Amino acid position 11 of HLA-DRß1 is a major determinant of chromosome 6p association with ulcerative colitis.

The major histocompatibility complex (MHC) on chromosome 6p is an established risk locus for ulcerative colitis (UC) and Crohn's disease (CD). We aimed to better define MHC association signals in UC and CD by combining data from dense single-nucleotide polymorphism (SNP) genotyping and from imputation of classical human leukocyte antigen (HLA) types, their constituent SNPs and corresponding amino acids in 562 UC, 611 CD and 1428 control subjects. Univariate and multivariate association analyses were performed, controlling for ancestry. In univariate analyses, absence of the rs9269955 C allele was strongly associated with risk for UC (P = 2.67 × 10(-13)). rs9269955 is a SNP in the codon for amino acid position 11 of HLA-DRß1, located in the P6 pocket of the HLA-DR antigen binding cleft. This amino acid position was also the most significantly UC-associated amino acid in omnibus tests (P = 2.68 × 10(-13)). Multivariate modeling identified rs9269955-C and 13 other variants in best predicting UC vs control status. In contrast, there was only suggestive association evidence between the MHC and CD. Taken together, these data demonstrate that variation at HLA-DRß1, amino acid 11 in the P6 pocket of the HLA-DR complex antigen binding cleft is a major determinant of chromosome 6p association with UC.

Mucosal T-cell immunoregulation varies in early and late inflammatory bowel disease.

BACKGROUND AND AIMS: Crohn's disease is a life-long form of inflammatory bowel disease (IBD) mediated by mucosal immune abnormalities. Understanding of the pathogenesis is limited because it is based on data from adults with chronic Crohn's disease. We investigated mucosal T-cell immunoregulatory events in children with early Crohn's disease. METHODS: Mucosal biopsies and T-cell clones were derived from children experiencing the first attack of Crohn's disease, children with long-standing Crohn's disease, infectious colitis, and children without gut inflammation. RESULTS: As in acute infectious colitis, interleukin (IL) 12 induced T cells from early Crohn's disease to acquire a strongly polarised T helper (Th) type 1 response characterised by high IFN-gamma production and IL12Rbeta2 chain expression. Th1 polarisation was not induced in clones from late Crohn's disease. Mucosal levels of IL12p40 and IL12Rbeta2 messenger RNA were significantly higher in children with early than late Crohn's disease. These results demonstrate that susceptibility to IL12-mediated modulation is strongly dependent on the stage of Crohn's disease. CONCLUSIONS: At the onset of Crohn's disease mucosal T cells appear to mount a typical Th1 response that resembles an acute infectious process, and is lost with progression to late Crohn's disease. This suggests that mucosal T-cell immunoregulation varies with the course of human IBD. Patients with the initial manifestations of IBD may represent an ideal population in which immunomodulation may have optimal therapeutic efficacy.

Fibrosis in ulcerative colitis is directly linked to severity and chronicity of mucosal inflammation.

BACKGROUND: Fibrosis in ulcerative colitis has remained largely unexplored despite its clinical implications. AIMS: This cross-sectional study was aimed at characterising the presence, anatomical location and degree of ulcerative colitis-associated fibrosis and its possible link to clinical parameters. METHODS: Seven hundred and six individual tissue cross-sections derived every 10 cm along the length of 89 consecutive Ulcerative colitis colectomy specimens were examined and compared to Crohn's disease colitis, diverticular disease and uninvolved areas from colorectal cancer patients. Degree of inflammation, fibrosis and morphometric measurements of all layers of the intestinal wall were evaluated. Three gastrointestinal pathologists independently assessed colon sections stained with haematoxylin and eosin, Masson trichrome and Sirius red. Clinical data were collected prospectively. RESULTS: Submucosal fibrosis was detected in 100% of ulcerative colitis colectomy specimens, but only in areas affected by inflammation. Submucosal fibrosis was associated with the severity of intestinal inflammation (Spearman correlations rho (95% confidence interval): 0.58 (P < 0.001) and histopathological changes of chronic mucosal injury, but not active inflammation. Colectomy for refractory disease rather than presence of dysplasia was associated with increased fibrosis and a thicker muscularis mucosae, whereas a thinner muscularis mucosae was associated with anti-tumour necrosis factor therapy. No feature on endoscopic mucosal biopsies could predict the underlying amount of fibrosis or the thickness of the muscularis mucosae. CONCLUSIONS: A significant degree of fibrosis and muscularis mucosae thickening should be considered as common complications of chronic progressive ulcerative colitis. These features may have clinical consequences such as motility abnormalities and increased wall stiffness.

