Defective IL10 signaling defining a subgroup of patients with inflammatory bowel disease

Phenotypic characterization of very early-onset IBD due to mutations in the IL10, IL10 receptor alpha or beta gene: a survey of the Genius Working Group

OBJECTIVE

Early-onset inflammatory bowel disease starting within the first months of life could be due to a particular genetic defect. We set up the GENetically determined ImmUne-mediated enteropathieS (GENIUS) network and collected infants with a proven defect of the IL10 axis for accurate phenotyping of disease presentation and evolution.

DESIGN

Ten patients with early-onset inflammatory bowel disease with confirmed mutations in IL10, IL10RA, or IL10RB genes were characterized on clinical, endoscopic-histological, immunobiological, and radiological findings. Functional assays to confirm defective responses to IL10 were performed on peripheral blood mononuclear cells.

RESULTS

A functional defect in IL10 signaling was confirmed in all IL10R patients tested. Disease started with severe diarrhea within the first 12 weeks in all patients. All infants showed Crohn's disease-like ulcerations limited to the colon with marked perianal inflammation (fissures, abscess, and fistula); disease progression to the small bowel occurred in only 1 patient. Four of the 10 patients had granulomata on histology, and all patients showed Crohn's disease-like mesenteric infiltration on imaging. Disease pattern was indistinguishable between IL10R alpha or beta chain or IL10 defects; autoimmunity was not observed. Mutations in IL10 were more frequently associated with bacterial and viral infections. Patients responded partially to treatment with steroids or anti-tumor necrosis factor drugs, whereas hematopoietic stem cell transplantation proved efficacious.

CONCLUSION

The importance of the IL10 pathway within the colonic mucosa is highlighted by the development of severe colitis within a few weeks in infants with mutations in IL10, IL10RA, or IL10RB. Immunosuppression failed to correct the defect in this pathway, which seems to be a key to controlling inflammation in the colon.

Inflammatory bowel disease: mechanisms, redox considerations, and therapeutic targets

Oxidative stress is thought to play a key role in the development of intestinal damage in inflammatory bowel disease (IBD), because of its primary involvement in intestinal cells' aberrant immune and inflammatory responses to dietary antigens and to the commensal bacteria. During the active disease phase, activated leukocytes generate not only a wide spectrum of pro-inflammatory cytokines, but also excess oxidative reactions, which markedly alter the redox equilibrium within the gut mucosa, and maintain inflammation by inducing redox-sensitive signaling pathways and transcription factors. Moreover, several inflammatory molecules generate further oxidation products, leading to a self-sustaining and auto-amplifying vicious circle, which eventually impairs the gut barrier. The current treatment of IBD consists of long-term conventional anti-inflammatory therapy and often leads to drug refractoriness or intolerance, limiting patients' quality of life. Immune modulators or anti-tumor necrosis factor α antibodies have recently been used, but all carry the risk of significant side effects and a poor treatment response. Recent developments in molecular medicine point to the possibility of treating the oxidative stress associated with IBD, by designing a proper supplementation of specific lipids to induce local production of anti-inflammatory derivatives, as well as by developing biological therapies that target selective molecules (i.e., nuclear factor-κB, NADPH oxidase, prohibitins, or inflammasomes) involved in redox signaling. The clinical significance of oxidative stress in IBD is now becoming clear, and may soon lead to important new therapeutic options to lessen intestinal damage in this disease.

Genome wide analysis of narcolepsy in China implicates novel immune loci and reveals changes in association prior to versus after the 2009 H1N1 influenza pandemic

