Is p-ANCA in ulcerative colitis directed against beta-glucuronidase?

Role of Serum Proteinase 3 Antineutrophil Cytoplasmic Antibodies in the Diagnosis, Evaluation of Disease Severity, and Clinical Course of Ulcerative Colitis

Background/Aims

Proteinase 3 antineutrophil cytoplasmic antibody (PR3-ANCA) is a serologic marker for granulomatosis with polyangiitis. However, recent studies have also shown their role as diagnostic markers for ulcerative colitis (UC). This study was performed to investigate the clinical roles of PR3-ANCAs in the disease severity, disease extension, and clinical course of UC.

Methods

Serum PR3-ANCAs were measured in 173 UC patients including 77 patients with new-onset patients UC diagnosed within 1 month, 110 patients with Crohn’s disease, 48 patients with other intestinal diseases, and 71 healthy controls. Associations between the PR3-ANCA titer and clinical data, such as disease severity, disease extension, and clinical course, were assessed. The clinical utility of PR3-ANCA measurement was evaluated by receiver operating characteristic (ROC) analysis.

Results

PR3-ANCA ≥3.5 U/mL demonstrated 44.5% sensitivity and 95.6% specificity for the diagnosis of UC in all patients. PR3-ANCA positivity was more prevalent in the 77 new-onset UC patients (58.4%). In this group, the disease severity and extension were more severe in PR3-ANCA positive patients than in PR3-ANCA negative group (p<0.001). After treatment, the partial Mayo scores were significantly decreased with the PR3-ANCA titers. The proportion of patients who required steroids for induction therapy was significantly higher among PR3-ANCA positive than negative group. ROC analysis revealed that PR3-ANCA ≥3.5 U/mL had 75% sensitivity and 69.0% specificity for steroid requirement in new-onset UC patients.

Conclusions

Our results indicate that PR3-ANCA measurement is useful not only for diagnosing UC but also for evaluating disease severity and extension and predicting the clinical course.

Diagnostic and clinical role of serum proteinase 3 antineutrophil cytoplasmic antibodies in inflammatory bowel disease

BACKGROUND AND AIM

Proteinase 3 antineutrophil cytoplasmic antibodies (PR3-ANCAs) are well-known serological markers for granulomatosis with polyangiitis, but their role as serological markers for inflammatory bowel disease remains uncertain. The present study aimed to evaluate the diagnostic and clinical role of PR3-ANCAs as markers for inflammatory bowel disease.

METHODS

Using a new methodology with chemiluminescence enzyme immunoassay, serum PR3-ANCA titers were assessed in 102 patients with ulcerative colitis (UC), 67 patients with Crohn's disease (CD), 44 controls with other intestinal diseases, and 66 healthy controls. Associations with clinical data were investigated. The diagnostic role of PR3-ANCAs was evaluated by receiver operating characteristic analysis.

RESULTS

Proteinase 3 antineutrophil cytoplasmic antibody titers were significantly higher in patients with UC than in those with CD patients, patients with intestinal diseases (intestinal controls), and healthy controls (all P < 0.001). Receiver operating characteristic analysis demonstrated an area under the curve of 0.85 (95% confidence interval: 0.83-0.87) and showed that the manufacturer's cutoff value (3.5 U/mL) had a sensitivity of 39.2% and specificity of 96.6% for UC. There was a significant difference between PR3-ANCA-positive and PR3-ANCA-negative patients with regard to disease duration (P < 0.05) and disease severity (P < 0.01).

CONCLUSIONS

Proteinase 3 antineutrophil cytoplasmic antibodies were significantly more prevalent in patients with UC than in those with CD and controls. Our results suggested the role of PR3-ANCAs as serological markers for aiding in diagnosing UC and evaluating disease severity. Further prospective studies are needed across multiple populations of patients and ethnic groups.

Serologic markers in inflammatory bowel disease

Inflammatory bowel disease (IBD) is an enduring disease involving mostly young people, with symptoms of bloody diarrhea and abdominal cramps. Several antibodies have been associated with IBD, the 2 most comprehensively studied being autoantibodies to neutrophils (atypical perinuclear anti-neutrophil cytoplasmic antibodies) and anti-Saccharomyces cerevisiae antibodies. This review focuses on the value of these antibodies for diagnosing IBD, differentiating Crohn disease from ulcerative colitis, indeterminate colitis, monitoring disease, defining clinical phenotypes, predicting response to therapy, and as subclinical markers. Pancreatic antibodies and newly identified anti-microbial antibodies (anti-outer membrane porin C, anti-I2, and anti-flagellin) are also reviewed.

