Probiotic bacteria have been shown to reinforce the different lines of gut defence: immune exclusion, immune elimination and immune regulation. On this basis, the strategy against allergic disease proposed here is based on the administration of tolerogenic gut-processed peptide fragments of a specific protein, in addition to the use of specific dietary compounds such as fatty acids and antioxidants, and introducing a microbial stimulus for the immature immune system by means of cultures of beneficial live micro-organisms characteristic of the healthy infant gut microbiota.

Bacteria and mucosal inflammation of the gut: lessons from Helicobacter pylori

The human gastrointestinal tract is colonized by an abundance of bacteria, which are in constant interaction with the epithelial lining usually leading to an intricate balance between tolerance and immunological response. There is ample evidence that the abundant presence of bacteria thus plays a role in the maintenance of human health, as well as in the induction of chronic inflammatory diseases of the gastrointestinal tract. Research in this field is, however, considerably hampered by the abundance of bacterial species, many of which have not even been characterized, and are difficult to culture specifically. These important limitations may to some extent be overcome by recent molecular biologic methods. Furthermore however, the adherent mucosal flora may differ largely from the luminal flora and that in excreta. These characteristics do not pertain to Helicobacter pylori, which generally colonizes the human stomach as a single strain with stable characteristics. Such colonization is stable throughout life, but can be treated. Furthermore, the association with chronic gastritis is very strong. For these reasons, H. pylori serves as an excellent model for the understanding of the processes involved in bacterial colonization and host response including mediation of immunoregulation, and the mechanisms by which this response can lead to disease.

Anti-Saccharomyces cerevisiae antibodies in twins with inflammatory bowel disease

BACKGROUND AND AIMS

An increased occurrence of anti-Saccharomyces cerevisiae antibodies (ASCA) is reported in unaffected members of families with Crohn's disease. Whether ASCA is a familial trait due to genetic factors or is caused by exposure to environmental factors is unknown. To assess the genetic influence of ASCA we studied its occurrence in a twin population.

PATIENTS AND METHODS

ASCA were analysed in 98 twin pairs with inflammatory bowel disease and were related to clinical phenotype and CARD15/NOD2 genotype.

RESULTS

ASCA were more common in Crohn's disease than in ulcerative colitis (40/70 (57%) twins v 5/43 (12%) twins). Associations with ileal Crohn's disease, stricturing/penetrating behaviour, and young age, but not CARD15/NOD2 were confirmed. ASCA were found in 1/20 (5%) healthy siblings in discordant monozygotic pairs with Crohn's disease compared with 7/27 (26%) in discordant dizygotic pairs. Using the intraclass correlation coefficient (ICC), no agreement in ASCA titres was observed in discordant twin pairs with Crohn's disease, in monozygotic (ICC = -0.02) or dizygotic (ICC = -0.26) pairs. In contrast, strong agreement was seen within concordant monozygotic twin pairs with Crohn's disease (ICC = 0.76).

CONCLUSIONS

These findings question the concept of ASCA as a marker of genetic susceptibility for Crohn's disease. The agreement in ASCA titres within concordant monozygotic twin pairs with Crohn's disease, suggests that the level of increase is genetically determined. We propose that ASCA are a marker of a response to an environmental antigen and that a specific gene(s) other than CARD15/NOD2 determines the level of response and perhaps also specific phenotypic characteristics.

Nucleotide-binding-oligomerization domain proteins and toll-like receptors: sensors of the inflammatory bowel diseases' microbial environment

PURPOSE OF REVIEW

Chronic inflammatory bowel diseases appear to result from inappropriate immune responses driven by apparently normal intestinal microflora in genetically susceptible hosts. This review focuses on recently described mechanisms balancing toll-like receptor and nucleotide-binding-oligomerization domain activation in the face of ubiquitous enteric flora.

RECENT FINDINGS

Toll-like receptor and nucleotide-binding-oligomerization domain signaling plays an integral role in the close collaboration between the intestinal epithelial cell monolayer and adjacent mucosal immune cells. Pathways activated by functional cytosolic nucleotide-binding-oligomerization domain proteins appear to interact with those mediated by membrane-associated toll-like receptors in the innate and adaptive immune defense against intra-and extracellular pathogens. Nucleotide-binding-oligomerization domain-mediated signaling may also control toll-like receptor-induced proinflammatory pathways.

SUMMARY

Intersections between toll-like receptor and nucleotide-binding-oligomerization domain pathways may exist to refine the host immune response to pathogens and prevent undesired immune stimulation driven by the intestinal microbiota. Deficient toll-like receptor and nucleotide-binding-oligomerization domain function due to genetic variability is associated with an increased susceptibility to the development of inflammatory bowel disease.

