Nonclassical CD1d-restricted NK T cells that produce IL-13 characterize an atypical Th2 response in ulcerative colitis

CD1 expression on antigen-presenting cells

CD1 proteins present self and microbial glycolipids to CD 1-restricted T cells, or in the case of CD1d, to NKT cells. The CD1 family in humans consists of group I proteins CDla, CDlb, CDlc, and CDle and the group II protein CDld. Rodents express only CDld, but as CD1d is broadly expressed and traffics to all endosomal compartments, this single CD1 family member is thereby able to acquire antigens in many subcellular compartments. A complete understanding of the CD 1 family requires an appreciation of which cells express CD1 and how CD1 contributes to the unique function of each cell type. While group I CD 1 expression is limited to thymocytes and professional APCs, CD1d has a wider tissue distribution and can be found on many nonhematopoietic cells. The expression and regulation of CD1 are presented here with particular emphasis on the function of CD1 in thymocytes, B cells, monocytes and macrophages, dendritic cells (DCs), and intestinal epithelial cells (IECs). Altered expression of CD 1 in cancer, autoimmunity, and infectious disease is well documented, and the implication of CD 1 expression in these diseases is discussed.

The role of TNFalpha in ulcerative colitis

Standard of care for ulcerative colitis involves long-term pharmacotherapy or colectomy. Approximately 20% to 30% of patients eventually require a colectomy because patients either do not respond or cannot tolerate the currently available pharmacotherapies. Advances in our knowledge of the pathophysiology of ulcerative colitis have highlighted the importance of cytokines such as tumor necrosis factor alpha (TNFalpha) in the inflammatory process. TNFalpha is a proinflammatory mediator that plays an integral role in the pathogenesis of inflammatory bowel disease. In addition, mounting evidence indicates a genetic association between TNFalpha and ulcerative colitis. Furthermore, increased TNFalpha levels have been demonstrated in studies of patients with ulcerative colitis. TNFalpha is likely an important component in the pathophysiology of ulcerative colitis, and thus agents targeting TNFalpha in ulcerative colitis have been studied. Recent randomized controlled trials have confirmed that biologic anti-TNFalpha therapy is effective in ulcerative colitis. Soluble TNFalpha receptors or biologic agents that suppress or inhibit TNFalpha production may also show therapeutic promise.

Clinical significance of mucosal suppressors of cytokine signaling 3 expression in ulcerative colitis

AIM: To investigate the clinical significance of mucosal expression of suppressors of cytokine signaling 1 (SOCS1) and SOCS3 in human ulcerative colitis (UC).

METHODS: Biopsy specimens for histological analysis and mRNA detection were obtained endoscopically from the rectum of 62 patients with UC (36 men; age 13-76 years). The patients were classified endoscopically according to Matts’ grade (grade 1 to 4). Expression of SOCS1 and SOCS3 mRNAs was quantified in samples by competitive reverse transcription-polymerase chain reaction (RT-PCR). GAPDH was used as an internal control for efficiency of RT-PCR and amount of RNA.

RESULTS: SOCS3 mRNA expression was significantly higher in inflamed mucosa of UC than in inactive mucosa. The level of expression was well correlated with the degree of both endoscopic and histologic inflammation. Interestingly, among the patients in remission, the group with relatively low expression of SOCS3 showed a higher rate of remission maintenance over a 12-mo period. In contrast, SOCS1 mRNA was expressed in both inflamed and non-inflamed colonic mucosa and was not correlated with the activity of colonic mucosa or prognosis.

CONCLUSION: These observations suggest that increased expression of mucosal SOCS3, but not of SOCS1, may play a critical role in the development of the colonic inflammation of UC.

Deficiency of invariant NK T cells in Crohn's disease and ulcerative colitis

The aim of this study was to investigate whether immunoregulatory invariant NK T cells are deficient in Crohn's disease or ulcerative colitis. Blood was collected for flow cytometry from 106 Crohn's disease, 91 ulcerative colitis, and 155 control subjects. Invariant NK T cells were assessed by Valpha24 and (alpha-galactosylceramide/CD1d tetramer markers. Intracellular cytokine was measured after in vitro anti-CD3 antibody stimulation. Valpha24+ T cells were quantified in ileocolonic biopsies as mRNA by real-time PCR and by immunofluorescence. Circulating invariant NK T cells were 5.3% of the control levels in Crohn's (P < 0.001) and 7.9% of the control levels in ulcerative colitis (P < 0.001). Interleukin-4 production was impaired in Crohn's disease and ulcerative colitis. Intestinal Valpha24 mRNA expression was 7% in Crohn's disease (P < 0.05) and 9% in ulcerative colitis (P < 0.05). Intestinal Valpha24+ T cells were 23% in Crohn's disease but not reduced in ulcerative colitis. We conclude that invariant NK T cells are deficient in Crohn's disease and in ulcerative colitis.

Intestinal epithelial cells from inflammatory bowel disease patients preferentially stimulate CD4+ T cells to proliferate and secrete interferon-gamma

Previous studies have suggested that intestinal epithelial cells (IECs) have the capacity to function as nonprofessional antigen presenting cells that in the normal state preferentially activate CD8+ T cells. However, under pathological conditions, such as those found in inflammatory bowel disease (IBD), persistent activation of CD4+ T cells is seen. The aim of this study was to determine whether the IBD IECs contribute to CD4+ T cell activation. Freshly isolated human IECs were obtained from surgical specimens of patients with or without IBD and cocultured with autologous or allogeneic peripheral blood T lymphocytes. Cocultures of normal T cells and IECs derived from IBD patients resulted in the preferential activation of CD4+ T cell proliferation that was associated with significant IFN-gamma, but not IL-2, secretion. Cytokine secretion and CD4+ T cell proliferation was inhibited by pretreatment of the IBD IECs with the anti-DR MAb L243. In contrast, normal IECs stimulated the proliferation and cytokine secretion by CD4+ T cells to a significantly lesser degree than IBD IECs. Furthermore, blockade of human leukocyte antigen-DR had a lesser effect in the normal IEC-CD4+ T cell cocultures. We conclude that IECs can contribute to the ongoing CD4+ T cell activation seen in IBD. We suggest that the apparent differences between the secreted levels of IFN-gamma indicate that it may play a dual role in intestinal homeostasis, in which low levels contribute to physiological inflammation whereas higher levels are associated with an uncontrolled inflammatory state.

Increased susceptibility to colitis and colorectal tumors in mice lacking core 3-derived O-glycans

Altered intestinal O-glycan expression has been observed in patients with ulcerative colitis and colorectal cancer, but the role of this alteration in the etiology of these diseases is unknown. O-glycans in mucin core proteins are the predominant components of the intestinal mucus, which comprises part of the intestinal mucosal barrier. Core 3–derived O-glycans, which are one of the major types of O-glycans, are primarily expressed in the colon. To investigate the biological function of core 3–derived O-glycans, we engineered mice lacking core 3 β1,3-N-acetylglucosaminyltransferase (C3GnT), an enzyme predicted to be important in the synthesis of core 3–derived O-glycans. Disruption of the C3GnT gene eliminated core 3–derived O-glycans. C3GnT-deficient mice displayed a discrete, colon-specific reduction in Muc2 protein and increased permeability of the intestinal barrier. Moreover, these mice were highly susceptible to experimental triggers of colitis and colorectal adenocarcinoma. These data reveal a requirement for core 3–derived O-glycans in resistance to colonic disease.

