Correlation of histopathologic evidence of disease activity with the presence of immunoglobulin-containing cells in the colons of patients with inflammatory bowel disease

Distinct patterns of naive, activated and memory T and B cells in blood of patients with ulcerative colitis or Crohn's disease

Both major subcategories of inflammatory bowel disease (IBD), ulcerative colitis and Crohn’s disease are characterized by infiltration of the gut wall by inflammatory effector cells and elevated biomarkers of inflammation in blood and feces. We investigated the phenotypes of circulating lymphocytes in the two types of IBD in treatment‐naive pediatric patients by analysis of blood samples by flow cytometry. Multivariate analysis was used to compare the phenotypes of the blood lymphocytes of children with ulcerative colitis (n = 17) or Crohn’s disease (n = 8) and non‐IBD control children with gastrointestinal symptoms, but no signs of gut inflammation (n = 23). The two IBD subcategories could be distinguished based on the results from the flow cytometry panel. Ulcerative colitis was characterized by activated T cells, primarily in the CD8⁺ population, as judged by increased expression of human leukocyte antigen D‐related (HLA‐DR) and the β1‐integrins [very late antigen (VLA)] and a reduced proportion of naive (CD62L⁺) T cells, compared with the non‐IBD controls. This T cell activation correlated positively with fecal and blood biomarkers of inflammation. In contrast, the patients with Crohn’s disease were characterized by a reduced proportion of B cells of the memory CD27⁺ phenotype compared to the non‐IBD controls. Both the patients with ulcerative colitis and those with Crohn’s disease showed increased percentages of CD23⁺ B cells, which we demonstrate here as being naive B cells. The results support the notion that the two major forms of IBD may partially have different pathogenic mechanisms.

NLRP3-Dependent and -Independent Processing of Interleukin (IL)-1β in Active Ulcerative Colitis

A contributing factor in the development of ulcerative colitis (UC) and Crohn’s disease (CD) is the disruption of innate and adaptive signaling pathways due to aberrant cytokine production. The cytokine, interleukin (IL)-1β, is highly inflammatory and its production is tightly regulated through transcriptional control and both inflammasome-dependent and inflammasome- independent proteolytic cleavage. In this study, qRT-PCR, immunohistochemistry, immunofluorescence confocal microscopy were used to (1) assess the mRNA expression of NLRP3, IL-1β, CASP1 and ASC in paired biopsies from UC and CD patient, and (2) the colonic localization and spatial relationship of NLRP3 and IL-1β in active and quiescent disease. NLRP3 and IL-1β were found to be upregulated in active UC and CD. During active disease, IL-1β was localized to the infiltrate of lamina propria immune cells, which contrasts with the near-exclusive epithelial cell layer expression during non-inflammatory conditions. In active disease, NLRP3 was consistently expressed within the neutrophils and other immune cells of the lamina propria and absent from the epithelial cell layer. The disparity in spatial localization of IL-1β and NLRP3, observed only in active UC, which is characterized by a neutrophil-dominated lamina propria cell population, implies inflammasome-independent processing of IL-1β. Consistent with other acute inflammatory conditions, these results suggest that blocking both caspase-1 and neutrophil-derived serine proteases may provide an additional therapeutic option for treating active UC.

Old and New Lymphocyte Players in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), encompassing Crohn's disease and ulcerative colitis, is a chronic intestinal inflammatory disorder characterized by diffuse accumulation of lymphocytes in the gut mucosa as a consequence of over-expression of endothelial adhesion molecules. The infiltrating lymphocytes have been identified as subsets of T cells, including T helper (Th)1 cells, Th17 cells, and regulatory T cells. The function of these lymphocyte subpopulations in the development of IBD is well-known, since they produce a number of pro-inflammatory cytokines, such as interferon-γ and interleukin-17A, which in turn activate mucosal proteases, thus leading to the development of intestinal lesions, i.e., ulcers, fistulas, abscesses, and strictures. However, the immune mechanisms underlying IBD are not yet fully understood, and knowledge about the function of newly discovered lymphocytes, including Th9 cells, innate lymphoid cells, mucosal-associated invariant T cells, and natural killer T cells, might add new pieces to the complex puzzle of IBD pathogenesis. This review summarizes the recent advances in the understanding of the role of mucosal lymphocytes in chronic intestinal inflammation and deals with the therapeutic potential of lymphocyte-targeting drugs in IBD patients.

Histologic scoring indices for evaluation of disease activity in ulcerative colitis

BACKGROUND

Disease activity can be determined using clinical, endoscopic or histologic criteria in patients with ulcerative colitis (UC). Persistent disease activity is associated with poor outcomes. Histologic disease activity has been shown to be associated with relapse, colectomy and colorectal cancer. The ability to objectively evaluate microscopic disease activity using histology is important for both clinical practice and clinical trials. However, the operating properties of the currently available histologic indices remain unclear.

OBJECTIVES

A systematic review was undertaken to identify and evaluate the development and operating characteristics of histologic disease activity indices used to assess disease activity in people with ulcerative colitis.

SEARCH METHODS

We searched MEDLINE, EMBASE, PubMed, CENTRAL and the Cochrane IBD Review Group Specialized Trials Register from inception to 2 December 2016 for applicable studies. There were no language or document type restrictions.

SELECTION CRITERIA

Any study design (e.g. randomized controlled trials, cohort studies, case series) that evaluated a histologic index in patients with UC were considered for inclusion. Eligible patients were adults (> 18 years), diagnosed with UC using conventional clinical, radiographic, endoscopic and histologic criteria.

DATA COLLECTION AND ANALYSIS

Two authors (MHM and CEP) independently reviewed the titles and abstracts of the studies identified from the literature search. A standardized form was used to assess eligibility of trials for inclusion and for data extraction.Two authors (MHM and CEP) independently extracted and recorded data, which included the number of patients enrolled, number of patients per treatment arm, patient characteristics including age and gender distribution, and the name of the histologic index. Outcomes (i.e. intra-rater reliability, inter-rater reliability, internal consistency, content validity, criterion validity, construct validity, responsiveness, and feasibility) were recorded for each trial.