The intestinal flora in inflammatory bowel disease: normal or abnormal?

PURPOSE OF REVIEW

The human gut is the natural habitat for a large and dynamic bacterial community. There is a substantial body of evidence implicating the resident flora in the pathogenesis of chronic intestinal inflammation. This review discusses the possible role of a microbial imbalance in the pathophysiology of inflammatory bowel disease.

RECENT FINDINGS

Recently developed molecular biologic tools suggest that a sizeable part of the microbial populations of the human gut remains to be defined. Conversely, the relevance of gut bacteria in the host's physiology is well documented. The specialised lymphoid follicles of the gut mucosa are the major sites for induction of effector and regulatory mechanisms of the intestinal immune system, and it is now becoming clear that resident and in-transit microorganisms play an essential role in the homeostasis of local and systemic immunity. An infectious origin of inflammatory bowel disease is not supported by our current knowledge. Several studies, however, have disclosed substantial differences in the intestinal flora between patients with inflammatory bowel disease and healthy subjects, in regard to both composition and mucosal colonisation. Aggressive species are abundant on the inflammatory bowel disease mucosal surface whereas protective genera are underrepresented, but the biologic relevance of these changes needs further investigation.

SUMMARY

A balanced microbial environment would likely help in both prevention and control of inflammatory bowel disease. Research is needed to identify microorganisms able to mediate immunoregulation in the gut mucosa.

Natural colonization with Helicobacter species and the development of inflammatory bowel disease in interleukin-10-deficient mice

BACKGROUND

The interleukin-10-deficient (IL-10-/-) mice maintained in specific-pathogen-free (SPF) conditions develop typhlocolitis when experimentally infected with Helicobacter species. However, there is limited information regarding the role of Helicobacter species that naturally colonize IL-10-/- mice in typhlocolitis development. The aim of this study was to examine in SPF IL-10-/- mice the association between natural colonization specific Helicobacter species and typhlocolitis development.

MATERIAL AND METHODS

Cecum and proximal colon from 72 C57BL/6 x 129/Ola IL-10-/- mice (8-20 weeks old) were removed for DNA extraction and histologic evaluation. Genus-specific polymerase chain reaction- denaturing gradient gel electrophoresis (PCR-DGGE) and species-specific PCR were used to detect Helicobacter species. Mice were grouped by age, sex, and Helicobacter colonization status, and their histologic scores were compared. The development of clinical typhlocolitis was observed in a further 12 mice.

RESULTS

Species-specific PCR showed that mice were colonized with Helicobacter ganmani and/or Helicobacter hepaticus. The PCR-DGGE detected H. ganmani, H. hepaticus and an H. ganmani-like organism. The histologic scores in mice colonized with H. hepaticus were significantly higher than that in mice colonized with H. ganmani. Male mice showed significantly higher histologic scores than female mice. Four of the 12 mice developed clinical typhlocolitis in 38 weeks.

CONCLUSION

Natural colonization with different Helicobacter species was found in IL-10-/- mice within the same breeding colony. The severity of typhlocolitis differed according to the colonizing Helicobacter species. Furthermore, the rate of typhlocolitis development in IL-10-/- mice naturally colonized with Helicobacter species was significantly slower than that reported in experimentally infected mice.

[Probiotics for inflammatory bowel disease]

Probiotics are defined as live microorganisms that may beneficially affect the host by improving the balance of the intestinal micro flora. In spontaneous animal models of inflammatory bowel disease (IBD), the influence of the enteric flora on gut inflammatory activity has been demonstrated, as germ free animals do not develop disease. Modification of the activity of the intestinal flora using probiotics has been investigated as a way of controlling IBD. However, there is still considerable work to be done before probiotics can be considered as part of the standard treatment of IBD. Probiotic cocktails should be carefully studied and the individual bacterial constituents evaluated in clinical settings. Several studies are currently underway to assess these issues. Further study of placebo controlled trial testing therapeutic role of probiotic bacteria in human trials is warranted.

[Probiotics and prebiotics for the treatment of inflammatory bowel disease]

Although the causes of inflammatory bowel disease including ulcerative colitis and Crohn's disease remain incompletely understood, increasing evidence implicates intestinal microflora in the pathogenesis of this disorder. Therefore, modulation of microflora with probiotics or prebiotics may offer a plausible therapeutic approach. While recent data support a potential therapeutic efficacy, such treatments need to be further assessed by large scale studies. A better understanding of the intestinal microflora and the mechanisms of their action may help us to develop more effective treatment for inflammatory bowel disease.