Antineutrophil cytoplasmic antibodies (ANCA)

Antineutrophil cytoplasmic antibodies (ANCA) are a sensitive and specific marker for ANCA-associated systemic vasculitis. Using indirect immunofluorescence on ethanol-fixed neutrophils, two major fluoroscopic patterns can be recognised: a diffuse cytoplasmic staining (C-ANCA), and a perinuclear/nuclear staining (P-ANCA). In patients with vasculitis, more of 90% of C-ANCA are directed against proteinase 3 (PR3-ANCA) whereas approximately 80-90% of P-ANCA recognise myelperoxidase (MPO-ANCA). Although C-ANCA (PR3-ANCA) is preferentially associated with Wegener's granulomatosis (WG), and P-ANCA (MPO-ANCA) with microscopic polyangiitis (MPA), idiopathic necrotising crescentic glomerulonephritis (iNCGN) and Churg-Strauss syndrome (CSS), there is not absolute specificity. Between 10-20% of patients with classical WG show P-ANCA (MPO-ANCA), and even a larger percentage of patients with MPA or CSS have C-ANCA (PR3-ANCA). Furthermore, it should be stressed that approximately 10-20% of patients with WG or MPA (and 40-50% of cases of CSS) have negative assay for ANCA. The best diagnostic performance is obtained when indirect immunofluorescence is combined with PR3 and MPO-specific ELISAs. ANCA with different and unknown antigen specificity are found in a variety of conditions other than AASV, including inflammatory bowel diseases, other autoimmune diseases, and infections where their clinical significance is unclear. ANCA levels are useful to monitor disease activity but should not be used by themselves to guide treatment. A significant increase in ANCA titres, or the reappearance of ANCA, should alert the clinicians and lead to a stricter patient control.

Antiproteinase 3- and antimyeloperoxidase-associated vasculitis

Antiproteinase 3- and antimyeloperoxidase-associated vasculitis. Wegener's granulomatosis, microscopic polyangiitis, and idiopathic pauci-immune necrotizing crescentic glomerulonephritis (NCGN) are strongly associated with antineutrophil cytoplasmic autoantibodies (ANCAs) directed against either proteinase 3 (anti-PR3) or myeloperoxidase (anti-MPO). This has led some investigators to prefer combining these diseases under the common heading of ANCA-associated vasculitides. However, it is increasingly recognized that there are characteristic differences between patients with anti-PR3 and those with anti-MPO-associated vasculitis. This review focuses on the clinical, histopathologic, and possibly pathophysiologic differences between anti-PR3- and anti-MPO-associated vasculitis. Although there is considerable overlap, the anti-PR3- and anti-MPO-associated vasculitides are each characterized by particular clinical and histopathological findings. Extrarenal organ manifestations and respiratory tract granulomas occur more frequently in patients with anti-PR3 than in those with anti-MPO. Anti-PR3-positive patients with NCGN generally have a more dramatic deterioration of their renal function compared with anti-MPO-positive patients. The term "ANCA-associated vasculitis" is considered as a useful concept in the presence of systemic vasculitis. Likewise, in the presence of vasculitis, the terms "anti-PR3-associated vasculitis" and "anti-MPO-associated vasculitis" are useful concepts.

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.

Antineutrophil cytoplasmic antibodies in Japanese patients with inflammatory bowel disease: prevalence and recognition of putative antigens

OBJECTIVE

Our aim was to investigate the prevalence of antineutrophil cytoplasmic antibodies (ANCA) in Japanese patients with ulcerative colitis (UC) and Crohn's disease (CD), and the putative antigens recognized by perinuclear staining pattern ANCA (p-ANCA)-positive sera.

METHODS

Sera from UC (n = 52) and CD (n = 43) patients, and from healthy controls (n = 74) were studied. The indirect immunofluorescence (IIF) method was used for the detection of ANCA and its binding pattern. p-ANCA-positive sera were studied further for putative antigens. ELISAs using lactoferrin (Lf), myeloperoxidase (MPO), and cathepsin G (Cat G) as antigens were performed.