Previous studies in narcolepsy, an autoimmune disorder affecting hypocretin (orexin) neurons and recently associated with H1N1 influenza, have demonstrated significant associations with five loci. Using a well-characterized Chinese cohort, we refined known associations in TRA@ and P2RY11-DNMT1 and identified new associations in the TCR beta (TRB@; rs9648789 max P = 3.7×10⁻⁹ OR 0.77), ZNF365 (rs10995245 max P = 1.2×10⁻¹¹ OR 1.23), and IL10RB-IFNAR1 loci (rs2252931 max P = 2.2×10⁻⁹ OR 0.75). Variants in the Human Leukocyte Antigen (HLA)- DQ region were associated with age of onset (rs7744020 P = 7.9×10⁻⁹ beta −1.9 years) and varied significantly among cases with onset after the 2009 H1N1 influenza pandemic compared to previous years (rs9271117 P = 7.8×10⁻¹⁰ OR 0.57). These reflected an association of DQB1*03:01 with earlier onset and decreased DQB1*06:02 homozygosity following 2009. Our results illustrate how genetic association can change in the presence of new environmental challenges and suggest that the monitoring of genetic architecture over time may help reveal the appearance of novel triggers for autoimmune diseases.

Narcolepsy-hypocretin deficiency results from a highly specific autoimmune attack on hypocretin cells. Recent studies have established antigen presentation by specific class II proteins encoded by (HLA DQB1*06:02 and DQA1*01:02) to the cognate T cell receptor as the main disease pathway, with a role for H1N1 influenza in the triggering process. Here, we have used a large and well-characterized cohort of Chinese narcolepsy cases to examine genetic architecture not observed in European samples. We confirmed previously implicated susceptibility genes (T cell receptor alpha, P2RY11), and identify new loci (ZNF365, IL10RB-IFNAR1), most notably, variants at the beta chain of the T cell receptor. We found that one HLA variant, (DQB1*03:01), is associated with dramatically earlier disease onset (nearly 2 years). We also identified differences in HLA haplotype frequencies among cases with onset following the 2009 H1N1 influenza pandemic as compared to before the outbreak, with fewer HLA DQB1*06:02 homozygotes. This may be the first demonstration of such an effect, and suggests that the study of changes in GWAS signals over time could help identify environmental factors in other autoimmune diseases.

A Mendelian predisposition to B-cell lymphoma caused by IL-10R deficiency

Monogenic interleukin-10 (IL-10) and IL-10 receptor (IL-10R) deficiencies cause very early onset severe inflammatory bowel disease. Here, we report that 5 patients with an IL-10R1 (n = 1) or IL-10R2 (n = 4) deficiency developed B-cell non-Hodgkin lymphoma between the ages of 5 and 6 years (which was recurrent in 1 patient). These lymphomas had some of the characteristics of diffuse large B-cell lymphomas and contained monoclonal, Epstein-Barr virus-negative germinal center B cells. The tumors displayed a remarkably homogeneous signature, with original activation of the nuclear factor κB pathway and a decrease in intratumor T-cell infiltration. Hence, IL-10R deficiency is associated with a high risk of developing B-cell lymphoma. Our results revealed an unexpected role of the IL-10R pathway in lymphomagenesis.

Molecular mechanisms and cell targets of Th17 cells in the gastrointestinal tract: an innate sense of adaptivity

T-helper (TH) 17 activation is crucial for protective immune responses against bacteria and fungi at mucosal surfaces, but it can also be implicated in the pathogenesis of several autoimmune and chronic inflammatory diseases, such as inflammatory bowel diseases (IBD). Although rapid progress was made elucidating induction and functional heterogeneity of Th17 responses, the underlying molecular effects of Th17 response including the most relevant different cell targets of Th17 cytokines remain poorly understood. Cytokines produced by Th17 cells have broad effects on both hematopoietic and nonhematopoietic cells and can act in synergy with various inflammatory factors. In this review, we will focus on the effects of Th17-derived cytokines in the gastrointestinal tract and discuss how Th17 responses can affect both innate and adaptive immunity and may contribute to the pathogenesis of inflammatory GI processes.