Sensitization to epithelial antigens in chronic mucosal inflammatory disease. Characterization of human intestinal mucosa-derived mononuclear cells reactive with purified epithelial cell-associated components in vitro.

To explore the auto-reactive potential of cells infiltrating the gut mucosa in idiopathic chronic inflammatory bowel disease, intestinal lamina propria mononuclear cells (LPMC) were isolated, characterized morphologically and phenotypically, and evaluated for antigen-specific reactivity. The last was assessed by quantitating LPMC cytotoxic capabilities against purified, aqueous-soluble, organ-specific epithelial cell-associated components (ECAC) characterized previously. Enzyme-isolated inflammatory bowel disease LPMC were constituted primarily by T lymphocytes (57 +/- 12% OKT 3-positive), B lymphocytes (18 +/- 9% surface immunoglobulin-positive), and macrophages (11 +/- 6% esterase-positive), and were responsive to phytohemagglutinin (mean uptake 86,933 cpm/5 X 10(5) cells). LPMC present in abnormal segments from 71% of patients with chronic inflammatory bowel disease were cytotoxic for ECAC isolated from colon (12.5 +/- 8.9% specific lysis) and small bowel (7.1 +/- 6.5%), but not for kidney control antigen (0.8 +/- 1.1%) isolated in a manner analogous to that used for ECAC (P less than 0.02). In contrast, despite comparable responses to phytohemagglutinin (mean uptake 59,200 cpm/5 X 10(5) cells), LPMC from histologically normal mucosa of patients with benign (adult megacolon, Hirshsprung's disease, diverticulosis) or malignant disease failed to lyse indicator cells labeled with colon-derived ECAC (0.3 +/- 0.08%), small bowel-derived ECAC (0.4 +/- 1.11%), or kidney antigen (0.29 +/- 0.79%). LPMC reactivity for individual gel-purified macromolecules of small bowel-derived ECAC (designated as the "P" series of components) was greatest against component P1 (by 2-3-fold), but was detectable against three other purified components as well. The addition of patient's serum did not enhance cytotoxicity to ECAC. Characterization of the cytotoxic cell showed that it was nonadherent to plastic surfaces, bore T lymphocyte-specific markers detectable by OKT 11 and OKT 3 monoclonal antibodies, and could be depleted by removal of cells with receptors for sheep erythrocytes. ECAC-specific reactivity was markedly reduced (greater than 93%) in most experiments when LPMC were preincubated for 1 h with ECAC. These data support the concept that autosensitization to several epithelial cell-associated components has occurred in patients with chronic inflammatory bowel disease, and provide initial evidence that antigen-specific, cell-mediated mechanisms may play a role in the pathogenesis of these disorders.

Review article: breath analysis in inflammatory bowel diseases.

