IL-10 signaling in dendritic cells controls IL-1ß-mediated IFNγ secretion by human CD4+ T cells: relevance to inflammatory bowel disease.

Uncontrolled interferon γ (IFNγ)-mediated T-cell responses to commensal microbiota are a driver of inflammatory bowel disease (IBD). Interleukin-10 (IL-10) is crucial for controlling these T-cell responses, but the precise mechanism of inhibition remains unclear. A better understanding of how IL-10 exerts its suppressive function may allow identification of individuals with suboptimal IL-10 function among the heterogeneous population of IBD patients. Using cells from patients with an IL10RA deficiency or STAT3 mutations, we demonstrate that IL-10 signaling in monocyte-derived dendritic cells (moDCs), but not T cells, is essential for controlling IFNγ-secreting CD4+ T cells. Deficiency in IL-10 signaling dramatically increased IL-1ß release by moDCs. IL-1ß boosted IFNγ secretion by CD4+ T cells either directly or indirectly by stimulating moDCs to secrete IL-12. As predicted a signature of IL-10 dysfunction was observed in a subgroup of pediatric IBD patients having higher IL-1ß expression in activated immune cells and macroscopically affected intestinal tissue. In agreement, reduced IL10RA expression was detected in peripheral blood mononuclear cells and a subgroup of pediatric IBD patients exhibited diminished IL-10 responsiveness. Our data unveil an important mechanism by which IL-10 controls IFNγ-secreting CD4+ T cells in humans and identifies IL-1ß as a potential classifier for a subgroup of IBD patients.

IL-10 signaling prevents gluten-dependent intraepithelial CD4+ cytotoxic T lymphocyte infiltration and epithelial damage in the small intestine.

Breach of tolerance to gluten leads to the chronic small intestinal enteropathy celiac disease. A key event in celiac disease development is gluten-dependent infiltration of activated cytotoxic intraepithelial lymphocytes (IELs), which cytolyze epithelial cells causing crypt hyperplasia and villous atrophy. The mechanisms leading to gluten-dependent small intestinal IEL infiltration and activation remain elusive. We have demonstrated that under homeostatic conditions in mice, gluten drives the differentiation of anti-inflammatory T cells producing large amounts of the immunosuppressive cytokine interleukin-10 (IL-10). Here we addressed whether this dominant IL-10 axis prevents gluten-dependent infiltration of activated cytotoxic IEL and subsequent small intestinal enteropathy. We demonstrate that IL-10 regulation prevents gluten-induced cytotoxic inflammatory IEL infiltration. In particular, IL-10 suppresses gluten-induced accumulation of a specialized population of cytotoxic CD4+CD8αα+ IEL (CD4+ CTL) expressing Tbx21, Ifng, and Il21, and a disparate non-cytolytic CD4+CD8α- IEL population expressing Il17a, Il21, and Il10. Concomitantly, IL-10 suppresses gluten-dependent small intestinal epithelial hyperproliferation and upregulation of stress-induced molecules on epithelial cells. Remarkably, frequencies of granzyme B+CD4+CD8α+ IEL are increased in pediatric celiac disease patient biopsies. These findings demonstrate that IL-10 is pivotal to prevent gluten-induced small intestinal inflammation and epithelial damage, and imply that CD4+ CTL are potential new players into these processes.

Macrophage-mediated gliadin degradation and concomitant IL-27 production drive IL-10- and IFN-γ-secreting Tr1-like-cell differentiation in a murine model for gluten tolerance.