Inflammatory bowel disease: cause and immunobiology

Crohn's disease and ulcerative colitis are idiopathic inflammatory bowel disorders. In this paper, we discuss how environmental factors (eg, geography, cigarette smoking, sanitation and hygiene), infectious microbes, ethnic origin, genetic susceptibility, and a dysregulated immune system can result in mucosal inflammation. After describing the symbiotic interaction of the commensal microbiota with the host, oral tolerance, epithelial barrier function, antigen recognition, and immunoregulation by the innate and adaptive immune system, we examine the initiating and perpetuating events of mucosal inflammation. We pay special attention to pattern-recognition receptors, such as toll-like receptors and nucleotide-binding-oligomerisation-domains (NOD), NOD-like receptors and their mutual interaction on epithelial cells and antigen-presenting cells. We also discuss the important role of dendritic cells in directing tolerance and immunity by modulation of subpopulations of effector T cells, regulatory T cells, Th17 cells, natural killer T cells, natural killer cells, and monocyte-macrophages in mucosal inflammation. Implications for novel therapies, which are discussed in detail in the second paper in this Series, are covered briefly.

Inflammatory bowel disease in relation to contact allergy: a patient-based study

OBJECTIVE

Inflammatory bowel disease (IBD) has previously been investigated with relation to allergic conditions; however, diverging results were found and there are only a few small studies focusing on delayed hypersensitivity. The aim of this study was to investigate whether there was an association between contact allergy (CA), which is a type IV hypersensitivity reaction of the skin, and IBD.

MATERIAL AND METHODS

A database consisting of a cohort of 13,315 patients, patch tested between 1985 and 2003, was linked with the Danish National Patient Registry using a unique personal identifier number. The patients were patch tested at a dermatology department with a long history of research in CA. By record linking with the Danish National Patient Registry, patients were identified who had either an International Classification of Disease (ICD) code for Crohn's disease (CD) or an ICD code for ulcerative colitis (UC) diagnosis. Using logistic regression, with the result of the patch test as the dependent variable, we calculated the odds ratios for IBD, CD and UC, adjusted for gender and age.

RESULTS

An inverse association between CA and IBD was found, odds ratio adjusted for age and gender 0.71 (CI 95% 0.53-0.94), which is mainly the result of an inverse association between CA and CD, odds ratio adjusted for age and gender 0.42 (CI 95% 0.23-0.76).

CONCLUSIONS

The association found between CA and IBD might be related to shared genetic factors or common environmental determinates. It may also be that having either disease result in skewness of the immune system might lead to an inverse disease association.

Therapeutic and prophylactic thalidomide in TNBS-induced colitis: Synergistic effects on TNF-α, IL-12 and VEGF production

AIM: To evaluated the therapeutic and prophylactic effect of thalidomide on 2, 4, 6-trinitrobenzene sulfonic acid (TNBS)-induced colitis. Thalidomide has been reported to downregulate the expression of tumor necrosis factor α (TNF-α), IL-12, and vascular endothelial growth factor (VEGF), hallmarks of intestinal inflammation in Crohn’s disease (CD).

METHODS: Male Wistar rats were divided in five groups of ten animals each. Four groups received a rectal infusion of TNBS in ethanol. The first group was sacrificed 7 d after colitis induction. The second and third groups received either thalidomide or placebo by gavage and were sacrificed at 14 d. The fourth group received thalidomide 6 h before TNBS administration, and was sacrificed 7 d after induction. The fifth group acted as the control group and colitis was not induced. Histological inflammatory scores of the colon were performed and lamina propria CD4+ T cells, macrophages, and VEGF+ cells were detected by immunohistochemistry. TNF-α and IL-12 were quantified in the supernatant of organ cultures by ELISA.

RESULTS: Significant reduction in the inflammatory score and in the percentage of VEGF+ cells was observed in the group treated with thalidomide compared with animals not treated with thalidomide. Both TNF-α and IL-12 levels were significantly reduced among TNBS induced colitis animals treated with thalidomide compared with animals that did not receive thalidomide. TNF-α levels were also significantly reduced among the animals receiving thalidomide prophylaxis compared with untreated animals with TNBS-induced colitis. Intestinal levels of TNF-α and IL-12 were significantly correlated with the inflammatory score and the number of VEGF+ cells.

CONCLUSION: Thalidomide significantly attenuates TNBS-induced colitis by inhibiting the intestinal production of TNF-α, IL-12, and VEGF. This effect may support the use of thalidomide as an alternate approach in selected patients with CD.

Cytokine therapy for Crohn's disease: advances in translational research

Crohn's disease (CD) and ulcerative colitis (UC), the two idiopathic inflammatory bowel diseases (IBDs), affect almost two million individuals in North America and several million worldwide. Cytokines are important in the pathogenesis of CD, and their manipulation has successfully reduced disease severity and maintained remission. Following the discovery of novel cytokines and the role they may play in gut mucosal immunity, as well as the emergence of new concepts and changing paradigms in CD pathogenesis, the roles of several cytokines have been elucidated and tested in both preclinical animal models and clinical trials of patients with IBD. Complementary to this, proof of concept for new cytokine targets is rapidly developing, with the possibility of future cytokine-based therapies that may offer greater specificity and decreased toxicity for the treatment of CD. This review discusses novel concepts in CD pathogenesis and the roles of cytokines in the initiation and perpetuation of disease. In addition, we review applications of cytokine-based therapies in human clinical trials and preclinical animal studies. Finally, we discuss novel cytokine targets not yet investigated in vivo and describe their potential contribution to CD pathogenesis.

Helminth infection enhances disease in a murine TH2 model of colitis

BACKGROUND & AIMS

There is convincing evidence from animal and human studies that infection with parasitic helminths can alleviate the histopathology and symptoms of colitis. Here the ability of the rat tapeworm Hymenolepis diminuta to affect the course of oxazolone-induced colitis (a TH2 model) was assessed.

METHODS

Mice were infected with H diminuta and 8 days later they received oxazolone (3 mg in 50% EtOH, intrarectal). On autopsy (3 or 7 days postoxazolone), disease severity was assessed by macroscopic clinical scores, histologic damage scores, myeloperoxidase and eosinophil peroxidase activity, and cytokine synthesis.

RESULTS

As gauged by all markers of gut function, infection with H diminuta caused a significant exacerbation of oxazolone-induced colitis. Indeed, while mice receiving oxazolone only began to recover approximately 3-4 days posttreatment, the cotreated group continued to deteriorate. Helminth infection, independent of oxazolone administration, enhanced IL-4, IL-5, IL-10, and IL-13 production from in vitro stimulated immune cells and evoked increases in colonic eosinophil peroxidase of cotreated mice. Finally, while knockout of natural killer (NK) and NK-T cells by administration of a neutralizing NK1.1 antibody reduced the inflammation in oxazolone and oxazolone + H diminuta-treated animals, mice in the latter group still displayed significant colitis.

