Segregation of pANCA antigenic recognition by DNase treatment of neutrophils: ulcerative colitis, type 1 autoimmune hepatitis, and primary sclerosing cholangitis

Clinical utility of serodiagnostic testing in suspected pediatric inflammatory bowel disease

OBJECTIVES

Confronted with nonspecific symptoms, accurate screening tests would be useful to clinicians to distinguish between functional childhood disorders and inflammatory bowel disease (IBD), thus avoiding invasive diagnostic testing. Traditional ulcerative colitis-specific perinuclear antineutrophil cytoplasmic antibody (pANCA) and Crohn's disease-specific anti-Saccharomyces cerevisiae antibody (ASCA) serodiagnostic assays have recently been modified, with ELISA cut-off values recalculated to maximize sensitivity. The aim of this study was to determine whether the combination of these serodiagnostic tests could maximize diagnostic accuracy and minimize invasive investigations in pediatric patients presenting with nonspecific symptoms suggestive of IBD.

METHODS

With investigators blinded to clinical diagnoses, ASCA, ANCA, and pANCA profiles were obtained prospectively from 128 patients undergoing complete diagnostic evaluation for IBD. In phase I, diagnostic accuracy and predictive values of the modified and traditional assays were compared for the IBD (n = 54) and non-IBD groups (n = 74). In phase II, the overall accuracy of a novel sequential diagnostic testing strategy was determined. Additionally, the potential number of invasive investigations avoided with the hypothetical application of this strategy to the cohort was determined.

RESULTS

For phase I, the modified serodiagnostic assay was more sensitive (81 vs 69%), whereas the traditional assay had a higher specificity (96 vs 72%) for IBD (p < 0.05) For phase II, false-positive diagnoses would have been reduced by 81%, yielding an overall sequential testing strategy accuracy of 84%.

CONCLUSIONS

The incorporation of sequential noninvasive testing into a diagnostic strategy may avoid unnecessary and costly evaluations and facilitate clinical decision making when the diagnosis of IBD in children is initially uncertain.

Anti-Saccharomyces cerevisiae antibodies (ASCA), phenotypes of IBD, and intestinal permeability: a study in IBD families

BACKGROUND

Serologic markers anti-Saccharomyces cerevisiae antibodies (ASCA) and antineutrophil cytoplasmic antibodies with perinuclear staining (pANCA) have been proposed to study the immunopathogenesis of IBD. Their measurement may allow better phenotyping of the disease and the detection of subclinical disease.

AIMS

To test the hypothesis that serological markers identify an immunologic trait related to disease susceptibility. We also wanted to test the hypothesis that ASCA is a marker related to abnormal tissue permeation by common antigens.

METHODS

We studied the prevalence of pANCA and ASCA in a large cohort of sporadic and familial inflammatory bowel diseases and their unaffected relatives and spouses. Kinetics of ASCA was studied and the relationship between ASCA and 51Cr-EDTA intestinal permeation was investigated.

RESULTS

ASCA was associated with sporadic Crohn's disease (CD) (63%), with Crohn's patients belonging to pure CD families (62%) and also with their unaffected family members (21%). pANCA was associated with UC (58%). The prevalence of ASCA in CD patients belonging to mixed families was strikingly low (33%). ASCA was a stable marker throughout the disease and was not related to an increased small intestinal permeability.

CONCLUSION

ASCA is strongly associated with familial CD in Belgium, and 21% of healthy family members also display the marker. The association is much weaker in patients belonging to mixed families. ASCA is a stable marker and is not a secondary phenomenon due to increased intestinal permeability.