MAIN RESULTS

In total, 126 reports describing 30 scoring indices were identified through the screening process. Eleven of the 30 scoring indices have undergone some form of index validation. Intra-rater reliability was assessed for eight scoring indices. Inter-rater reliability was evaluated for all 11 of the scoring indices. Three of the indices underwent content validation. Two of the included scoring indices assessed criterion validity. Six of the included scoring indices explored content validity. Two of the included scoring indices were tested for responsiveness.

AUTHORS' CONCLUSIONS

The Nancy Index and the Robarts Histopathology Index have undergone the most validation in that four operating properties including reliability, content validity, construct validity (hypothesis testing) and criterion validity have been tested. However, none of the currently available histologic scoring indices have been fully validated. In order to determine the optimal endpoint for histologic healing in UC, more research is required. The optimal index would need to be fully validated.

Eosinophilia - associated basal plasmacytosis: an early and sensitive histologic feature of inflammatory bowel disease

Basal plasmacytosis is an early-onset and highly predictive feature of inflammatory bowel disease (IBD), but may have several restrictions in routine histology. Considering evidences about cooperation between eosinophils and plasma cells in IBD pathogenesis, we investigated immunostain of these two cells as a marker of disease. 343 samplings from 83 patients (52 IBD, 31 non-IBD colitis) were evaluated. The sections were stained with monoclonal antibodies against plasma cells (CD138 and MUM1), and eosinophils (CD193). Eosinophilia-associated basal plasmacytosis (EBP) was related with the histologic diagnosis of IBD (90.3% IBD and 35.4% non-IBD colitides, p < 0.005, sensitivity 90.4%). A strong relation was detected between the occurrence of EBP and (i) the achieving of a complete endoscopic mapping; (ii) the presence of other characteristic lesions of IBD in single segmental sampling, although EBP was evident in more than 40% of samples without other IBD-related lesions. EBP is a sensitive histologic feature of IBD, especially at the first endoscopic sampling, even in the absence of the other characteristic histologic lesions, and may help in formulating a more precise diagnosis in this setting.

Cytokine-producing B cells: a translational view on their roles in human and mouse autoimmune diseases

B-cell depletion therapy has beneficial effects in autoimmune diseases. This is only partly explained by an elimination of autoantibodies. How does B-cell depletion improve disease? Here, we review preclinical studies showing that B cells can propagate autoimmune disorders through cytokine production. We also highlight clinical observations indicating the relevance of these B-cell functions in human autoimmunity. Abnormalities in B-cell cytokine production have been observed in rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease, and systemic lupus erythematosus. In the first two diseases, B-cell depletion erases these abnormalities, and improves disease progression, suggesting a causative role for defective B-cell cytokine expression in disease pathogenesis. However, in the last two disorders, the pathogenic role of B cells and the effect of B-cell depletion on cytokine-producing B cells remain to be clarified. A better characterization of cytokine-expressing human B-cell subsets, and their modulation by B cell-targeted therapies might help understanding both the successes and failures of current B cell-targeted approaches. This may even lead to the development of novel strategies to deplete or amplify selectively pathogenic or protective subsets, respectively, which might be more effective than global depletion of the B-cell compartment.

Systematic review: histological remission in inflammatory bowel disease. Is 'complete' remission the new treatment paradigm? An IOIBD initiative

BACKGROUND AND AIMS

Advances in the medical management of inflammatory bowel disease (IBD) have altered treatment targets. Endoscopic mucosal healing is associated with better outcomes in IBD, though less is known about the significance of achieving histological remission. Our aim was to perform a systematic review to investigate whether histological or 'complete' remission constitutes a further therapeutic target in IBD.

METHODS

A bibliographic search was performed on the 1st of October 2013 and subsequently on the 1st of March 2014 of online databases (OVID SP MEDLINE, OVID EMBASE, National Pubmed Central Medline, Cochrane Library, ISI, conference abstracts), using MeSH terms and key words: ("inflammatory bowel diseases" OR "crohn disease" OR "ulcerative colitis" OR "colitis") AND ("mucosal healing" OR "histological healing" OR "pathological healing" OR "histological scoring" OR "pathological scoring").

RESULTS

The search returned 2951 articles. 120 articles were cited in the final analysis. There is no validated definition of histological remission in IBD. There are 22 different histological scoring systems for IBD, none of which are fully validated. Microscopic inflammation persists in 16-100% of cases of endoscopically quiescent disease. There is evidence that histological remission may predict risk of complications in ulcerative colitis beyond endoscopic mucosal healing, though data are scarce in Crohn's disease.

CONCLUSIONS

Histological remission in IBD represents a target distinct from endoscopic mucosal healing, not yet routinely sought in clinical trials or practice. There remains a need for a standardized and validated histological scoring system and to confirm the prognostic value of histological remission as a treatment target in IBD.

Histologic evaluation of ulcerative colitis: a systematic review of disease activity indices

BACKGROUND

Ulcerative colitis (UC) is an idiopathic inflammatory disorder. Currently, the main goals of treatment are to induce and maintain clinical and/or endoscopic remission. However, evidence indicates that persistent disease activity on colonic biopsies in the setting of clinical or endoscopic remission is an independent predictor of poor outcomes. A number of previous studies have proposed histologic indices for use in specific trials of UC. The aim of this study was to systematically review the existing histological indices for UC and assess their potential use in both patient management and clinical trials.

METHODS

We performed a systematic review of histological indices evaluating disease activity in UC. MEDLINE (Ovid), EMBASE (Ovid), PubMed, the Cochrane Library (CENTRAL), and Digestive Diseases Week (DDW) abstracts of randomized and/or controlled trials clinical trials were searched from inception to February 2013 for applicable studies. Data from these studies were reviewed and analyzed.