BACKGROUND: There is an urgent need for cheap, reproducible, easy to perform and specific biomarkers for diagnosis, differentiation and stratification of inflammatory bowel disease (IBD) patients. Technical advances allow for the determination of volatile organic compounds in the human breath to differentiate between health and disease. AIM: Review and discuss medical literature on volatile organic compounds in exhaled human breath in GI disorders, focusing on diagnosis and differentiation of IBD. METHODS: A systematic search in PubMed, Ovid Medline and Scopus was completed using appropriate keywords. In addition, a bibliography search of each article was performed. RESULTS: Mean breath pentane, ethane, propane, 1-octene, 3-methylhexane, 1-decene and NO levels were elevated (P < 0.05 to P < 10(-7)) and mean breath 1-nonene, (E)-2-nonene, hydrogen sulphide and methane were decreased in IBD compared to healthy controls (P = 0.003 to P < 0.001). A combined panel of 3 volatile organic compounds (octene, (E)-2-nonene and decene) showed the best discrimination between paediatric IBD and controls (AUC 0.96). Breath condensate cytokines were higher in IBD compared to healthy individuals (P < 0.008). Breath pentane, ethane, propane, isoprene and NO levels correlated with disease activity in IBD patients. Breath condensate interleukin-1ß showed an inverse relation with clinical disease activity. CONCLUSIONS: Breath analysis in IBD is a promising approach that is not yet ready for routine clinical use, but data from other gastrointestinal diseases suggest the feasibility for use of this technology in clinical practice. Well-designed future trials, incorporating the latest breath detection techniques, need to determine the exact breath metabolome pattern linked to diagnosis and phenotype of IBD.

Eosinophils within the healthy or inflamed human intestine produce substance P and vasoactive intestinal peptide.

The purpose of this study was to show if inflammatory cells within healthy or diseased human intestinal mucosa produce some regulatory neuropeptides. First, inflammatory cells were isolated from the intestinal lamina propria of 11 patients with ulcerative colitis or Crohn's disease. Also collected were cells from anatomically normal intestine derived from five patients requiring bowel resection for diseases not related to inflammatory bowel disease. Extracts of these isolated cells contained authentic substance P (SP) and vasoactive intestinal peptide (VIP) as shown by RIA and their elution profiles on HPLC. Immunostaining of cells from nine of 13 additional patients localized immunoreactive SP and VIP to secretory granules within most mucosal eosinophils. No other cell types stained positive. Messenger RNA encoding SP and VIP was localized to lamina propria eosinophils by in situ hybridization. Mucosa inflammatory cells, from eight of nine more patients, cultured in vitro, released detectable amounts of VIP, but not SP. It is concluded that intestinal eosinophils produce SP and VIP. Since the eosinophils store and release more VIP than SP, it is possible that VIP is the preferred secretory product.

T cell receptor vß gene expression in inflammatory bowel disease lamina propria lymphocytes: evidence for altered vß gene usage.

: In this study the TCR-Vß repertoire expressed in T cells of lamina propria mononuclear cells (LPMC) and peripheral blood mononuclear cells (PBMC) was examined using a reverse transcription-PCR (RT-PCR) technique for TCR-Vß mRNA. Using a qualitative RT-PCR method, LPMC of patients with IBD and control individuals were shown to contain mRNA for each of 20 TCR-Vß families, indicating that IBD is not associated with a major deletion or expansion of any TCR-Vß family. Subsequently, using a quantitative method for four frequently expressed TCR-Vß families, it was shown that the pattern of TCR-Vß expression was different in PBMC and LPMC of both IBD patients and control individuals. In addition, it was shown that the LPMC/PBMC ratio of mean mRNA values for TCR-Vß2, but not for TCR-Vß6, 7, and 14 was lower in IBD patients than control individuals. These results show that the TCR-Vß repertoire in PBMC and LPMC is different both in IBD patients and control individuals. In addition, they show that the TCR-Vß repertoire is altered in IBD, possibly due to an immune response to disease specific antigens, superantigens or neoantigens.

Pitfalls in cytokine analysis in inflammatory bowel disease.