Central role of the gut epithelial barrier in the pathogenesis of chronic intestinal inflammation: lessons learned from animal models and human genetics

The gut mucosa is constantly challenged by a bombardment of foreign antigens and environmental microorganisms. As such, the precise regulation of the intestinal barrier allows the maintenance of mucosal immune homeostasis and prevents the onset of uncontrolled inflammation. In support of this concept, emerging evidence points to defects in components of the epithelial barrier as etiologic factors in the pathogenesis of inflammatory bowel diseases (IBDs). In fact, the integrity of the intestinal barrier relies on different elements, including robust innate immune responses, epithelial paracellular permeability, epithelial cell integrity, as well as the production of mucus. The purpose of this review is to systematically evaluate how alterations in the aforementioned epithelial components can lead to the disruption of intestinal immune homeostasis, and subsequent inflammation. In this regard, the wealth of data from mouse models of intestinal inflammation and human genetics are pivotal in understanding pathogenic pathways, for example, that are initiated from the specific loss of function of a single protein leading to the onset of intestinal disease. On the other hand, several recently proposed therapeutic approaches to treat human IBD are targeted at enhancing different elements of gut barrier function, further supporting a primary role of the epithelium in the pathogenesis of chronic intestinal inflammation and emphasizing the importance of maintaining a healthy and effective intestinal barrier.

Molecular diagnosis of infantile onset inflammatory bowel disease by exome sequencing

Pediatric-onset inflammatory bowel disease (IBD) is known to be associated with severe disease, poor response to therapy, and increased morbidity and mortality. We conducted exome sequencing of two brothers from a non-consanguineous relationship who presented before the age of one with severe infantile-onset IBD, failure to thrive, skin rash, and perirectal abscesses refractory to medical management. We examined the variants discovered in all known IBD-associated and primary immunodeficiency genes in both siblings. The siblings were identified to harbor compound heterozygous mutations in IL10RA (c.784C>T, p.Arg262Cys; c.349C>T, p.Arg117Cys). Upon molecular diagnosis, the proband underwent successful hematopoietic stem cell transplantation and demonstrated marked clinical improvement of all IBD-associated clinical symptoms. Exome sequencing can be an effective tool to aid in the molecular diagnosis of pediatric-onset IBD. We provide additional evidence of the safety and benefit of HSCT for patients with IBD due to mutations in the IL10RA gene.

The role of the innate and adaptive immune system in pediatric inflammatory bowel disease

Recent translational studies have provided new insights into the pathogenesis of pediatric-onset inflammatory bowel disease. Registry studies have identified distinct clinical phenotypes with increasing age of onset; this has led to a revision of the clinical phenotyping system, now termed the Paris classification system. It is recognized that there are infantile (age, <1 years), very early onset (VEO) (age, 1-10 years), and early onset (age, 10-17 years) forms of disease. Rare genetic mutations affecting antimicrobial and anti-inflammatory pathways have been discovered in infantile and VEO forms, although genetic pathways identified in early onset disease have been similar to adult-onset inflammatory bowel disease. An increasing incidence in the infantile and VEO forms has suggested an important environmental influence. This is likely ultimately expressed through alterations in the enteric flora (dysbiosis) and dysregulated immune responses to the flora, which are recognized as a critical trigger for mucosal inflammation. These data should ultimately guide new pathogenic models of disease, which will inform both therapy in individual patients and disease prevention in their at-risk family members.

Why interleukin-10 supplementation does not work in Crohn’s disease patients

Inflammatory bowel diseases (IBD) such as Crohn’s disease (CD) or ulcerative colitis are chronic intestinal disorders, which are on the increase in “Westernised” countries. IBD can be caused by both genetic and environmental factors. Interleukin-10 (IL-10) is an immunoregulatory cytokine that has been identified as being involved in several diseases including IBD. Studies have shown that polymorphisms in the promoter region reduce serum levels of IL-10 and this reduction has been associated with some forms of IBD. Mouse models have shown promising results with IL-10 supplementation, as such IL-10 supplementation has been touted as being a possible alternative treatment for CD in humans. Clinical trials have shown that recombinant human IL-10 is safe and well tolerated up to a dose of 8 μg/kg. However, to date, the results of the clinical trials have been disappointing. Although CD activity was reduced as measured by the CD activity index, IL-10 supplementation did not result in significantly reduced remission rates or clinical improvements when compared to placebo. This review discusses why IL-10 supplementation is not effective in CD patients currently and what can be addressed to potentially make IL-10 supplementation a more viable treatment option in the future. Based on the current research we conclude that IL-10 supplementation is not a one size fits all treatment and if the correct population of patients is chosen then IL-10 supplementation could be of benefit.