Activation of RegIIIbeta/gamma and interferon gamma expression in the intestinal tract of SCID mice: an innate response to bacterial colonisation of the gut

BACKGROUND AND AIMS

The mechanisms by which commensal bacteria provoke intestinal inflammation in animal models of inflammatory bowel disease (IBD) remain incompletely defined, leading to increasing interest in the innate immune response of the colonic mucosa to bacterial colonisation.

METHODS

Using gene expression profiling of colonic RNA from C.B17.SCID germ free mice and those colonised with altered Schaedler's flora, we investigated the innate immune response to bacterial colonisation in vivo. The two most consistently induced gene groups were RegIIIbeta and gamma as well as interferon gamma (IFN-gamma) response genes.

RESULTS

Using quantitative reverse transcription-polymerase chain reaction, we showed that RegIIIbeta, RegIIIgamma, and IFN-gamma were constitutively expressed in the colon of conventionally housed SCID mice compared with either germ free SCID or conventionally housed BALB/c mice. Induction of these genes was reproduced by chronic monoassociation of germ free SCID mice with either of two separate gut commensal bacterial species-segmented filamentous bacteria and Schaedler's Escherichia coli. The cellular source for IFN-gamma on monoassociation of SCID mice with Schaedler's E coli was localised to a subset of intraepithelial natural killer (IENK) cells that express asialo-GM1. In vivo IFN-gamma immunoneutralisation studies failed to demonstrate any alteration in RegIIIbeta or gamma expression.

CONCLUSIONS

Thus bacterial colonisation of the colon independently activates two distinct innate immune cell types at the mucosal interface with the colonic lumen, intestinal epithelial cells, and IENK cells, a response that may be regulated by the adaptive immune system. These innate immune responses may play a role in the pathogenesis of colitis in SCID adoptive transfer models in mice and possibly in patients with IBD.

Aetiology of inflammatory bowel disease (IBD): role of intestinal microbiota and gut-associated lymphoid tissue immune response

The aetiology of inflammatory bowel disease (IBD) probably involves a combination of genetic predisposition and environmental factors that may be channelled through an abnormality in gut-barrier function, with a loss of antigen tolerance. Some genetic markers that predispose to inflammatory disease have been identified (alleles DR2, DRB1*0103, DRB1*12 and mutations in the NOD2/CARD15 gene on chromosome 16). Alterations in the pattern of cytokine production by T cell subclasses leading to loss of tolerance to oral antigens have been documented. Moreover, a number of environmental factors (cigarette smoking, use of non-steroid anti-inflammatory drugs, psychological stress and the presence of the caecal appendix) have been postulated as a trigger of IBD. It has also been suggested that the gut microbiota plays a major role in the development and persistence of IBD, and numerous modifications of intestinal microbiota composition have been identified. As a result, manipulation of the microbiota with antibiotics is a current therapeutic strategy; more recently, however, a number of studies have reported promising results when using probiotic organisms to manipulate gut microbiota composition in order to restore tolerance to microbial antigens of the host's own microbiota.

The beneficial effects of microflora, especially obligate anaerobes, and their products on the colonic environment in inflammatory bowel disease

Because intestinal microflora play a pivotal role in the development of inflammatory bowel disease (IBD), there is currently some interest in alternating the composition of the microflora toward a potentially more remedial community. This paper summarizes the clinical and experimental efficacy of the manipulation of microflora by the use of antibiotics, probiotics, and prebiotics in IBD. Germinated barley foodstuff (GBF) is a prebiotic whose unique characteristics make it highly suitable for applications in IBD. It also helps prolong remission in remissive ulcerative colitis (UC) patients and also attenuates clinical activity in non-remissive UC patients. GBF has shown to be converted into a preferential nutrient, butyrate, for colonocytes through the action of Eubacterium and Bifidobacterium, and this bacterial butyrate can provide anti-inflammatory effects. The probiotic approaches for IBD include VSL#3, Nissle1917, Clostridium butyricum, and Bifidobacterium-fermented milk. In this paper, we summarize the distinctive role of another probiotic, Eubacterium limosum (E. limosum), which is a commensal microorganism that is promoted by GBF administration. The metabolites of E. limosum included butyrate, which can accelerate intestinal epithelial growth and inhibit IL-6 production. This new probiotic approach may be useful as an adjunctive IBD treatment in the future. Although these strategies hold great promise and appear to be useful in some settings, more experimental and clinical studies are needed to firmly establish their relevance.

