Lymphocyte homing and its role in the pathogenesis of IBD

Infant respiratory infections modulate lymphocyte homing to breast milk

Introduction

Chemokines and their receptors are essential for leukocyte migration to several tissues, including human milk. Here, we evaluated the homing of T and B lymphocyte subsets to breast milk in response to ongoing respiratory infections in the nursing infant.

Methods

Blood and mature milk were collected from healthy mothers of nurslings with respiratory infections (Group I) and from healthy mothers of healthy nurslings (Group C). Total lymphocyte, T and B cells, their subset numbers, and the expression of the homing receptors CCR5, CCR6, CCR10, and CXCR3 in these cells were evaluated in milk. Maternal serum and milk chemokine, cytokine, and IgA and IgG antibody levels were also quantified.

Results

All milk lymphocyte numbers were greater in Group I than in Group C. All CD4 T-cell subsets expressing CCR5, CCR6, and CXCR3 were higher in Group I. Within the CD8 T-cell subsets, only CCR6 and CXCR3 were higher in Group I, while CCR5 expression was higher in Group I exclusively for activated CD8 T cells. Group I showed greater numbers of all CCR6+ B-cell subsets and CXCR3+ naive B cells and plasma cells than did Group C. Infection of the nurslings promoted increased CCL20, CXCL10, IL-6, IL-8, total IgA, and IgG levels in the milk.

Conclusion

Respiratory infections in nursing infants stimulate an increase in cytokines and chemokines in breast milk, facilitating the recruitment and activation of lymphocytes. This process may promote immunological tolerance and help in the maturation of the infant's immune system, providing an additional strategy for passive maternal-infant protection.

Immune cell trafficking: a novel perspective on the gut-skin axis

Immune cell trafficking, an essential mechanism for maintaining immunological homeostasis and mounting effective responses to infections, operates under a stringent regulatory framework. Recent advances have shed light on the perturbation of cell migration patterns, highlighting how such disturbances can propagate inflammatory diseases from their origin to distal organs. This review collates and discusses current evidence that demonstrates atypical communication between the gut and skin, which are conventionally viewed as distinct immunological spheres, in the milieu of inflammation. We focus on the aberrant, reciprocal translocation of immune cells along the gut-skin axis as a pivotal factor linking intestinal and dermatological inflammatory conditions. Recognizing that the translation of these findings into clinical practices is nascent, we suggest that therapeutic strategies aimed at modulating the axis may offer substantial benefits in mitigating the widespread impact of inflammatory diseases.

Understanding the molecular mechanisms of anti-trafficking therapies and their clinical relevance in inflammatory bowel disease

In patients with inflammatory bowel disease (IBD), a combination of dysbiosis, increased intestinal permeability, and insufficient regulatory responses facilitate the development of chronic inflammation, which is driven by a complex interplay between the mucosal immune system and the environment and sustained by immune priming and ongoing cellular recruitment to the gut. The localization of immune cells is mediated by their expression of chemokine receptors and integrins, which bind to chemokines and adhesion molecules, respectively. In this article, we review the mechanisms of action of anti-trafficking therapies for IBD and consider clinical observations in the context of the different mechanisms of action. Furthermore, we discuss the evolution of molecular resistance to anti-cytokines, in which the composition of immune cells in the gut changes in response to treatment, and the potential implications of this for treatment sequencing. Lastly, we discuss the relevance of mechanism of action to combination therapy for IBD.

Performance of Machine Learning Algorithms for Predicting Disease Activity in Inflammatory Bowel Disease

This study aimed to explore the effectiveness of predicting disease activity in patients with inflammatory bowel disease (IBD), using machine learning (ML) models. A retrospective research was undertaken on IBD patients who were admitted into the First Affiliated Hospital of Wenzhou Medical University between September 2011 and September 2019. At first, data were randomly split into a 3:1 ratio of training to test set. The least absolute shrinkage and selection operator (LASSO) algorithm was applied to reduce the dimension of variables. These variables were used to generate seven ML algorithms, namely random forests (RFs), adaptive boosting (AdaBoost), K-nearest neighbors (KNNs), support vector machines (SVMs), naïve Bayes (NB), ridge regression, and eXtreme gradient boosting (XGBoost) to train to predict disease activity in IBD patients. SHapley Additive exPlanation (SHAP) analysis was performed to rank variable importance. A total of 876 participants with IBD, consisting of 275 ulcerative colitis (UC) and 601 Crohn's disease (CD), were retrospectively enrolled in the study. Thirty-three variables were obtained from the clinical characteristics and laboratory tests of the participants. Finally, after LASSO analysis, 11 and 5 variables were screened out to construct ML models for CD and UC, respectively. All seven ML models performed well in predicting disease activity in the CD and UC test sets. Among these ML models, SVM was more effective in predicting disease activity in the CD group, whose AUC reached 0.975, sensitivity 0.947, specificity 0.920, and accuracy 0.933. AdaBoost performed best for the UC group, with an AUC of 0.911, sensitivity 0.844, specificity 0.875, and accuracy 0.855. ML algorithms were available and capable of predicting disease activity in IBD patients. Based on clinical and laboratory variables, ML algorithms demonstrate great promise in guiding physicians' decision-making.

Transwell In Vitro Cell Migration and Invasion Assays

Cell migration and invasion have essential roles in both normal physiology and disease. As such, methodologies to assess cell migratory and invasive capacities are necessary to elucidate normal cell processes and underlying mechanisms of disease. Here, we describe commonly used transwell in vitro methods for the study of cell migration and invasion. The transwell migration assay involves the chemotaxis of cells through a porous membrane after the establishment of a chemoattractant gradient using two medium-filled compartments. The transwell invasion assay involves the addition of an extracellular matrix on top of the porous membrane which only permits chemotaxis of cells which possess invasive properties such as tumor cells.

Single-balloon Enteroscopy for Evaluation of Small Bowel Crohn Disease Strictures: Peripheral Blood Lymphocytes As a Risk Factor for Strictures

BACKGROUND

Few reports have focused on single-balloon enteroscopy (SBE) for evaluation of small bowel Crohn disease (CD) strictures. The aim of this study was to analyze the relationships between peripheral blood inflammatory markers and small bowel CD strictures observed by SBE.

MATERIALS AND METHODS

CD patients who underwent SBE between January 2016 and December 2020 were enrolled. The clinical characteristics and peripheral blood inflammatory markers were collected and analyzed to screen for predictive factors significantly associated with small bowel CD strictures.

RESULTS

A total of 221 CD patients underwent SBE. The lymphocyte (LC) counts in peripheral blood were significantly lower in the active group (n=178) than in the inactive group (n=43) according to the simple endoscopic score for CD (SES-CD), P =0.011, and was correlated with the SES-CD ( r =-0.134, P =0.047). The LC levels were significantly lower in the stricture group (n=116) than in the nonstricture group (n=105) based on whether small bowel strictures developed, P =0.000, and LC was a risk factor for strictures in the multivariate analysis [hazard ratio (HR), 2.332; 95% CI, 1.102-4.937; P =0.027]. In the subgroup analysis, LC levels notably decreased after stricture aggravation ( P =0.000). Forty-seven patients who underwent small bowel resection underwent SBE at 6 to 12 months after surgery. The LC level was significantly lower in the postoperative patients with strictures ( P =0.025), and LC (HR, 4.444; 95% CI, 1.265-15.617; P =0.020) was a risk of postoperative strictures by univariate analysis, but the age at diagnosis (HR, 6.462; 95% CI, 1.272-22.560; P =0.022) was an independent risk factor by multivariate analysis.

CONCLUSION

Peripheral blood LC levels were correlated with SES-CD and gradually decreased as the intestinal stricture increased in small bowel CD patients. The LC level was also significantly lower in the postoperative CD patients with strictures. The level of LC was a risk factor for small bowel strictures. These results suggest that peripheral blood LC could be a novel marker of small bowel CD strictures to guide CD diagnosis and therapy.