RESULTS

After systematically applying inclusion criteria, we identified 108 scientific articles including 88 clinical studies and 21 related clinical reviews. Eighteen indices of histological activity in UC were identified and reviewed.

CONCLUSIONS

Although multiple histological scoring indices for assessment of UC disease activity currently exist, none of these instruments were developed using a formal validation process and their operating properties remain poorly understood. Future studies are needed to address this deficiency.

Mucosal CXCR4+ IgG plasma cells contribute to the pathogenesis of human ulcerative colitis through FcγR-mediated CD14 macrophage activation

BACKGROUND

Chronic inflammation characterised by IgG-producing plasma cell infiltration of colonic mucosa is a histological hallmark of ulcerative colitis (UC); however, whether its function is pathogenic or protective remains unclear.

OBJECTIVE

To explore the contribution of intestinal IgG plasma cells to UC pathogenesis.

METHODS

We isolated lamina propria mononuclear cells (LPMCs) from intestinal mucosa of UC patients and analysed the characteristics of intestinal plasma cells (expression profiles of differentiation molecules and chemokine receptors). We investigated the involvement of IgG-immune complex (IC)-Fc gamma receptor (FcγR) signalling in intestinal inflammation by examining the cytokine production by LPMCs in response to IgG-IC stimulation.

RESULTS

IgG plasma cells that were markedly increased in number in the inflamed mucosa of UC patients showed a distinct expression profile (CD19(+)CD27(low), CCR10(low)CXCR4(high)) compared with IgA plasma cells (CD19(+/-)CD27(high), CCR10(high)CXCR4(-/low)). In vitro IgG-IC stimulation activated intestinal CD14 macrophages that were increased in number in the inflamed mucosa of UC patients via FcγRI and FcγRII, and induced the extensive production of pro-inflammatory cytokines such as tumour necrosis factor (TNF) and interleukin-1β (IL-1β), comparable to the effect of commensal bacteria stimulation. Co-stimulation with IgG-IC and commensal bacteria increased TNF and IL-1β production more than stimulation with the latter alone. Furthermore, IgG-IC notably up-regulated the expression of TL1A, whereas commensal bacteria specifically induced IL-23.

CONCLUSIONS

Collectively, these results demonstrate a novel aspect of UC pathogenesis in which unique IgG plasma cells infiltrate the inflamed mucosa via CXCR4, and critically influence UC pathogenesis by exacerbating mucosal inflammation through the activation of 'pathogenic' intestinal CD14 macrophages via IgG-IC-FcγR signalling.

Inflammatory bowel disease biopsies: updated British Society of Gastroenterology reporting guidelines

Accurate histopathological assessment of biopsies is important for the diagnosis, subclassification, and management of chronic idiopathic inflammatory bowel disease (IBD). British Society of Gastroenterology (BSG) guidelines for the initial histopathological diagnosis of IBD were published in 1997. Changes since then include: more widespread use of full colonoscopy; greater recognition of the effects of time and treatment; improved documentation of variations in anatomical distribution; better understanding of the mimics of IBD; significant progress in clinical management; and modifications of terminology. Accordingly, an update is required. These revised guidelines aim to optimise the quality and consistency of reporting of biopsies taken for the initial diagnosis of IBD by summarising the literature and making recommendations based on the available evidence. Advice from existing clinical guidelines is also taken into account. Among the subjects discussed are: distinguishing IBD from other colitides, particularly infective colitis; subclassification of IBD (as ulcerative colitis, Crohn's disease, or IBD unclassified); the discriminant value of granulomas; aspects of disease distribution, including discontinuity in ulcerative colitis; time-related changes; differences between paediatric and adult IBD; the role of ileal and upper gastrointestinal biopsies; differential diagnoses such as diverticular colitis and diversion proctocolitis; and dysplasia. The need to correlate the histological features with clinical and endoscopic findings is emphasised. An approach to the conclusion of an IBD biopsy report based on the acronym Pattern, Activity, Interpretation, Dysplasia (PAID) is suggested. The key recommendations are listed at the end of the document.

Prognostic value of serologic and histologic markers on clinical relapse in ulcerative colitis patients with mucosal healing

OBJECTIVES

Endoscopic mucosal healing is a key endpoint for the treatment of ulcerative colitis (UC). The role of microscopic activity in predicting disease relapse has not been fully assessed. We aimed to investigate the predictive role of serologic and histologic markers on disease relapse in UC patients with endoscopically inactive disease.

METHODS

Adult UC patients with endoscopically inactive disease (Mayo 0) and a 12-month follow-up between 2008 and 2011 were retrospectively included. An expert pathologist evaluated all colonic biopsies for histologic activity (Geboes score) and the presence of basal plasmacytosis. Blood samples collected around the time of endoscopy were analyzed. Disease relapse, defined as a clinical Mayo score ≥3, was documented during follow-up.

RESULTS

The study cohort consisted of 75 patients (53% men, median age 47 years). Despite normal endoscopy, histology showed inflammatory activity with a Geboes score ≥3.1 in 40% and basal plasmacytosis in 21% of patients. At 12 months, clinical relapse was observed in 20% (n=15) of patients. Presence of basal plasmacytosis (P=0.007) and a Geboes score ≥3.1 (P=0.007) were predictive of disease relapse. Using multivariate analysis, the presence of basal plasmacytosis was predictive of clinical relapse (odds ratio (OR) 5.13 (95% confidence interval (CI): 1.32-19.99), P=0.019), whereas the use of biologicals at endoscopy favored remission (OR 0.24 (95% CI: 0.05-1.01), P=0.052).

CONCLUSIONS

We demonstrated that the presence of basal plasmacytosis predicts UC clinical relapse in patients with complete mucosal healing. We recommend closer follow-up and optimization of medical therapy in patients with basal plasmacytosis.