Low levels of antibodies against E. coli and mycobacterial 65kDa heat shock proteins in patients with inflammatory bowel disease

OBJECTIVE AND DESIGN

The aim of the present study was to support and extend our initial observation, where we found low levels of antibodies against mycobacterial 65kD heat shock proteins in patients with inflammatory bowel disease (IBD). For this purpose we tested a new group of 124 patients with IBD, and beside measuring antibodies to Mycobacterium bovis 65kD heat shock protein (Hsp65) and human 60kD heat shock protein (Hsp60) as described previously, we also determined IgG antibody levels to Hsp65 from E. coli, called GroEL.

PATIENTS AND CONTROL SUBJECTS

seventy-four patients with Crohn's disease (CD) (30 males, 44 females, 33 (27-45) years old, median (interquartile range)) and 50 patients with ulcerative colitis (UC) (22 males, 28 females, 38 (30-50) years old) were involved in the study. 110 healthy subjects (34 males, 76 females, 47 (37-53) years old) served as controls. Study subjects were consecutive patients referred to an IBD center for complex treatment of the disease. Methods and statistical analysis: The amounts of IgG-type antibodies reacting with proteins of the chaperonin 60 family were assessed by ELISA. Since the antibody levels to heat-shock proteins as variables were not normally distributed, non-parametric Mann-Whitney test and Dunn post hoc test were used for group comparisons.

RESULTS

Median levels of anti-GroEL (7,5 (3,5-18,3)) and anti-Hsp65 (4,8 (2,1-7,85)) were significantly (GroEL p = 0,008; and Hsp65 p < 0,001) lower in the IBD patients than in the healthy subjects (GroEL: 10,0 (5,4-31,0); Hsp65: 7,04 (4,66-12,77)). However this difference was found to be restricted to the CD patients (GroEL: 7,5 (3,7-14,2); p < 0,05; Hsp65: 4,35 (1,90-6,94); p < 0,001). We did not find difference in the concentration of anti-human Hsp60 IgG levels between patients (Hsp60: 45,5 (24,9-69,0)) and healthy controls (38,4 (21,6-69,4). Regarding the serum concentrations of each antibody tested there was no significant difference between the active and inactive stage of disease.

CONCLUSION

Our present findings support conclusion of our previous work, antibody levels not only for Mycobacterium bovis hsp65 but for E. coli GroEl were found to be decreased as well. In contrast no changes in the concentrations of human anti-hsp60 antibodies were observed. These findings indicate that production of antibodies to 65 kDa bacterial heat shock proteins is selectively impaired in IBD.

Probiotic Lactobacillus spp. diminish Helicobacter hepaticus-induced inflammatory bowel disease in interleukin-10-deficient mice

Clinical and experimental evidence has demonstrated the potential role of probiotics in the prevention or treatment of inflammatory bowel disease. Probiotic clones with direct immunomodulatory activity may have anti-inflammatory effects in the intestine. We investigated the roles of tumor necrosis factor alpha (TNF-alpha)-inhibitory Lactobacillus clones with a pathogen-induced murine colitis model. Murine-derived probiotic lactobacilli were selected in vitro for their ability to inhibit TNF-alpha secretion by Helicobacter hepaticus-stimulated macrophages. Interleukin-10 (IL-10)-deficient mice were treated with probiotic Lactobacillus reuteri in combination with Lactobacillus paracasei and then challenged with H. hepaticus. Ten weeks postinoculation, the severity of typhlocolitis was assessed by histologic examination of the cecocolic region. Intestinal proinflammatory cytokine responses were evaluated by real-time quantitative reverse transcriptase PCR and immunoassays, and the quantities of intestinal H. hepaticus were evaluated by real-time PCR. Intestinal colonization by TNF-alpha-inhibitory lactobacilli reduced intestinal inflammation in H. hepaticus-challenged IL-10-deficient mice despite similar quantities of H. hepaticus in cocolonized animals. Proinflammatory colonic cytokine (TNF-alpha and IL-12) levels were lowered in Lactobacillus-treated animals. In this H. hepaticus-challenged IL-10-deficient murine colitis model, lactobacilli demonstrated probiotic effects by direct modulation of mucosal inflammatory responses.

Physiological basis for novel drug therapies used to treat the inflammatory bowel diseases I. Pathophysiological basis and prospects for probiotic therapy in inflammatory bowel disease

Mechanisms underlying the conditioning influence of the intestinal flora on mucosal homeostasis, including development and function of immune responses, are attracting increasing scientific scrutiny. The intestinal flora is a positive asset to host defense, but some of its components may, in genetically susceptible hosts, become a risk factor for development of inflammatory bowel disease (IBD). It follows that strategies to enhance assets or offset microbial liabilities represent a therapeutic option; therein lies the rationale for manipulation of the flora in IBD. In addition, the diversity of regulatory signalling among the flora and host epithelum, lymphoid tissue, and neuromuscular apparatus is an untapped reservoir from which novel therapeutics may be mined. Moreover, the capacity to engineer food-grade or commensal bacteria to deliver therapeutic molecules to the intestinal mucosa promises to extend the scope of microbial manipulation for the benefit of mankind.