Analysis of cytokine production and function is an indispensable tool to study Crohn's disease and ulcerative colitis. This analysis has generated a tremendous amount of data, but a clear interpretation of results has been hampered by limited attention paid to several patient- and sample-related pitfalls. These include: clinical parameters; the relative value of circulating vs. intestinal cytokine levels; the selection of tissue specimens and their processing method; the specific cellular source of each cytokine; the effect of cytokine inducers; and the technique utilized to obtain qualitative or quantitative data on cytokine protein or mRNA. Once all of these crucial variables are taken into proper perspective, a better understanding will emerge of the true role of cytokines in the pathogenesis of inflammatory bowel disease.

Crohn's disease and ulcerative colitis mucosal T cells are stimulated by intestinal epithelial cells: implications for immunosuppressive therapy.

BACKGROUND: Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory diseases, and their pathogenesis is attributed, in part, to alterations of the mucosal immune system. This study was designed to define the possible contribution of epithelial cells to the activation of lamina propria T lymphocytes (LPTs) in CD and UC. METHODS: LPTs isolated from CD, UC, and control surgical specimens were cocultured with freshly isolated allogeneic or autologous epithelial cells or epithelial cell lines. Resulting T-cell proliferation was evaluated by tritiated thymidine incorporation on day 5. RESULTS: When intestinal epithelial cells were used to stimulate mucosal T-cell proliferation, CD and UC LPTs were less responsive than control LPTs (p < 0.05 and p < 0.03, respectively). This difference between inflamed and control T cells was consistently observed by using a variety of different intestinal epithelial cell types. CONCLUSIONS: CD and UC mucosal T cells are hyporesponsive to activation by intestinal epithelial cells when compared with control LPTs. Elucidating the mechanism underlying the differential activation of CD and UC LPTs may help to better understand the immunopathogenesis of these conditions.

Inflammatory bowel disease: dogmas and heresies.

Perception of a disease state by the practising physician is based on how easily the diagnosis can be made and how predictable the outcome of the chosen therapy is. The academic investigator perceives the same disease based on how well its cause and mechanism are understood, and how rational pathophysiology-based treatments are. Because of incomplete knowledge, neither the practising physician nor the academic investigator are comfortable in dealing with inflammatory bowel disease, and both seek help in the dogmas and heresies inevitably associated with chronic disease of unknown aetiology.

Selective resistance of mucosal T-cell activation to immunosuppression in Crohn's disease.

BACKGROUND & AIMS: The inappropriately high state of T-cell activation found in Crohn's disease could be due to failure to respond to inhibitory signals. We tested the hypothesis that Crohn's disease mucosal T-cells are resistant to the immunosuppressive action of interleukin4. PATIENTS: Patients with Crohn's disease, ulcerative colitis, and other malignant and non-malignant conditions undergoing bowel resection. METHODS: The effect of interleukin-4 on lamina propria mononuclear cells from Crohn's disease, ulcerative colitis and control mucosa was assessed on various T-cell functions: interleukin-2-induced cytotoxicity, soluble interleukin-2 receptor and interleukin-2 production, and expression of mRNA for interleukin-2R and interferon-gamma. RESULTS: Cytotoxicity of control and ulcerative colitis cells was markedly decreased by interleukin-4, whereas Crohn's disease cells failed to be inhibited. Addition of interleukin-4 to interleukin-2-stimulated cultures decreased soluble interleukin-2R production significantly less in Crohn's disease and ulcerative colitis than control cells. In the same cultures, residual levels of interleukin-2 were significantly increased in control and ulcerative colitis, but not Crohn's disease cultures. Finally, Crohn's disease cells were significantly more resistant to interleukin-4-mediated inhibition of spontaneous and interleukin-2-induced expression of interleukin-2Ralpha and interferon-gamma mRNA compared to control cells. CONCLUSIONS: The effector function, receptor expression and cytokine production of Crohn's disease mucosal T-cells are resistant to interleukin4-mediated inhibition. Failure to respond to down-regulatory signals may contribute to persistent T-cell activation and chronicity of inflammation in Crohn's disease.