Pathology of inflammatory bowel diseases (IBD): variability with time and treatment

The diagnosis of chronic idiopathic IBD and the differential diagnosis between Crohn's disease and ulcerative colitis can be made in most cases on cumulative clinical, radiological, endoscopical, biochemical and pathological evidence. Diagnostic difficulties can however, occur in fulminant colitis, in early onset disease and in long-standing disease. The microscopic evaluation of disease activity is based on the presence of active inflammation. Effective medical treatment has however, an influence upon the morphology and the evolution of the lesions and hence can affect the diagnostic features and the microscopic features used for the assessment of disease activity. A literature review was performed on clinical drug trials in IBD and the effect of the drugs upon the microscopic features. Several studies have shown that the diagnostic microscopic features and the features characteristic for disease activity vary with time and treatment. For an adequate analysis of biopsy samples of patients with IBD the pathologist should be aware of the duration of the symptoms and the type of treatment given to the patient.

Pathology of inflammatory bowel diseases (IBD): variability with time and treatment

The diagnosis of chronic idiopathic IBD and the differential diagnosis between Crohn's disease and ulcerative colitis can be made in most cases on cumulative clinical, radiological, endoscopical, biochemical and pathological evidence. Diagnostic difficulties can however, occur in fulminant colitis, in early onset disease and in long-standing disease. The microscopic evaluation of disease activity is based on the presence of active inflammation. Effective medical treatment has however, an influence upon the morphology and the evolution of the lesions and hence can affect the diagnostic features and the microscopic features used for the assessment of disease activity. A literature review was performed on clinical drug trials in IBD and the effect of the drugs upon the microscopic features. Several studies have shown that the diagnostic microscopic features and the features characteristic for disease activity vary with time and treatment. For an adequate analysis of biopsy samples of patients with IBD the pathologist should be aware of the duration of the symptoms and the type of treatment given to the patient.

Clinical, biological, and histologic parameters as predictors of relapse in ulcerative colitis

BACKGROUND & AIMS

Ulcerative colitis (UC) is a chronic relapsing inflammatory bowel disease. We aimed to assess whether clinical, biological, and histologic parameters in quiescent UC predict time to clinical relapse.

METHODS

Seventy-four patients with clinically and endoscopically determined inactive UC were followed up for 1 year or for a shorter period if they had a relapse. Serum erythrocyte sedimentation rate; C-reactive protein, interleukin (IL)-1beta, IL-6, and IL-15 values; anti-neutrophil cytoplasmic antibody titers; and rectal biopsy specimens were obtained at baseline, at 6 and 12 months, and/or at relapse. Multivariate survival analysis was performed to determine independent predictors of clinical relapse.

RESULTS

Twenty-seven patients relapsed (19/42 women; 8/32 men). Multivariate Cox regression analysis retained younger age (P = 0.003; hazard ratio, 0.4 per decade), greater number of prior relapses in women (P < 0.001; hazard ratio, 1.6 per prior relapse), and basal plasmacytosis (P = 0.003; hazard ratio, 4.5) on rectal biopsy specimens as predictors of shorter time to clinical relapse. Kaplan-Meier survival curves showed the 20-30-year-old age group and women with more than 5 prior relapses to be groups with shorter times to relapse.

CONCLUSIONS

Younger age, multiple previous relapses (for women), and basal plasmacytosis on rectal biopsy specimens were independent predictors of earlier relapse. These findings may help identify patients with inactive UC who will require optimal maintenance medical therapy.

Immunoglobulin leakiness in scid mice with CD4(+) T-cell-induced chronic colitis

Inflammatory bowel disease in scid mice is initiated by transplantation of CD4(+) T-cells from immunocompetent syngenic donor mice. As the disease progresses, immunoglobulin (Ig)-containing cells appear in the gut lamina propria, suggesting that locally accumulating Ig may play a role in disease development. In the present work we have investigated the relationship between disease progression and patterns or levels of Ig isotypes in the feces of scid mice suffering from an ongoing colitis. The data clearly showed that the severity or progression of the disease did not influence the levels of IgA, IgG1, IgG2a, IgG2b, and IgG3, whereas the level of fecal IgM increased during the course of colitis. The presence of the serum protein alpha-1-antitrypsin in fecal extracts from diseased mice suggests that some of the fecal Ig has leaked through the inflamed epithelial membrane into the gut lumen. Finally, Ig-containing cells were observed in mesenteric lymph nodes and in the spleen, suggesting that the fecal Ig is produced both systemically and locally in the gut wall. In conclusion, the present results demonstrate that the level of IgM increases as colitis progresses. Also, the five remaining major Ig isotypes are increased in the gut lumen of scid mice with colitis, but the individual Ig types vary randomly during the course of the disease. Thus, it is unlikely that immunoglobulins are involved in the immunopathogenesis of this model of colitis.

Accumulation of immunoglobulin-containing cells in the gut mucosa and presence of faecal immunoglobulin in severe combined immunodeficient (scid) mice with T cell-induced inflammatory bowel disease (IBD)

Scid mice transplanted either with a gut wall graft or with low numbers of purified CD4+ T cells from immunocompetent syngeneic donor mice show clinical signs of IBD 3-4 months post-transplantation. The disease is mediated by mucosa-infiltrating CD4+ TCR alphabeta+ T cells. The pathology of 52 individual colon segments obtained from 20 gut wall- or CD4+ T cell-transplanted diseased scid mice was evaluated by histology and the numbers of infiltrating immunoglobulin-containing cells were determined. In particular, cells positive for IgM, IgA and non-inflammatory immunoglobulin isotypes such as IgG1 and IgG2b were found to accumulate in colon segments displaying the most severe histopathology, including inflammatory cellular infiltration, epithelial hyperplasia and ulcerative lesions. Compared with colon segments of normal C.B-17 mice, the lesional scid colon shows increased levels of cells positive for the IgG classes. Faecal extracts of the CD4+ T cell-transplanted scid mice revealed the presence of all six murine immunoglobulin isotypes. Disease progression was accompanied by an increased level of excreted IgM and IgG3 and decreased levels of IgA. It is concluded that locally secreted immunoglobulins may play an immunomodulating role in the pathological changes observed in the present model of T cell-induced inflammatory bowel disease.