CONCLUSIONS

We have shown that H diminuta infection is beneficial in other models of colitis. The current data is presented as a caveat to the position that parasitic helminths in general can be considered as a therapy for heterogeneous inflammatory disorders without careful analysis of the immunologic basis of the condition.

The fundamental basis of inflammatory bowel disease

Two broad hypotheses have arisen regarding the fundamental nature of the pathogenesis of inflammatory bowel diseases (IBDs, which include ulcerative colitis and Crohn disease). The first contends that primary dysregulation of the mucosal immune system leads to excessive immunologic responses to normal microflora. The second suggests that changes in the composition of gut microflora and/or deranged epithelial barrier function elicits pathologic responses from the normal mucosal immune system. Here we examine these hypotheses and conclude that IBD is indeed characterized by an abnormal mucosal immune response but that microbial factors and epithelial cell abnormalities can facilitate this response.

MTP regulated by an alternate promoter is essential for NKT cell development

Microsomal triglyceride transfer protein (MTP), an endoplasmic reticulum lipid transfer protein critical for apolipoprotein B (apoB) secretion, regulates CD1d antigen presentation. We identified MTP variant 1 (MTPv1), a novel splice variant of mouse MTP, by polymerase chain reaction and Northern analysis in non-apoB-secreting tissues, including thymocytes and antigen-presenting cells (APCs). Edman degradation of MTPv1 isolated from transfected cells revealed three unique residues; however, recombinant MTP and MTPv1 had an equivalent protein disulfide isomerase association, subcellular localization, triglyceride transfer, phospholipid transfer, response to inhibitors, and ability to support apoB secretion. MTP and MTPv1 efficiently transferred phosphatidylethanolamine to CD1d in vitro. NKT cells fail to develop in fetal thymic organ culture (FTOC) treated with MTP antagonists. MTP-inhibited FTOCs produced negligible numbers of CD1d tetramer-positive cells and exhibited marked defects in IL-4 production upon stimulation with anti-CD3 or alpha-galactosylceramide-pulsed APCs. CD1d expression on CD4(+)CD8(+) FTOC cells was unaffected by MTP inhibition. Thus, our results demonstrate that MTPv1 in thymocytes is critical to NKT cell development. We hypothesize that, when MTP is inactive, CD1d traffics to the cell surface and presents no lipid or a lipid that is incapable of mediating NKT cell selection and/or is refractory to lysosomal editing.

Expression and functional characterization of FOXP3+ CD4+ regulatory T cells in ulcerative colitis

BACKGROUND

CD4+CD25+ regulatory T cells (TR) can prevent or treat experimental murine colitis but little is known about their potential role in human inflammatory bowel disease (IBD). FOXP3 is a transcription factor that plays a critical role in the development and function of CD4+CD25+ TR. The aim of this study was to examine the presence and functional characteristics of TR cells in colonic lymphoid tissues in patients with ulcerative colitis (UC).

METHODS

FOXP3 expression was assessed by flow cytometry, immunohistochemistry, and reverse-transcriptase polymerase chain reaction (RT-PCR). Functional characterization of CD4+CD25+ cells was analyzed by suppression of proliferation and secretion of cytokines by cocultured effector CD4+CD25- T cells.

RESULTS

FOXP3 +CD4+ T cells are increased in the lamina propria (LP) of inflamed and noninflamed areas of UC colon compared to normal colon. CD4+CD25+ T cells in UC mesenteric lymph nodes (MLN) express FOXP3 mRNA and protein and suppress the proliferation of autologous MLN CD4+CD25 T cells. The suppressor activity of MLN CD4+CD25+ T cells is cell contact-dependent but cytokine-independent. In addition, CD4+CD25+ T cells potently suppress the production of both Thl (IFN-gamma, IL-2) and Th2 (IL-5, IL-13) cytokines by cocultured CD4+CD25 T cells. FOXP3' cells localized in the T-cell-rich areas of MLN and occasionally present in the follicles.

CONCLUSIONS

There is an expansion of FOXP3+CD4+ T cells in mucosal lymphoid tissues in UC. CD4+CD25+ isolated from UC MLN express FOXP3 and display features of TR cells in spite of active mucosal inflammation. These data suggest that their suppressor activity may be abrogated in vivo or they are unable to counterbalance the chronic mucosal inflammation in UC.

Advances in the pathogenesis of inflammatory bowel disease

Most people do not develop inflammatory bowel disease (IBD) in spite of the density of the commensal flora. In the past few years, several areas of gut mucosal immunology have emerged that will permit advances in the management of IBD at the bedside. The commensal flora is only beginning to be fully appreciated as another metabolic organ in the body. Innate immunity as it relates to the gut has complemented our understanding of the adaptive immune response. The most important susceptibility gene described for Crohn's disease, the NOD2 gene, participates in the innate immune response to pathogens. Patients carrying NOD2 mutations have an increased adaptive immune response to commensal organisms as measured by higher titers of antimicrobial antibodies, such as anti-CBir and anti-Saccharomyces cerevisiae antibodies. Toll-like receptors expressed by antigen-presenting cells (APCs) in the gut and intestinal epithelial cells also play a role in recognition of intestinal flora. Within the APC category, dendritic cells link the innate and adaptive immune systems and shape the nature of the adaptive immune response to commensal bacteria. With respect to adaptive immunity, a new signaling pathway involving a distinct helper CD4 T-cell subset producing interleukin-17 may become a target for the treatment of chronic inflammatory diseases. This review focuses on developments likely to culminate in advances in patient care.

Hypothesis about mechanisms through which nicotine might exert its effect on the interdependence of inflammation and gut barrier function in ulcerative colitis

Ulcerative colitis (UC) is characterized by impairment of the epithelial barrier and the formation of ulcer-type lesions, which result in local leaks and generalized alterations of mucosal tight junctions. Ultimately, this results in increased basal permeability. Although disruption of the epithelial barrier in the gut is a hallmark of inflammatory bowel disease and intestinal infections, it remains unclear whether barrier breakdown is an initiating event of UC or rather a consequence of an underlying inflammation, evidenced by increased production of proinflammatory cytokines. UC is less common in smokers, suggesting that the nicotine in cigarettes may ameliorate disease severity. The mechanism behind this therapeutic effect is still not fully understood, and indeed it remains unclear if nicotine is the true protective agent in cigarettes. Nicotine is metabolized in the body into a variety of metabolites and can also be degraded to form various breakdown products. It is possible these metabolites or degradation products may be the true protective or curative agents. A greater understanding of the pharmacodynamics and kinetics of nicotine in relation to the immune system and enhanced knowledge of gut permeability defects in UC are required to establish the exact protective nature of nicotine and its metabolites in UC. This review suggests possible hypotheses for the protective mechanism of nicotine in UC, highlighting the relationship between gut permeability and inflammation, and indicates where in the pathogenesis of the disease nicotine may mediate its effect.