Antibacterial and antimycobacterial treatment for inflammatory bowel disease

A variety of medicines have been used for the treatment of inflammatory bowel disease. Antibacterial therapy has demonstrated promise by both improving symptoms and causing disease remission. The mechanism is unknown, but may be related to either eliminating a key pathogen, decreasing the number of bacterial secretory products or defective particles, a direct immunomodulating effect, or reducing secondary bacterial invasion. Historically, a large number of bacterial species have been suspected as being major contributors to the etiology of inflammatory bowel disease, including ulcerative colitis and Crohn's disease. Many trials of antibacterial agents have been carried out in inflammatory bowel disease. Recently, treatments have focused on Gram-negative anaerobes and mycobacteria. The present paper briefly reviews antimicrobial and antimycobacterial treatments in inflammatory bowel disease.

Gut flora in health and disease: potential role of probiotics

In a young evolving science, there are always more questions than answers. That is also the situation in the emerging field of Probiotics, and this was made very clear at the International Probiotics Workshop in Amsterdam. In the report of this workshop, we present a selection of the most urgent questions in the field of probiotics. In addition, we propose a few strategies for the future of probiotics research. During the workshop, 120 experts--from disciplines including Human Nutrition, Gastroenterology, Nutritional Therapy, Cell Biology, Microbiology and Immunology--discussed new views on microbe-host interactions and the role of probiotics in prevention and alleviation of gastro-intestinal, atopic and auto-immune diseases. There is a general consensus among the experts that administering defined strains can help in preventing and curing gut flora related diseases: the first clinical trials show a promising role for probiotics. But the system is very complex, and most underlying mechanisms are still unclear. Rapid progress in this field will depend largely on the collaboration between fundamental researchers from different disciplines and medical specialists. Besides, more clinical studies are required to convince authorities and the public of the value of microbial therapies.

[Role of intestinal flora in inflammatory bowel disease and probiotics place in their management]

The pathogenic role of certain microorganism of intestinal flora has been demonstrated in experimental colitis in animals and strongly suspected in inflammatory bowel disease in human, especially in Crohn's disease and pouchitis. Probiotics are living non pathogenic microorganisms that, upon oral ingestion exert benefits on human health by modulating enteric flora or by stimulation of local immune system. The aim of this article is to remind the role of intestinal flora in inflammatory bowel disease, the mechanism of inflammation induced by this flora and to review through the literature, the different clinical studies performed with probiotics in human.

Good bug, bad bug: in the case of enteric inflammatory disease does the epithelium decide?

Many studies demonstrate that intestinal inflammation is either initiated or exaggerated by a component of the normal microbiota, most likely commensal bacteria or products derived from these organisms. We review the nature of human inflammatory bowel disease, the evidence for the involvement of the normal bacterial flora in these disorders and the relevance of maintaining the integrity of the epithelial barrier. Moreover, we, and others, have shown abnormal mitochondria structure in tissue resections from patients with inflammatory bowel disease and tissues from rodents that demonstrated psychological stress-induced increases in epithelial permeability. Thus, we also consider the possibility that a defect in epithelial mitochondrial function would predispose an individual to respond to their commensal bacteria flora--no longer considering them as a beneficial passive inhabitant, but rather perceiving them as a threatening and pro-inflammatory stimulus. In support of this postulate, we discuss our recent findings from an in vitro model showing that the human colon-derived T84 cell line exposed to the metabolic stressor, dinitrophenol, and the non-pathogenic, non-invasive, Escherichia coli (strain HB101) display a loss of barrier function, increased signal transduction and increased production of the chemokine, interleukin 8.

Spatial organization of bacterial flora in normal and inflamed intestine: A fluorescence in situ hybridization study in mice

AIM: To study the role of intestinal flora in inflammatory bowel disease (IBD).

METHODS: The spatial organization of intestinal flora was investigated in normal mice and in two models of murine colitis using fluorescence in situ hybridization.

RESULTS: The murine small intestine was nearly bacteria-free. The normal colonic flora was organized in three distinct compartments (crypt, interlaced, and fecal), each with different bacterial compositions. Crypt bacteria were present in the cecum and proximal colon. The fecal compartment was composed of homogeneously mixed bacterial groups that directly contacted the colonic wall in the cecum but were separated from the proximal colonic wall by a dense interlaced layer. Beginning in the middle colon, a mucus gap of growing thickness physically separated all intestinal bacteria from contact with the epithelium. Colonic inflammation was accompanied with a depletion of bacteria within the fecal compartment, a reduced surface area in which feces had direct contact with the colonic wall, increased thickness and spread of the mucus gap, and massive increases of bacterial concentrations in the crypt and interlaced compartments. Adhesive and infiltrative bacteria were observed in inflamed colon only, with dominant Bacteroides species.