Evaluation of B and T lymphocytes and plasma cells in colonic mucosa from healthy dogs and from dogs with inflammatory bowel disease

The aim of this study was to investigate the subpopulations of lymphocytes in the colonic mucosa of healthy dogs and dogs with inflammatory bowel disease (IBD). Fourteen normal dogs and 13 dogs with IBD were examined. Endoscopic biopsy specimens of colonic mucosa from each dog were stained specifically for pan T lymphocytes (CD3) and pan B lymphocytes (CD79a), and for plasma cells with methyl green pyronin (MGP) stain. Cells were counted by means of a grid and statistical analysis was performed on the data collected. B and T lymphocytes were also counted in the glandular epithelium of normal dogs and dogs with IBD and the normal and abnormal groups compared statistically. Healthy dogs had significantly lower numbers of T cells in the lamina propria and glandular epithelium and significantly lower numbers of B cells in the lamina propria. Significant group differences for plasma cells were not evident. Our results indicate that in IBD a chronic cellular immune reaction is present in the diseased gut involving increased numbers of B and T lymphocytes.

Solid phase competitive luminescence immunoassay for immunoglobulin A in faeces: development and clinical validation

We describe a new simple solid-phase competitive luminescence immunoassay (LIA) for the determination of immunoglobulin A (IgA) in faeces. The assay utilizes an anti-alpha-chain IgA antibody which is coated to polystyrene beads and acridinium ester-labelled human IgA as tracer and, therefore, measures both monomeric and polymeric IgA. Dilution recovery of an internal standard was 96, 100 and 103%. Interassay and intra-assay coefficients of variation (C.V.) ranged from 4.5 to 12.9%. The upper limit of normal of faecal IgA in 122 healthy controls was found to be 300 mg/l IgA (mean 73 mg/l, specificity of 99.2%). Patients with inactive Crohn's disease (Crohn's disease activity index (CDAI < 150, n = 14) had faecal IgA values up to 3317 mg/l (mean 1073 mg/l; P < 0.0001). In the active group (CDAI > 150, n = 26) faecal IgA values ranged from 49 to 4094 mg/l (mean 1253 mg/l; P < 0.0001). Patients with ulcerative colitis were divided into a group with active disease (n = 18) and a remission group (n = 16) with values up to 1843 mg/l faecal IgA (man 486 mg/l; P < 0.0032) and up to 602 mg/l faecal IgA (mean 176 mg/l; P < 0.4833), respectively. We also studied patients with non-inflammatory diseases of the gut with this assay. This LIA has proved to be a reliable method for the determination of elevated faecal IgA concentrations and for the detection of pathological findings in the gastrointestinal tract, especially in Crohn's disease.

Alterations in the mucosal immune system in ulcerative colitis and Crohn's disease

Emphasis is now being placed upon obtaining a better understanding of the regulatory cytokines that normally downregulate acute intestinal inflammation. These inhibitory cytokines appear to be missing or not functioning properly in patients with inflammatory bowel disease (IBD), thereby leading to perpetuation of inflammation. As we obtain an increased understanding of immune and inflammatory regulatory processes in the intestine, we will be able to devise better future therapeutic strategies for use in our IBD patients.

Immunoglobulin-containing cells in the colonic mucosa in patients with human intestinal spirochaetosis

The relative proportions of cells containing the various classes of immunoglobulins in the colonic mucosa were determined in eight patients with human intestinal spirochaetosis (HIS) and in eight controls. All specimens were taken from colonic resections performed because of adenocarcinoma. None of the cases with HIS showed an inflammatory reaction in the mucosa as judged subjectively by light microscopy. Cases with HIS had smaller proportions of IgD- and IgE-positive cells and a larger proportion of IgA cells as compared with the controls, whereas the proportions of IgG and IgM cells were similar in the two groups. Taking into account the large individual variations in the proportions of immunoglobulins in both groups, our findings must be interpreted with caution. However, our results do not support the previous demonstration of increased percentages of IgE-positive cells in patients with HIS.

Anti-immunoglobulin E-stimulated ion transport in human large and small intestine

BACKGROUND

Mast-cell regulation of intestinal ion transport, previously shown in animals and cultured cells, was examined in surgically resected human bowel in this study.

METHODS

Changes in short-circuit current (Isc) in response to rabbit anti-human immunoglobulin (Ig) E or control serum, histamine, and electrical stimulation were measured in muscle-stripped, noninflamed segments of intestine mounted in Ussing chambers. Chloride-free buffer, pyrilamine, piroxicam, sodium cromoglycate, and tetrodotoxin were examined for their effect on Isc responses to these stimuli.

RESULTS

Within 1-2 minutes of adding anti-IgE serum, a specific monophasic rise in Isc (peaking at 7-10 minutes) was observed in large and small intestine. This response was reduced approximately 80% in chloride-free buffer and inhibited by the histamine1-receptor antagonist, pyrilamine, and the cyclo-oxygenase inhibitor, piroxicam, implicating histamine and prostaglandins as mediators of the ion transport changes. The mast-cell stabilizer, sodium cromoglycate, reduced anti-IgE responses in the small, but not large, intestine. Approximately 50% inhibition of anti-IgE responses in colon by the neurotoxin, tetrodotoxin, indicated that nerves were involved.

CONCLUSIONS

These results suggest that activation of mast cells releases mediators that stimulate intestinal ion transport through direct epithelial action and via nerves. This study provides important evidence that immunoregulation of intestinal ion transport does occur in humans.