Effect of rebamipide on the colonic barrier in interleukin-10-deficient mice

Our aim was to study the effect of a mucosal protective agent, rebamipide, on the colonic barrier and the immune response in colitis-prone interleukin-10-deficient (IL-10-/-) C57BL/6 mice infected with Helicobacter hepaticus. After sacrifice, in all mice, control, or previously infected with H. hepaticus, or previously infected and treated with rebamipide enema, a histological examination of colonic samples was performed, intestinal permeability was studied in Ussing chamber, and mesenteric lymph node proliferation and cytokine secretion were measured. Mice treated with rebamipide presented a reinforcement of the distal colonic epithelial barrier, an increase of mesenteric lymph node cells proliferation, and of IFNgamma and IL-12 secretion. These results indicate that in IL-10-/- mice with mild colitis, rectally administered rebamipide reinforces the distal colonic barrier and has a slight Th1 immuno-stimulatory effect on mesenteric lymph node cells. These properties could be helpful in the management of some inflammatory bowel diseases.

Role of interleukin-13 in cancer, pulmonary fibrosis, and other T(H)2-type diseases

Interleukin (IL)-13 plays a major role in various inflammatory diseases including cancer, asthma, and allergy. It mediates a variety of different effects on various cell types including B cells, monocytes, natural killer cells, endothelial cells, and fibroblasts. IL-13 binds to two primary receptor chains IL-13Ralpha1 and IL-13Ralpha2. The IL-13Ralpha2 but not IL-13Ralpha1 chain binds IL-13 with high affinity and is overexpressed in a variety of human cancer cells derived from glioma, squamous cell carcinoma of head and neck, and AIDS-associated Kaposi's sarcoma. We have also demonstrated that IL-13Ralpha2 expression is greatly increased in lung cells when mice were challenged intranasally with bleomycin or Aspergillus fumigatus. In addition, IL-13Ralpha2 increased in surgical lung biopsies from patients with usual interstitial pneumonia, nonspecific interstitial pneumonia, and respiratory bronchiolitic interstitial pneumonia of unknown origin. Based on various studies, it is concluded that IL-13Ralpha2-expressing cells are involved in various pulmonary pathological conditions. In contrast, normal tissues such as brain, lung, endothelial cells, and head and neck tissues express IL-13Ralpha1 chain, but show only marginal expression of IL-13Ralpha2 chain. Thus, IL-13Ralpha2 chain may serve as a novel biomarker for diseased cells such as cancer or fibrosis and a target for receptor-directed therapeutic agents. To target IL-13R, a recombinant fusion protein composed of IL-13 and a derivative of Pseudomonas exotoxin (PE) has been produced. This cytotoxin termed as IL-13PE38QQR or IL-13PE38, or IL-13PE is highly and specifically cytotoxic to a variety of human tumor cell lines. In preclinical models of human glioblastoma, head and neck and AIDS-associated Kaposi's cancer, IL-13PE has been found to have significant antitumor activity at a tolerated dose. Several phase I clinical trials have been completed in patients with recurrent malignant glioma. Recently a phase III clinical trial (PRECISE) in patients with recurrent malignant glioma has been completed recruiting a total of 294 patients. IL-13PE cytotoxin has also shown a significant therapeutic effect in preclinical bleomycin or A. fumigatus or Schistosoma mansoni-induced pulmonary pathology including granulomatous fibrosis in mouse models. A clinical study in these diseases has yet to be initiated.

Characterization of Foxp3+CD4+CD25+ and IL-10-secreting CD4+CD25+ T cells during cure of colitis

CD4+CD25+ regulatory T cells can prevent and resolve intestinal inflammation in the murine T cell transfer model of colitis. Using Foxp3 as a marker of regulatory T cell activity, we now provide a comprehensive analysis of the in vivo distribution of Foxp3+CD4+CD25+ cells in wild-type mice, and during cure of experimental colitis. In both cases, Foxp3+CD4+CD25+ cells were found to accumulate in the colon and secondary lymphoid organs. Importantly, Foxp3+ cells were present at increased density in colon samples from patients with ulcerative colitis or Crohn's disease, suggesting similarities in the behavior of murine and human regulatory cells under inflammatory conditions. Cure of murine colitis was dependent on the presence of IL-10, and IL-10-producing CD4+CD25+ T cells were enriched within the colon during cure of colitis and also under steady state conditions. Our data indicate that although CD4+CD25+ T cells expressing Foxp3 are present within both lymphoid organs and the colon, subsets of IL-10-producing CD4+CD25+ T cells are present mainly within the intestinal lamina propria suggesting compartmentalization of the regulatory T cell response at effector sites.

A role for natural killer T cells in asthma

In several mouse models, natural killer T cells have recently been found to be required for the development of airway hyper-reactivity, a cardinal feature of asthma. Moreover, in patients with chronic asthma, natural killer T cells with a T-helper-2-like phenotype (that is, that express CD4 and produce T helper 2 cytokines) are present in the lungs in large numbers. In this Opinion article, we suggest that natural killer T cells, which express a restricted T-cell receptor and respond to glycolipids rather than protein antigens, have a previously unsuspected but crucial role, distinct from that of T helper 2 cells, in the pathogenesis of asthma.

Mechanisms of disease: pathogenesis of Crohn's disease and ulcerative colitis

Crohn's disease and ulcerative colitis are idiopathic, chronic, relapsing, inflammatory conditions that are immunologically mediated. Although their exact etiologies remain uncertain, results from research in animal models, human genetics, basic science and clinical trials have provided important new insights into the pathogenesis of chronic, immune-mediated, intestinal inflammation. These studies indicate that Crohn's disease and ulcerative colitis are heterogeneous diseases characterized by various genetic abnormalities that lead to overly aggressive T-cell responses to a subset of commensal enteric bacteria. The onset and reactivation of disease are triggered by environmental factors that transiently break the mucosal barrier, stimulate immune responses or alter the balance between beneficial and pathogenic enteric bacteria. Different genetic abnormalities can lead to similar disease phenotypes; these genetic changes can be broadly characterized as causing defects in mucosal barrier function, immunoregulation or bacterial clearance. These new insights will help develop better diagnostic approaches that identify clinically important subsets of patients for whom the natural history of disease and response to treatment are predictable.

Excess IL-12 but not IL-23 accompanies the inflammatory bowel disease associated with common variable immunodeficiency

BACKGROUND & AIMS

Common variable immunodeficiency (CVID) patients can develop an idiopathic inflammatory bowel disease resulting in chronic diarrhea and life-threatening malabsorption. This study was designed to assess the status of the gastrointestinal tract and to define the mucosal immune abnormalities in patients with and without symptomatic gut inflammatory disease.

METHODS

CVID patients underwent tests of gut absorption, peripheral blood mononuclear cell phenotyping, and upper and lower endoscopy for histology and lamina propria mononuclear cell (LPMC) cytokine production.

RESULTS

CVID patients with gastrointestinal symptoms differed from asymptomatic CVID patients by having significantly longer duration of disease and lower body mass index, D-xylose absorption, serum albumin, CD4/CD45RA cells, CD3/CD25 cells, and natural killer cells. Symptomatic CVID patients showed diffuse histologic inflammatory changes in the duodenal and colonic mucosa including villus blunting, increased lamina propria and intraepithelial lymphocytes, and epithelial apoptosis, less frequently seen in asymptomatic patients. LPMCs from symptomatic CVID patients produced significantly higher T-helper (Th) 1 cytokines, interleukin-12, and interferon-gamma. Compared with the Th1 cytokines produced by LPMCs from Crohn's disease, CVID patients did not produce excess amounts of interleukin-23, interleukin-17, or tumor necrosis factor-alpha.