IL-10 promotes production of intestinal mucus by suppressing protein misfolding and endoplasmic reticulum stress in goblet cells

BACKGROUND & AIMS

Protein misfolding and endoplasmic reticulum (ER) stress have been observed in intestinal secretory cells from patients with inflammatory bowel diseases and induce intestinal inflammation in mice. However, it is not clear how immune factors affect ER stress and therefore disease symptoms.

METHODS

We analyzed the effects of interleukin (IL)-10 on ER stress in intestinal tissues in wild-type C57BL/6, Winnie, IL-10(-/-), and Winnie × IL-10(+/-) mice. In Winnie mice, misfolding of the intestinal mucin Muc2 initiates ER stress and inflammation. We also analyzed the effects of different inhibitors of IL-10 signaling and the N-glycosylation inhibitor tunicamycin in cultured human LS174T goblet cells.

RESULTS

Administration of neutralizing antibodies against IL-10 or its receptor (IL-10R1) to Winnie mice rapidly exacerbated ER stress and intestinal inflammation compared with mice given vehicle (controls). Antibodies against IL-10 also increased accumulation of misfolded Muc2 in the ER of goblet cells of Winnie mice and increased T-cell production of inflammatory cytokines. Winnie × IL-10(+/-) mice and IL-10(-/-) mice with a single Winnie allele each developed more severe inflammation than Winnie mice or IL-10(-/-) mice. Administration of tunicamycin to wild-type mice caused intestinal ER stress, which increased when IL-10R1 was blocked. In LS174T cells, induction of ER stress with tunicamycin and misfolding of MUC2 were reduced by administration of IL-10; this reduction required STAT1 and STAT3. In LS174T cells incubated with tunicamycin, IL-10 up-regulated genes involved in MUC2 folding and in ER-associated degradation and maintained correct folding of MUC2, its transport from the ER, and its O-glycosylation and secretion.

CONCLUSIONS

IL-10 prevents protein misfolding and ER stress by maintaining mucin production in goblet cells and helps the intestine preserve the mucus barrier.

IL-10R polymorphisms are associated with very-early-onset ulcerative colitis

BACKGROUND

Interleukin-10 (IL-10) signaling genes are attractive inflammatory bowel disease (IBD) candidate genes as IL-10 restricts intestinal inflammation, IL-10 polymorphisms have been associated with IBD in genome-wide association studies, and mutations in IL-10 and IL-10 receptor (IL-10R) genes have been reported in immunodeficient children with severe infantile-onset IBD. Our objective was to determine if IL-10R polymorphisms were associated with early-onset IBD (EO-IBD) and very-early-onset IBD (VEO-IBD).

METHODS

Candidate-gene analysis of IL10RA and IL10RB was performed after initial sequencing of an infantile onset-IBD patient identified a novel homozygous mutation. The discovery cohort included 188 EO-IBD subjects and 188 healthy subjects. Polymorphisms associated with IBD in the discovery cohort were genotyped in an independent validation cohort of 422 EO-IBD subjects and 480 healthy subjects.

RESULTS

We identified a homozygous, splice-site point mutation in IL10RA in an infantile-onset IBD patient causing a premature stop codon (P206X) and IL-10 insensitivity. IL10RA and IL10RB sequencing in the discovery cohort identified five IL10RA polymorphisms associated with ulcerative colitis (UC) and two IL10RB polymorphisms associated with Crohn's disease (CD). Of these polymorphisms, two IL10RA single nucleotide polymorphisms, rs2228054 and rs2228055, were associated with VEO-UC in the discovery cohort and replicated in an independent validation cohort (odds ratio [OR] 3.08, combined P = 2 x 10(-4); and OR 2.93, P = 6 x 10(-4), respectively).

CONCLUSIONS

We identified IL10RA polymorphisms that confer risk for developing VEO-UC. Additionally, we identified the first splice site mutation in IL10RA resulting in infantile-onset IBD. This study expands the phenotype of IL10RA polymorphisms to include both severe arthritis and VEO-UC.