CONCLUSION: The proximal and distal colons are functionally different organs with respect to the intestinal flora, representing a bioreactor and a segregation device. The highly organized structure of the colonic flora, its specific arrangement in different colonic segments, and its specialized response to inflammatory stimuli indicate that the intestinal flora is an innate part of host immunity that is under complex control.

Evaluation of assays for perinuclear antineutrophilic cytoplasmic antibodies and antibodies to Saccharomyces cerevisiae in dogs with inflammatory bowel disease

OBJECTIVE

To evaluate the use of immunofluorescence asssays for perinuclear antineutrophilic cytoplasmic antibodies (pANCAs) and antibodies to Saccharomyces cerevisiae (ASCAs) in dogs with inflammatory bowel disease (IBD) and assess the clinical value of these serologic markers of the disease.

ANIMALS

39 dogs with IBD, 18 dogs with acute diarrhea, 19 dogs with chronic non-IBD-associated diarrhea, 26 healthy dogs of various breeds and age, and 22 healthy young working dogs.

PROCEDURE

Sera obtained from the dogs in each group were added to canine granulocyte- and Saccharomyces cerevisiae-mounted slides for detection of pANCAs and ASCAs via immunofluorescence techniques. Sensitivity and specificity (with 95% confidence intervals [CIs]) were calculated for the group of dogs with IBD versus each of the 2 groups of healthy dogs, the group of dogs with acute diarrhea, and the group of dogs with chronic non-IBD-associated diarrhea.

RESULTS

Among the 39 dogs with IBD, 20 yielded positive results via the pANCA assay (sensitivity, 0.51 [95% CI, 0.35 to 0.67]) and 17 yielded positive results via the ASCA assay (sensitivity, 0.44 [95% CI, 0.22 to 0.69]). The specificity of the pANCA assay in the 4 groups of non-IBD-affected dogs ranged from 0.83 (95% CI, 0.85 to 0.96) to 0.95 (95% CI, 0.72 to 1.00).

CONCLUSIONS AND CLINICAL RELEVANCE

Immunofluorescence assays for pANCA and ASCA appear to be useful for the detection of IBD in dogs. The pANCA immunofluorescence assay had high specificity for canine IBD, and pANCAs appear to be accurate markers of intestinal inflammation.

Effects of feeding a probiotic preparation (SIM) containing inulin on the severity of colitis and on the composition of the intestinal microflora in HLA-B27 transgenic rats

An overly aggressive immune response to the intestinal microflora in a genetically susceptible host background has been implicated in the pathogenesis of inflammatory bowel diseases. We measured the impact of a probiotic preparation (SIM) containing inulin on the severity of colitis and on intestinal microflora profiles of HLA-B27-beta(2)-microglobulin transgenic (TG) rats. SIM is a mixture of lactobacilli, bifidobacteria, and inulin. Two-month-old TG rats received either SIM or water. Control TG rats received metronidazole, alone or in combination with SIM, for 8 weeks. Nontransgenic rats received SIM or water. The cecal content was removed for analysis of the intestinal microflora by PCR combined with denaturing gradient gel electrophoresis. The colon was scored for histological evidence of inflammation, colonic myeloperoxidase activity and interleukin-1beta RNA levels were measured photometrically or by real-time quantitative PCR. At 4 months, the colonic inflammation of TG rats treated with SIM was histologically diminished compared to that in untreated TG rats (2.2 +/- 0.2 versus 2.9 +/- 0.1; P </= 0.03). The administration of SIM altered the microflora profiles of TG rats by increasing the diversity and stimulating specifically the growth of Bifidobacterium animalis. The probiotic bacteria added to SIM were below the detection level in cecal stool samples at the end of the study period. The administration of SIM resulted in a measurable impact on the cecal microflora profiles of TG rats with attenuation of colitis. The lack of detection of any added probiotic bacteria in the cecal content suggests that prebiotic inulin is the major effective compound.