CONCLUSIONS

The idiopathic inflammatory bowel disease associated with gastrointestinal symptoms in CVID is a unique combination of diverse histologic findings accompanied by excessive Th1 cytokine production, distinct from that in Crohn's disease. These data show that human gut mucosal inflammatory disease can occur with excess interleukin-12 and interferon-gamma production alone and provide a rationale for developing targeted therapies for this complication of CVID.

Long-term effectiveness of azathioprine in IBD beyond 4 years: a European multicenter study in 1176 patients

In Crohn's disease the optimal duration of azathioprine treatment is still controversial and for ulcerative colitis only limited data are available to support its efficacy. Charts of 1176 patients with IBD from 16 European centers were analyzed. Flare incidences and steroid dosages were assessed for the time before and during treatment and after discontinuation. Within the first 4 years, azathioprine suppressed flare incidence and steroid consumption in both diseases (P < 0.001). While in CD discontinuation after 3-4 years did not lead to reactivation, this was the case in UC. However, continuation beyond 4 years further improved clinical activity in CD and steroid requirement in both diseases (P < 0.001). Discontinuation of azathioprine may thus be considered after 3-4 years in CD patients in complete remission without steroid requirement. In all other CD patients and for UC patients in general, continuation seems beneficial. These results support a novel differential algorithm for long-term azathioprine therapy in IBD.

CD1d mediates T-cell-dependent resistance to secondary infection with encephalomyocarditis virus (EMCV) in vitro and immune response to EMCV infection in vivo

The innate and adaptive immune responses have evolved distinct strategies for controlling different viral pathogens. Encephalomyocarditis virus (EMCV) is a picornavirus that can cause paralysis, diabetes, and myocarditis within days of infection. The optimal innate immune response against EMCV in vivo requires CD1d. Interaction of antigen-presenting cell CD1d with distinct natural killer T-cell ("NKT") populations can induce rapid gamma interferon (IFN-gamma) production and NK-cell activation. The T-cell response of CD1d-deficient mice (lacking all NKT cells) against acute EMCV infection was further studied in vitro and in vivo. EMCV persisted at higher levels in CD1d-knockout (KO) splenocyte cultures infected in vitro. Furthermore, optimal resistance to repeat cycles of EMCV infection in vitro was also shown to depend on CD1d. However, this was not reflected in the relative levels of NK-cell activation but rather by the responses of both CD4(+) and CD8(+) T-cell populations. Repeated EMCV infection in vitro induced less IFN-gamma and alpha interferon (IFN-alpha) from CD1d-deficient splenocytes than with the wild type. Furthermore, the level of EMCV replication in wild-type splenocytes was markedly and specifically increased by addition of blocking anti-CD1d antibody. Depletion experiments demonstrated that dendritic cells contributed less than the combination of NK and NKT cells to anti-EMCV responses and that none of these cell types was the main source of IFN-alpha. Finally, EMCV infection in vivo produced higher levels of viremia in CD1d-KO mice than in wild-type animals, coupled with significantly less lymphocyte activation and IFN-alpha production. These results point to the existence of a previously unrecognized mechanism of rapid CD1d-dependent stimulation of the antiviral adaptive cellular immune response.

Etiopathogenesis of inflammatory bowel diseases

Theories explaining the etiopathogenesis of inflammatory bowel disease (IBD) have been proposed ever since Crohn’s disease (CD) and ulcerative colitis (UC) were recognized as the two major forms of the disease. Although the exact cause(s) and mechanisms of tissue damage in CD and UC have yet to be completely understood, enough progress has occurred to accept the following hypothesis as valid: IBD is an inappropriate immune response that occurs in genetically susceptible individuals as the result of a complex interaction among environmental factors, microbial factors, and the intestinal immune system. Among an almost endless list of environmental factors, smoking has been identified as a risk factor for CD and a protective factor for UC. Among microbial factors, no convincing evidence indicates that classical infectious agents cause IBD, while mounting evidence points to an abnormal immune response against the normal enteric flora as being of central importance. Gut inflammation is mediated by cells of the innate as well as adaptive immune systems, with the additional contribution of non-immune cells, such as epithelial, mesenchymal and endothelial cells, and platelets.

The effect of acute psychologic stress on systemic and rectal mucosal measures of inflammation in ulcerative colitis

BACKGROUND & AIMS

Recent studies suggest that life events and chronic stress increase the risk of relapse in inflammatory bowel disease. Our aim was to study the effects of acute psychologic stress on systemic and rectal mucosal inflammatory responses in patients with inactive ulcerative colitis (UC).

METHODS

Twenty-five patients with inactive UC and 11 healthy volunteers (HV) underwent an experimental stress test. Ten patients with UC and 11 HV underwent a control procedure. Before and after each procedure, systemic inflammatory response was assessed by serum interleukin (IL)-6 and IL-13 concentrations, tumor necrosis factor (TNF)-alpha and IL-6 production by lipopolysaccharide (LPS)-stimulated whole blood, leukocyte count, natural killer (NK) cell numbers, platelet activation, and platelet-leukocyte aggregate (PLA) formation. In patients with UC, rectal mucosal inflammation was assessed by TNF-alpha, IL-13, histamine and substance P release, reactive oxygen metabolite (ROM) production, mucosal blood flow (RMBF) and histology.

RESULTS

Stress increased pulse (P < .0001) and systolic BP (P < .0001). In UC, stress increased LPS-stimulated TNF-alpha and IL-6 production by 54% (P = .004) and 11% (P = .04), respectively, leukocyte count by 16% (P = .01), NK cell count by 18% (P = .0008), platelet activation by 65% (P < .0001), PLA formation by 25% (P = .004), mucosal TNF-alpha release by 102% (P = .03), and ROM production by 475% (P = .001) and reduced rectal mucosal blood flow by 22% (P = .05). The control protocol did not change any of the variables measured. There were no differences between the responses of the patients with UC and HV.

CONCLUSIONS

Acute psychologic stress induces systemic and mucosal proinflammatory responses, which could contribute to exacerbations of UC in ordinary life.

Interfering with interferons in inflammatory bowel disease

Early experience of fontolizumab, a humanised anti‐interferon γ antibody, in active Crohn's disease has shown that the drug caused a significant decrease in endoscopic severity scores and CRP and was reasonably well tolerated. Fontolizumab may be worthy of further clinical trials

CD1d- and MR1-restricted invariant T cells: of mice and men

CD1d-restricted natural killer T cells and MR1-restricted mucosal associated invariant T (MAIT) cells constitute two subsets of unconventional T cells that are phylogenetically conserved. Therefore, they are thought to play an essential role within the immune system. MR1-restricted MAIT cell selection is dependent upon B cells, and their accumulation in the gut lamina propria and mesenteric lymph node requires the commensal bacterial flora. These features suggest that MAIT cells could be involved in tolerance or immunity to infections in the gut. As for natural killer T cells, the recent identification of one endogenous ligand, isoglobotrihexosylceramide, and of a family of bacterial agonists is an important advance for understanding their thymic selection and their role during infections.