IgG subclass distribution in serum and rectal mucosa of monozygotic twins with or without inflammatory bowel disease

Serum samples from 26 monozygotic twin pairs concordant or discordant with regard to inflammatory bowel disease, and rectal biopsies from 42 twins of the same subject group, were examined for IgG subclasses. They were all compared with normal controls. Almost all affected twins were in clinical remission. Paired immunofluorescence staining of the rectal mucosa showed that those with ulcerative colitis had a significantly higher (p < 0.01) proportion of IgG1 producing mucosal immunocytes than normal controls (78.1% v 55.9%). Conversely, the IgG2 cell fraction was significantly reduced (15.9% v 34.6%). Healthy twins from ulcerative colitis pairs tended to show a raised proportion of IgG1 cells and the IgG2 cell fraction was significantly reduced (p < 0.05). In discordant ulcerative colitis twin pairs, no difference appeared in the cellular IgG subclass pattern between healthy and affected twins. Furthermore, the proportion of IgG1 in these healthy and diseased twins showed good correlation (T = 0.867). The results in rectal mucosa of twins with Crohn's disease were widely scattered and affected twins did not differ significantly from normal controls. Healthy twins, however, showed a marginally raised IgG1 cell proportion, but no correlation was seen between the IgG subclass fractions in discordant Crohn's disease twin pairs. The serum concentrations of IgG1 and IgG2 did not differ from normal controls in twins of either category. These results suggested that in ulcerative colitis, the aberrant mucosal production of IgG1 and IgG2 does not depend on active disease, but is apparently at least partially explained by a genetic impact. Conversely, the mucosal IgG subclass pattern in Crohn's disease appears to be determined mainly by exogenous variables.

Mucosal capillary thrombi in rectal biopsies

We studied the initial rectal biopsy from 46 patients in whom subsequent follow-up established the diagnosis of either self-limited colitis or inflammatory bowel disease. An additional 12 non-inflamed rectal biopsies were also studied. There was between 2 and 8 years of follow-up in each of these cases. Staining for fibrin (MSB, fibrinogen), platelets (factor XIIIA, Y2/51), and capillary basement membrane (reticulin, collagen 4) was performed to identify thrombotic material within capillaries. Mucosal capillary thrombi were best identified by staining for factor XIIIA; thrombi were observed in 8/13 cases of ulcerative colitis, 4/10 cases of Crohn's disease, 1/3 cases of unspecified inflammatory bowel disease and 5/20 cases of self-limited colitis. The presence of capillary thrombi was not related to the severity of inflammation, but none of the control biopsies showed capillary thrombi. Their presence seems of little diagnostic value in distinguishing inflammatory bowel disease from self-limited colitis. The pathogenetic significance of these mucosal capillary thrombi is uncertain.

Immunoglobulin G (IgG), IgG1, and IgG2 determinations from endoscopic biopsy specimens in control, Crohn's disease, and ulcerative colitis subjects

Acute exacerbations of chronic inflammatory bowel disease (ulcerative colitis and Crohn's disease) are characterised by an increase in immunoglobulin G (IgG) positive cells in the mucosa, whereas uninflamed mucosa of inflammatory bowel disease patients displays only moderately increased or normal numbers of these cells. Previous data suggest that acute exacerbations of ulcerative colitis and Crohn's disease can be distinguished by different IgG subclass expression of mucosal immunocytes and a different IgG subclass production pattern of lamina propria lymphocytes. A procedure to obtain enough intestinal mononuclear cells from biopsy specimens to measure in vitro IgG and IgG1 production in control subjects and various patient groups has been established. IgG2 could be measured in Crohn's disease and ulcerative colitis only, as the concentrations in control subjects were below the sensitivity of the ELISA method. We found that IgG and IgG1 production correlated with the degree of local inflammation in both diseases, even in slightly inflamed mucosa, compared with control subjects. The proportion of IgG1 subclass was significantly increased in severely inflamed mucosa of both ulcerative colitis and Crohn's disease patients. A major difference between Crohn's disease and ulcerative colitis mucosa is apparent in mild or no inflammation. In Crohn's disease mucosa in remission, the IgG1/IgG ratio is comparable with that in controls, yet ulcerative colitis mucosa still displays significantly increased proportions of IgG1. In addition, the IgG2/IgG ratio is 0.12 in ulcerative colitis and 0.19 in Crohn's disease patients. The results show the dependence of local IgG and IgG1 production on the degree of inflammation and that an increase in subclass IgG1 in ulcerative colitis is present at all stages, including remission. These findings support the hypothesis that different immunoregulatory mechanisms are involved in Crohn's disease and ulcerative colitis. Environmental stimuli or genetic background may be responsible for the observed differences.

Value of counting colonic mucosal Ig-containing cells in the differential diagnosis of chronic inflammatory bowel disease

AIMS

To investigate whether counting cells containing immunoglobulin (Ig) subclass in colonic biopsy specimens of patients with chronic inflammatory bowel disease, in addition to conventional histological evaluation, can improve the differentiation of patients with Crohn's disease from those with ulcerative colitis.

METHODS

The colonic and rectal biopsy specimens of 40 patients with chronic inflammatory bowel disease, comprising 20 patients with Crohn's disease and 20 with ulcerative colitis, were used and sections were stained specifically for IgA, IgM, and IgG heavy chains using an indirect immune peroxidase method. The immunoglobulin subclass containing cells were counted using an ocular grid counting method in a light microscope. A linear stepwise discriminant analysis was performed on Ig subclass containing cell counts in combination with 16 reproducible histological features. The results of this discriminant analysis were compared with the results of the discriminant analyses in which only the histological features were used.

RESULTS

Applying stepwise discriminant analysis, two histological features (an excess of histiocytes in the lamina propria and the villous or irregular aspect of the mucosal surface) in combination with IgMax were selected as the most discriminatory parameters that distinguish Crohn's disease from ulcerative colitis. IgMmax was defined as the maximum value of the mean percentage of IgM containing cells over all the biopsy locations. The use of this combination resulted in a better classification in 20% of the patients with Crohn's disease and in 9% of the patients with ulcerative colitis compared with the use of histological features alone.