RESULTS

ANCA was positive in 40 of the 52 (76.9%) UC (p-ANCA in 33) and in 32 of the 43 (74.4%) CD (p-ANCA in 31) patients. UC and CD patients showed significantly higher titers of p-ANCA than controls; however, no significant difference was observed between UC and CD. In UC, 23, 17, and nine of the 33 patients with p-ANCA-positive sera showed reactivity with Lf, MPO, and Cat-G, respectively. In CD, 21, 20, and 11 of the 31 patients with p-ANCA-positive sera showed reactivity with Lf, MPO, and Cat-G, respectively. Fourteen of the UC and six of the CD patients showed reactivity with two different antigens, and seven of the UC and 11 of the CD patients showed reactivity with all three antigens. The presence of anti-Lf and anti-MPO antibodies was further confirmed by Western blotting.

CONCLUSIONS

ANCA is useful in distinguishing patients with IBD from normal subjects but is not sufficient for the differential diagnosis of CD and UC. p-ANCA reactivity might be derived from the recognition of heterogeneous neutrophil-associated antigens.

Escherichia coli and Proteus mirabilis inhibit the perinuclear but not the circulating antineutrophil cytoplasmic antibody reaction

BACKGROUND

Perinuclear antineutrophil cytoplasmic antibodies (P-ANCA) are found in 48%-83% of serum samples from patients with ulcerative colitis (UC). Their pathogenic role and initiating stimuli are unknown. In contrast to patients with vasculitides and ANCA reactivities, the antibodies in UC patients do not react with myeloperoxidase (MPO) or proteinase 3 (PR3). The aim of the present study was to investigate whether bacterial species of the intestinal tract and other sources could interfere with P-ANCA in sera from patients with UC.

METHODS

Seventeen P-ANCA-positive and anti-MPO-negative serum samples from patients with UC were tested with Escherichia coli 014 and Staphylococcus aureus Wood 46. Six of these serum samples with different P-ANCA titres were selected to test further the influence of 15 different gram-negative or gram-positive bacterial strains. Six anti-MPO positive P-ANCA, 5 anti-PR3 positive C-ANCA, and 10 antinuclear antibody (ANA)-positive serum samples were used as controls. The antineutrophil cytoplasmic antibodies (ANCAs) were analysed by an indirect immunofluorescence method (IIF) on ethanol-fixed neutrophils, and the ANAs were tested by IIF on HEp-2 cells or rat liver tissues. The bacteria used in the experiments were either live or killed by formalin or glutaraldehyde fixation or heated at 80 degrees C for 30 min. The test was first performed as a bacterial absorption test with sedimented organisms and then at various temperatures with the supernatant from suspension of live bacteria.

RESULTS

Both MPO-positive and MPO-negative P-ANCA reactivity was abolished by absorption of patient sera with live E. coli and Proteus mirabilis but not with bacteria representing members of 10 other species, suggesting that antibody reactivity was absorbed away. However, continued experiments indicated that the inhibition of P-ANCA was not due to classic antigen-antibody interactions but rather to decomposition of the antigenic substrate of the neutrophils by factors present in the supernatants of live E. coli and P. mirabilis. The activity of the supernatant was temperature-dependent, with strong activity at room temperature and 37 degrees C, no activity at 0 degrees C, and abolished by mild heat treatment (56 degrees or 60 degrees C). No activity was shown in the supernatants from bacteria treated with formaldehyde or glutaraldehyde.

CONCLUSIONS

Soluble material from live E. coli and P. mirabilis has the capacity to decompose the antigenic substrate of neutrophils responsible for both MPO-positive and MPO-negative P-ANCA, most probably brought about through enzymatic activity. Anti PR3-positive C-ANCA were not affected, which suggests substrate specificity of the proposed enzymatic activity.

Catalase and alpha-enolase: two novel granulocyte autoantigens in inflammatory bowel disease (IBD)

In IBD, the target antigens of anti-neutrophil cytoplasmic autoantibodies (ANCA) have not been fully identified, which limits the analysis of the diagnostic significance as well as of the possible pathophysiological role of these antibodies. In this study, we identify the target antigens of ANCA in large groups of patients with ulcerative colitis (UC) and Crohn's disease (CD). Apart from antibodies against lactoferrin and bactericidal/permeability-increasing protein (BPI), which have been reported before, antibodies against two novel granulocyte antigens were identified: antibodies against a 57/56-kD doublet were found in 38% of samples from UC patients and in 26% of samples from CD patients, whereas antibodies against a 47-kD protein were found in 10% of samples from UC patients and in 18% of samples from CD patients. Partial purification and amino acid sequence analysis identified the 57-kD protein as catalase and the 47-kD protein as alpha-enolase. This study is the first to report catalase and alpha-enolase as granulocyte antigens for autoantibodies in IBD.