Dendritic cells: the commanders-in-chief of mucosal immune defenses

PURPOSE OF REVIEW

Intestinal dendritic cells have emerged as key regulators of immunity to pathogens, oral tolerance and intestinal inflammation. Studies have begun to elucidate the regulatory mechanisms responsible for defining region- and compartment-specific phenotypes and functions of dendritic cells in mucosal tissues.

RECENT FINDINGS

Specific subsets of dendritic cells appear to be associated with the various routes for antigen acquisition in the intestine. The constant sampling of intestinal antigenic content ensures establishment of tolerance to commensal bacteria and food antigens. Tolerance development to oral antigens is restricted to the mucosal immune system. Other advances have provided insight into the molecular basis of microbial recognition and innate immune responses by intestinal dendritic cells. Differences in the involvement of dendritic cells have begun to emerge in Crohn's disease and ulcerative colitis and link gene regulation in dendritic cells to therapeutic responses.

SUMMARY

A major focus of mucosal immunology will be to understand how diverse dendritic cell subsets cooperate in regulating homeostasis and host defense in the different intestinal immune compartments. This will be pivotal to understanding how the mucosal immune system makes the distinction between commensal microbiota, pathogens and self antigens.

New mediators of immunity and inflammation in inflammatory bowel disease

PURPOSE OF REVIEW

In both Crohn's disease and ulcerative colitis, the tissue damage results from an inappropriate or exaggerated immune response to antigens of the gut microflora. This review summarizes current knowledge regarding the role of immune-inflammatory mediators in the pathogenesis of inflammatory bowel disease.

RECENT FINDINGS

Despite having a common basis in overresponsiveness to luminal antigens, Crohn's disease and ulcerative colitis are immunologically distinct entities. Crohn's disease is associated with a Th1 T cell-mediated response, characterized by enhanced production of interferon-gamma and tumor necrosis factor-alpha. Interleukin (IL)-12 and, possibly, IL-23 govern the Th1 cell differentiation, but optimal induction and stabilization of polarized Th1 cells would require additional cytokines, such as IL-15, IL-18 and IL-21. In ulcerative colitis, the local immune response is less polarized, but it is characterized by CD1-reactive natural killer T cell production of IL-13. Beyond these differences, Crohn's disease and ulcerative colitis share important end-stage effector pathways of intestinal injury, which are mediated by an active cross-talk between immune and non-immune mucosal cells.

SUMMARY

The clarification of the complex network of immune-inflammatory mediators operating in the gut of patients with inflammatory bowel disease has led to the identification of new targets that could, in turn, drive the development of effective biological therapies.

Role of apolipoproteins in gammadelta and NKT cell-mediated innate immunity

Recent findings reveal unanticipated connections between the fields of lipid metabolism and immunology. They concern gammadelta and NKT cells, nonconventional T cell populations that do not recognize protein antigens and are involved in immunity against cancer, defense against infections, or in regulation of classical immune responses. In this review, we summarize data linking perturbations of apolipoprotein levels and nonconventional T cells with inflammatory processes such as autoimmune diseases or atherosclerosis. We integrate and discuss recent findings on the implication of apolipoproteins in antigen recognition by gammadelta and NKT cells, with emphasis on apolipoproteins A-I and E. These findings also provide indications that apolipoproteins influence antitumor immunosurveillance.

IL-18 stimulates IL-13-mediated IFN-gamma-sensitive host resistance in vivo

IL-4 and IL-13 are up-regulated during in vivo responses to many nematode parasites, but increasing evidence suggests that increases in IL-13 can also occur independently of the IL-4-dominant Th2 response. Blocking B7 after Trichuris muris inoculation inhibits resistance and IL-4 elevations, instead resulting in an IFN-gamma-dominant response associated with susceptibility. However, blocking IFN-gamma under these conditions restores IL-13-dependent resistance. In this study, we examined the mechanism of IL-13 up-regulation and associated protection during this in vivo immune response. CD4+ T cells and DX5+ TCR- cells were identified as the major producers of IL-13, and the DX5+ TCR- cells were phenotyped as NK cells, since they expressed CD11b, IL-2Rbeta and Ly49C but not c-kit or Fc epsilonRI. NK cell-derived IL-13 elevations were T cell-dependent, as CD4+ T cell depletion blocked IL-13 production by mesenteric lymph node cells and induced susceptibility. IL-13 expression was increased independently of IL-12; however, blocking IL-18 function inhibited IL-13 production and increased susceptibility. These results indicate that CD4+ T cells and NK cells are the major sources of IL-13 during the in vivo Th1 response induced by B7 blockade and that under these conditions, IL-18 is specifically required for the in vivo up-regulation of IL-13 production and associated host protection.

A nonclassical non-Valpha14Jalpha18 CD1d-restricted (type II) NKT cell is sufficient for down-regulation of tumor immunosurveillance

The importance of immunoregulatory T cells has become increasingly apparent. Both CD4⁺CD25⁺ T cells and CD1d-restricted NKT cells have been reported to down-regulate tumor immunity in mouse tumor models. However, the relative roles of both T cell populations have rarely been clearly distinguished in the same tumor models. In addition, CD1d-restricted NKT cells have been reported to play a critical role not only in the down-regulation of tumor immunity but also in the promotion of the immunity. However, the explanation for these apparently opposite roles in different tumor models remains unclear. We show that in four mouse tumor models in which CD1d-restricted NKT cells play a role in suppression of tumor immunity, depletion of CD4⁺CD25⁺ T cells did not induce enhancement of immunosurveillance. Surprisingly, among the two subpopulations of CD1d-restricted NKT cells, Vα14Jα18⁺ (type I) and Vα14Jα18⁻ (type II) NKT cells, type I NKT cells were not necessary for the immune suppression. These unexpected results may now resolve the paradox in the role of CD1d-restricted NKT cells in the regulation of tumor immunity, in that type II NKT cells may be sufficient for negative regulation, whereas protection has been found to be mediated by α-galactosylceramide–responsive type I NKT cells.

Revisiting the immunomodulators tacrolimus, methotrexate, and mycophenolate mofetil: their mechanisms of action and role in the treatment of IBD

Inflammatory bowel diseases (IBDs) are thought to result from unopposed immune responses to normal gut flora in a genetically susceptible host. A variety of immunomodulating therapies are applied for the treatment of patients with IBDs. The first-line treatment for IBDs consists of 5-aminosalicylate and/or budesonide. However, these first-line therapies are often not suitable for continuous treatment or do not suffice for the treatment of severe IBD. Recently, efforts have been made to generate novel selective drugs that are more effective and have fewer side effects. Despite promising results, most of these novel drugs are still in a developmental stage and unavailable for clinical application. Yet, another class of established immunomodulators exists that is successful in the treatment of inflammatory bowel diseases. While waiting for emerging novel therapies, the use of these more established drugs should be considered. Furthermore, one of the advantages of using established immunomodulators is the well-documented knowledge on the long-term side effects and on the mechanisms of action. In this review, the authors discuss 3 well-known immunomodulators that are being applied with increased frequency for the treatment of IBD: tacrolimus, methotrexate, and mycophenolate mofetil. These agents have been used for many years as treatment modalities for immunosuppression after organ transplantation, for the treatment of cancer, and for immunomodulation in several other immune-mediated diseases. First, this review discusses the potential targets for immunomodulating therapies in IBDs. Second, the immunomodulating mechanisms and effects of the 3 immunomodulators are discussed in relationship to these treatment targets.

