Functional CD4+CD25high regulatory T cells are enriched in the colonic mucosa of patients with active ulcerative colitis and increase with disease activity

BACKGROUND: Factors determining the extension and degree of inflammation in the colonic mucosa of patients with ulcerative colitis (UC) are largely unknown, but CD4+CD25high regulatory T cells (Tregs) have been implicated to play an important role in suppressing inflammation. Therefore, the aims of this study were to determine whether colonic Tregs have suppressive effects on colonic effector T cells in UC and to analyze the association between segmental colonic Treg distribution and disease activity. MATERIALS AND METHODS: The suppressive activity of colonic CD4+CD25high Tregs from patients with active UC was determined in coculture assays measuring proliferation and cytokine production. The frequency of Tregs and the expression of the Treg marker FOXP3 were analyzed with flow cytometry and RT-PCR in isolated cells and the whole mucosa from patients with active and inactive disease, as well as healthy mucosa. RESULTS: Colonic CD4+CD25high T cells from patients with UC suppressed the proliferation and cytokine secretion of colonic effector CD4+ T cells. Healthy controls but not patients with UC had lower Treg frequencies in the sigmoid than in the ascending colon. Patients with UC with active disease had increased frequency of colonic Tregs. The frequency of Tregs was positively correlated with colonic disease activity and serum C-reactive protein. CONCLUSIONS: Colonic CD4+CD25high Tregs are able to suppress colonic effector T cell activity in vitro, and the Treg frequency in the inflamed intestine increases with disease activity in patients with active UC. This suggests that Tregs may be outnumbered by other inflammatory cells or that their suppressive activity may be influenced by the in vivo environment.     

Systemic antibodies towards mucosal bacteria in ulcerative colitis and Crohn's disease differentially activate the innate immune response

BACKGROUND AND AIMS: The mucosa in ulcerative colitis (UC) is replete with antibody producing plasma B cells and polymorphonuclear leucocytes (PMN). This combination of effector cells requires a crosslinking antigen to evoke an antibody driven PMN inflammatory response via their Fc receptors. The stimulus for activation is thought to be commensal bacteria colonising the gut mucosa. The aim of this investigation was to compare the principal culturable bacterial populations on the rectal mucosa of UC patients, and to determine whether specific antibodies towards these bacteria can activate infiltrating PMN through opsonisation. This would provide an explanation for this chronic inflammatory condition. METHODS: Bacteria colonising rectal tissue were characterised using chemotaxonomic techniques. Systemic antibody responses were measured against total antigens and surface antigens of these organisms in UC and Crohn's disease (CD) patients, together with healthy controls. Antibody enhancement of the respiratory burst in PMN was also investigated, against a range of mucosal isolates. RESULTS: Distinct differences were observed in some bacterial populations in UC biopsies, which were generally reflected in antibody responses towards these organisms. UC patients had higher IgG responses to surface antigens, primarily IgG1, whereas the response in CD was mainly IgG2. Antibodies from UC patients greatly enhanced the respiratory burst in PMN, in response to individual bacterial species. CONCLUSIONS: Changes in mucosal bacteria, and a switch from internal to surface antigen/antibody reactivity of a predominantly IgG1 type, leads to greater opsonisation of the respiratory burst in PMN, providing a mechanism for maintaining the inflammatory state in UC.     

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.     

Effect of smoking on inflammatory bowel disease： Is it disease or organ specific？

Smoking is an important environmental factor in inflammatory bowel disease （IBD） with differing effects in ulcerative colitis （UC） and Crohn＇s disease （CD）. Never smoking and formerly smoking increase the risk of UC, whereas smoking exacerbates the course of CD. The potential mechanisms involved in this dual relationship are yet unknown. A reasonable assumption is that smoking has different effects on the small and large intestine. This assumption is based on animal and human studies that show that the effects of smoking/nicotine on CD and UC depend on the site of inflammation and not on the type of disease.     