The Gut and Kidney Crosstalk in Immunoglobulin A Nephropathy

Immunoglobulin A nephropathy(IgAN) is the most common primary glomerulonephritis worldwide. The working model for the pathogenesis of IgAN involves a multistep process starting from the production of galactose-deficient and polymeric immunoglobulin A-1 (gd-IgA1) that enters systemic circulation from gut-associated lymphoid tissue (GALT). Galactose-deficient IgA are targeted by endogenous IgG, leading to the formation of circulating immune complexes that deposit in the mesangium and resulting in glomerular inflammation. Disease onset and relapses are often associated with gut infections, supporting the hypothesis that the gut plays an important pathogenic role. In the presence of microbial pathogens or food antigens, activated dendritic cells in the gut mucosa induce T cell dependent and independent B cell differentiation into IgA secreting plasma cells. In IgAN patients, this promotes the systemic release of mucosal gd-IgA1. Not all bacterial strains have the same capacity to elicit IgA production, and little is known about the antigen specificity of the pathogenic gd-IgA1. However, efficacy of treatments targeting gut inflammation support a pathogenic link between the bowel immune system and IgAN. Herein, we review the evidence supporting the role of gut inflammation in IgAN pathogenesis.

Retinoic Acid Signaling Is Compromised in DSS-Induced Dysbiosis

Obesity and malnutrition both cause dysbiosis and dampen retinoic acid (RA) signaling pathways, which play pivotal roles in biological processes. The current study evaluates a hypothesis that colitis-associated dysbiosis also has systemic negative impacts on RA signaling. Thus, we studied the effects of inflammation, under a vitamin A-sufficient condition, on RA signaling using mouse colitis models induced by dextran sulfate sodium. That data showed that intestinal inflammation resulted in reduced RA signaling in the liver, brain, gut, and adipose tissues measured by analyzing the expression of genes encoding for the synthesis, oxidation, transport, and receptor of RA. The expression of RA-regulated gut homing molecules including α4β7 integrin, and CCR9, along with MADCAM1 were all reduced in colitis mice revealing compromised immunity due to reduced RA signaling. The data also showed that the development of colitis was accompanied by dysbiosis featured with reduced Lactobacillaceae and Verrucomicrobiaceae but an expansion of Erysipelotrichaceae and others. Colitis resulted in reduced butyrate-producing bacteria and increased methane-generating bacteria. Additionally, dysbiosis was associated with induced Il-1β, Ifn-γ, and Tnf-α mRNA but reduced Il-22, Il-17f, and Rorγt transcripts in the colon. Together, intestinal inflammation inhibits RA signaling in multiple organs. RA is essential in regulating various biological processes, it is critical to detect RA signaling reduction in tissues even when vitamin A deficiency is absent. Moreover, probiotics can potentially prevent dysbiosis and reverse compromised RA signaling, having systemic health benefits.

Sphingosine 1-phosphate modulation and immune cell trafficking in inflammatory bowel disease

Immune cell trafficking is a critical element of the intestinal immune response, both in homeostasis and in pathological conditions associated with inflammatory bowel disease (IBD). This process involves adhesion molecules, chemoattractants and receptors expressed on immune cell surfaces, blood vessels and stromal intestinal tissue as well as signalling pathways, including those modulated by sphingosine 1-phosphate (S1P). The complex biological processes of leukocyte recruitment, activation, adhesion and migration have been targeted by various monoclonal antibodies (vedolizumab, etrolizumab, ontamalimab). Promising preclinical and clinical data with several oral S1P modulators suggest that inhibition of lymphocyte egress from the lymph nodes to the bloodstream might be a safe and efficacious alternative mechanism for reducing inflammation in immune-mediated disorders, including Crohn's disease and ulcerative colitis. Although various questions remain, including the potential positioning of S1P modulators in treatment algorithms and their long-term safety, this novel class of compounds holds great promise. This Review summarizes the critical mediators and mechanisms involved in immune cell trafficking in IBD and the available evidence for efficacy, safety and pharmacokinetics of S1P receptor modulators in IBD and other immune-mediated disorders. Further, it discusses potential future approaches to incorporate S1P modulators into the treatment of IBD.

CD45RA+CD62L- ILCs in human tissues represent a quiescent local reservoir for the generation of differentiated ILCs

Innate lymphoid cells (ILCs) are highly plastic and predominantly mucosal tissue-resident cells that contribute to both homeostasis and inflammation depending on the microenvironment. The discovery of naïve-like ILCs suggests an ILC differentiation process that is akin to naïve T cell differentiation. Delineating the mechanisms that underlie ILC differentiation in tissues is crucial for understanding ILC biology in health and disease. Here, we showed that tonsillar ILCs expressing CD45RA lacked proliferative activity, indicative of cellular quiescence. CD62L distinguished two subsets of CD45RA⁺ ILCs. CD45RA⁺CD62L⁺ ILCs (CD62L⁺ ILCs) resembled circulating naïve ILCs because they lacked the transcriptional, metabolic, epigenetic, and cytokine production signatures of differentiated ILCs. CD45RA⁺CD62L^- ILCs (CD62L^- ILCs) were epigenetically similar to CD62L⁺ ILCs but showed a transcriptional, metabolic, and cytokine production signature that was more akin to differentiated ILCs. CD62L⁺ and CD62L^- ILCs contained uni- and multipotent precursors of ILC1s/NK cells and ILC3s. Differentiation of CD62L⁺ and CD62L^- ILCs led to metabolic reprogramming including up-regulation of genes associated with glycolysis, which was needed for their effector functions after differentiation. CD62L^- ILCs with preferential differentiation capacity toward IL-22-producing ILC3s accumulated in the inflamed mucosa of patients with inflammatory bowel disease. These data suggested distinct differentiation potential of CD62L⁺ and CD62L^- ILCs between tissue microenvironments and identified that manipulation of these cells is a possible approach to restore tissue-immune homeostasis.

Rhein regulates redox-mediated Nlrp3 inflammasome activation in intestinal inflammation through macrophage-activated crosstalk

BACKGROUND AND PURPOSE

Macrophage infiltration and activation is a critical step during acute colitis. Redox-mediated Nlrp3 inflammasome activation in macrophages plays a critical role in mediating colonic inflammatory responses. Rhein isolated from the rhizome of rhubarb exhibits anti-inflammatory effects in various diseases. However, its role in regulating acute colonic inflammation is unexplored. This study was designed to investigate the protective mechanisms of rhein during acute gut inflammation and its regulation in macrophage activation.

EXPERIMENTAL APPROACH

The inhibitory effect of rhein on Nlrp3 inflammasome was evaluated in activated macrophages and colitic mice. The expressions of inflammatory mediators, inflammasome complex and redox-related signaling were analyzed by ELISA kits, western blots, immunofluorescence staining and qRT-PCR. Besides, the phenotype of macrophages was also assessed by flow cytometry. Colonic inflammation was evaluated by histological analysis.

KEY RESULTS

Rhein significantly decreased IL-1β secretion via Nlrp3 inflammasome by disturbing its complex assembly in macrophages. Rhein also activated Nrf2-HO1-NQO1 pathway, inhibited Nox2 subunits expression and translocation to regulate redox balance. Moreover, rhein attenuated inflammatory responses by mediating macrophage polarization from M1 to M2 phenotype. NF-κB, AP-1 and MAPK signalings were also involved in improving inflammatory conditions by rhein. In mice with acute intestinal inflammation, rhein treatment attenuated clinical features, reduced macrophage infiltration into the damaged lesions to alleviate colonic inflammation.

CONCLUSION AND IMPLICATIONS

Rhein regulated redox-mediated Nlrp3 inflammasome activation to protect against acute colitis, by interfering with macrophage accumulation and polarization. These findings provide a promising strategy of novel compounds for regulating mucosal inflammation in gastrointestinal disorders.