The natural killer T lymphocyte: a player in the complex regulation of autoimmune diabetes in non-obese diabetic mice

Manipulation of the immune response to specifically prevent autoaggression requires an understanding of the complex interactions that occur during the pathogenesis of autoimmunity. Much attention has been paid to conventional T lymphocytes recognizing peptide antigens presented by classical major histocompatibility complex (MHC) class I and II molecules, as key players in the destructive autoreactive process. A pivotal role for different types of regulatory T lymphocytes in modulating the development of disease is also well established. Lately, CD1d-restricted natural killer T (NKT) lymphocytes have been the subject of intense investigation because of their ability to regulate a diversity of immune responses. The non-classical antigen presenting molecule CD1d presents lipids and glycolipids to this highly specialized subset of T lymphocytes found in both humans and mice. From experimental models of autoimmunity, evidence is accumulating that NKT cells can protect from disease. One of the best studied is the murine type 1 diabetes model, the non-obese diabetic (NOD) mouse. While the NKT cell population was first recognized to be deficient in NOD mice, augmenting NKT cell activity has been shown to suppress the development of autoimmune disease in this strain. The mechanism by which CD1d-restricted T cells exert this function is still described incompletely, but investigations in NOD mice are starting to unravel specific effects of NKT cell regulation. This review focuses on the role of CD1d-restricted NKT cells in the control of autoimmune diabetes.

Recent advances in the etiology and treatment of inflammatory bowel disease

Crohn's disease and ulcerative colitis, together comprising the inflammatory bowel diseases, currently affect up to 2 million people in the western developed countries. The pathogenesis of the disease is a complex one in which genetic, immunogenic, microbial and environmental factors contribute to the etiology of the disease. Recent advances in understanding the molecular mechanisms that determine this complex entity have provided insight for promising new therapies.

Increased intratumor Valpha24-positive natural killer T cells: a prognostic factor for primary colorectal carcinomas

PURPOSE

Human invariant natural killer T (NKT) cells are novel, distinct lymphocyte populations with a restricted T-cell receptor repertoire (Valpha24-Vbeta11). They play a pivotal role in immunoregulation and in antitumor activities. This study focused on Valpha24+ NKT cells in colorectal carcinomas and their clinicopathologic significance.

EXPERIMENTAL DESIGN

Valpha24+ NKT-cell infiltration immunohistochemistry was studied in a total of 103 colorectal carcinoma cases. The degree of NKT-cell infiltration in tumors was evaluated as low (<7 NKT cells/5 HPF) or high (> or =7 NKT cells/5 HPF). The correlation between the degree of infiltrated Valpha24+ NKT cells and clinicopathologic variables was studied statistically.

RESULTS

A small number of Valpha24+ NKT cells were found in the normal colorectal mucosa (2.6 +/- 3.7 cells/5 HPF); however, their number increased remarkably in colorectal carcinomas (15.2 +/- 16.3 cells/5 HPF; P = 0.0003) and a majority showed phenotype of activation. Higher NKT-cell infiltration was more frequent in women than in men (P = 0.034) and correlated with fewer lymph node metastases (P = 0.042). Patients with high NKT-cell infiltration showed higher overall (P = 0.018) as well as disease-free (P = 0.0006) survival rates. Intratumor NKT-cell infiltration was an independent prognostic factor for the overall (P = 0.033) and disease-free (P = 0.0064) survival rates.

CONCLUSIONS

Increased infiltration of Valpha24+ NKT cells was observed in colorectal carcinomas. Higher Valpha24+ NKT-cell infiltration in colorectal carcinomas was an independent prognostic factor for favorable prognosis.

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Circulating levels of leptin, adiponectin, resistin, and ghrelin in inflammatory bowel disease

BACKGROUND

There is evidence that adipocytokines play an important role in metabolism and in inflammation. Because human metabolism dramatically changes in inflammatory bowel disease (IBD) and chronic inflammation is the hallmark of the disease, we studied serum levels of leptin, adiponectin, resistin, and ghrelin in patients with ulcerative colitis (UC) and Crohn's disease (CD) in comparison with healthy controls (HC).

METHODS

Leptin, adiponectin, resistin, and active ghrelin serum levels were measured in 100 IBD patients (46 UC and 54 CD) and in 60 matched HC using commercially available enzyme-linked immunosorbent assays. Leptin, adiponectin, resistin, and ghrelin levels were correlated with disease activity, type, localization, and treatment.

RESULTS

Mean serum leptin levels were 10.6+/-2.0 ng/mL in UC patients, 12.5+/-2.6 ng/mL in CD patients, and 15.0+/-1.8 ng/mL in HC (P=.01). Mean serum adiponectin levels were 9514.8+/-787.8 ng/mL in UC patients, 7651.1+/-613 ng/mL in CD patients, and 7270.6+/-559.4 ng/mL in HC (P=.05). Mean serum resistin levels were 21.2+/-2.2 ng/mL in UC patients, 18.7+/-1.6 ng/mL in CD patients and 11.8+/-0.6 ng/mL in HC (P=.0002). Mean serum ghrelin levels were 48.2+/-4.2 pg/mL in UC patients, 49.4+/-4.6 pg/mL in CD patients and 14.8+/-3.0 pg/mL in HC (P<.0001). Serum levels of these adipocytokines were not correlated with either C-reactive protein levels or the clinical indices of activity. No association between serum adipocytokines levels and disease localization in both UC and CD patients was found. Only serum ghrelin was significantly higher in ileal compared with colonic CD (P=.04).

CONCLUSIONS

Serum levels of adiponectin, resistin, and active ghrelin are increased whereas serum levels of leptin are decreased in patients with IBD. Further studies are needed to elucidate the role of adipocytokines in IBD.

MDR1 gene: susceptibility in Spanish Crohn's disease and ulcerative colitis patients

BACKGROUND

The multidrug resistance MDR1 gene codes for a membrane transporter associated with inflammatory bowel disease. The polymorphism Ala893Ser/Thr (G2677T/A) previously showed significant association with Crohn's disease (CD) and the Ile1145Ile (C3435T) with ulcerative colitis (UC). We studied the association of both polymorphisms in an independent population to reveal the impact of the MDR1 gene on predisposition to inflammatory bowel disease.

METHODS

Case-control study with 321 CD and 330 UC white Spanish patients recruited from the same center, and 352 healthy ethnically matched controls.

RESULTS

A significant association of MDR1 C3435T with CD was observed (CC vs (CT + TT): P = 0.007; OR [95% CI] = 1.58 [1.12-2.23]). A CD susceptibility haplotype 2677T/C3435 was identified. No difference between UC patients as a whole and controls could be detected.

