Carol E. Semrad

Co-adjuvant effects of retinoic acid and IL-15 induce inflammatory immunity to dietary antigens

Under physiological conditions the gut-associated lymphoid tissues not only prevent the induction of a local inflammatory immune response, but also induce systemic tolerance to fed antigens. A notable exception is coeliac disease, where genetically susceptible individuals expressing human leukocyte antigen (HLA) HLA-DQ2 or HLA-DQ8 molecules develop inflammatory T-cell and antibody responses against dietary gluten, a protein present in wheat. The mechanisms underlying this dysregulated mucosal immune response to a soluble antigen have not been identified. Retinoic acid, a metabolite of vitamin A, has been shown to have a critical role in the induction of intestinal regulatory responses. Here we find in mice that in conjunction with IL-15, a cytokine greatly upregulated in the gut of coeliac disease patients, retinoic acid rapidly activates dendritic cells to induce JNK (also known as MAPK8) phosphorylation and release the proinflammatory cytokines IL-12p70 and IL-23. As a result, in a stressed intestinal environment, retinoic acid acted as an adjuvant that promoted rather than prevented inflammatory cellular and humoral responses to fed antigen. Altogether, these findings reveal an unexpected role for retinoic acid and IL-15 in the abrogation of tolerance to dietary antigens.

Reprogramming of CTLs into natural killer-like cells in celiac disease

Celiac disease is an intestinal inflammatory disorder induced by dietary gluten in genetically susceptible individuals. The mechanisms underlying the massive expansion of interferon γ–producing intraepithelial cytotoxic T lymphocytes (CTLs) and the destruction of the epithelial cells lining the small intestine of celiac patients have remained elusive. We report massive oligoclonal expansions of intraepithelial CTLs that exhibit a profound genetic reprogramming of natural killer (NK) functions. These CTLs aberrantly expressed cytolytic NK lineage receptors, such as NKG2C, NKp44, and NKp46, which associate with adaptor molecules bearing immunoreceptor tyrosine-based activation motifs and induce ZAP-70 phosphorylation, cytokine secretion, and proliferation independently of T cell receptor signaling. This NK transformation of CTLs may underlie both the self-perpetuating, gluten-independent tissue damage and the uncontrolled CTL expansion leading to malignant lymphomas in severe forms of celiac disease. Because similar changes were detected in a subset of CTLs from cytomegalovirus-seropositive patients, we suggest that a stepwise transformation of CTLs into NK-like cells may underlie immunopathology in various chronic infectious and inflammatory diseases.

Complications associated with double balloon enteroscopy at nine US centers.

BACKGROUND & AIMS Double balloon enteroscopy (DBE) was introduced into the US in 2004. Potential complications include perforation, pancreatitis, and gastrointestinal bleeding. Prevalence and risk factors for complications have not been described in a US population. METHODS We conducted a retrospective study of DBE complications in 9 US centers. We obtained detailed information for each complication including patient history, maneuvers performed during the DBE, and presence of altered surgical anatomy. RESULTS We collected data from 2478 DBE examinations performed from 2004 to 2008. The dataset included 1691 (68%) anterograde DBE, 722 (29%) retrograde DBE (including 5 per-stomal DBEs), and 65 (3%) DBE-facilitated endoscopic retrograde cholangiopancreatography ERCP cases. There were a total of 22 (0.9%) major complications including perforation in 11 (0.4%), pancreatitis in 6 (0.2%), and bleeding in 4 (0.2%) patients. One of 6 cases of pancreatitis occurred post retrograde DBE. Perforations occurred in 3/1691 (0.2%) anterograde examinations and 8/719 (1.1%) retrograde DBEs (P = .004). Eight (73%) perforations occurred during diagnostic DBE examinations. Four of 8 retrograde DBE perforations occurred in patients with prior ileoanal or ileocolonic anastomoses. In the subset of 219 examinations performed in patients with surgically altered anatomy, perforations occurred in 7 (3%), including 1/159 (0.6%) anterograde DBE examinations, 6/60 (10%) retrograde DBEs, and 1 of 5 (20%) peristomal DBE examinations (P < .005 compared with patients without surgically altered anatomy). CONCLUSIONS DBE is associated with a higher complication rate compared with standard endoscopic procedures. The perforation rate was significantly elevated in patients with altered surgical anatomy undergoing diagnostic retrograde DBE examinations.