Morphologic Study on Lymphocyte Homing in Duck Tembusu Virus-Infected Duck Spleen

The present study was designed to analyze the histologic and cytologic changes of lymphocyte homing in noninfected and duck Tembusu virus (DTMUV)-infected duck spleens. At first, we investigated the noninfected structure that facilitates lymphocyte homing. Under light and electron microscopy, results showed that sheath capillaries were located in the white pulp of the spleen, and the endothelial cells of sheath capillaries were cuboidal in shape, which is a typical characteristic of high endothelial venules. To monitor the lymphocyte homing, 5,6-carboxy fluoresceindiacetate succinimidyl ester (CFSE)-labeled lymphocytes that were intravenously injected into noninfected ducks appeared in the periellipsoidal sheaths (PELS), which proved that lymphocytes can return to the spleen through sheath capillaries. Furthermore, proteoglycans (PGs) associated with homing factors were positively observed in sheath capillaries and PELS by colloidal iron staining. This suggests that PGs are associated with lymphocyte homing. The results of the DTMUV infection experiment showed that PELS appeared vacuolized at 3 dpi. The spleen tissue gradually recovered at 5 and 7 dpi. In addition, the lymphocytes increased around sheath capillaries, and the expression of PGs in sheath capillaries increased after virus infection. Meanwhile, the gaps between endothelial cells were enlarged, and the lymphocytes were mainly in the lumen and basement membrane. In conclusion, lymphocytes could recruit into the spleen through sheath capillaries, and PGs participated and promoted the lymphocyte homing, suggesting that the unique high endothelial capillaries favor lymphocyte homing, which promotes tissue repair and antigen clearance in the duck.

Identification of Chemical Compounds from Artemisia gmelinii using UPLC-QTOF-MS/MS and their Regulatory Effects on Immune Responses in DSS-Induced Colitis Mice

Artemisia gmelinii Web. ex Stechm. (AG), a popular medicinal herb in Asia, has been used as a common food ingredient in Korea and is traditionally known for its anti-inflammatory properties. Therefore, in this study, we aimed to investigate whether AG relieves IBD, a classic chronic inflammatory disease of the gastrointestinal tract. We identified 35 chemical compounds in AG ethanol extract using ultra-high-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry. In mice with DSS-induced IBD, AG administration attenuated the disease activity index and the serum and colonic levels of inflammatory cytokines and chemokines. AG treatment decreased nuclear factor-[Formula: see text]B (NF-[Formula: see text]B) signaling, a key mediator of inflammation, in the mouse colons. Additionally, AG extract enhanced immune responses in lymphoid tissues such as spleen and Peyer's patches. Thus, AG consumption potently ameliorated IBD symptoms and improved immune signaling in lymphoid tissues.

Distinct integrin activation pathways for effector and regulatory T cell trafficking and function

Integrin activation mediates lymphocyte trafficking and immune functions. Conventional T cell (Tconv cell) integrin activation requires Rap1-interacting adaptor molecule (RIAM). Here, we report that Apbb1ip-/- (RIAM-null) mice are protected from spontaneous colitis due to IL-10 deficiency, a model of inflammatory bowel disease (IBD). Protection is ascribable to reduced accumulation and homing of Tconv cells in gut-associated lymphoid tissue (GALT). Surprisingly, there are abundant RIAM-null regulatory T cells (T reg cells) in the GALT. RIAM-null T reg cells exhibit normal homing to GALT and lymph nodes due to preserved activation of integrins αLβ2, α4β1, and α4β7. Similar to Tconv cells, T reg cell integrin activation and immune function require Rap1; however, lamellipodin (Raph1), a RIAM paralogue, compensates for RIAM deficiency. Thus, in contrast to Tconv cells, RIAM is dispensable for T reg cell integrin activation and suppressive function. In consequence, inhibition of RIAM can inhibit spontaneous Tconv cell-mediated autoimmune colitis while preserving T reg cell trafficking and function.

Dextran sulfate sodium mouse model of inflammatory bowel disease evaluated for systemic genotoxicity via blood micronucleus and Pig-a gene mutation assays

Inflammatory bowel disease (IBD) is an important risk factor for gastrointestinal cancers. Inflammation and other carcinogenesis-related effects at distal, tissue-specific sites require further study. In order to better understand if systemic genotoxicity is associated with IBD, we exposed mice to dextran sulfate sodium salt (DSS) and measured the incidence of micronucleated cells (MN) and Pig-a mutant phenotype cells in blood erythrocyte populations. In one study, 8-week-old male CD-1 mice were exposed to 0, 1, 2, 3 or 4% w/v DSS in drinking water. The 4-week in-life period was divided into four 1-week intervals-alternately on then off DSS treatment. Low volume blood samples were collected for MN analysis at the end of each week, and cardiac blood samples were collected at the end of the 4-week period for Pig-a analyses. The two highest doses of DSS were observed to induce significant increases in reticulocyte frequencies. Even so, no statistically significant treatment-related effects on the genotoxicity biomarkers were evident. While one high-dose mouse showed modestly elevated MN frequencies during the DSS treatment cycles, it also exhibited exceptionally high reticulocyte frequencies (e.g. 18.7% at the end of the second DSS cycle). In a second study, mice were treated with 0 or 4% DSS for 9-18 consecutive days. Exposure was continued until rectal bleeding or morbidity was evident, at which point the treatment was terminated and blood was collected for MN analysis. The Pig-a assay was conducted on samples collected 29 days after the start of treatment. The initial blood specimens showed highly elevated reticulocyte frequencies in DSS-exposed mice (mean ± SEM = 1.75 ± 0.10% vs. 13.04 ± 3.66% for 0 vs. 4% mice, respectively). Statistical analyses showed no treatment-related effect on MN or Pig-a mutant frequencies. Even so, the incidence of MN versus reticulocytes in the DSS-exposed mice were positively correlated (linear fit R2 = 0.657, P = 0.0044). Collectively, these results suggest that in the case of the DSS CD-1 mouse model, systemic effects include stress erythropoiesis but not remarkable genotoxicity. To the extent MN may have been slightly elevated in a minority of individual mice, these effects appear to be secondary, likely attributable to stimulated erythropoiesis.

Food Effect on a Single High Dose of Carotegrast Methyl, an Oral Antagonist of α4-Integrin, in Healthy Male Subjects: A Randomised, Placebo-Controlled, Double-Blind Study

Background and Objectives

Carotegrast methyl, a novel prodrug, oral antagonist of α4-integrin, is in development for the treatment of active ulcerative colitis. This randomised, placebo-controlled, double-blind, crossover study evaluated the effect of food on the pharmacokinetics and pharmacodynamics as well as the safety profile after a single dose of carotegrast methyl in healthy male subjects.

Methods

Subjects were randomised to receive a single dose of carotegrast methyl (240, 480 or 960 mg) or placebo in a 6:2 ratio and received the study drug under both fed and fasted conditions separated by an 8-day washout. The pharmacokinetic profiles of carotegrast methyl and its active metabolite, carotegrast, were assessed. The pharmacodynamic profile was evaluated according to a change in the peripheral lymphocyte count. Safety was monitored throughout.

Results

Based on the area under the time curve from zero to the time of the last quantifiable concentration (AUC_last), food reduced systemic exposure to both carotegrast methyl and carotegrast by 21–57% and 5–29%, respectively. The fed-to-fasted ratio of least square means for the increase in the lymphocyte count was almost at unity in each dose, indicating no food effect on pharmacodynamics. The time  ≥ 90% of maximum effect was prolonged dose dependently, suggesting that a 960 mg-dose can provide a long-lasting effect. Reported adverse events were all mild.