Clinical outcome in IL-10- and IL-10 receptor-deficient patients with or without hematopoietic stem cell transplantation

BACKGROUND

Inherited deficiencies of IL-10 or IL-10 receptor (IL-10R) lead to immune dysregulation with life-threatening early-onset enterocolitis.

OBJECTIVES

We sought to gather clinical data of IL-10/IL-10R-deficient patients and devise guidelines for diagnosis and management, including hematopoietic stem cell transplantation (HSCT).

METHODS

We enrolled 40 patients with early-onset enterocolitis and screened for mutations in IL10/IL10R using genetic studies, functional studies, or both of the IL-10 signaling pathway. Medical records of IL-10/IL-10R-deficient patients were reviewed and compiled.

RESULTS

Of 40 patients, we identified 7 with novel mutations, predominantly in consanguineous families with more than 1 affected member. IL-10/IL-10R-deficient patients had intractable enterocolitis, perianal disease, and fistula formation. HSCT was carried out in 2 patients with IL-10 deficiency and 1 patient with IL-10R α chain deficiency and proved to be an effective therapy, leading to rapid improvement of clinical symptoms and quality of life.

CONCLUSION

Because the defect in patients with IL-10/IL-10R deficiency resides in hematopoietic lineage cells and their colitis is resistant to standard immunosuppressive therapy, HSCT should be considered early as a potentially curative therapeutic option.

Pediatric ulcerative colitis associated with autoimmune diseases: a distinct form of inflammatory bowel disease?

BACKGROUND

The pathogenesis of inflammatory bowel disease (IBD) is multifactorial, with some patients presenting additional autoimmune symptoms. Inflammatory colitis associated with autoimmune (AI) liver disease appears to have clinical features different from those of "classical" ulcerative colitis (CUC). The aim of this study was to describe these features, in order to differentiate a subgroup of colitis associated with autoimmunity (CAI) from CUC.

METHODS

Twenty-eight consecutive children with inflammatory colitis associated with primary sclerosing cholangitis (PSC), celiac disease, or AI hepatitis were compared with a matched control group of 27 children with isolated UC. Clinical course, histology, as well as inflammatory profile in the colonic mucosa based on real-time polymerase chain reaction (PCR) were analyzed.

RESULTS

In CAI the main digestive symptoms at disease onset were abdominal pain (12/28) and bloody strings in the stool (12/28), along with a high prevalence of autoimmune diseases in relatives, as compared with bloody diarrhea in the CUC group (26/27). At diagnosis, pancolitis was seen in 18/28 CAI patients compared with 8/27 in UC. In CAI, the pathological findings were different from CUC: 1) major lesions predominantly located in the right colon; 2) pseudo-villous appearance of the mucosa, and strong infiltration with eosinophils; 3) mild glandular lesions; and 4) differing inflammatory infiltrate with reduced FOXP3, interleukin (IL)-2, and thymic stromal lymphopoietin (TSLP) levels. Evolution in CAI was less aggressive, requiring less corticosteroids/immunomodulators.

CONCLUSIONS

Precise clinical, histological, and molecular analyses reveal marked differences between patients with CUC and those with associated AI phenomena, supporting the hypothesis of a distinct AI presentation of IBD.

Interleukin-10 and interleukin-10-receptor defects in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease characterized by abdominal pain, bloody diarrhoea, and malabsorption leading to weight loss. It is considered the result of inadequate control of an excessive reaction of the immune system to the resident flora of the gut. Like other primary immunodeficiencies, IL-10 and IL-10 receptor (IL10R) deficiency present with IBD and demonstrate the sensitivity of the intestine to any changes of the immune system. Both IL-10 and IL10R deficiency cause severe early-onset enterocolitis and can be successfully treated by hematopoietic stem cell transplantation (HSCT).

Pathogenesis of spondyloarthritis: autoimmune or autoinflammatory?