Identification of histone H1 as a cognate antigen of the ulcerative colitis-associated marker antibody pANCA

Perinuclear anti-neutrophil cytoplasmic antibody (pANCA)(4)is a predominant serum marker of ulcerative colitis (UC), and a familial trait associated with disease susceptibility and disease associated MHC haplotypes. This study characterizes the pANCA antigen defined by representative UC-pANCA human monoclonal antibodies, Fab 5-3 and 5-2. Western blot analysis probed with Fab 5-3 revealed specific binding to a nuclear protein doublet (apparent MW=32-33 kDa) expressed in several cell types. Purification and tryptic peptide sequencing identified the protein as histone H1, and this specificity was confirmed by Fab 5-3 binding to purified H1. Rabbit anti-histone H1 immunostaining and Western blot analysis confirmed that the pANCA epitope is preferentially immunoaccessible in polymorphonuclear neutrophils (PMN). The epitope was localized to the COOH-terminal region by site-specific proteolysis, and recombinant deletants further localized binding activity for both Fab 5-2 and 5-3 to two non-overlapping segments (AA 69-171 and 172-226) associated with a recurring PKKAK motif. Serum IgG binding was detectable to these segments, but was not significantly correlated with pANCA titer or disease status. These findings indicate that histone H1 bears a recurring COOH-terminal epitope recognized by monoclonal ulcerative colitis-associated pANCA marker antibodies, but this epitope is not a predominant specificity of serum pANCA.

Mast cell and neuroendocrine cytoplasmic autoantigen(s) detected by monoclonal pANCA antibodies

pANCA is a marker antibody expressed in most patients with ulcerative colitis, and its cognate antigen is potentially an immunologic target in this disease. This study evaluates whether pANCA detects an autoantigen that is expressed in the colonic mucosa. Immunohistochemistry of colon specimens with human pANCA monoclonal antibodies (Fab 5-2 and 5-3) revealed a minor population of immunoreactive mucosal cells bearing a cytoplasmic vesicle antigen. By distribution, morphology, and tryptase expression, these were identified as mast cells. Immunofluorescent analysis revealed similar immunoreactivity of mouse mast cell lines and human KU812. Western analysis of mouse mast cell lines revealed immunoreactive proteins, and these were distinct from previously proposed pANCA antigens (histone H1, HMG 1 and 2, and neutrophil vesicle antigens). Cognate antigen for Fab 5-2 and 5-3 was also expressed in other tissue mast cells, cerebellar neurons, and pancreatic islet cells. These findings identify a novel cytoplasmic autoantigen(s) associated with UC by its presence in colonic mucosa and recognition by a disease-associated marker antibody.

Are anti-neutrophil cytoplasmic antibodies (ANCA) clinically useful in inflammatory bowel disease (IBD)?

Since the first detection of ANCA in IBD, numerous studies have dealt with their prevalence, antigenic specificities, clinical significance, pathophysiological role, and their induction. This review summarizes the information obtained from those studies and shows that ANCA are not directly useful as diagnostic and prognostic factors in IBD. ANCA were detected in 50-85% of patients with ulcerative colitis (UC) and 10-20% of patients with Crohn's disease (CD). Multiple target antigens are recognized by these autoantibodies, including both cytoplasmic and nuclear proteins. A pathophysiological role for ANCA in IBD is far from clear. On the one hand, it is suggested that ANCA are genetic markers of susceptibility for IBD, and on the other hand, the induction of ANCA in those diseases may just be an epiphenomenon of chronic inflammation. We discuss recent evidence that ANCA may be induced by a break-through of tolerance towards bacterial antigens.

Serologic testing for inflammatory bowel disease

OBJECTIVES

To determine the accuracy of anti-neutrophil cytoplasmic antibodies (ANCAs) and anti-Saccharomyces cerevisiae antibodies (ASCA) in distinguishing patients with inflammatory bowel disease from patients with other disorders, seen in a pediatric gastroenterology clinic setting, and in distinguishing ulcerative colitis (UC) from Crohn's disease (CD).

STUDY DESIGN

Serum samples from 120 children with new or established diagnoses of UC (n = 25) or CD (n = 20) and control children (n = 74) were analyzed in blinded fashion for the presence of IgG ANCAs and IgA and IgG ASCA.