Conclusions

Despite the reduced systemic exposure to both carotegrast methyl and carotegrast, food had no effect on the increase in lymphocyte count. A single administration of carotegrast methyl up to 960 mg was found to be safe.

Electronic supplementary material

The online version of this article (10.1007/s40261-019-00879-1) contains supplementary material, which is available to authorized users.

β7 Integrin Inhibition Can Increase Intestinal Inflammation by Impairing Homing of CD25hiFoxP3+ Regulatory T Cells

BACKGROUND & AIMS

Integrin α4β7 mediates lymphocyte trafficking to the gut and gut-associated lymphoid tissues, a process critical for recruitment of effector lymphocytes from the circulation to the gut mucosa in inflammatory bowel disease (IBD) and murine models of intestinal inflammation. Antibody blockade of β7 integrins generally is efficacious in IBD; however, some patients fail to respond, and a few patients can experience exacerbations. This study examined the effects of loss of β7 integrin function in murine models of IBD.

METHODS

In a mouse IBD model caused by lack of interleukin 10, a cytokine important in CD25hiFoxP3+ regulatory T cell (Treg) function, genetic deletion of β7 integrin or antibody blockade of α4β7-mucosal addressin cell adhesion molecule-1 interaction paradoxically exacerbated colitis.

RESULTS

Loss of β7 impaired the capacity of Tregs homing to the gut and therefore suppress intestinal inflammation in an adoptive T-cell transfer model; however, the intrinsic suppressive function of β7-deficient Tregs remained intact, indicating that the β7 deficiency selectively impacts gut homing. Deletion of β7 integrin did not worsen colitis in an acute dextran sodium sulfate model in which Treg number and function were normal.

CONCLUSIONS

In Integrin subunit beta (Itgb)7-/-Il10-/- mice, loss of β7-dependent Treg homing to gut-associated lymphoid tissues combined with loss of intrinsic Treg function exacerbated intestinal inflammation. These results suggest that IBD patients with reduced CD25hiFoxP3+ Treg numbers or function or lack of interleukin 10 could be at risk for failure of α4β7 blocking therapy.

Chemokines and Chemokine Receptors as Therapeutic Targets in Inflammatory Bowel Disease; Pitfalls and Promise

The principal targets for anti-chemokine therapy in inflammatory bowel disease (IBD) have been the receptors CCR9 and CXCR3 and their respective ligands CCL25 and CXCL10. More recently CCR6 and its ligand CCL20 have also received attention, the expression of the latter in enterocytes being manipulated through Smad7 signalling. These pathways, selected based on their fundamental role in regulating mucosal immunity, have led to the development of several therapeutic candidates that have been tested in early phase clinical trials with variable clinical efficacy. In this article, we appraise the status of chemokine-directed therapy in IBD, review recent developments, and nominate future areas for therapeutic focus.

Transmission of integrin β7 transmembrane domain topology enables gut lymphoid tissue development

Sun et al. establish the importance of transmission of changes in β-integrin transmembrane domain (TMD) topology in physiological integrin affinity modulation and biological function. Introduction of a flexible kink in the β7 integrin TMD blocks talin-mediated agonist-induced α4β7 integrin activation and function in gut lymphoid tissue development.

Integrin activation regulates adhesion, extracellular matrix assembly, and cell migration, thereby playing an indispensable role in development and in many pathological processes. A proline mutation in the central integrin β3 transmembrane domain (TMD) creates a flexible kink that uncouples the topology of the inner half of the TMD from the outer half. In this study, using leukocyte integrin α4β7, which enables development of gut-associated lymphoid tissue (GALT), we examined the biological effect of such a proline mutation and report that it impairs agonist-induced talin-mediated activation of integrin α4β7, thereby inhibiting rolling lymphocyte arrest, a key step in transmigration. Furthermore, the α4β7(L721P) mutation blocks lymphocyte homing to and development of the GALT. These studies show that impairing the ability of an integrin β TMD to transmit talin-induced TMD topology inhibits agonist-induced physiological integrin activation and biological function in development.

Effect of PF-00547659 on Central Nervous System Immune Surveillance and Circulating β7+ T Cells in Crohn's Disease: Report of the TOSCA Study

BACKGROUND AND AIMS

Progressive multifocal leukoencephalopathy [PML], a brain infection associated with anti-integrin drugs that inhibit lymphocyte translocation from bloodstream to tissue, can be fatal. Decreased central nervous system [CNS] immune surveillance leading to this infection has been reported in patients with multiple sclerosis or Crohn's disease treated with anti-integrin antibody natalizumab. PF-00547659 is an investigational human monoclonal antibody for inflammatory bowel disease, targeted against α4β7-mucosal addressin cell-adhesion molecule-1 [the integrin ligand selectively expressed in the gut]. We hypothesised that this selective agent would not affect central nervous system immune surveillance.

METHODS

Cerebrospinal fluid from five healthy volunteers, and from 10 patients with Crohn's disease previously treated with immunosuppressants, was evaluated to assess the feasibility of the study. Subsequently, 39 patients with active Crohn's disease and previous immunosuppression were evaluated over 12 weeks of PF-00547659-induction therapy. We measured total lymphocytes, T cell subsets in cerebrospinal fluid, and circulating β7+ memory cells. Disease activity was assessed using the Harvey-Bradshaw Index.

RESULTS

Patients treated with PF-00547659 had no reduction of cerebrospinal fluid lymphocytes, T-lymphocyte subsets, or CD4:CD8 ratio, whereas circulating β7+ memory cells increased significantly. A total of 28/35 [80%] patients had a clinical response and 27/34 [79%] had disease remission. Treatment-related adverse events, none serious, were reported in 23/49 [47%] patients.

CONCLUSIONS

In patients with active Crohn's disease, natalizumab therapy increases the risk for PML, and the increased risk is thought to be associated with iatrogenic leukopenia within the CNS. PML under PF-00547659 may be a lesser concern, as this agent did not reduce lymphocytes or T cell subsets in the cerebrospinal fluid.

Intestinal mononuclear cells primed by systemic interleukin-12 display long-term ability to aggravate colitis in mice

To address whether the burst of systemic interleukin-12 (IL-12) influences intestinal inflammation elicited by luminal stimuli, we induced IL-12 release by cDNA injection in C57BL/6 mice and simultaneously started dextran sulphate sodium administration. The sequence of the inflammatory response triggered by IL-12 release was characterized by assessing myeloperoxidase activity and histological damage in colon samples on days 1, 3, 5 and 7 after colitis induction. To evaluate the persistence of IL-12 priming, colitis was induced in mice 7 or 60 days after cDNA injection. Under IL-12 influence, the development of acute colitis presented a faster and selective infiltration of inflammatory mononuclear cells in the lamina propria. Recruitment was driven by systemic cytokines rather than luminal antigens. Interestingly, when colitis was triggered 7 or 60 days after the cytokine storm, cells maintained the ability to worsen clinical signs of intestinal inflammation. Together, a systemic IL-12 burst effectively primed intestinal cells that became more prone to develop inflammatory responses. Activation was long-lasting because intestinal cells maintained their inflammatory potential and their ability to aggravate colitis.

Gut Mesenchymal Stromal Cells in Immunity

Mesenchymal stromal cells (MSCs), first found in bone marrow (BM), are the structural architects of all organs, participating in most biological functions. MSCs possess tissue-specific signatures that allow their discrimination according to their origin and location. Among their multiple functions, MSCs closely interact with immune cells, orchestrating their activity to maintain overall homeostasis. The phenotype of tissue MSCs residing in the bowel overlaps with myofibroblasts, lining the bottom walls of intestinal crypts (pericryptal) or interspersed within intestinal submucosa (intercryptal). In Crohn's disease, intestinal MSCs are tightly stacked in a chronic inflammatory milieu, which causes their enforced expression of Class II major histocompatibility complex (MHC). The absence of Class II MHC is a hallmark for immune-modulator and tolerogenic properties of normal MSCs and, vice versa, the expression of HLA-DR is peculiar to antigen presenting cells, that is, immune-activator cells. Interferon gamma (IFNγ) is responsible for induction of Class II MHC expression on intestinal MSCs. The reversal of myofibroblasts/MSCs from an immune-modulator to an activator phenotype in Crohn's disease results in the formation of a fibrotic tube subverting the intestinal structure. Epithelial metaplastic areas in this context can progress to dysplasia and cancer.

