Ken Croitoru

Regulation of Abortion by γλ T Cells

PROBLEM: T cells are present at the feto‐maternal interface, but their function during pregnancy has not been fully elucidated. T cells bearing γλ T‐cell receptor (TCR) may be particularly important, as some subsets can react to trophoblast cells by producing cytokines, such as interleukin‐2 (IL‐2).

Canadian Association of Gastroenterology Clinical Practice Guidelines: The Use of Tumour Necrosis Factor-Alpha Antagonist Therapy in Crohn’s Disease

BACKGROUND Guidelines regarding the use of infliximab in Crohns disease were previously published by the Canadian Association of Gastroenterology in 2004. However, recent clinical findings and drug developments warrant a review and update of these guidelines. OBJECTIVE To review and update Canadian guidelines regarding the use of tumour necrosis factor-alpha antibody therapy in both luminal and fistulizing Crohns disease. METHODS A consensus group of 25 voting participants developed a series of recommendation statements that addressed pertinent clinical questions and gaps in existing knowledge. An iterative voting and feedback process was used in advance of the consensus meeting in conjunction with a systematic literature review to refine the voting statements. These statements were brought to a formal consensus meeting held in Montreal, Quebec (March 2008), wherein each statement underwent discussion, reformulation, voting and subsequent revision until group consensus was obtained (at least 80% agreement). OUTCOME The 47 voting statements addressed three themes: induction therapy, maintenance therapy and safety issues. As a result of the iterative process, 23 statements achieved consensus and were submitted for publication. CONCLUSION In the past five years, tumour necrosis factor-alpha antagonist therapy has become a cornerstone in the management of moderate-to-severe Crohns disease refractory to conventional treatment algorithms. The evidentiary base supporting the use of these drugs in Crohns disease is substantial and strengthened by results from longterm clinical and molecular studies. However, significant gaps in knowledge exist, particularly with regard to treatment failure. Confidence in the safety of these drugs is increasing, provided that therapy is administered in a clinical setting in which potential complications can be readily recognized and treated.

Canadian Association of Gastroenterology Clinical Practice Guidelines: the use of infliximab in Crohn's disease.

These guidelines are presented as a follow-up to the original Canadian Association of Gastroenterology Clinical Practice Guidelines: The use of infliximab in Crohns disease, published in the Canadian Journal of Gastroenterology (1). The original guidelines represented publications between 1998 and 2000. The current guidelines have been updated to reflect knowledge gained from two pivotal randomized clinical trails, with the use of infliximab in the maintenance of inflammatory Crohns disease in remission (2) and in the maintenance of fistulous Crohns disease in remission (3).

Inhalation Tolerance Is Induced Selectively in Thoracic Lymph Nodes but Executed Pervasively at Distant Mucosal and Nonmucosal Tissues

Under immunogenic conditions, both the site of initial Ag exposure and consequent T cell priming in specific draining lymph nodes (LNs) imprint the ensuing immune response with lasting tissue-selective tropism. With respect to immune tolerance, whether the site of tolerance induction leads to compartmentalized or, alternatively, pervasive tolerance has not been formally investigated. Using a murine model of inhalation tolerance, we investigated whether the induction of respiratory mucosal tolerance precludes the development of de novo Th2 sensitization upon subsequent exposure to the same Ag at distant mucosal (gut) and nonmucosal (cutaneous) sites. By tracking the proliferation of CFSE-labeled OVA-TCR transgenic CD4+ T cells upon OVA inhalation in vivo, we defined the site of tolerance induction to be restricted to the thoracic LNs. Expectedly, inhalation tolerance prevented de novo Th2 sensitization upon subsequent exposure to the same Ag at the same site. Importantly, although gut- and skin-draining LNs were not used during tolerance induction, de novo Ag-specific proliferation and Th2 differentiation in these LNs, as well as memory/effector Th2 responses in the gut (allergic diarrhea) and skin (late-phase cutaneous responses) were inhibited upon immunogenic challenge to the same Ag. Interestingly, this pervasive tolerogenic phenotype was not associated with the presence of suppressive activity throughout the lymphatics; indeed, potent suppressive activity was detected solely in the spleen. These data indicate that while inhalation tolerance is selectively induced in local thoracic LNs, its tolerogenic activity resides systemically and leads to pervasive immune tolerance in distant mucosal and nonmucosal sites.