Changes in the expression and distribution of the inducible and endothelial nitric oxide synthase in mucosal biopsy specimens of inflammatory bowel disease

OBJECTIVE: The role of nitric oxide (NO) in the pathophysiology of inflammatory bowel disease (IBD) is controversial. The aim of this study was to investigate the expression and localization of nitric oxide synthase isoforms (iNOS, eNOS) in IBD colonic mucosa. MATERIAL AND METHODS: Forty-four patients with IBD (24 ulcerative colitis (UC), 20 Crohn's disease (CD) and 16 controls) were investigated by colonoscopy. iNOS and eNOS in tissue sections was demonstrated by histochemistry (NADPH-diaphorase reaction) and immunohistochemistry. Cell type analysis and quantitative assessment of the iNOS immunoreactive (IR) cells and densitometry of iNOS in immunoblots were also performed. RESULTS: iNOS-IR cells were significantly numerous in inflamed mucosa of UC (64+/-4 cells/mm2) than in CD (4+/-2 cells/mm2). iNOS-IR/CD15-IR cells showed significant elevation in inflamed (i) versus uninflamed (u) UC mucosa (UCu 8+/-3%, UCi 85+/-10%) In CD, the percentage of iNOS-IR/CD68-IR cells was lower in inflamed sites (CDu 23+/-8%, CDi 4+/-3%). Immunoblot of biopsies revealed significant elevation of iNOS in active UC compared with uninflamed sites, whereas in CD no significant changes were detected. Differences were observed in eNOS and endothelial marker CD31 immunoreactivity. In patients with UC and in controls the ratios of eNOS/CD31-IR vessels were 82.3% and 92.0% respectively, whereas in CD the ratio was 8.3% with a concomitantly significant increase of CD31-IR vessels. The distribution and morphological characteristics of the NOS-IR inflammatory cells and endothelia were similar to those showing NADPH-diaphorase reactivity. CONCLUSIONS: Differences observed in the expression and distribution of NOS isoforms in immune and endothelial cells may contribute to better understanding of the structural and physiological changes in UC and CD.     

Interleukin-12 and Th1 immune response in Crohn＇s disease： Pathogenetic relevance and therapeutic inplication

Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory disorders of the gastrointestinal tract that share clinical and pathological characteristics. The most accredited hypothesis is that both CD and UC result from a deregulated mucosal immune response to normal constituents of the gut microflora. Evidence, however, indicates that the main pathological processes in these two diseases are distinct. In CD, the tissue-damaging inflammatory reaction is driven by activated type 1 helper T-cell (Th1), whereas a humoral response predominates in UC. Consistently, a marked accumulation of macrophages making interleukin (IL)-12, the major Th1-inducing factor, is seen in CD but not in UC mucosa. Preliminary studies also indicate that administration of a monoclonal antibody blocking the IL-12/p40 subunit can be useful to induce and maintain clinical remission in CD patients. Notably, the recently described IL-23 shares the p40 subunit with IL-12, raising the possibility that the clinical benefit of the anti-IL-12/p40 antibody in CD may also be due to the neutralization of IL-23 activity. This review summarizes the current information on the expression and functional role of IL-12 and IL-12-associated signaling pathways both in patients with CD and experimental models of colitis, thus emphasizing major differences between IL-12 and IL-23 activity on the development of intestinal inflammation.     

Interleukin-12 and Th1 immune response in Crohn''s disease: Pathogenetic relevance and therapeutic inplication

Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory disorders of the gastrointestinal tract that share clinical and pathological characteristics.The most accredited hypothesis is that both CD and UC result from a deregulated mucosal immune response to normal constituents of the gut microflora. Evidence,however, indicates that the main pathological processes in these two diseases are distinct. In CD, the tissuedamaging inflammatory reaction is driven by activated type 1 helper T-cell (Th1), whereas a humoral response predominates in UC. Consistently, a marked accumulation of macrophages making interleukin (IL)-12, the major Th1-inducing factor, is seen in CD but not in UC mucosa.Preliminary studies also indicatethat administration of a monoclonal antibody blocking the IL-12/p40 subunit can be useful to induce and maintain clinical remission in CD patients. Notably, the recently described IL-23 shares the p40 subunit with IL-12, raising the possibility that the clinical benefit of the anti-IL-12/p40 antibody in CD may also be due to the neutralization of IL-23 activity. This review summarizes the current information on the expression and functional role of IL-12 and IL-12-associated signaling pathways both in patients with CD and experimental models of colitis, thus emphasizing major differences between IL-12 and IL-23 activity on the development of intestinal inflammation.     