Celiac disease is caused by inflammatory T-cell responses against the insoluble dietary protein gliadin. We have shown that, in humanized mice, oral tolerance to deamidated chymotrypsin-digested gliadin (CT-TG2-gliadin) is driven by tolerogenic interferon (IFN)-γ- and interleukin (IL)-10-secreting type 1 regulatory T-like cells (Tr1-like cells) generated in the spleen but not in the mesenteric lymph nodes. We aimed to uncover the mechanisms underlying gliadin-specific Tr1-like-cell differentiation and hypothesized that proteolytic gliadin degradation by splenic macrophages is a decisive step in this process. In vivo depletion of macrophages caused reduced differentiation of splenic IFN-γ- and IL-10-producing Tr1-like cells after CT-TG2-gliadin but not gliadin peptide feed. Splenic macrophages, rather than dendritic cells, constitutively expressed increased mRNA levels of the endopeptidase Cathepsin D; macrophage depletion significantly reduced splenic Cathepsin D expression in vivo and Cathepsin D efficiently degraded recombinant γ-gliadin in vitro. In response to CT-TG2-gliadin uptake, macrophages enhanced the expression of Il27p28, a cytokine that favored differentiation of gliadin-specific Tr1-like cells in vitro, and was previously reported to increase Cathepsin D activity. Conversely, IL-27 neutralization in vivo inhibited splenic IFN-γ- and IL-10-secreting Tr1-like-cell differentiation after CT-TG2-gliadin feed. Our data infer that endopeptidase mediated gliadin degradation by macrophages and concomitant IL-27 production drive differentiation of splenic gliadin-specific Tr1-like cells.

Colonic tolerance develops in the iliac lymph nodes and can be established independent of CD103(+) dendritic cells.

Tolerance to harmless exogenous antigens is the default immune response in the gastrointestinal tract. Although extensive studies have demonstrated the importance of the mesenteric lymph nodes (MLNs) and intestinal CD103(+) dendritic cells (DCs) in driving small intestinal tolerance to protein antigen, the structural and immunological basis of colonic tolerance remain poorly understood. We show here that the caudal and iliac lymph nodes (ILNs) are inductive sites for distal colonic immune responses and that colonic T cell-mediated tolerance induction to protein antigen is initiated in these draining lymph nodes and not in MLNs. In agreement, colonic tolerance induction was not altered by mesenteric lymphadenectomy. Despite tolerance development, CD103(+)CD11b(+) DCs, which are the major migratory DC population in the MLNs, and the tolerance-related retinoic acid-generating enzyme RALDH2 were virtually absent from the ILNs. Administration of ovalbumin (OVA) to the distal colon did increase the number of CD11c(+)MHCII(hi) migratory CD103(-)CD11b(+) and CD103(+)CD11b(-) DCs in the ILNs. Strikingly, colonic tolerance was intact in Batf3-deficient mice specifically lacking CD103(+)CD11b(-) DCs, suggesting that CD103(-) DCs in the ILNs are sufficient to drive tolerance induction after protein antigen encounter in the distal colon. Altogether, we identify different inductive sites for small intestinal and colonic T-cell responses and reveal that distinct cellular mechanisms are operative to maintain tolerance at these sites.

Randomized clinical trial of the effect of gum chewing on postoperative ileus and inflammation in colorectal surgery.

BACKGROUND: Postoperative ileus (POI) is a common complication following colorectal surgery that delays recovery and increases length of hospital stay. Gum chewing may reduce POI and therefore enhance recovery after surgery. The aim of the study was to evaluate the effect of gum chewing on POI, length of hospital stay and inflammatory parameters. METHODS: Patients undergoing elective colorectal surgery in one of two centres were randomized to either chewing gum or a dermal patch (control). Chewing gum was started before surgery and stopped when oral intake was resumed. Primary endpoints were POI and length of stay. Secondary endpoints were systemic and local inflammation, and surgical complications. Gastric emptying was measured by ultrasonography. Soluble tumour necrosis factor receptor 1 (TNFRSF1A) and interleukin (IL) 8 levels were measured by enzyme-linked immunosorbent assay. RESULTS: Between May 2009 and September 2012, 120 patients were randomized to chewing gum (58) or dermal patch (control group; 62). Mean(s.d.) length of hospital stay was shorter in the chewing gum group than in controls, but this difference was not significant: 9·5(4·9) versus 14·0(14·5) days respectively. Some 14 (27 per cent) of 52 analysed patients allocated to chewing gum developed POI compared with 29 (48 per cent) of 60 patients in the control group (P = 0·020). More patients in the chewing gum group first defaecated within 4 days of surgery (85 versus 57 per cent; P = 0·006) and passed first flatus within 48 h (65 versus 50 per cent; P = 0·044). The decrease in antral area measured by ultrasonography following a standard meal was significantly greater among patients who chewed gum: median 25 (range -36 to 54) per cent compared with 10 (range -152 to 54) per cent in controls (P = 0·004). Levels of IL-8 (133 versus 288 pg/ml; P = 0·045) and TNFRSF1A (0·74 versus 0·92 ng/ml; P = 0·043) were lower among patients in the chewing gum group. Fewer patients in this group developed a grade IIIb complication (2 of 58 versus 10 of 62; P = 0·031). CONCLUSION: Gum chewing is a safe and simple treatment to reduce POI, and is associated with a reduction in systemic inflammatory markers and complications. REGISTRATION NUMBER: NTR2867 (http://www.trialregister.nl).