Difference in clinical presentation, immunology profile and treatment response of type 1 autoimmune hepatitis between United Kingdom and Singapore patients

Background

Autoimmune hepatitis (AIH) is an immune-mediated liver disease of unknown etiology. Increasing incidence of AIH in Asian patients has been reported. However, the phenotypic difference of Asian patients in Europe and Asia has still not been explored.

Aim

To evaluate the clinical presentation, biochemical and immunological profiles, treatment response and survival outcome of type 1 AIH from two tertiary liver transplant centres (United Kingdom and Singapore).

Method

Patients who fulfilled the simplified diagnostic scoring criteria of AIH were included in the study. Patients with overlap syndrome were excluded.

Results

Totals of 40 Asian patients and 159 Caucasian patients from the University Hospital of Birmingham National Health Service Foundation Trust, UK, were compared with 57 Asian patients from Singapore General Hospital, Singapore. Asian patients from Singapore present significantly much later (median 55 vs. 32 years, p < 0.001), had higher MELD (p < 0.001) with lower albumin (p < 0.001) and higher bilirubin (p < 0.001) and lower ASMA positivity (p < 0.001) at diagnosis compared to UK Asian. Jaundice at presentation was much higher in Singapore Asian patients compared to UK Asian (53 vs. 30 %) but cirrhosis at diagnosis was more common in UK patients. Associated autoimmune conditions were less commonly seen in Singapore Asians. Comparing between UK cohorts, Asian patients present at younger age and have higher IgG level compared to Caucasian. Overall, 5-year transplant-free survival in all three cohorts was similar (p = 0.846).

Conclusion

We demonstrate that AIH patients from Singapore present at older age with jaundice and have a low positivity of SMA. Despite these differences, transplant-free survival is similar in the two groups.

Safety and Efficacy of AJM300, an Oral Antagonist of α4 Integrin, in Induction Therapy for Patients With Active Ulcerative Colitis

BACKGROUND & AIMS

AJM300 is an orally active small-molecule antagonist of the α4 integrin subunit. We performed a randomized trial to investigate the efficacy and safety of AJM300 in patients with active ulcerative colitis (UC).

METHODS

In a double-blind, placebo-controlled, phase 2a study, 102 patients with moderately active UC (Mayo Clinic scores of 6-10, endoscopic subscores ≥2, and rectal bleeding subscores ≥1) who had inadequate response or intolerance to mesalamine or corticosteroids were randomly assigned to receive AJM300 (960 mg) or placebo 3 times daily for 8 weeks. The primary end point was a clinical response at week 8, defined as a decrease in Mayo Clinic score of at least 3 points and a decrease of at least 30% from baseline, with a decrease in the rectal bleeding subscore of at least 1 point or an absolute rectal bleeding subscore of 0 or 1.

RESULTS

Clinical response rates were 62.7% and 25.5% at week 8 in the AJM300 group and placebo group, respectively (odds ratio [OR] = 5.35; 95% confidence interval [CI]: 2.23-12.82; P = .0002). Rates of clinical remission (Mayo Clinic score ≤2 and no subscore >1) were 23.5% and 3.9% in the AJM300 group and placebo groups, respectively (OR = 7.81; 95% CI: 1.64-37.24; P = .0099), and rates of mucosal healing (endoscopic subscores of 0 or 1) were 58.8% and 29.4% (OR = 4.65; 95% CI: 1.81-11.90; P = .0014). No serious adverse event, including progressive multifocal leukoencephalopathy, was observed, although more investigations are needed to confirm the safety profile of this drug.

CONCLUSIONS

AJM300 was well tolerated and more effective than placebo in inducing clinical response, clinical remission, and mucosal healing in patients with moderately active UC. ClinicalTrials.jp no: JapicCTI-132293.

Mechanisms of tissue injury in autoimmune liver diseases

Autoimmune diseases affecting the liver are mainly represented by autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC). The characteristic morphologic patterns of injury are a chronic hepatitis pattern of damage in AIH, destruction of small intrahepatic bile ducts in PBC and periductal fibrosis and inflammation involving larger bile ducts in PSC. The factors responsible for initiation and perpetuation of the injury in all the three autoimmune liver diseases are not understood completely but are likely to be environmental triggers on the background of genetic variation in immune regulation. In this review, we summarise the current understanding of the mechanisms underlying the breakdown of self-tolerance in autoimmune liver diseases.

Intestinal wall thickness detected by multidetector spiral computed tomography enterography predicts the disease severity of Crohn's disease

OBJECTIVE

Multidetector spiral computed tomography enterography (MSCTE) and ileocolonoscopy are used in evaluating inflammatory situation of Crohn's disease (CD) patients. The purpose of this study was to determine the disease severity of CD patients by combining the intestinal wall thickness by MSCTE with ileocolonoscopy.

MATERIAL AND METHODS

This retrospective study included 50 patients with terminal ileal CD. Diagnosis was confirmed based on clinical features, endoscopy, and pathology. Patients underwent both MSCTE and ileocolonoscopy. Ileal wall thickness was measured and the disease severity was evaluated by CD activity index (CDAI). Intestinal mucosal lesions were scored by the simple endoscopic score for CD (SES-CD).

RESULTS

Of the 50 patients with active terminal ileal CD, the comparison of scores between SES-CD and CDAI showed significant association with Spearman's rank correlation coefficient (p < 0.01). There were statistically significant correlation between the wall thickness and the SES-CD (p < 0.0001) as well as CDAI (p < 0.001), respectively, but no significant correlation between the wall thickness and the C-reactive protein (CRP) was found (p = 0.43). Moreover, we found that the wall thickness was preferential to predict the disease severity in the terminal ileal CD.

CONCLUSION

MSCTE, in combination with ileocolonoscopy, is reliable to identify disease severity in CD patients and provides more accurate information in the diagnosis and treatment.

Insights from immunology: new targets for new drugs?

Rapid advances in our understanding of inflammatory bowel diseases have resulted from the synthesis of data from experimental and genetic studies. These have suggested a wide range of potential immunological targets with both local and systemic scope. Drugs to several of these targets have now reached phase I/II studies, and are discussed in the context of their scientific rationale. However, despite the advent of new classes of therapeutics targeting cellular trafficking and intracellular mediators of cytokine signalling, the armamentarium of effective therapeutics remains sparse. Only with more detailed experimental medicine studies will this imbalance be resolved.

Decrease of peripheral and intestinal NKG2A-positive T cells in patients with ulcerative colitis

To investigate the role of inhibitory natural killer receptors (iNKRs) in inflammatory bowel disease (IBD), we analyzed the expression of NKG2A, one of the iNKRs, on T cells in a mouse colitis model and human IBD. During the active phase of dextran sulfate sodium (DSS)-induced mouse colitis, the frequency of NKG2A+ T cells was significantly decreased in the peripheral blood, and increased in the intestine, suggesting the mobilization of this T cell subset to the sites of inflammation. Administration of anti-NKG2A antibody increased the number of inflammatory foci in DSS-induced colitis, suggesting the involvement of NKG2A+ T cells in this colitis model. In ulcerative colitis (UC) patients, the frequency of peripheral blood NKG2A+ T cells was significantly decreased, compared with Crohn's disease (CD) patients and healthy controls, regardless of clinical conditions such as treatment modalities and disease activity. Notably, in sharp contrast to the DSS-induced mouse colitis model, the frequency of NKG2A+ cells among intestinal T cells was also decreased in UC patients. These results suggest that inadequate local infiltration of NKG2A+ T cells may be involved in the pathogenesis of UC.