CD40 and CD86 upregulation with divergent CMRF44 expression on blood dendritic cells in inflammatory bowel diseases

OBJECTIVE: Dendritic cells (DC) are the only antigen-presenting cells that can activate na?ve T lymphocytes and initiate a primary immune response. They are also thought to have a role in immune tolerance. DC traffic from the blood to peripheral tissue where they become activated. They then present antigen and the costimulating signals necessary to initiate an immune response. In this study, we investigated the number, subsets, and activation pattern of circulating and intestinal DC from patients with clinically mild ulcerative colitis (UC) or Crohn's disease. METHODS: Patients were recruited, if they were not taking immunosuppressive therapy, and were assessed for clinical severity of their disease using for UC, the Clinical Activity Index, and for Crohn's disease, the Crohn's Disease Activity Index. Blood CD11c+ and CD11c- DC subsets, expression of costimulatory antigens, CD86 and CD40, and the early differentiation/activation antigen, CMRF44, were enumerated by multicolor flow cytometry of lineage negative (lin- = CD3-, CD19-, CD14-, CD16-) HLA-DR+ DC. These data were compared with age-matched healthy and the disease control groups of chronic noninflammatory GI diseases (cGI), acute noninflammatory GI diseases (aGI), and chronic non-GI inflammation (non-GI). In addition, cryostat sections of colonoscopic biopsies from healthy control patients and inflamed versus noninflamed gut mucosa of inflammatory bowel disease (IBD) patients were examined for CD86+ and CD40+ lin- cells. RESULTS: Twenty-one Crohn's disease and 25 UC patients, with mean Crohn's Disease Activity Index of 98 and Clinical Activity Index of 3.1, and 56 healthy controls, five cGI, five aGI, and six non-GI were studied. CD11c+ and CD11c- DC subsets did not differ significantly between Crohn's, UC, and healthy control groups. Expression of CD86 and CD40 on freshly isolated blood DC from Crohn's patients appeared higher (16.6%, 31%) and was significantly higher in UC (26.6%, 46.3%) versus healthy controls (5.5%, 25%) (p = 0.004, p = 0.012) and non-GI controls (10.2%, 22.8%) (p = 0.012, p = 0.008), but not versus cGI or aGI controls. CD86+ and CD40+ DC were also present in inflamed colonic and ileal mucosa from UC and Crohn's patients but not in noninflamed IBD mucosa or normal mucosa. Expression of the CMRF44 antigen was low on freshly isolated DC, but it was upregulated after 24-h culture on DC from all groups, although significantly less so on DC from UC versus Crohn's or healthy controls (p = 0.024). The CMRF44+ antigen was mainly associated with CD11c+ DC, and in UC was inversely related to the Clinical Activity Index (r = -0.69, p = 0.0002). CONCLUSIONS: There is upregulation of costimulatory molecules on blood DC even in very mild IBD but surprisingly, there is divergent expression of the differentiation/activation CMRF44 antigen. Upregulation of costimulatory molecules and divergent expression of CMRF44 in blood DC was also apparent in cGI and aGI but not in non-GI or healthy controls, whereas intestinal CD86+ and CD40+ DC were found only in inflamed mucosa from IBD patients. Persistent or distorted activation of blood DC or divergent regulation of costimulatory and activation antigens may have important implications for gut mucosal immunity and inflammation.     

Immunolocalization and expression of kallistatin and tissue kallikrein in human inflammatory bowel disease

The distribution of tissue kallikrein (TK) and its plasma inhibitor, kallistatin in plasma and intestinal tissue, was studied in patients with active ulcerative colitis (UC) and Crohn's disease (CD). TK was localized to goblet cells and kallistatin to epithelial cells of normal human intestine. Both proteins are visualized in macrophages inside granulomas in CD as well as in plasmocytes in both CD and UC. Intestinal tissue kallikrein (ITK) and kallistatin are significantly decreased in inflamed intestine compared to noninflammatory controls. TK mRNA is significantly decreased in intestinal biopsy samples from active UC patients compared with inactive patients or controls. Immunoreactive TK is present in plasma in very low concentrations in patients and did not differ in normal subjects. Plasma kallistatin was significantly decreased in patients with active disease compared to normal controls. Our data suggest that release of TK during inflammation plays a role in inflammatory bowel disease.     