CONCLUSIONS

Morphometric enumeration of Ig subclass containing cells in colonic mucosal biopsy specimens has diagnostic value as a means of differentiating individual patients with Crohn's disease from those with ulcerative colitis.

Expression of leukocyte adhesion molecules by mucosal mononuclear phagocytes in inflammatory bowel disease

Leukocyte adhesion molecules are important in cell-cell interactions of the immune system. Lymphocyte function-associated antigen 1 (cluster designation 11a) mediates interactions between T cells and mononuclear phagocytes through its ligand, the intercellular adhesion molecule 1 (CD54), whereas complement receptors 3 (CD 11b) and 4 (CD11c) are involved in complement-mediated phagocytosis. Expression of CD11 molecules and intercellular adhesion molecule 1 was studied in colonic biopsy specimens from 20 patients with inflammatory bowel disease and 10 normal controls. In normal colon, few mononuclear phagocytes expressed lymphocyte function-associated antigen 1 and intercellular adhesion molecule 1 at high densities. The major adhesion molecule was CD11c. Thus, the largest population of normal colonic mononuclear phagocytes was represented by quiescent, resident macrophages with likely phagocytic function. In inflammatory bowel disease, mononuclear phagocytes showed only a slight increase in CD11a expression and no significant change in expression of CD11b and CD11c. By contrast, the percentage of mononuclear phagocytes expressing intercellular adhesion molecule 1 was increased from 6.9% +/- 3.9% in controls to 69.2% +/- 12.8% in ulcerative colitis (P less than 0.001) and to 45.7% +/- 22.8% in Crohn's disease (P less than 0.01), showing a close relationship with histological activity. The increased expression of intercellular adhesion molecule 1 in inflammatory bowel disease indicates a state of immunological activation induced by local release of inflammatory cytokines. Such induction of intercellular adhesion molecule 1 on mononuclear phagocytes may be important in the maintenance of chronic inflammation by facilitating interactions with T cells and T-cell antigen recognition.

Immunological study of histologically non-involved jejunum during Crohn's disease: evidence for reduced in vivo secretion of secretory IgA

We studied the local humoral immunity of histologically non-involved jejunum in patients with Crohn's disease. Normal subjects and patients with ulcerative colitis served as controls. Jejunal fluid samples were collected during segmental jejunal perfusion, under an occluding balloon and the in vivo jejunal secretion of the following proteins was determined: albumin, orosomucoid, transferrin, alpha 2-macroglobulin, secretory component, monomeric and polymeric IgA, IgG, and IgM. The densities and number of IgA-, IgG-, and IgM-containing cells in the lamina propria of the jejunum were measured on perendoscopic biopsies. Jejunal secretion of polymeric IgA and the density of IgA-containing plasma cells in the lamina propria were significantly lower in patients with Crohn's disease than in both control groups. This abnormal intestinal immune response, which was not correlated to the activity of the disease, might be involved in its pathogenesis.

Inhibition of antibody secretion by 5-aminosalicylic acid

We have examined the effects of sulfasalazine and its metabolites sulfapyridine and 5-aminosalicylic acid on antibody secretion by normal peripheral blood and intestinal mononuclear cells. Sulfasalazine and 5-aminosalicylic acid both inhibited pokeweed mitogen-stimulated secretion of immunoglobulins (Igs) A, G, and M by peripheral blood mononuclear cells in a dose-dependent manner, whereas sulfapyridine had little effect. Sulfasalazine and 5-aminosalicylic acid also inhibited spontaneous secretion of IgA by intestinal mononuclear cells, but sulfapyridine did not. Sulfasalazine inhibited pokeweed mitogen-stimulated lymphocyte proliferation, while 5-aminosalicylic acid and sulfapyridine exhibited minimal inhibition. Sulfasalazine was toxic for peripheral blood mononuclear cells, whereas 5-aminosalicylic acid and sulfapyridine were not toxic. Thus, the inhibition of antibody secretion by sulfasalazine was due to direct toxicity. On the other hand, 5-aminosalicylic acid, the therapeutically active component of sulfasalazine, was neither toxic nor antiproliferative, and appeared to exert its effects on metabolic pathways directly related to antibody synthesis. The calculated ID50 values of 5-aminosalicylic acid for antibody secretion were 1.35 mM for IgA and 1.05 mM for IgG, concentrations that are achieved in the colons of treated individuals. Indomethacin did not inhibit antibody secretion at pharmacologically relevant concentrations. 5-Aminosalicylic acid mediated inhibition of antibody secretion may play a role in inflammatory bowel disease by stopping antibody-mediated memory events involved in the induction or perpetuation of the disease process.

Humoral reaction in the inflamed colon in Hirschsprung's disease and ulcerative colitis

An immunological study of B cells in patients with colitis that was associated with Hirschsprung's disease was undertaken and compared with that in patients with ulcerative colitis and in normal controls. There was an appreciable increase in IgA and a decrease in IgG in both disease groups. Humoral reaction in colitis associated with Hirschsprung's disease seems to be indistinguishable from that in ulcerative colitis and possibly in other inflammatory bowel diseases.

Defective in vitro gamma interferon production and elevated serum immunoreactive thymosin beta 4 levels in patients with inflammatory bowel disease

Gamma interferon (IFN-gamma) production by peripheral blood mononuclear cells (PBM) was measured in 21 patients with Crohn's disease, in 15 patients with ulcerative colitis, in 12 patients with non-IBD gastrointestinal disease (disease control), and in 28 healthy controls. T-cell subset proportions and serum levels of thymosin alpha 1 and thymosin beta 4, two hormonelike thymic peptides, were also determined. No differences were seen in T-cell subset proportions in patients with Crohn's disease or ulcerative colitis when compared to healthy controls or to the disease-control group. In vitro IFN-gamma production was markedly decreased in Crohn's disease and in untreated, but not treated, patients with ulcerative colitis. Preincubation of PBM prior to the addition of inducer mitogen resulted in enhanced IFN-gamma production in patients with Crohn's disease or ulcerative colitis which significantly exceeded that seen either in healthy controls or in the disease-control group. Serum thymosin alpha 1 levels were comparable in all study groups; however, serum thymosin beta 4 concentrations were significantly higher in all patient groups than in the healthy controls. These results confirm a defective in vitro IFN-gamma production in patients with IBD which is apparently independent of endocrine thymus regulation.