Reovirus infection triggers inflammatory responses to dietary antigens and development of celiac disease

A nonpathogenic virus can promote inflammatory immunity to dietary antigens and may be linked to the development of celiac disease. Viruses compound dietary pathology Reoviruses commonly infect humans and mice asymptomatically. Bouziat et al. found that immune responses to two gut-infecting reoviruses take different paths in mice (see the Perspective by Verdu and Caminero). Both reoviruses invoked protective immune responses, but for one reovirus, when infection happened in the presence of a dietary antigen (such as gluten or ovalbumin), tolerance to the dietary antigen was lost. This was because this strain prevented the formation of tolerogenic T cells. Instead, it promoted T helper 1 immunity to the dietary antigen through interferon regulatory factor 1 signaling. Celiac disease patients also exhibited elevated levels of antibodies against reovirus. Science, this issue p. 44; see also p. 29 Viral infections have been proposed to elicit pathological processes leading to the initiation of T helper 1 (TH1) immunity against dietary gluten and celiac disease (CeD). To test this hypothesis and gain insights into mechanisms underlying virus-induced loss of tolerance to dietary antigens, we developed a viral infection model that makes use of two reovirus strains that infect the intestine but differ in their immunopathological outcomes. Reovirus is an avirulent pathogen that elicits protective immunity, but we discovered that it can nonetheless disrupt intestinal immune homeostasis at inductive and effector sites of oral tolerance by suppressing peripheral regulatory T cell (pTreg) conversion and promoting TH1 immunity to dietary antigen. Initiation of TH1 immunity to dietary antigen was dependent on interferon regulatory factor 1 and dissociated from suppression of pTreg conversion, which was mediated by type-1 interferon. Last, our study in humans supports a role for infection with reovirus, a seemingly innocuous virus, in triggering the development of CeD.

Distinct and Synergistic Contributions of Epithelial Stress and Adaptive Immunity to Functions of Intraepithelial Killer Cells and Active Celiac Disease

BACKGROUND & AIMS The mechanisms of tissue destruction during progression of celiac disease are poorly defined. It is not clear how tissue stress and adaptive immunity contribute to the activation of intraepithelial cytotoxic T cells and the development of villous atrophy. We analyzed epithelial cells and intraepithelial cytotoxic T cells in family members of patients with celiac disease, who were without any signs of adaptive antigluten immunity, and in potential celiac disease patients, who have antibodies against tissue transglutaminase 2 in the absence of villous atrophy. METHODS We collected blood and intestinal biopsy specimens from 268 patients at tertiary medical centers in the United States and Italy from 2004 to 2012. All subjects had normal small intestinal histology. Study groups included healthy individuals with no family history of celiac disease or antibodies against tissue transglutaminase 2 (controls), healthy family members of patients with celiac disease, and potential celiac disease patients. Intraepithelial cytotoxic T cells were isolated and levels of inhibitory and activating natural killer (NK) cells were measured by flow cytometry. Levels of heat shock protein (HSP) and interleukin 15 were measured by immunohistochemistry, and ultrastructural alterations in intestinal epithelial cells (IECs) were assessed by electron microscopy. RESULTS IECs from subjects with a family history of celiac disease, but not from subjects who already had immunity to gluten, expressed higher levels of HS27, HSP70, and interleukin-15 than controls; their IECs also had ultrastructural alterations. Intraepithelial cytotoxic T cells from relatives of patients with celiac disease expressed higher levels of activating NK receptors than cells from controls, although at lower levels than patients with active celiac disease, and without loss of inhibitory receptors for NK cells. Intraepithelial cytotoxic T cells from potential celiac disease patients failed to up-regulate activating NK receptors. CONCLUSIONS A significant subset of healthy family members of patients with celiac disease with normal intestinal architecture had epithelial alterations, detectable by immunohistochemistry and electron microscopy. The adaptive immune response to gluten appears to act in synergy with epithelial stress to allow intraepithelial cytotoxic T cells to kill epithelial cells and induce villous atrophy in patients with active celiac disease.

Inhibition of Na/H Exchange in Avian Intestine by Atrial Natriuretic Factor

Effects of 8-bromo-cGMP (8-Br-cGMP) and synthetic rat atriopeptin III (APIII) on sodium absorption by isolated chicken villus enterocytes and intact chicken ileal mucosa were determined. In isolated cells, both agents significantly decreased initial rates of influx of 22Na and caused a persistent decrease in intracellular pH (pHi); effects that are not additive to those caused by amiloride (10(-3) M). The ED50 for APIII was 0.3 nM. In intact mucosa, both 8-Br-cGMP (10(-4) M) and 5-(N-methyl-N-isobutyl)amiloride (MIBA) (10(-5) M) reduced JNams and JNa.net, their effects were not additive. APIII (10(-7) M) significantly increased cellular cGMP but not cAMP. Both 8-Br-cGMP (10(-4) M) and APIII (10(-7) M) stimulated a persistent increase in cytosolic calcium (Cai), which could be prevented by pretreating the cells with the cytosolic calcium buffering agent MAPTAM or with H-8, an inhibitor of cyclic nucleotide-dependent protein kinases. Furthermore, pretreatment of cells with H-8 or the calmodulin inhibitor, calmidazolium (CM), prevented the effects of 8-Br-cGMP and APIII on pHi. However, the pHi response to subsequent addition of the calcium-ionophore ionomycin was blocked only by CM and not by H-8. These data suggest that APIII and 8-Br-cGMP inhibit amiloride-sensitive Na/H exchange by increasing Cai, an event requiring activation of cGMP-dependent protein kinase.

Small bowel tumors.