T-cell co-stimulatory molecules are upregulated on intestinal macrophages from inflammatory bowel disease mucosa.

BACKGROUND AND AIMS: Macrophages play an important role during mucosal inflammation in inflammatory bowel disease (IBD). As the co-stimulatory molecules B7-1 (CD80) and B7-2 (CD86) play an integral role in the activation of T cells by antigen-presenting cells (APC) we investigated the surface expression of B7-1 and B7-2 on colonic macrophages from normal and IBD mucosa. METHODS: Intestinal macrophages were isolated from biopsies of 13 control persons and 14 patients with IBD (seven with Crohn's disease (CD); and seven with ulcerative colitis (UC)). Cells were characterized by triple fluorescence flow cytometrical analysis using CD33 as macrophage marker. RESULTS: The expression of B7-1 (CD80) (9.2% +/- 4.2%) and B7-2 (CD86) (15.1% +/- 7.3%) was low on colonic macrophages from normal mucosa, indicating only a low antigen presenting potential. However, on macrophages from IBD colon there was a significant increase in the expression of co-stimulatory molecules (CD80, 33.8% +/- 8.9%, P = 0.00005 vs. control; CD86, 39.9% +/- 8.8%, P = 0.00002). There was no significant difference between CD and UC in the expression of CD80 (CD, 31.3% +/- 6.7%; UC, 34.4% +/- 13.3%) and CD86 (CD, 41.9% +/- 3.8%; UC, 35.6% +/- 13.8%). While in normal mucosa only 10.6% +/- 4.9% of the macrophages expressed CD14, more than 90% of the CD86/CD80 positive cells of the inflamed mucosa were positive for CD14. CONCLUSION: Colonic macrophages from normal mucosa rarely express the co-stimulatory molecules CD80 and CD86. In IBD a new macrophage population is found with high expression of co-stimulatory molecules presumably responsible for the perpetuated immune response.     

Systemic and local evidence of increased Fas-mediated apoptosis in ulcerative colitis

BACKGROUND AND AIMS: Recent studies suggest that Fas-mediated apoptosis is involved in the pathogenesis of inflammatory bowel disease (IBD). This study was conducted to clarify whether soluble forms of Fas (sFas) and Fas ligand (sFasL) are concerned with inflammation in IBD. METHODS AND PATIENTS: Concentration of serum sFas and sFasL was measured by enzyme-linked immunosorbent assay in 10 patients with ulcerative colitis (UC), 10 with Crohn's disease (CD) in both active and remission stages, and 20 controls. Expression of Fas and sFas in colonic mucosa was examined by western blot. Distribution of Fas and FasL in colonic mucosa was examined by immunohistochemistry in 20 UC, 20 CD, and 10 non-IBD colitis patients and in 10 controls. Apoptotic cells were examined by TUNEL. RESULTS: Concentration of systemic sFas was significantly lower in active UC than controls. The number of FasL-containing cells was significantly higher in active UC than in remission UC, non-IBD colitis, and controls. Apoptotic cells were increased in active UC. CONCLUSIONS: Our results demonstrate that systemic and local Fas-mediated apoptosis is promoted in UC, which might be involved in the pathogenesis in UC.     

Genetic and pathogenetic insights into inflammatory bowel disease

Crohn’s disease (CD) and ulcerative colitis (UC) are chronic inflammatory disorders of the gastrointestinal tract that share clinical and pathologic characteristics. The most credible hypothesis is that CD and UC result from an inappropriate and exaggerated mucosal immune response to normal constituents of the mucosal microflora that is in part genetically determined. However, there is reason to believe that the main pathologic processes in these two diseases are distinct. For example, the CARD15/NOD2 gene has been identified as a susceptibility gene for CD but not for UC. Moreover, the study of patients and mouse models of inflammatory bowel disease has clearly shown that, in CD, the tissue-damaging inflammatory reaction is driven by interleukin-12-activated Th1 cells, whereas a humoral response predominates in UC.     