RESULTS

The highest sensitivity for detecting inflammatory bowel disease, 71%, was achieved by using ANCAs and ASCA together. The best test for UC was ANCAs, which had a sensitivity of 80%. However, the ANCA pattern characteristic of UC, perinuclear ANCAs eliminated by DNAse, had a sensitivity of 60%. High-titer ANCAs were specific for UC, whereas ASCA were specific for CD.

CONCLUSIONS

Testing for ANCAs and ASCA together did not achieve sensitivity necessary for population screening. However, ANCAs and ASCA may be helpful in evaluating children suspected of having inflammatory bowel disease and in distinguishing UC from CD.

pANCA antibodies in patients with anterior uveitis: identification of a marker antibody usually associated with ulcerative colitis

A pANCA autoantibody (antineutrophil cytoplasmic antibody, perinuclear pattern) has been described in uveitis patients, but its correlation with systemic illnesses and the specific type of pANCA has not been defined. The goals of this study were to determine the (1) frequency of pANCA autoantibodies in uveitis, (2) systemic associations in the pANCA + uveitis patients, and (3) type of pANCA antigen recognized by the uveitis-associated autoantibody. Serum was obtained from 59 patients with anterior uveitis or panuveitis and from nonuveitis controls. A detailed medical and family history was obtained from each subject at the time of phlebotomy. Sera were screened by neutrophil ELISA to determine the frequency of ANCA positivity. Immunofluorescence assays were then used to differentiate cANCA from pANCA. The specificity of the pANCA + antibodies was further characterized by DNase 1 sensitivity and granule antigen ELISAs. ANCA antibodies were detected in 29% of all patients with panuveitis or anterior uveitis. In 41% of these ANCA + patients, serum antibody detected a perinuclear antigen that was sensitive in all cases to DNase 1. The majority of pANCA + uveitis patients were either HLA-B27 positive or had systemic evidence of immune-mediated diseases. Two pANCA + patients had no medical or family history of other immune-mediated diseases. This study identifies a subset of uveitis patients distinguished by expression of a specific pANCA marker antibody. The characteristics of this antibody are similar to the pANCA antibody present in most patients with ulcerative colitis. Expression of the pANCA autoantibody in uveitis patients is a susceptibility marker for other immune-mediated diseases.

Autoimmune hepatitis overlapping with primary sclerosing cholangitis in five cases

OBJECTIVE

We report five cases (four male; median age 20 yr, range 14-38 yr) of an autoimmune hepatitis/primary sclerosing cholangitis overlap syndrome. The patients presented with jaundice, elevated serum aminotransferase and alkaline phosphatase activities, hyperglobulinemia with high immunoglobulin G (IgG) levels, circulating antinuclear and/or smooth muscle autoantibodies (> or = 1:40), and moderate to severe interface hepatitis on liver biopsy (with biliary features in four).

METHODS

All five fulfilled criteria for diagnosis of "definite" autoimmune hepatitis and showed marked responses to prednisolone and azathioprine therapy, with relapses occurring during reduction or withdrawal of treatment. Cholangiographic features of primary sclerosing cholangitis were found in three patients at presentation and after intervals of 7 and 14 yr in the other two. Only two had evidence of inflammatory bowel disease. Diagnostic criteria for identifying those patients who may benefit from immunosuppressive therapy were reviewed.

RESULTS

Review of the literature revealed only 11 similar cases that were sufficiently well described for comparison. However, in contrast to these and the present cases, preliminary data from other studies have suggested a marked association with ulcerative colitis and a poor response to immunosuppressive therapy.

CONCLUSIONS

It is recommended that the possibility of an autoimmune hepatitis/primary sclerosing cholangitis overlap syndrome responsive to immunosuppressive therapy should be considered in any patient presenting with a hepatitic illness with hyperglobulinemia, antinuclear or smooth muscle autoantibodies, and biliary changes on liver biopsy. Cholangiography should be considered in such patients.