Identity and ranking of colonic mesenchymal stromal cells

Although ongoing clinical trials utilize systemic administration of bone-marrow mesenchymal stromal cells (BM-MSCs) in Crohn's disease (CD), nothing is known about the presence and the function of mesenchymal stromal cells (MSCs) in the normal human bowel. MSCs are bone marrow (BM) multipotent cells supporting hematopoiesis with the potential to differentiate into multiple skeletal phenotypes. A recently identified new marker, CD146, allowing to prospectively isolate MSCs from BM, renders also possible their identification in different tissues. In order to elucidate the presence and functional role of MSCs in human bowel we analyzed normal adult colon sections and isolated MSCs from them. In colon (C) sections, resident MSCs form a net enveloping crypts in lamina propria, coinciding with structural myofibroblasts or interstitial stromal cells. Nine sub-clonal CD146(+) MSC lines were derived and characterized from colon biopsies, in addition to MSC lines from five other human tissues. In spite of a phenotype qualitative identity between the BM- and C-MSC populations, they were discriminated and categorized. Similarities between C-MSC and BM-MSCs are represented by: Osteogenic differentiation, hematopoietic supporting activity, immune-modulation, and surface-antigen qualitative expression. The differences between these populations are: C-MSCs mean intensity expression is lower for CD13, CD29, and CD49c surface-antigens, proliferative rate faster, life-span shorter, chondrogenic differentiation rare, and adipogenic differentiation completely blocked. Briefly, BM-MSCs, deserve the rank of progenitors, whereas C-MSCs belong to the restricted precursor hierarchy. The presence and functional role of MSCs in human colon provide a rationale for BM-MSC replacement therapy in CD, where resident bowel MSCs might be exhausted or diverted from their physiological functions.

Immunotherapy in inflammatory bowel disease

Inflammatory bowel disease affects an increasing number of patients worldwide and is associated with significant morbidity. The dysregulation of the immune system with increased expression of proinflammatory cytokines and increased mucosal expression of vascular adhesion molecules play an important role in its pathogenesis. Strategies targeting TNF-alpha and alpha4-integrin have led to the development of novel therapies for treatment of patients with IBD. This article discusses the efficacy of immunologic agents currently approved for treating Crohn disease and ulcerative colitis and reviews the risks and challenges associated with their use.

Risk factors for inflammatory bowel diseases according to the "hygiene hypothesis": a case-control, multi-centre, prospective study in Southern Italy

BACKGROUND

Ulcerative colitis (UC) and Crohn's disease (CD) are inflammatory bowel diseases (IBD) of unknown aetiology. The 'hygiene hypothesis' (HH) suggests that several hygiene-related factors may have contributed to the increased incidence of IBD. The aim of the study was to evaluate risk factors for IBD related to HH in a cohort of IBD patients from the south of Italy.

METHODS

We prospectively performed a one-year, questionnaire-based, case-control, multi-centre study focusing on the principal risk factors for IBD according to HH. We investigated the main surrogate markers of HH (helmintic infections and antibiotics in childhood; breastfeeding; family size/sibship;urban upbringing; personal and domestic hygiene in childhood) in UC and CD patients, in comparison with a control group of healthy subjects. In addition, the traditional risk factors for IBD were also recorded.

RESULTS

The study population included 527 cases of UC, 468 CD and 562 controls. None of the surrogate risk factors of HH was significantly associated with IBD. On the contrary, the traditional risk factors confirmed their statistical significance in this IBD population. Familial aggregation: OR 4.07 for UC; OR 4.83 for CD; smoking: OR 0.38 for UC; OR 1.40 for CD; appendectomy: OR 0.28 for UC; OR 1.61 for CD.

CONCLUSION

Even though risk factors associated to the HH have been proposed as a possible explanation for the increasing calendar trend of IBD incidence, their role does not appear to be statistically significant. Familial aggregation, smoking habits and appendectomy still remain the main risk factors associated with IBD.

The anti-TNF-α antibody infliximab indirectly regulates PECAM-1 gene expression in two models of in vitro blood cell activation

Chronic inflammatory bowel diseases can be successfully treated with antibodies against the acute phase mediator TNF-α. The process of activation and of extravasation of inflammatory cells from the blood into the 'stressed' tissue site is controlled by cytokines and chemokines, which attract leukocytes and by adhesion molecules, which mediate their attachment and transmigration toward the affected cell(s). The changes in the gene expression of adhesion molecules taking place in those cells before attachment have been less investigated. Changes of PECAM-1, ICAM-1 and vascular cell adhesion molecule-1 (VCAM-1) gene expression were studied in phytohaemagglutinin (PHA)- and lipolysaccharide (LPS)-treated human peripheral blood leukocytes (PBLs), granulocytes and the human monocyte cell line U-937. Cells were treated either with PHA or with LPS in the presence or absence of infliximab and incubated with TNF-α, IFN-γ and/or transforming growth factor beta (TGF-β) and treated as above. Activation of PBLs by PHA or LPS treatment triggered a sharp upregulation of ICAM-1, VCAM-1 gene expression and a time-dependent downregulation of PECAM-1 gene expression reaching a minimum 4 h from start of the experiment. The anti-TNF-α antibody infliximab, by neutralizing TNF-α and IFN-γ production, completely reversed PECAM-1 mRNA downregulation and ICAM-1 and VCAM-1 upregulation. Immunostaining of PBLs cytospins with antibodies against PECAM-1 and ICAM-1 confirmed RT-PCR and western blot results. PBLs IFN-γ or TNF-α treatment downregulated PECAM-1 in parallel with the upregulation of ICAM-1 and VCAM-1 gene expression, whereas TGF-β upregulated PECAM-1- and downregulated ICAM-1 and VCAM-1 gene expression counteracting the effect of TNF-α or IFN-γ. Similar results were obtained in human U937 cells and in granulocyte cultures by TNF-α or IFN-γ treatment. Taken together, these results suggest that infliximab, blocking TNF-α and IFN-γ production, exerts its anti-inflammatory effect through inhibiting downregulation of PECAM-1 gene expression and upregulation of ICAM-1 and VCAM-1 expression in leukocytes of the peripheral blood. These results also suggest that TGF-β may thus be of therapeutic importance as an anti-inflammatory agent.

B lymphocyte intestinal homing in inflammatory bowel disease

BACKGROUND

Inflammatory bowel disease (IBD) is thought to be due to an abnormal interaction between the host immune system and commensal microflora. Within the intestinal immune system, B cells produce physiologically natural antibodies but pathologically atypical anti-neutrophil antibodies (xANCAs) are frequently observed in patients with IBD. The objective is to investigate the localisation of immunoglobulin-producing cells (IPCs) in samples of inflamed intestinal tissue taken from patients with IBD, and their possible relationship with clinical features.

METHODS

The IPCs in small intestinal, colonic and rectal biopsy specimens of patients with IBD were analysed by means of immunofluorescence using polyclonal rabbit anti-human Ig and goat anti-human IgM. The B cell phenotype of the IPC-positive samples was assessed using monoclonal antibodies specific for CD79, CD20, CD23, CD21, CD5, λ and κ chains. Statistical correlations were sought between the histological findings and clinical expression.

RESULTS

The study involved 96 patients (64 with ulcerative colitis and 32 with Crohn's disease). Two different patterns of B lymphocyte infiltrates were found in the intestinal tissue: one was characterised by a strong to moderate stromal localisation of small IgM+/CD79+/CD20-/CD21-/CD23-/CD5± IPCs (42.7% of cases); in the other (57.3%) no such small IPCs were detected in stromal or epithelial tissues. IPCs were significantly less frequent in the patients with Crohn's disease than in those with ulcerative colitis (p = 0.004).