CONCLUSIONS

New evidence supports the role of the MDR1 gene on CD susceptibility. Therefore, considering our results and those from others, the MDR1 gene behaves as a common risk factor for both CD and UC. We discovered that the C3435 allele conferring susceptibility to CD is different from the described 3435T UC risk allele.

Inflammatory bowel disease: epidemiology, pathogenesis, and therapeutic opportunities

Ulcerative colitis (UC) and Crohn's disease (CD), the primary constituents of inflammatory bowel disease (IBD), are precipitated by a complex interaction of environmental, genetic, and immunoregulatory factors. Higher rates of IBD are seen in northern, industrialized countries, with greater prevalence among Caucasians and Ashkenazic Jews. Racial gaps are closing, indicating that environmental factors may play a role. IBD is multigenic, with the most clearly established genetic link between certain NOD2 variants and CD. Regardless of the underlying genetic predisposition, a growing body of data implicates a dysfunctional mucosal immune response to commensal bacteria in the pathogenesis of IBD, especially CD. Possible triggers include a chronic inflammatory response precipitated by infection with a particular pathogen or virus or a defective mucosal barrier. The characteristic inflammatory response begins with an infiltration of neutrophils and macrophages, which then release chemokines and cytokines. These in turn exacerbate the dysfunctional immune response and activate either TH1 or TH2 cells in the gut mucosa, respectively associated with CD and, less conclusively, with UC. Elucidation of immunological and genetic factors indicate multiple points at which the inflammatory cascade may be interrupted, yielding the possibility of precise, targeted therapies for IBD.

IL-13 signaling through the IL-13alpha2 receptor is involved in induction of TGF-beta1 production and fibrosis

Interleukin (IL)-13 is a major inducer of fibrosis in many chronic infectious and autoimmune diseases. In studies of the mechanisms underlying such induction, we found that IL-13 induces transforming growth factor (TGF)-beta(1) in macrophages through a two-stage process involving, first, the induction of a receptor formerly considered to function only as a decoy receptor, IL-13Ralpha(2). Such induction requires IL-13 (or IL-4) and tumor necrosis factor (TNF)-alpha. Second, it involves IL-13 signaling through IL-13Ralpha(2) to activate an AP-1 variant containing c-jun and Fra-2, which then activates the TGFB1 promoter. In vivo, we found that prevention of IL-13Ralpha(2) expression reduced production of TGF-beta(1) in oxazolone-induced colitis and that prevention of IL-13Ralpha(2) expression, Il13ra2 gene silencing or blockade of IL-13Ralpha(2) signaling led to marked downregulation of TGF-beta(1) production and collagen deposition in bleomycin-induced lung fibrosis. These data suggest that IL-13Ralpha(2) signaling during prolonged inflammation is an important therapeutic target for the prevention of TGF-beta(1)-mediated fibrosis.

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Treatment of murine Th1- and Th2-mediated inflammatory bowel disease with NF-kappa B decoy oligonucleotides

The Th1 and Th2 T cell responses that underlie inflammatory bowel diseases (IBDs) are likely to depend on NF-kappaB transcriptional activity. We explored this possibility in studies in which we determined the capacity of NF-kappaB decoy oligodeoxynucleotides (decoy ODNs) to treat various murine models of IBD. In initial studies, we showed that i.r. (intrarectal) or i.p. administration of decoy ODNs encapsulated in a viral envelope prevented and treated a model of acute trinitrobenzene sulfonic acid-induced (TNBS-induced) colitis, as assessed by clinical course and effect on Th1 cytokine production. In further studies, we showed that NF-kappaB decoy ODNs were also an effective treatment of a model of chronic TNBS-colitis, inhibiting both the production of IL-23/IL-17 and the development of fibrosis that characterizes this model. Treatment of TNBS-induced inflammation by i.r. administration of NF-kappaB decoy ODNs did not inhibit NF-kappaB in extraintestinal organs and resulted in CD4+ T cell apoptosis, suggesting that such treatment is highly focused and durable. Finally, we showed that NF-kappaB decoy ODNs also prevented and treated oxazolone-colitis and thus affect a Th2-mediated inflammatory process. In each case, decoy administration led to inflammation-clearing effects, suggesting a therapeutic potency applicable to human IBD.

Therapeutic targeting of alpha 4-integrins in chronic inflammatory diseases: tipping the scales of risk towards benefit?

Inhibition of leukocyte trafficking via alpha4-integrin antibody blockade has recently become a validated therapeutic approach for several inflammatory diseases, including multiple sclerosis, ulcerative colitis and Crohn's disease. In the midst of this recent success, 3 patients receiving chronic treatment with the anti-alpha4 antagonist natalizumab (Tysabri) for the treatment of multiple sclerosis or Crohn's disease, developed JC-virus related progressive multifocal leukoencephalopathy (PML). These unforeseen consequences suggest that long term blockade of alpha4-integrins might prevent trafficking of non-pathogenic lymphocytes that are essential for viral immunosurveillance. In the current issue of the European Journal of Immunology Bjursten and colleagues report that long term treatment with anti-alpha4-integrin antibodies results in exacerbation of the murine model of colitis induced by the targeted deletion of the heterotrimeric G protein subunit Galphai2. In order to properly evaluate the efficacy and safety of anti-alpha4-integrin therapy, the relationship between these observations in an immunologically altered animal model and human clinical disease needs to be carefully measured.

Possible role of REG Ialpha protein in ulcerative colitis and colitic cancer

BACKGROUND AND AIMS

Although regenerating gene (REG) Ialpha protein may be involved in the inflammation and carcinogenesis in the gastrointestinal tract, its pathophysiological role in ulcerative colitis (UC) and the resulting colitic cancer remains unclear. We investigated expression of the REG Ialpha gene and its protein in UC and colitic cancer tissues. We examined whether cytokines are responsible for REG Ialpha gene expression and whether REG Ialpha protein has a trophic and/or an antiapoptotic effect on colon cancer cells.

METHODS

Expression of REG Ialpha mRNA and its gene product in UC tissues was analysed by real time reverse transcription-polymerase chain reaction and immunohistochemistry, respectively. The effects of cytokines on REG Ialpha promoter activity were examined in LoVo cells by luciferase reporter assay. The effects of REG Ialpha protein on growth and H(2)O(2) induced apoptosis were examined in LoVo cells by MTT and TUNEL assays, respectively.

RESULTS

REG Ialpha protein was strongly expressed in inflamed epithelium and in dysplasias and cancerous lesions in UC tissues. The level of REG Ialpha mRNA expression in UC tissues correlated significantly with severity of inflammation and disease duration. REG Ialpha promoter activity was enhanced by stimulation with interferon gamma or interleukin 6. REG Ialpha protein promoted cell growth and conferred resistance to H(2)O(2) induced apoptosis in LoVo cells. REG Ialpha protein promoted Akt phosphorylation and enhanced Bcl-xL and Bcl-2 expression in LoVo cells.

CONCLUSIONS

The REG Ialpha gene is inducible by cytokines and its gene product may function as a mitogenic and/or an antiapoptotic factor in the UC-colitic cancer sequence.