PURPOSE OF REVIEW

Spondyloarthritis (SpA) is a chronic immune-mediated inflammatory disease of unknown origin. Here we aim to review whether SpA is driven by T-cell and/or B-cell autoreactivity or by abnormal innate immune responses.

RECENT FINDINGS

SpA does not share genetic risk factors, female predominance, presence of disease-specific autoantibodies and response to T-cell or B-cell-targeted therapies with prototypical autoimmune diseases like rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Growing evidence indicates that increased responsiveness of innate immune cells such as macrophages, mast cells and neutrophils drives inflammation in SpA. The altered innate immune response may be related to nonantigen-presenting functions of HLA-B27, including the induction of an unfolded protein response, and can be triggered by bacterial and mechanical stress. Innate immune cells appear to be the main producers of both pro-inflammatory (tumor necrosis factor, IL-1, IL-23, IL-17) and anti-inflammatory (IL-10) cytokines in SpA.

SUMMARY

The predominance of myeloid above lymphoid alterations suggests an autoinflammatory rather than autoimmune origin of inflammation in SpA. Therefore, targeting innate cells or their inflammatory mediators may be more effective than T-cell or B-cell-directed therapies.

Management of pediatric ulcerative colitis: joint ECCO and ESPGHAN evidence-based consensus guidelines

BACKGROUND AND AIMS

Pediatric ulcerative colitis (UC) shares many features with adult-onset disease but there are some unique considerations; therefore, therapeutic approaches have to be adapted to these particular needs. We aimed to formulate guidelines for managing UC in children based on a systematic review (SR) of the literature and a robust consensus process. The present article is a product of a joint effort of the European Crohn's and Colitis Organization (ECCO) and the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN).

METHODS

A group of 27 experts in pediatric IBD participated in an iterative consensus process including 2 face-to-face meetings, following an open call to ESPGHAN and ECCO members. A list of 23 predefined questions were addressed by working subgroups based on a SR of the literature.

RESULTS

A total of 40 formal recommendations and 68 practice points were endorsed with a consensus rate of at least 89% regarding initial evaluation, how to monitor disease activity, the role of endoscopic evaluation, medical and surgical therapy, timing and choice of each medication, the role of combined therapy, and when to stop medications. A management flowchart, based on the Pediatric Ulcerative Colitis Activity Index (PUCAI), is presented.

CONCLUSIONS

These guidelines provide clinically useful points to guide the management of UC in children. Taken together, the recommendations offer a standardized protocol that allows effective, timely management and monitoring of the disease course, while acknowledging that each patient is unique.

[The future of inflammatory bowel disease from the perspective of Digestive Disease Week 2012]

The new information presented in Digestive Disease Week has allowed us to speculate on the future of inflammatory bowel disease. Manipulation of diet and the microbioma will probably play an increasingly important role in the treatment of this disease and, in the long term, in its prevention. Biological agents will probably be used earlier and more widely; new information on levels of biological agents, mucosal healing and new comparative studies will also allow these agents to be used in a more precise and personalized way. In addition to infliximab, adalimumab, natalizumab and certolizumab, other biological agents will be employed; among the first of these to be used will be ustekinumab, golimumab and vedolizumab. In the near future, biological agents will be used as frequently in ulcerative colitis as in Crohn's disease. New healthcare models will be developed that will progressively include greater participation among patients and nurses. The ability to predict new diagnostic and prognostic models will allow decisions to be more individualized.

Healing of intestinal inflammation by IL-22

An interleukin (IL)-10 family cytokine, IL-22 is characterized by several unique biological properties, including 1) the target restricted to innate cells; 2) the distinct expression pattern between large and small intestines; 3) alteration of the cellular source depending on several factors; 4) the dual abilities to serve as protective versus proinflammatory mediators in inflammatory responses; and 5) the close association with some major inflammatory bowel disease (IBD) susceptibility genes. The major functions of IL-22 in the intestine are the stimulation of epithelial cells to produce a wide variety of antibacterial proteins, the reinforcement of mucus barrier through stimulation of mucin 1 production under intestinal inflammatory conditions, and the enhancement of epithelial regeneration with goblet cell restitution. Through these beneficial functions, IL-22 contributes to the improvement of some types of experimental chronic colitis, which are mediated by T helper (Th)1 or Th2 responses. Most important, studies using both loss-of-function and gain-of-function approaches have clearly demonstrated the ability of IL-22 to promote intestinal wound healing from acute intestinal injury. These findings highlight IL-22 as an attractive and promising target for future IBD therapy. Alternatively, the enormous progress in the field of IL-22 biology has also suggested more complicated mechanisms with the IL-22 pathway than previously predicted. This review article briefly summarizes previous and current knowledge on IL-22 particularly associated with intestinal inflammation.