CONCLUSION

Our findings suggest that different immunopathogenetic pathways underlie chronic intestinal inflammation with different clinical expressions. The presence of small B lymphocytes resembling B-1 cells also seemed to be negatively associated with Crohn's disease. It can therefore be inferred that the gut contains an alternative population of B cells that have a regulatory function.

Gut-tropic T cells that express integrin α4β7 and CCR9 are required for induction of oral immune tolerance in mice

BACKGROUND & AIMS

Induction of oral immune tolerance (OT) blocks proinflammatory responses to orally administered antigens and might be used to treat autoimmune conditions. We investigated whether gut-tropic T cells that express the integrin α4β7 and the chemokine receptor CCR9 are required for OT.

METHODS

Skin delayed-type hypersensitivity and experimental autoimmune encephalomyelitis were used to monitor OT in mice. To assess the role of receptors that mediate localization of lymphocytes to the gut (gut-homing receptors) in induction of OT, we studied CCR9(-/-) and β7(-/-) mice and also blocked the α4β7 ligand MAdCAM-1 in wild-type mice. We used DEREG and Scurfy mice to assess the role of Foxp3(+) regulatory T cells (Treg) and IL-10(-/-) and IL-10Rβ(-/-) mice to examine the role of interleukin (IL)-10 in induction of OT.

RESULTS

OT could not be induced in CCR9(-/-) or β7(-/-) mice, or when MAdCAM-1 was blocked in wild-type mice, indicating that gut-homing receptors are required for oral tolerization. Consistent with the role of all-trans retinoic acid in inducing gut-homing T cells, OT could not be induced in mice depleted of vitamin A. OT was rescued in CCR9(-/-) mice following adoptive transfer of wild-type T cells, but not CCR9(-/-) or β7(-/-) T cells. Gut-homing T cells are therefore necessary and sufficient to induce OT. Wild-type Treg and IL-10 were required to restore OT to CCR9(-/-) mice, indicating that homing and functional differentiation of IL-10-producing Treg in the gut is required for OT. Conversely, transfer of CCR9(-/-) or β7(-/-) T cells to wild-type mice partially inhibited OT.

CONCLUSIONS

Expression of CCR9 and α4β7 on T cells and their subsequent localization to the gut is required for induction of OT in mice. Therapies designed to block gut-homing receptors might, under some conditions, interfere with normal tolerogenic mechanisms in the intestinal mucosa.

Mucosal gene expression of cell adhesion molecules, chemokines, and chemokine receptors in patients with inflammatory bowel disease before and after infliximab treatment

OBJECTIVES

Inflammatory bowel disease (IBD) is characterized by a continuous influx of leukocytes into the gut wall. This migration is regulated by cell adhesion molecules (CAMs), and selective antimigration therapies have been developed. This study investigated the effect of infliximab therapy on the mucosal gene expression of CAMs in IBD.

METHODS

Mucosal gene expression of 69 leukocyte/endothelial CAMs and E-cadherin was investigated in 61 IBD patients before and after first infliximab infusion and in 12 normal controls, using Affymetrix gene expression microarrays. Quantitative reverse transcriptase-PCR (qRT-PCR), immunohistochemistry, and western blotting were used to confirm the microarray data.

RESULTS

When compared with control colons, the colonic mucosal gene expression of most leukocyte/endothelial adhesion molecules was upregulated and E-cadherin gene expression was downregulated in active colonic IBD (IBDc) before therapy, with no significant colonic gene expression differences between ulcerative colitis and colonic Crohn's disease. Infliximab therapy restored the upregulations of leukocyte CAMs in IBDc responders to infliximab that paralleled the disappearance of the inflammatory cells from the colonic lamina propria. Also, the colonic gene expression of endothelial CAMs and of most chemokines/chemokine receptors returned to normal after therapy in IBDc responders, and only CCL20 and CXCL1-2 expression remained increased after therapy in IBDc responders vs. control colons. When compared with control ileums, the ileal gene expression of MADCAM1, THY1, PECAM1, CCL28, CXCL1, -2, -5, -6, and -11, and IL8 was increased and CD58 expression was decreased in active ileal Crohn's disease (CDi) before therapy, and none of the genes remained dysregulated after therapy in CDi responders vs. control ileums. This microarray study identified a number of interesting targets for antiadhesion therapy including PECAM1, IL8, and CCL20, besides the currently studied α4β7 integrin-MADCAM1 axis.

CONCLUSIONS

Our data demonstrate that many leukocyte/endothelial CAMs and chemokines/chemokine receptors are upregulated in inflamed IBD mucosa. Controlling the inflammation with infliximab restores most of these dysregulations in IBD. These results show that at least part of the mechanism of anti-tumor necrosis factor-α therapy goes through downregulation of certain adhesion molecules.

The CC' and DE loops in Ig domains 1 and 2 of MAdCAM-1 play different roles in MAdCAM-1 binding to low- and high-affinity integrin alpha4beta7

Lymphocyte homing is regulated by the dynamic interaction between integrins and their ligands. Integrin α4β7 mediates both rolling and firm adhesion of lymphocytes by modulating its affinity to the ligand, mucosal addressin cell adhesion molecule-1 (MAdCAM-1). Although previous studies have revealed some mechanisms of α4β7-MAdCAM-1 binding, little is known about the different molecular bases of the low- and high-affinity α4β7-MAdCAM-1 interactions, which mediate rolling and firm adhesion of lymphocytes, respectively. Here, we found that two loops in immunoglobulin domains 1 and 2 (D1 and D2) of MAdCAM-1 played different roles in MAdCAM-1 binding to low-affinity (inactive) and high-affinity (activated) α4β7. The Asp-42 in the CC' loop of D1 was indispensable for MAdCAM-1 binding to both low-affinity and high-affinity α4β7. The other CC' loop residues except for Arg-39 and Ser-44 were essential for MAdCAM-1 binding to both inactive α4β7 and α4β7 activated by SDF-1α or talin, but not required for MAdCAM-1 binding to Mn2+-activated α4β7. Single amino acid substitution of the DE loop residues mildly decreased MAdCAM-1 binding to both inactive and activated α4β7. Notably, removal of the DE loop greatly impaired MAdCAM-1 binding to inactive and SDF-1α- or talin-activated α4β7, but only decreased 60% of MAdCAM-1 binding to Mn2+-activated α4β7. Moreover, DE loop residues were important for stabilizing the low-affinity α4β7-MAdCAM-1 interaction. Thus, our findings demonstrate the distinct roles of the CC' and DE loops in the recognition of MAdCAM-1 by low- and high-affinity α4β7 and suggest that the inactive α4β7 and α4β7 activated by different stimuli have distinct conformations with different structural requirements for MAdCAM-1 binding.

Beta7 integrin deficiency suppresses B cell homing and attenuates chronic ileitis in SAMP1/YitFc mice

Lymphocyte recruitment to intestinal tissues depends on β(7) integrins. In this study, we studied disease severity and lymphocyte recruitment into the small intestine in SAMP1/YitFc mice, which develop chronic ileitis with similarity to human Crohn's disease. To assess the role of β(7) integrins in chronic ileitis, we generated SAMP1/YitFc lacking β(7) integrins (SAMP1/YitFc Itgb7(-/-)) using a congenic strain developed via marker-assisted selection. We analyzed ileal inflammation in SAMP1/YitFc and SAMP1/YitFc Itgb7(-/-) mice by histopathology and the distribution of T and B lymphocytes in the mesenteric lymph nodes (MLNs) by flow cytometry. Short-term (18 h) adoptive transfer experiments were used to study the in vivo homing capacity of T and B lymphocytes. In both young (<20 wk) and old (20-50 wk) SAMP1/YitFc Itgb7(-/-) mice, ileitis was reduced by 30-50% compared with SAMP1/YitFc mice. SAMP1/YitFc Itgb7(-/-) mice showed a dramatic 67% reduction in the size of their MLNs, which was caused by a 85% reduction in lymphocyte numbers and reduced short-term B cell homing. Flow cytometric analysis revealed a highly significant decrease in the percentage of B cells in MLNs of SAMP1/YitFc Itgb7(-/-) mice. Cotransfer of SAMP1/YitFc MLN B cells but not SAMP1/YitFc Itgb7(-/-) MLN B cells along with CD4(+) T cells resulted in exacerbated ileitis severity in SCID mice. Our findings suggest that β(7) integrins play an essential role in spontaneous chronic ileitis in vivo by promoting homing of disease-exacerbating B cells to MLNs and other intestinal tissues.