Inflammatory bowel disease. Current concepts of pathogenesis and implications for therapy.

Inflammatory bowel disease (IBD) still presents major challenges to the understanding of its cause, mechanisms of inflammation, and therapeutic choices to control the damaged tissue. Both types of IBD, ulcerative colitis and Crohn's disease, have been known and investigated for over half century but neither one is fully understood nor can be satisfactorily managed. While many gaps in our knowledge still exist, the last two decades have witnessed an unprecedented progress not only in the etiology but mainly in the mechanisms underlying the chronic inflammatory response. The pattern of IBD epidemiology has drastically changed since World War II, with an increased frequency in countries that have adopted a ''westernized'' life style. A parallel and important phenomenon is the continuous drop in age of onset in children. Unfortunately, only few epidemiological clues are available, with the exception of smoking and diet. What in smoking alters the course of IBD is still a mystery and which, among thousands of additives, could represent a risk factor will remain unknown for the foreseeable future. The current emphasis on the study of the enteric flora as the source of potential antigens against which the mucosal immune system reacts appear well justified. The data from animal models appears particularly convincing. Thus, after decades of relying almost exclusively on patient-derived information, numerous animal models are generating precious new information on IBD pathogenesis. In experimental IBD the genetic background of the animal markedly influences the course of the disease, and the same is probably true in humans. The identification of NOD2 as the first mutated gene associated with a subgroup of Crohn's disease patients is the first evidence that genetics are pointing to the right direction for understanding how the environment interacts with genes to cause IBD. For many years immunology has been the main source of scientific information on mechanisms of IBD. Cytokines, chemokines and other soluble factors dominate immunological studies aimed at understanding how different anti-inflammatory and pro-inflammatory mediators are improperly regulated and how immune imbalance can be restored. The extent to which T-cells live or die is also a key determinant of chronicity. In addition to classical immune cells, epithelial, endothelial, mesenchymal and nerve cells are slowly gaining more importance in IBD pathogenesis, as they contribute to the ultimate fate of tissue damage. Medical and surgical therapies are vastly better now that they were only a couple of decades ago, but they are still far from satisfactory. Steroid and aminosalicylates are still the most common drugs after 60 years of use, and it is time to renovate our therapeutic approach to a more effective one. The value of biologicals has been highlighted by the recent success of anti-TNF therapy. Timing of therapy must also change. The concept of the step-by-step approach is slowly fading away, and the idea of an ''all-out'' approach with multiple concomitant drugs early in the disease is gaining credibility. New reports on early aggressive therapies, and the demonstration that early and late experimental IBD are caused by different mechanisms are changing the way we think about managing IBD. Both ulcerative colitis and Crohn's disease will continue to challenge the medical establishment for year to come, but the possibility that IBD can be conquered is more realistic now that never before.

Immune events associated with inflammatory bowel disease.

Immunologic abnormalities have been implicated in the etiology of inflammatory bowel disease (IBD). Defects of systemic immunity and of local (intestinal) immunity have been studied. The numbers of T and B lymphocytes and their characteristics seem to vary with the disease, but no cause-and-effect relationship has been established. The presence of anticolon antibodies in patients with ulcerative colitis suggests that these antibodies could be involved in IBD, but they have also been found in other conditions. In the peripheral blood, abnormalities of cell-mediated immunity are inconsistent and suggest that they are not fundamental defects of the disease. The hypothesis that the inflammatory process is a result of immune-mediated intestinal tissue damage is being extensively studied. The high familial incidence of the disease suggests a role of histocompatibility locus antigens, but no reproducible association can be established. In vivo and in vitro studies of mucosal mononuclear cells have revealed abnormalities of immunoglobulin production, some types of cytotoxicity against gut-derived antigens, and altered lymphokine production associated with the disease. Further studies of the intestinal immune system would seem to be the most fruitful line of research.