Nerves and neuropeptides in the regulation of mucosal immunity

The subject of mucosal immunity continues to generate considerable interest. It is clear that the presentation of antigen to the nucosa, especially in the form of replicating virus or live attenuated organisms produces a local mucosal immune response. This response is better than if the antigens are presented in other-forms, and certainly better than if they are presented via other routes1–3 . Thus, the experiments performed some fifty years ago on immunization of volunteers against dysentery by oral immunization4 with Shigella organisms, which produced incomplete but definite protection amongst those vaccinate, clearly hold up.

13C urea breath test for (Helicobacter pylori): determination of the optimal cut-off point in a Canadian community population.

AIM To determine the test characteristics and the optimal cut-off point for the (13)C urea breath test ((13)C UBT) in a Canadian community laboratory setting. METHODS Of 2232 patients (mean age +/- SD: 51+/-21 years, 56% female) who completed a (13)C UBT, 1209 were tested to evaluate the primary diagnosis of (Helicobacter pylori) infection and 1023 were tested for confirmation of eradication following treatment. Cluster analysis was performed on the (13)C UBT data to determine the optimal cut-off point and the risk of false-positive and false-negative results. Additionally, 176 patients underwent endoscopic biopsy to allow validation of the sensitivity and specificity of the (13)C UBT against histology and microbiology using the calculated cut-off point. RESULTS The calculated cut-off points were 3.09 delta/1000 for the whole study population (n=2232), 3.09 delta/1000 for the diagnosis group (n=1209) and 2.88 delta/1000 for the post-treatment group (n=1023). When replacing the calculated cut-off points by a practical cut-off point of 3.0 delta/1000, the risk of false-positive and false-negative results was lower than 2.3%. The (13)C UBT showed 100% sensitivity and 98.5% specificity compared with histology and microbiology (n=176) for the diagnosis of active (H pylori) infection. CONCLUSIONS The (13)C UBT is an accurate, noninvasive test for the diagnosis of (H pylori) infection and for confirmation of cure after eradication therapy. The present study confirms the validity of a cut-off point of 3.0 delta/1000 for the (13)C UBT when used in a large Canadian community population according to a standard protocol.

Interaction of the Mucosal Immune and Peripheral Nervous Systems

This chapter discusses the interaction of the mucosal immune and peripheral nervous systems. The extensive microanatomical relationships between mast cells and nerves, especially the correlation between the density of these two cell types and the physiological evidence for communication between them, has led to search for growth factors that might sustain both mast cells and nerves. The multitude of different neurotransmitter substances potentially released in mucosal tissues could have a multiplicity of effects on the immune system. The circuitry could be complex, or, perhaps, the delivery of messages from one cell to another could be augmented by local concentration effects such as those seen at the site of release from nerve varicosities. Neuroendocrine complexes have also been described in the lamina propria in the vermiform appendix, and scattered, sparsely granulated neuroendocrine cells have been reported in the gastric mucosa. The complex cellular and molecular circuitry of the in vivo situation might overcome the events observed in vitro . Perhaps changes in vascular permeability and the expression of leukocyte adhesion molecules, which result in the migration of immune cells at a site of injury, may be of considerably more significance than activation of protein synthetic and proliferative pathways, at least in the acute phase.

The establishment of a national tissue bank for inflammatory bowel disease research in Canada.