Intestinal dendritic cells: their role in bacterial recognition, lymphocyte homing, and intestinal inflammation

Dendritic cells (DCs) play a key role in discriminating between commensal microorganisms and potentially harmful pathogens and in maintaining the balance between tolerance and active immunity. The regulatory role of DC is of particular importance in the gut where the immune system lies in intimate contact with the highly antigenic external environment. Intestinal DC constantly survey the luminal microenvironment. They act as sentinels, acquiring antigens in peripheral tissues before migrating to secondary lymphoid organs to activate naive T cells. They are also sensors, responding to a spectrum of environmental cues by extensive differentiation or maturation. Recent studies have begun to elucidate mechanisms for functional specializations of DC in the intestine that may include the involvement of retinoic acid and transforming growth factor-β. Specialized CD103(+) intestinal DC can promote the differentiation of Foxp3(+) regulatory T cells via a retinoic acid-dependent process. Different DC outcomes are, in part, influenced by their exposure to microbial stimuli. Evidence is also emerging of the close interaction between bacteria, epithelial cells, and DC in the maintenance of intestinal immune homeostasis. Here we review recent advances of functionally specialized intestinal DC and their mechanisms of antigen uptake and recognition. We also discuss the interaction of DC with intestinal microbiota and their ability to orchestrate protective immunity and immune tolerance in the host. Lastly, we describe how DC functions are altered in intestinal inflammation and their emerging potential as a therapeutic target in inflammatory bowel disease.

Lactobacillus plantarum prevents the upregulation of adhesion molecule expression in an experimental colitis model

BACKGROUND

Lactobacillus consumption has been shown to attenuate the severity of experimental colitis. Whether the effects of Lactobacillus on colitis are related to modulation of leukocyte recruitment into the inflamed intestine is unclear.

AIMS

To investigate the effect of Lactobacillus plantarum daily intragastric administration on lymphocyte homing and intestinal inflammation in interleukin 10 (IL-10) knockout mice, an experimental model of colitis.

METHODS

Two groups of ten IL-10 knockout mice were fed phosphate buffered saline containing Lactobacillus plantarum 1258 or unmodified vehicle for 4 weeks. Two groups of ten wild-type mice were used as controls. At killing, the bowels were histologically scored and evaluated by transmission electron microscopy. Mucosal addressin cell adhesion molecule 1 (MAdCAM-1) and intercellular adhesion molecule 1 (ICAM-1) expression were determined by immunohistochemistry. The levels of proinflammatory cytokines, tumor necrosis factor alpha (TNF-alpha), and interferon gamma (IFN-gamma) were determined by ELISA. In addition, levels of CD3, alpha4beta7, ICAM-1, and MAdCAM-1 were determined by reverse-transcription polymerase chain reaction and Western blot.

RESULTS

L. plantarum treatment improved the histological damage score in KO mice compared to untreated KO mice. L. plantarum significantly attenuated the expression of MAdCAM-1, ICAM-1, CD3, and alpha4beta7, but did not affect the levels of TNF-alpha and IFN-gamma when treated KO mice were compared to untreated KO mice.

CONCLUSIONS

L. plantarum interfered with the upregulation of adhesion molecules observed in IL-10 knockout mice compared to wild-type mice, attenuating the symptoms of colitis.

Anti-adhesion molecule therapy for inflammatory bowel disease

Although biologic agents directed against tumor necrosis factor alpha (TNFα) continue to be an effective therapeutic strategy for patients with inflammatory bowel disease (IBD), approximately 30% of patients with Crohn's disease (CD) who are refractory to standard treatment do not respond to induction therapy with TNFα inhibitors and, of those who initially respond, 50% or more cease to respond within a year. Moreover, their use can be associated with significant safety issues. Clearly, there is a need to target alternative pathways involved in the inflammatory process. IBD is driven by the trafficking of lymphocytes from the circulation into the gut tissue that is mediated by adhesive interactions between the lymphocytes and endothelial cells. The adhesion molecules involved represent attractive targets for the development of new therapeutics which should aid in the resolution of existing inflammation, prevent recurrence of inflammation, and may potentially lead to long-term control of disease. In this article we review current opportunities and challenges facing anti-adhesion therapy in IBD, and discusses recent clinical development efforts that have focused on having an impact on two particular adhesive interactions: α(4)-integrin/MAdCAM-1 and β(2)-integrin/ICAM-1. Of particular interest is natalizumab, a humanized monoclonal antibody against human α(4) integrin that is approved for the treatment of patients with moderately-to-severely active CD and evidence of active inflammation. This agent represents an efficacious therapeutic option for patients who do not respond to, or have failed, a TNF-α inhibitor.

Gatekeepers of intestinal inflammation

The intestine is subjected to a barrage of insults from food, bacterial flora, and pathogens. Despite this constant antigenic challenge, the mucosal tissues lining the intestinal tract remain largely under control. The mechanisms regulating the homeostatic balance in the gut have been investigated for many years by many groups, but the precise nature of the regulatory control remains elusive. In this review, we provide an overview of pathways proposed to be involved in dampening the inflammatory response and maintaining the homeostatic balance in the intestine, and how these pathways may be disrupted in ulcerative colitis and Crohn's disease.

Hereditary multiple intestinal atresias: 2 new cases and review of the literature

Intestinal atresias are a common cause of newborn bowel obstruction (Dalla Vecchia LK, Grosfeld JL, West KW, et al, Intestinal atresia and stenosis: a 25-year experience with 277 cases. Arch Surg 1998; 133[5]:490-496). Hereditary multiple intestinal atresias, first reported by Guttman et al in 1973, is the rarest form of multiple atresias (Guttman FM, Braun P, Garance PH, et al, Multiple atresias and a new syndrome of hereditary multiple atresias involving the gastrointestinal tract from stomach to rectum. J Pediatr Surg 1973;8:633-640; Bass J, Pyloric atresia associated with multiple intestinal atresias and immune deficiency. J Pediatr Surg 2002;37:941-942.). It has been proposed to be autosomal recessive, to involve atresias in a variable combination of sites from stomach to rectum, and to be universally fatal (Bilodeau A, Prasil P, Cloutier R, et al, Hereditary multiple intestinal atresia: thirty years later. J Pediatr Surg 2004;39:726-730; Moreno LA, Gottrand F, Turck D, et al, Severe combined immunodeficiency syndrome associated with autosomal recessive familial multiple gastrointestinal atresias: study of a family. Am J Med Genet 1990;37:143-146). Patients have significant intestinal dysfunction and unrelenting sepsis stemming from a poorly defined, severe immunologic defect. Our case report presents 2 full siblings to nonconsanguineous parents with pyloric atresia, multiple small bowel and colonic atresias, and severe immune dysfunction. Care was withdrawn within 3 months of life on both siblings after multiple bouts of sepsis. Data suggest that the immune defect may not be primary, but in fact be secondary to intestinal dysfunction. Although the subjects in this article ultimately had fatal outcomes, a comprehensive immunologic/physiologic picture is presented in hopes of furthering the understanding of this grave disease.