Evidence for contrasuppression in patients with Crohn's disease

Patients with Crohn's disease (CD) have elevated numbers of Vicia villosa agglutinin (VVA) binding cells in the peripheral blood. These cells represent a major subset of activated peripheral T cells. VVA binding T lymphocytes express either the T8 or the T4 determinant on their cell surface. In contrast in normal controls only a minor subset of peripheral T cell expresses binding sites for VVA. The majority of these cells coexpress T8. VVA binding T cells display no helper activity. Only in a subfraction of patients with CD and not in normal controls these cells mediate contrasuppressor activity for Ig and in particular for IgA. This subgroup of patients is characterized by the lack of extramucosal manifestations. It has now been shown that VVA binding T cells in their majority do not possess phenotypic features of helper inducer cells. This further supports the hypothesis of their involvement in contrasuppression. Moreover it was shown that IgA produced in the presence of VVA binding T cells is IgA1 and IgA2 (ratio 2:1) which are both modulated by VVA binding T cells.

Activated Fc alpha T cells in Crohn's disease are involved in regulation of IgA

Activated peripheral T cells (APT) of patients with Crohn's disease (CD) have been analysed for the expression of IgA-Fc receptors and for competence of IgA regulation. It was found that within the subset of APT an increased number of cells express binding sites for IgA (IgA-Fc), that was not found in other diseases with elevated numbers of APT. Moreover the number of IgA-Fc receptor expressing T cells was found to be increased in the inflamed mucosa too. Cocultures with autologous B cells revealed that isolated IgA-Fc receptor bearing T cells of patients with CD suppress IgA secretion. These data support the hypothesis that APT are involved in the immunopathogenesis of CD.

Local immune response to gastric Campylobacter in non-ulcer dyspepsia

Colonising Campylobacter pyloridis were identified histologically in gastric biopsy specimens from 89% of 83 patients with non-ulcer dyspepsia and chronic gastritis, but not in 58 dyspeptic patients with normal mucosa. The presence and population density of organisms was associated with the presence of intraepithelial neutrophils. In vivo coating of the organisms by host immunoglobulin was investigated by immunoperoxidase staining of IgA, IgG, and IgM in 54 biopsy specimens. IgA coated bacteria were seen in all cases of active gastritis, and in 60% of biopsy specimens without intraepithelial neutrophils. Coating with IgG or IgM, or both, was correlated with activity of gastritis and was rarely seen in the absence of a neutrophil infiltrate.

Immunohistological characterization of intraepithelial and lamina propria lymphocytes in control ileum and colon and in inflammatory bowel disease

Using monoclonal antibodies to T and B lymphocytes, to natural killer cells, and to HLA-DR antigen, we characterized the lymphocyte population within the epithelial and lamina propria regions in control intestine and colon, and in grossly involved and in grossly uninvolved intestine and colon of patients with active inflammatory bowel disease. There were significantly more intraepithelial T cells in control ileum than in control colon. In comparison to control, there was a heterogeneity of alterations in intraepithelial and lamina propria T lymphocyte subsets (T11+, T8+, T4+) in inflammatory bowel disease. B lymphocytes were not detected within the lamina propria, except when found in and adjacent to lymphoid aggregates. Leu 7+ cells were uncommon in the lamina propria of control ileum and colon and in diseased tissues. The majority of intraepithelial lymphocytes did not express HLA-DR. Epithelial cells of control colon did not express HLA-DR while epithelial cells of control ileal tissues and of diseased colonic and ileal specimens expressed HLA-DR antigen. Only small numbers of lamina propria T cells expressed HLA-DR in both control and disease tissues. There was intense expression of HLA-DR by monocytes and modest expression of HLA-DR by capillary and lymphatic endothelial cells. The induction of HLA-DR expression by diseased colonic epithelium and the observation that lymphatic endothelium expresses HLA-DR are new observations, and we established that Leu 7+ cells are present in very small numbers in both normal and diseased intestine and colon.

The human gastrointestinal secretory immune system in health and disease

The main function of secretory IgA is to exert immune exclusion; that is, by intimate cooperation with innate non-specific defence mechanisms, it dampens down penetration of soluble antigens and inhibits epithelial colonisation of bacteria and viruses. Secretory IgM may exert a similar protective function in the gut as its local synthesis sometimes is markedly increased, especially in selective IgA deficiency. IgG should not be considered a secretory immunoglobulin because its external translocation depends on passive intercellular diffusion. By activating complement, antibodies of this isotype may cause increased mucosal permeability and tissue damage. IgG may thus contribute to persistent immunopathology in mucosal lesions. The same is true for IgE antibodies which, in atopic individuals, may be carried into the gut mucosa by mast cells and cause their degranulation with histamine release. Secretory IgA and secretory IgM are the products of two cell types: plasma cells synthesise IgA dimers and IgM pentamers which, by non-covalent association, become complexed with the secretory component (SC) which is synthesized by serous-type glandular cells. The adsorption of the Ig polymers to the SC-expressing epithelial cells depends on J chain-determined binding sites. This fact gives biological significance to the striking J chain expression shown by mucosal immunocytes regardless of the Ig class they produce. The immunocytes populating the gut mucosa apparently belong to relatively early memory B cell clones. The obvious functional goal of J chain expression at this stage of clonal differentiation is local generation of SC-binding IgA and IgM polymers. In various gut diseases, altered immune regulation results in a disproportionately increased number of J chain-negative IgG-producing cells in the mucosa. Such altered immunological homeostasis may contribute to perpetuation of inflammatory bowel diseases.