Platelet-activating factor and distinct chemokines are elevated in mucosal biopsies of erosive compared with non-erosive reflux disease patients and controls.

BACKGROUND: A distinction between symptomatic non-erosive reflux disease (NERD) and erosive esophagitis (EE) patients is supported by the presence of inflammatory response in the mucosa of EE patients, leading to a damage of mucosal integrity. To explore the underlying mechanism of this difference, we assessed inflammatory mediators in mucosal biopsies from EE and NERD patients and compared them with controls. METHODS: Nineteen NERD patients, 15 EE patients, and 16 healthy subjects underwent endoscopy after a 3-week washout from PPI or H(2) antagonists. Biopsies obtained from the distal esophagus were examined by quantitative real-time polymerase chain reaction (qPCR) and multiplex enzyme-linked immunosorbent assay for selected chemokines and lyso-PAF acetyltransferase (LysoPAF-AT), the enzyme responsible for production of platelet-activating factor (PAF). KEY RESULTS: Expression of LysoPAF-AT and multiple chemokines was significantly increased in mucosal biopsies derived from EE patients, when compared with NERD patients and healthy controls. Upregulated chemokines included interleukin 8, eotaxin-1, -2, and -3, macrophage inflammatory protein-1α (MIP-1α), and monocyte chemoattractant protein-1 (MCP-1). LysoPAF-AT and the chemokine profile in NERD patients were comparable with healthy controls. CONCLUSIONS & INFERENCES: Levels of selected cytokines and Lyso-PAF AT were significantly higher in the esophageal mucosa of EE patients compared with NERD and control patients. This difference may explain the distinct inflammatory response occurring in EE patients' mucosa. In contrast, as no significant differences existed between the levels of all mediators in NERD and control subjects, an inflammatory response does not appear to play a major role in the pathogenesis of the abnormalities found in NERD patients.

Critical role of the CD40 CD40-ligand pathway in regulating mucosal inflammation-driven angiogenesis in inflammatory bowel disease.

BACKGROUND AND AIMS: Angiogenesis is a novel component in inflammatory bowel disease (IBD) pathogenesis. We have previously shown that immune-nonimmune interactions through the CD40-CD40-ligand (CD40L) pathway might sustain gut inflammation, although their effect on regulating inflammation-driven angiogenesis is unknown. The present study evaluated the role of the CD40-CD40L interaction in the promotion of immune-mediated angiogenesis in IBD. METHODS: Human nonimmune cells of colonic origin-namely, human intestinal fibroblasts (HIFs) and human intestinal microvascular endothelial cells (HIMECs)-were activated with either soluble CD40L (sCD40L), or CD40(+) D1.1 cells or CD40L-activated lamina propria T (LPT) cells before measuring pro-angiogenic cytokine release. Blocking antibodies to either CD40 or CD40L were used to disrupt the CD40-CD40L interaction. The dextran sodium sulphate (DSS) model of experimental colitis in CD40 and CD40L knockout mice was established to assess whether the CD40-CD40L pathway was implicated in controlling inflammation-driven angiogenesis in vivo. RESULTS: Engagement of CD40 on HIFs promoted the release of vascular endothelial growth factor (VEGF), interleukin-8 (IL-8) and hepatocyte growth factor (HGF). LPT cells were potent inducers of pro-angiogenic cytokine secretion by HIFs. Supernatants from sCD40L-activated HIFs induced migration of HIMECs and tubule formation, both of which were inhibited by blocking antibodies to either VEGF, IL-8 or HGF. Both CD40- and CD40L-deficient mice were protected from DSS-induced colitis and displayed a significant impairment of gut inflammation-driven angiogenesis, as assessed by microvascular density. CONCLUSIONS: The CD40-CD40L pathway appears to be crucially involved in regulating inflammation-driven angiogenesis, suggesting that strategies aimed at blocking CD40-CD40L interactions might be beneficial in acute and chronic intestinal injury.