The Crohns and Colitis Foundation of Canada (CCFC) has established a national bank for tissue, serum and blood from patients with inflammatory bowel disease (IBD). Investigators from across the country submit material to the bank together with clinical data. Investigators may access their own patient information from the bank for their own study purposes, but the distribution of tissue is restricted to specific CCFC-funded projects. Currently, tissues are being collected from newly diagnosed, untreated IBD patients to support a recent initiative aimed at characterizing microbes in colonic and ileal biopsies from such patients. In the future, criteria for the submission of tissue will be tailored to specific research questions. This bank is believed to be the first national bank of its kind dedicated to research in Crohns disease and ulcerative colitis

Immunomodulation of Helicobacter Infection

Helicobacter pylori leads to a chronic infection in humans that is associated with gastric inflammation and a vigorous immune response. Despite the humoral and cellular responses that can be detected in both human and animal models of helicobacter infection, the immune response fails to eliminate the organism. Eradication failure may be due to the niche in which H pylori confines itself, well away from direct contact with elements of the immune system. Alternatively, the general tendency of the intestinal immune response to down- regulate reactivity to noninvasive luminal bacteria also may contribute to the failure to eliminate helicobacter infection. Results of vaccine studies in mouse models indicate that modulating the helper T cell response from a T helper cell type 1 to a T helper cell type 2 response likely is required for the prevention and elimination of helicobacter infection. Understanding the mechanisms by which the immune response controls bacterial infections will allow for the design of novel strategies of immune modulation and the development of vaccines for both the treatment and prevention of H pylori.

Sa1234 RNA-Seq Derived Whole Blood Gene Expression Signature As a Biomarker for Differential Diagnosis and Intestinal Inflammation in Inflammatory Bowel Disease

Introduction: In the last two decades the therapeutic paradigm of Crohns disease (CD) has changed dramatically thanks to the use of biological drugs. In this scenario, we must consider the pivotal role of tumor necrosis factor-alpha (TNF-α), a pro-inflammatory cytokine, in the pathogenesis and relapse of CD. High levels of TNF-α have been associated with the development of intestinal inflammation in CD and blocking this cytokine with anti-TNF-α molecules may result in mucosal healing. In addition several studies have shown increased TNF-α levels in the serum and in the intestinal mucosa of patients with CD. However, little is known about the course of TNF-α levels and their relationship with disease recurrence in CD patients during maintenance treatment with Adalimumab. Aim: We assessed TNF-α levels in patients with CD who were in maintenance treatment with ADA and correlated them with clinical and endoscopic disease activity. Methods: In this prospective observational cohort study, performed at a single tertiary referral center, 23 [14M/9F; mean age 41 (range 21-66) infliximab-Naive patients with CD in maintenance treatment with ADA were included and followed-up. Blood samples were drawn at standardized time points (i.e. at 6, 12, 18, 24 months and in case of CD relapse) just before ADA injection. Antibodies against ADA (AAA) were measured using an homogenous mobility shift assay (HMSA; Prometheus Lab, San Diego, United States). Blood samples were considered positive for AAA presence if ≥1.7 U/mL. Disease activity was assessed at the same points by means of the Harvey-Bradshaw Index (HBI, remission 16). Moreover, endoscopic activity was assessed at baseline and at the time of relapse by means of CD endoscopic index (CDEIS 5 responder, CDEIS<3 complete endoscopic remission and mucosal healing). Results: We have data from 133 blood samples. AAA were observed in 26/133 (19.5%) samples, and 10/26 (38.5%) had a value of AAA ≥1.7 U/mL. TNF-α levels were present in all samples assessed (Mean 4.4, range 027.2). As shown in the figure, per-patient median TNF-α levels were strongly correlated with median HBI scores (r2=0.702, p<0.0001). Moreover, TNF levels were also correlated with CDEIS (r2=0.350, p=0.001). Conclusion: TNF-α levels strongly correlated with disease activity based on HBI and CDEIS indices in patients with CD in maintenance treatment with ADA. Indeed, moderate to severe patients often have high sustained TNF-α levels.