Probiotics and gastrointestinal diseases

There is increasing evidence indicating health benefits by consumption of foods containing microorganisms, i.e. probiotics. A number of clinical trials have been performed to evaluate the effects in the prevention and treatment of gastrointestinal diseases caused by pathogenic microorganisms or by disturbances in the normal microflora. Gastrointestinal infections caused by Helicobacter pylori, traveller's diarrhoea, rotavirus diarrhoea, antibiotic-associated diarrhoea (AAD) and Clostridium difficile-induced diarrhoea are conditions that have been studied. There are also studies performed on the preventive effect of probiotics on radiation-induced diarrhoea and diarrhoea in tube-fed patients. Inflammatory bowel disease and irritable bowel syndrome, two idiopathic conditions where alterations in the normal microflora have been implicated as responsible for initiation, are two further areas where the use of probiotics has been regarded as promising. The results from clinical studies have not been conclusive in that the effects of probiotics have been strain-dependent and different study designs have been used. Treatment of acute diarrhoea in children and prevention of AAD are the two most justified areas for the application of probiotics.

Role of antibiotics in the management of inflammatory bowel disease: a review

The current model of pathogenesis for inflammatory bowel disease (IBD) is a dysregulated immune system that is triggered by an environmental factor in a genetically susceptible individual. Although much about this model remains unproven, it is believed that bacteria are often the environmental factor driving the inflammatory response. This is supported by indirect evidence that antibiotics are of benefit in the treatment of Crohn's disease (CD) and pouchitis, and observations that enteric infections may result in activation of ulcerative colitis disease activity. In CD, limited studies have demonstrated that metronidazole, ciprofloxacin, and rifaximin improve clinical disease activity, and this is more pronounced in the treatment of colonic disease and for perianal fistulas (with metronidazole and ciprofloxacin). In addition, limited evidence supports the use of metronidazole in the prevention of recurrence after resection in CD. Antibiotics have not shown substantial benefit in the treatment of ulcerative colitis, but a variety of antimicrobial agents have a definite role in the treatment of acute and recurrent or chronic pouchitis. The absence of specifically identified organisms that are primarily responsible for the observed clinical picture remains the challenge to confirming the relationship between bacteria and IBD. A proposal for future therapies is provided that might include a combination therapy aimed at both a reduction in pathogenetic bacteria and immune modulation to achieve the most durable remission of disease.

New insights into the pathogenesis of inflammatory bowel disease

Several important advances have been made over the past few years that have expanded our knowledge of the immunology of the gut and its complex interactions with commensal organisms. Critical developments in our understanding of the pathogenesis of inflammatory bowel diseases include the discovery of Toll-like receptors and the identification of not one but two susceptibility genes for Crohn's disease. We have furthered our understanding significantly concerning the role of dendritic cells in the development of gut inflammation. In addition, a novel hypothesis suggesting a protective role for helminthic infections is gaining experimental evidence and direct clinical applicability. In this review we summarize these key developments in the pathophysiology of inflammatory bowel disease and attempt to ascribe clinical relevance where applicable.

Johne's disease, inflammatory bowel disease, and Mycobacterium paratuberculosis

Johne's disease is a chronic diarrhea affecting all ruminants. Mycobacterium avium subsp. paratuberculosis (MAP), a slowly growing mycobacteria, is the etiologic agent. There is also a concern that MAP might be a causative agent of some cases of inflammatory bowel disease in humans, especially Crohn's disease. Food products including pasteurized bovine milk have been suggested as potential sources of human infection. This review addresses microbial factors that may contribute to its pathogenicity. In addition, the experimental evidence defining MAP as the cause of Johne's disease and the issues and controversies surrounding its potential pathogenic role in humans are discussed.

Intestinal epithelial cell regulation of mucosal inflammation

The intestinal epithelium serves as one of human's primary interfaces with the outside world. This interface is very heavily colonized with bacteria and yet permits absorption of life-sustaining nutrients while protecting the tissues below from microbial onslaught. Although the gut epithelium had been classically thought to achieve this function primarily by functioning as a passive, albeit highly selective, barrier, research over the last decade has demonstrated that in fact the epithelium plays a very active role in protecting the host from the bacteria that colonize it. As a consequence of its mediation of mucosal immunity, intestinal epithelial dysfunction appears to be central to diseases associated with aberrant gut mucosal immune responses such as inflammatory bowel disease (IBD). This article reviews: (1) how the gut epithelium participates in regulating innate immune inflammatory responses to enteric pathogens, (2) how these responses may regulate the adaptive immune system, (3) mechanisms that may resolve acute inflammation, and (4) how epithelial dysfunction may participate in regulating both the active and chronic phases of IBD.

Infrequency of colonization with Oxalobacter formigenes in inflammatory bowel disease: possible role in renal stone formation

BACKGROUND AND AIM

Calcium oxalate renal stones (RS) and hyperoxaluria are common in patients with inflammatory bowel disease (IBD). The absence of intestinal oxalate degrading bacteria, Oxalobacter formigenes, may cause hyperoxaluria in IBD. The aim of the present study was to examine: (i) the colonization of O. formigenes in patients with IBD and controls and to correlate its presence with urinary oxalate excretion; and (ii) urinary analytes contributing to RS in IBD.