Comparative evaluation of unfixed and fixed human neutrophils for determination of antineutrophil cytoplasmic antibodies by indirect immunofluorescence

BACKGROUND

Antineutrophil cytoplasmic antibodies (ANCAs) are found in the sera of patients with vasculitides and ulcerative colitis. Using indirect immunofluorescence on ethanol fixed neutrophils, ANCAs can be divided into two types: those that give a cytoplasmic staining pattern (C-ANCA) and those that give a perinuclear staining pattern (P-ANCA). Some studies have indicated that the perinuclear staining pattern might be an artefact of alcohol fixation.

AIMS

To observe any changes seen in the ANCA staining pattern using indirect immunofluorescence on unfixed neutrophils or neutrophils that had been fixed by ethanol, acetone, or paraformaldehyde. In addition, the effects of the different fixation methods on the sensitivity of the indirect immunofluorescence test were evaluated.

METHODS

Twenty one sera from patients with ulcerative colitis and 19 from healthy controls were studied. In addition, 17 sera from patients with vasculitides, including eight with proteinase 3 (PR 3) positive C-ANCA and nine with myeloperoxidase (MPO) positive P-ANCA were included in the study. Antineutrophil cytoplasmic antibodies were analysed by indirect immunofluorescence on unfixed neutrophils or cells fixed by ethanol, acetone, or paraformaldehyde.

RESULTS

All the ulcerative colitis associated ANCA positive sera presented a peri-nuclear staining pattern on both unfixed and fixed cells. The acetone and paraformaldehyde fixations decreased the ulcerative colitis P-ANCA titres. Paraformaldehyde fixation also decreased the MPO positive P-ANCA titres. In indirect immunofluorescence, the staining patterns of all the eight PR 3 positive C-ANCA sera and eight of the nine MPO positive P-ANCA sera did not change, even if unfixed or fixed cells were used.

CONCLUSIONS

The ANCA staining patterns are not affected by the fixation method used, and are the same as when unfixed neutrophils are used; this suggests that the P-ANCA pattern is not an artefact of alcohol fixation. Furthermore, this study confirms that on ethanol fixed neutrophils, the antigen of ulcerative colitis associated P-ANCA is better exposed than on acetone or paraformaldehyde fixed cells.

Antineutrophil cytoplasmic antibodies in sera from colectomised ulcerative colitis patients and its relation to the presence of pouchitis

BACKGROUND

Few studies have evaluated the influence of colectomy on antineutrophil cytoplasmic antibody (ANCA) positivity in ulcerative colitis (UC). In small series of patients it has been suggested that ANCA positivity in UC might be predictive for development of pouchitis after colectomy.

AIMS

To assess the prevalence of ANCA in UC patients treated by colectomy and a Brooke's ileostomy (UC-BI) or ileal pouch anal anastomosis (UC-IPAA), and the relation between the presence of ANCA, the type of surgery, and the presence of pouchitis.

SUBJECTS

63 UC patients treated by colectomy (32 with UC-BI and 31 with UC-IPAA), 54 UC, and 24 controls.

METHODS

Samples were obtained at least two years after colectomy. ANCA were detected by indirect immunofluorescent assay.

RESULTS

There were no differences between patients with (36.3%) or without pouchitis (35.0%) and between patients with UC (55%), UC-BI (40.6%), and UC-IPAA (35.4%). However, ANCA prevalence significantly decreases in the whole group of operated patients (38.0%) compared with non-operated UC (p = 0.044).

CONCLUSIONS

The prevalence of ANCA in operated patients was significantly lower than in non-operated UC, suggesting that it might be related either to the presence of inflamed or diseased tissue. ANCA persistence is not related to the surgical procedure and it should not be used as a marker for predicting the development of pouchitis.