Although rare, small bowel tumors may cause significant morbidity and mortality if left undetected. New endoscopic modalities allow full examination of the small bowel with improved diagnosis. However, isolated mass lesions may be missed by capsule endoscopy or incomplete balloon-assisted enteroscopy. Therefore the use of radiologic imaging and intraoperative enteroscopy for diagnosis should not be forgotten. Endoscopic resection of small bowel polyps and certain vascular tumors is possible but requires proper training. Advances in endoscopic tools are likely to broaden the endoscopic management of small bowel tumors. This article describes the general features of small bowel tumors, clinical presentation, and diagnostic tests followed by a description of the more common tumor types and their management.

Double-balloon enteroscopy in Crohn's disease: findings and impact on management in a multicenter retrospective study.

BACKGROUND Double-balloon enteroscopy (DBE) is effective in visualizing the small bowel to perform biopsy sampling and interventions. Few studies have evaluated the utility of DBE in patients with known or suspected Crohns disease (CD). OBJECTIVE To evaluate the use of DBE in the diagnosis and impact on patient management in known and suspected CD and to compare capsule endoscopy (CE) with DBE findings. DESIGN Retrospective study from August 2004 to August 2009 of DBE procedures. SETTING Five academic, tertiary U.S. centers. PATIENTS Patients with known or suspected CD. MAIN OUTCOME MEASURES Diagnostic yield, impact on patient management, and comparison of DBE to CE findings in patients with known and suspected CD. RESULTS We analyzed 98 DBE procedures performed in 81 patients (38 with known CD and 43 with suspected CD). For patients with CD, common indications were abdominal pain and bleeding/anemia. The diagnostic yield was 87% (33/38 patients). The impact on subsequent management decisions was 82% (31/38). Common indications for DBE in patients with suspected CD were abnormal CE or other imaging. The diagnostic yield was 79% (34/43 patients). The impact on subsequent management decisions was 77% (33/43). In 17% of patients (14/81), DBE failed to reach the target lesion. There was 1 perforation, 3 strictures dilated, and 1 of 2 retained capsules recovered. When CE was followed by DBE, 46% of lesions were confirmed on DBE. LIMITATIONS Retrospective analysis, imperfect criterion standard. CONCLUSIONS DBE is an effective technique for assessment of the small bowel in known and suspected CD and affects management. Failure to reach target areas with DBE is not uncommon, and perforations can occur. There is poor correlation between CE and DBE.

Gastro 2013 APDW/WCOG Shanghai Working Party Report: Chronic diarrhea: Definition, classification, diagnosis

Diarrhea is best defined as passage of loose stools often with more frequent bowel movements. For clinical purposes, the Bristol Stool Form Scale works well to distinguish stool form and to identify loose stools. Laboratory testing of stool consistency has lagged behind. Acute diarrhea is likely to be due to infection and to be self‐limited. As diarrhea becomes chronic, it is less likely to be due to infection; duration of 1 month seems to work well as a cut‐off for chronic diarrhea, but detailed scientific knowledge is missing about the utility of this definition. In addition to duration of diarrhea, classifications by presenting scenario, by pathophysiology, and by stool characteristics (e.g. watery, fatty, or inflammatory) may help the canny clinician refine the differential diagnosis of chronic diarrhea. In this regard, a careful history remains the essential part of the evaluation of a patient with diarrhea. Imaging the intestine with endoscopy and radiographic techniques is useful, and biopsy of the small intestine and colon for histological assessment provides key diagnostic information. Endomicroscopy and molecular pathology are only now being explored for the diagnosis of chronic diarrhea. Interest in the microbiome of the gut is increasing; aside from a handful of well‐described infections because of pathogens, little is known about alterations in the microbiome in chronic diarrhea. Serological tests have well‐defined roles in the diagnosis of celiac disease but have less clearly defined application in autoimmune enteropathies and inflammatory bowel disease. Measurement of peptide hormones is of value in the diagnosis and management of endocrine tumors causing diarrhea, but these are so rare that these tests are of little value in screening because there will be many more false‐positives than true‐positive results. Chemical analysis of stools is of use in classifying chronic diarrhea and may limit the differential diagnosis that must be considered, but interpretation of the results is still evolving. Breath tests for assessment of carbohydrate malabsorption, small bowel bacterial overgrowth, and intestinal transit are fraught with technical limitations that decrease sensitivity and specificity. Likewise, tests of bile acid malabsorption have had limited utility beyond empirical trials of bile acid sequestrants.

Gastric Mucosal Necrosis With Vascular Degeneration Induced by Doxycycline

We encountered 2 patients who underwent esophagogastroduodenoscopy for epigastric abdominal pain, which showed gastric mucosal erosions covered with adherent exudate. Microscopic examination of biopsies from the lesions obtained from the 2 cases revealed characteristic pathologic abnormalities that shared striking similarities. These included superficial mucosal necrosis and capillary vascular degenerative change in a background of reactive or chemical gastropathy. Further review of records identified ongoing oral doxycycline use in both patients. After cessation of the drug both patients’ symptoms resolved. A follow-up esophagogastroduodenoscopy in 1 patient showed normal gastric mucosa. This pattern of injury had not been previously described and seems to be characteristic for doxycycline-induced gastric mucosal toxicity. Recognition of the clinical, endoscopic, and pathologic features described here may facilitate prompt diagnosis and management of this condition.