METHODS

Stool samples were studied for O. formigenes using polymerase chain reaction and Southern blotting in patients with IBD (n = 48: ulcerative colitis, 37; Crohn's disease, 11), RS (n = 87) and healthy subjects that were used as controls (n = 48). Levels of urinary oxalate, citrate, calcium, magnesium, creatinine and uric acid were estimated spectrophotometrically in each patient and in 13 controls for 24 h.

RESULTS

Five of the 48 (10.4%) patients with IBD had RS. Five of the 48 (10.4%) patients with IBD, 25 of the 87 (29%) with RS and 27 of the 48 (56%) controls were colonized with O. formigenes (P < 0.001 for RS vs controls and P = 0.01 for RS vs IBD). Patients without O. formigenes had higher urinary oxalate than those with it (IBD, median 0.48 [range 0.11-2.09]vs 0.43 [range 0.16-1.10] mmol/24 h, P = NS; RS, median 0.59 mmol/24 h, range 0.14-1.90 vs 0.44 mmol/24 h, range 0.23-0.97; P = 0.008, Mann-Whitney U-test). Median excretion of oxalate was higher in IBD and RS than in controls (0.47 [0.11-2.09], 0.56 [0.14-1.9] and 0.41 [0.21-0.62] mmol/24 h; P < 0.01), respectively. Median calcium was also higher in IBD and RS than in controls (6.50 [1.38-21.00], 6.78 [1.55-20.30] and 4.99 [1.47-9.60] mmol/24 h; P < 0.05, Kruskal-Wallis H-test), respectively. Median urinary magnesium was higher in IBD than in RS and controls (4.57 [1.50-12.30], 3.60 [0.90-6.35] and 2.49 [0.74-4.80]; P < 0.001, Kruskal-Wallis H-test), respectively. Urinary citrate excretion was comparable in IBD, RS and controls.

CONCLUSIONS

Patients with IBD and RS rarely have O. formigenes in their stools as compared with controls; this may contribute to hyperoxaluria in IBD. Hyperoxaluria and hypercalciuria may contribute to RS in patients with IBD. Hypermagnesuria in patients with IBD may protect them from RS.

Host-bacterial interactions in inflammatory bowel disease

Large numbers of different bacterial species are resident in the lumen of the distal gastrointestinal tract. The normal intestinal host-microbial interactions are not well understood, but the relationship is generally believed to be either mutually beneficial or beneficial to one without disadvantage to the other. Animal model and clinical studies suggest that IBD (inflammatory bowel disease) may develop in a susceptible individual when the normal host-bacterial relationship is dysregulated. In addition to rodent models, this article reviews studies that have investigated the cellular and molecular mechanisms of interactions between intestinal mucosal cells and the resident luminal bacteria in healthy individuals and patients with ulcerative colitis and Crohn's disease. Mechanisms by which the intestinal mucosa is able to avoid pro-inflammatory responses to commensal bacteria (and their products) but able to respond appropriately to luminal pathogens is currently an area of active investigation. Such studies are beginning to provide important clues regarding possible alterations in the mucosa that lead to the development of pro-inflammatory responses to resident bacteria in patients with IBD. Approaches to alter the intestinal microflora for therapeutic purposes and their potential mechanisms of action are also discussed.

Detection of Helicobacter species DNA by quantitative PCR in the gastrointestinal tract of healthy individuals and of patients with inflammatory bowel disease

In many animal species different intestinal Helicobacter species have been described and a few species are associated with intestinal infection. In humans, the only member of the Helicobacter family which is well described in literature is Helicobacter pylori. No other Helicobacter-associated diseases have definitely been shown in humans. We developed a sensitive quantitative PCR to investigate whether Helicobacter species DNA can be detected in the human gastrointestinal tract. We tested gastric biopsies (including biopsies from H. pylori positive persons), intestinal mucosal biopsies and fecal samples from healthy persons, and intestinal mucosal biopsies from patients with inflammatory bowel disease (IBD) for the presence of Helicobacter species. All gastric biopsies, positive for H. pylori by culture, were also positive in our newly developed PCR. No Helicobacter species were found in the mucosal biopsies from patients with IBD (n = 50) nor from healthy controls (n = 25). All fecal samples were negative. Our study suggests that Helicobacter species, other than H. pylori, are not present in the normal human gastrointestinal flora and our results do not support a role of Helicobacter species in IBD.