Importance of antineutrophil cytoplasmic antibodies in primary sclerosing cholangitis and ulcerative colitis: prevalence, titre, and IgG subclass

Antineutrophil cytoplasmic antibodies (ANCA) have been reported in up to 87% of patients with primary sclerosing cholangitis with or without ulcerative colitis (PSC +/- UC) and in 68% of those with UC only. Compared with other liver and diarrhoeal diseases, ANCA have high specificity for PSC (+/- UC) and UC only. This study aimed to determine the prevalence and significance of ANCA in these two diseases and whether the ANCA titre or IgG subclass, or both, could distinguish between PSC + UC and UC only. Subjects included 63 patients with PSC, 85 with UC, 17 with coeliac disease, and 10 with dermatitis herpeteformis and 36 normal subjects. ANCA was detected using the immunoalkaline phosphatase method. The IgG subclass of ANCA was determined in 27 PSC + UC and 30 UC only patients using a panel of mouse monoclonal antibodies specific for the IgG subclasses. At a serum dilution of 1:5, ANCA had a diagnostic sensitivity of 65% for all PSC and 45% for UC only. For PSC + UC the sensitivity was 70% at 1:5 (p = 0.004 v UC only). At 1:50, the sensitivity values were 54% and 25% respectively for PSC + UC and UC only (p = 0.0006). In PSC, ANCA positivity was significantly associated with extensive involvement of the biliary tree but not with other clinical parameters. In UC only, the median disease duration was significantly greater in ANCA positive patients. The PSC + UC ANCA showed increased IgG3 compared with UC only ANCA (p < 0.05), together with increased IgG2 and IgG4 (p = NS). ANCA is a diagnostic marker in PSC and UC. While the higher titres and different IgG subclass distribution of ANCA in PSC + UC patients compared with those with UC only may reflect differences in underlying immune regulation, determination of the ANCA titre and IgG subclass is unlikely to have a role in distinguishing between PSC + UC and UC only ANCA. Future identification of the antigen(s) for ANCA should allow the development of a more sensitive and specific test for the diagnosis of these two conditions and also determine if ANCA is associated with UC or PSC.

Anti-neutrophil cytoplasmic antibodies in Japanese children with ulcerative colitis

OBJECTIVE

To investigate the diagnostic value of anti-neutrophil cytoplasmic antibodies (ANCA) in the diagnosis of ulcerative colitis (UC) in Japanese children.

METHODOLOGY

Serum samples from 23 children with UC (17 Japanese, 6 non-Japanese), 27 children with Crohn's disease (CD) (10 Japanese, 17 non-Japanese), 10 children with other diarrhoeal diseases, and 33 normal, healthy adult volunteers were assayed for ANCA using an indirect immunofluorescence technique.

RESULTS

ANCA were detected in 6/17 (35%) UC patients and 0/10 (0%) CD patients in Japanese children, and in 3/6 (50%) UC patients and 3/17 (18%) CD patients in non-Japanese children. The difference in prevalence between Japanese and non-Japanese children with UC was not statistically significant (P > 0.05). ANCA were not found in other diarrhoeal patients and volunteers.

CONCLUSIONS

Although ANCA have been reported to be useful in the diagnosis of UC in adults, they may be of limited use in Japanese children. This might reflect the heterogeneity of UC.

Antineutrophil cytoplasmic antibodies (ANCA) in idiopathic pulmonary hemosiderosis

Four children were diagnosed with idiopathic pulmonary hemosiderosis (IPH), over a period of 4 years. Retrospectively, antineurtrophil cytoplasmic antibodies (ANCA) were studied by indirect immunofluorescence (IIF) and ELISA in 18 sera from these patients, stored at -20 degrees C. ANCA-positive sera, from 1/20 to 1/1, 200 dilution, were found in 3/4 of the patients, by IIF. The patient with the highest titre of ANCA died 3 months later during an acute crisis, the other two patients need a minimal dose of steroids. In one case only, a patient who is still without treatment, had no ANCA. The antibodies anti-myeloperoxidase and anti-proteinase-3 were negative or at border line levels. Rheumatoid factor, antinuclear (Hep-2), anti-endomysial, anti-reticulin and antibasement membrane antibodies were negative in all sera. The surviving patients were followed-up for more than 10 years with no systemic or renal disease appearances. The presence of serum ANCA may help to classify children with pulmonary haemorrhage and may have a prognostic value.