How does knowledge from translational research impact our clinical care of pediatric inflammatory bowel disease patients?

Recent translational studies have provided new insights into pathogenesis, disease behavior, and treatment responses in pediatric Inflammatory Bowel Disease (IBD). Registry studies have identified distinct clinical phenotypes with increasing age of onset; this has led to a revision of the clinical phenotyping system, now termed the Paris classification system. It is recognized that there are infantile (age <2 years), very early onset (VEO, age 2-10), and early onset (EO, age 10-17) forms of disease. Rare genetic mutations affecting anti-microbial and anti-inflammatory pathways have been discovered in infantile and VEO forms, while genetic pathways identified in EO disease have been similar to adult-onset IBD. Genetic and serologic patterns measured soon after diagnosis have been shown to be associated with more aggressive stricturing behavior; these patterns may now be used clinically to help predict disease course. More recently, clinical and genetic models have been developed that, if validated, could be used to predict treatment responses.

Dendritic cells a double-edge sword in autoimmune responses

Dendritic cells (DC) are antigen-presenting cells that play a pivotal role in regulating innate and adaptive immune responses. In autoimmunity, DC act as a double-edged sword since on one hand they initiate adaptive self-reactive responses and on the other they play a pivotal role in promoting and maintaining tolerance. Thus, DC are the most important cells in either triggering self-specific responses or in negatively regulating auto-reactive responses. The latter function is mediated by DC in the steady-state or specialized subsets of DC, named tolerogenic DC. Clinical and experimental evidence indicate that prolonged presentation of self-antigens by DC is crucial for the development of destructive autoimmune diseases, and defects in tolerogenic DC functions contribute to eradication of self-tolerance. In recent years, DC have emerged as therapeutic targets for limiting their immunogenicity against self-antigens, while tolerogenic DC have been conceived as therapeutic tools to restore tolerance. The purpose of this review is to give a general overview of the current knowledge on the pathogenic role of DC in patients affected by autoimmune diseases. In addition, the protective role of tolerogenic DC will be addressed. The currently applied strategies to block immune activation or to exploit the tolerogenic potential of DC will be discussed.

Risk of infection and prevention in pediatric patients with IBD: ESPGHAN IBD Porto Group commentary

Combined immunosuppression by immunomodulators and biological therapy has become standard in the medical management of moderate-to-severe inflammatory bowel disease (IBD) because of clearly demonstrated efficacy. Clinical studies, registries, and case reports warn of the increased risk of infections, particularly opportunistic infections; however, already in the steroid monotherapy era, patients are at risk because it is accepted that a patient should be considered immunosuppressed when receiving a daily dose of 20 mg of prednisone for 2 weeks. Prescriptions increasingly involve azathioprine, methotrexate, and various biological agents. The TREAT registry evaluated safety in >6000 adult patients, half of them treated with infliximab (IFX) for about 1.9 years. IFX-treated patients had an increased risk of infections and this was associated with disease severity and concomitant prednisone use. The REACH study, evaluating the efficacy of IFX in children with moderate-to-severe Crohn disease, refractory to immunomodulatory treatment, reports serious infections as the major adverse events and their frequency is higher with shorter treatment intervals. The combination of immunosuppressive medications is a risk factor for opportunistic infections. Exhaustive guidelines on prophylaxis, diagnosis, and management of opportunistic infections in adult patients with IBD have been published by a European Crohn's and Colitis Organization working group, including clear evidence-based statements. We have reviewed the literature on infections in pediatric IBD as well as the European Crohn's and Colitis Organization guidelines to present a commentary on infection prophylaxis for the pediatric age group.