Antineutrophil cytoplasmic antibody subtypes in children and adolescents after ileal pouch-anal anastomosis for ulcerative colitis

BACKGROUND

Perinuclear antineutrophil cytoplasmic antibodies occur frequently in adult patients with chronic pouchitis after colectomy and ileal pouch-anal anastomosis for ulcerative colitis. The purpose of the study was to determine the prevalence of perinuclear antineutrophil cytoplasmic antibodies and cytoplasmic antineutrophil cytoplasmic antibody in children and adolescents who undergo colectomy and ileal pouch-anal anastomosis for ulcerative colitis and familial adenomatous polyposis.

METHODS

Five groups of children and adolescents (age, <20 years) were studied, with the following histories: acute pouchitis and history of ulcerative colitis; chronic pouchitis and history of ulcerative colitis; pouchitis with Crohn's disease features and a history of ulcerative colitis; no pouchitis and a history of ulcerative colitis; and familial adenomatous polyposis, with or without pouchitis. Antineutrophil cytoplasmic antibody levels and titers were detected in postoperative sera by enzyme-linked immunosorbent assay, and positive results were subtyped by indirect immunofluorescence.

RESULTS

The frequency of perinuclear antineutrophil cytoplasmic antibodies and cytoplasmic antineutrophil cytoplasmic antibody in patients with a history of ulcerative colitis were 67% and 15%, compared with a 0% presence in patients with familial adenomatous polyposis (p < 0.001). There was no significant correlation between the frequency of perinuclear antineutrophil cytoplasmic antibodies and ulcerative colitis patient subgroups (patients with and without pouchitis, 66% and 75%). Similarly, there was no significant correlation between the frequency of cytoplasmic antineutrophil cytoplasmic antibodies among ulcerative colitis patient subgroups (patients with and without pouchitis, 19% and 8%). The frequency of cytoplasmic antineutrophil cytoplasmic antibody in patients with Crohn's disease features (50%), was increased, but this difference was not significant.

CONCLUSIONS

There is a high frequency of perinuclear antineutrophil cytoplasmic antibodies in children and adolescents who undergo ileal pouch-anal anastomosis for ulcerative colitis, whether or not they have pouchitis. The frequency of cytoplasmic antineutrophil cytoplasmic antibody is lower in this patient population. Additional studies will be required to determine whether the presence of cytoplasmic antineutrophil cytoplasmic antibody is associated with the postoperative development of features of Crohn's disease.

Ulcerative colitis: an immunological disease?

Ulcerative colitis is an inflammatory disease of the large intestine of unknown aetiology. The nature of the inflammatory infiltrate together with the response to corticosteroids suggests that an abnormal immune response is at work. The key question of whether the immune system is responding to an abnormal breach in the mucosa due to another primary abnormality or whether the primary defect lies within the immune response itself has not been answered. Thus far, it is clear that both T and B cell compartments are involved in the persistence of inflammation but the initial interactions that take place in the mucosa in terms of antigen processing and presentation have not been adequately investigated. Those critical steps and potential defects that push T cells and B cells into a heightened state of activation need to be identified.

Association of antineutrophil cytoplasmic antibodies with resistance to treatment of left-sided ulcerative colitis: results of a pilot study

OBJECTIVE

To determine the frequency of antineutrophil cytoplasmic antibodies with perinuclear staining in patients with treatment-resistant left-sided ulcerative colitis.

METHODS

We studied four groups: treatment-resistant left-sided ulcerative colitis, treatment-responsive left-sided ulcerative colitis, ulcerative colitis historical controls, and healthy control subjects. Antineutrophil cytoplasmic antibodies were detected by enzyme-linked immunosorbent assay, and positive results were confirmed by demonstration of a perinuclear staining pattern by indirect immunofluorescence assay.

RESULTS

The frequency of perinuclear antineutrophil cytoplasmic antibodies was significantly greater in treatment-resistant left-sided ulcerative colitis (90%) than in treatment-responsive left-sided ulcerative colitis (62%) (P = 0.03) or in ulcerative colitis historical controls (60%).

CONCLUSION

The increased frequency of perinuclear antineutrophil cytoplasmic antibodies in treatment-resistant left-sided ulcerative colitis suggests a possible association between these antibodies and relative resistance to medical therapy in patients with ulcerative colitis.