Endogenous vagal activation dampens intestinal inflammation independently of splenic innervation in postoperative ileus.

Postoperative ileus is encountered by patients undergoing open abdominal surgery and is characterized by intestinal inflammation associated with impaired gastrointestinal motility. We recently showed that inflammation of the gut muscularis triggered activation of the vagal efferent pathway mainly targeting the inflamed zone. In the present study we investigate further the modulatory role of endogenous activation of the vagal motor pathway on the innate immune response. Intestinal or splenic denervation was performed two weeks prior to intestinal manipulation (IM) or laparotomy (L). Twenty-four hour post-surgery, the gastrointestinal transit, immune cell influx, and pro-inflammatory cytokine levels were measured in the gut muscularis. Manipulation of the small intestine led to a delay in intestinal transit, an influx of leukocytes and increased pro-inflammatory cytokine expression. Surgical lesion of the vagal branch that selectively innervates the small intestine did not further delay the intestinal transit but significantly enhanced the expression levels of the pro-inflammatory cytokines IL-1ß and IL-6 in the gut muscularis. Splenic denervation did not affect intestinal inflammation or gastrointestinal transit after intestinal manipulation. Our study demonstrates that selective vagotomy, leaving the splenic innervation intact, increases surgery-induced intestinal inflammation. These data suggest that endogenous activation of the vagal efferent pathway by intestinal inflammation directly dampens the local immune response triggered by intestinal manipulation independently of the spleen.

Neuroanatomical evidence demonstrating the existence of the vagal anti-inflammatory reflex in the intestine.

BACKGROUND: The cholinergic anti-inflammatory pathway is proposed to be part of the so-called vago-vagal 'inflammatory reflex'. The aim of this study is to provide neuro-anatomical evidence to support the existence of a functional neuronal circuit and its activation in response to intestinal inflammation. METHODS: The expression of c-fos was evaluated at different levels of the neurocircuitry in the course of postoperative ileus (POI) in a mouse model. Specific activation of the motor neurons innervating the inflamed intestine and the spleen was monitored by retrograde tracing using cholera toxin-b. The role of the vagal afferent pathway nerve was evaluated by selective vagal denervation of the intestine. KEY RESULTS: Abdominal surgery resulted in subtle inflammation of the manipulated intestine at 24 h (late phase), but not after 2 and 6 h (early) after surgery. This local inflammation was associated with activation of neurons in the nucleus of the solitary tract and in the dorsal nucleus of the vagus. The vagal output mainly targeted the inflamed zone: 42% of motor neurons innervating the intestine expressed c-fos IR in contrast to 7% of those innervating the spleen. Vagal denervation of the intestine abolished c-fos expression in the brain nuclei involved in the neuronal network activated by intestinal inflammation. CONCLUSIONS & INFERENCES: Our data demonstrate that intestinal inflammation triggers a vagally mediated circuit leading mainly to activation of vagal motor neurons connected to the inflamed intestine. These findings for the first time provide neuro-anatomical evidence for the existence of the endogenous 'inflammatory reflex' and its activation during inflammation.