Fas/Fas ligand expression and characteristics of primed CD45RO+ T cells in the inflamed mucosa of ulcerative colitis

BACKGROUND: Chronic immune activation in the colon is characteristic of ulcerative colitis (UC). Fas/Fas ligand (FasL) system is a mechanism responsible for activation-induced cell death (AICD), which maintains homeostasis within the immune system. Thus, Fas/FasL expression on activated colonic T cells of UC patients, as well as the susceptibility of such T cells to AICD was investigated in order to determine the role of activated colonic T cells in the long lasting inflammation in UC. METHODS: Fas, FasL, and CD45RO expression on peripheral blood and colonic T cells of UC patients were assayed by flow cytometry. Apoptosis of colonic T cells induced by anti Fas antibody was assessed using the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) assay. RESULTS: The majority of colonic T cells expressed both CD45RO and Fas in the colonic mucosa, a situation that was quite different from that in the peripheral blood. The number of CD45RO+CD8+ and Fas+CD8+ T cells was significantly lower in UC patients than the controls, unlike the number of Fas+CD4+ T cells. In contrast, the number of both CD45RO+CD4+ and CD45RO+CD8+ T cells in UC mucosa expressing FasL was significantly higher than in the controls. While Fas mediated apoptosis of CD45RO+CD8+ T cells was higher in UC patients than the controls, the number of apoptotic CD45RO+CD4+ T cells from UC mucosa was not. CONCLUSIONS: In UC patients, CD45RO+CD4+ T cells are less sensitive to apoptotic signals mediated by Fas. These phenomena may contribute to the pathogenesis of UC.     

Radical induction theory of ulcerative colitis

To propose a new pathogenesis called Radical Induction to explain the genesis and progression of ulcerative colitis (UC). UC is an inflammatory bowel disease. Colonic inflammation in UC is mediated by a buildup of white blood cells (WBCs) within the colonic mucosal lining; however, to date there is no answer for why WBCs initially enter the colonic mucosa to begin with. A new pathogenesis termed "Radical Induction Theory" is proposed to explain this and states that excess un-neutralized hydrogen peroxide, produced within colonic epithelial cells as a result of aberrant cellular metabolism, diffuses through cell membranes to the extracellular space where it is converted to the highly damaging hydroxyl radical resulting in oxidative damage to structures comprising the colonic epithelial barrier. Once damaged, the barrier is unable to exclude highly immunogenic fecal bacterial antigens from invading the normally sterile submucosa. This antigenic exposure provokes an initial immune response of WBC infiltration into the colonic mucosa. Once present in the mucosa, WBCs are stimulated to secrete toxins by direct exposure to fecal bacteria leading to mucosal ulceration and bloody diarrhea characteristic of this disease.     

An increased number of CD40-high monocytes in patients with Crohn's disease

OBJECTIVE: CD40-CD40 ligand (CD40L) interaction is essential for the T-lymphocyte-dependent immune response. This interaction may be operational in the pathogenesis of inflammatory bowel diseases (IBD). The present study examined the expression of CD40 in peripheral blood mononuclear cells (PBMNCs) and tissue specimens, and CD40-stimulated interleukin (IL)-12 release from PBMNCs in IBD. METHODS: The expression of CD40 in PBMNCs and tissue inflammatory cells was examined by flowcytometry and immunohistochemistry, respectively. IL-12 release was measured in cultured media of PBMNCs by an enzyme-linked immunosorbent assay. RESULTS: Most peripheral blood B-lymphocytes expressed CD40 in all subjects. However, in ulcerative colitis (UC) patients, a significantly increased mean fluorescence intensity (MFI) of CD40 on B-lymphocytes was detected, compared with control subjects and patients with Crohn's disease (CD). In contrast, both the percentage positivity and MFI of CD40 on monocytes of active CD subjects were significantly increased, compared with the other groups. In active CD patients, a high level of IL-12 release from PBMNCs was observed by CD40 stimulation, compared with those of the other groups. When primed with IFN-gamma, PBMNCs from inactive CD patients released a significantly high level of IL-12, probably via stimulation by the CD40 monoclonal antibody. In the affected mucosa of CD, numerous CD40-positive cells were demonstrated, and they were also CD68-positive, suggesting these double CD40/ CD68-positive cells are tissue macrophages. CONCLUSIONS: These results suggest that the examination of CD40 expression in PBMNCs might enable the differentiation of CD from UC. CD40-high monocytes in CD patients may play a role in the pathogenesis of CD.