Maintenance of small intestinal and colonic tolerance by IL-10-producing regulatory T cell subsets

The intestinal mucosa is continuously exposed to harmless exogenous antigens derived from food proteins and microbiota. Continuous surveillance by suppressive regulatory T cells prevents inflammatory responses to these antigens thereby maintaining intestinal homeostasis. The nature of the antigenic pressure varies at different locations of the intestinal tract. In agreement with this strong microenvironmental control, small intestinal and colonic regulatory T cell homeostasis varies considerably. In this review, we summarize the substantial advances that have been made in dissecting the phenotype and function of intestinal regulatory T cells, discuss how microbiota can modulate the intestinal regulatory T cell pool and review the crucial role of the immunoregulatory cytokine interleukin-10 (IL-10) in shaping and maintenance of mucosal tolerance.

Exome sequencing identifies novel compound heterozygous mutations of IL-10 receptor 1 in neonatal-onset Crohn's disease

Inflammatory bowel disease is well recognized for a strong genetic involvement in its pathogenesis. Homozygous mutations in interleukin-10 receptor 1 (IL-10R1) identified by linkage analysis were shown to be involved in this disorder. However, the underlying molecular mechanism and the causal nature of the mutations in the disease process remain to be clarified. In this study, using whole exome sequencing, we identified novel compound heterozygous missense mutations in the extracellular domain of IL-10R1 in a Crohn's disease patient from a non-consanguineous family. These mutations did not affect IL-10R1 expression, nor IL-10 binding. However, they abrogated IL-10R1 phosphorylation induced by IL-10, therefore leading to impaired STAT3 activation and suppression of inflammatory responses. After reconstitution with wild-type IL-10R1, the patient cells showed fully restored IL-10R function including IL-10-induced STAT3 activation and expression of suppressor of cytokine signaling 3. Thus, our results demonstrated that the mutations in IL-10R1 extracellular domain impair IL-10R1 activation rather than IL-10 binding, indicating these residues are important in IL-10 signal transduction through IL-10R1. The reconstitution data also confirmed the causality of the IL-10R1 mutations.

IL-10 and IL-10 receptor defects in humans

Inflammatory bowel disease (IBD), which includes Crohn's disease (CD) and ulcerative colitis (UC), is chronic in nature and is characterized by abdominal pain, diarrhea, bleeding, and malabsorption. It is considered a complex multigenic and multifactorial disorder that results from disturbed interactions between the immune system and commensal bacteria of the gut. Recent work has demonstrated that IBD with an early-onset within the first months of life can be monogenic: mutations in IL-10 or its receptor lead to a loss of IL-10 function and cause severe intractable enterocolitis in infants and small children. Both IL-10 and IL-10 receptor deficiency can be successfully treated by hematopoietic stem cell transplantation.

Role of microbiota in postnatal maturation of intestinal T-cell responses

PURPOSE OF REVIEW

Taking advantage of their rapid growth and capacity for continuous genetic adaptation, prokaryotes have colonized all possible ecological environments on earth, including the body surfaces of eukaryotes and their gastrointestinal tract. The mammalian gut contains a complex community of 10 bacteria with a meta-genome containing 1500-fold more genes than the human genome. The forces that control the relationships between eukaryotic hosts and their intestinal bacterial symbionts have, thus, become a major focus of interest.

RECENT FINDINGS

Recent data have highlighted how the dialogue between mammalian hosts and their microbiota stimulates the postnatal maturation of an efficient intestinal barrier that promotes niche colonization by symbiotic bacteria and opposes colonization by pathogens. Herein, we review microbiota-induced T-cell responses and discuss how individual bacteria may shape the balance between regulatory and inflammatory responses. We will also show how host factors might influence the outcome of gut immune responses and affect the structure of the microbiota.

SUMMARY

Deciphering host-microbiota reciprocal influence may not only help in understanding the recent outburst of intestinal inflammatory diseases but also point to strategies able to maintain or restore intestinal homeostasis.