Anti-neutrophil cytoplasmic antibodies (ANCA): their detection and significance: report from workshops

Elevated Myeloperoxidase-DNA Complex Levels in Sera of Patients with IgA Vasculitis

INTRODUCTION

IgA vasculitis is a systemic disease that results from the entrapment of circulating IgA-containing immune complexes in small-vessel walls in the skin, kidneys, and gastrointestinal tract. An excessive formation of neutrophil extracellular traps (NETs) is involved in the pathogenesis of vasculitis, especially in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. This study aimed to clarify whether NETs are implicated in IgA vasculitis.

METHODS

Twenty-two patients with IgA vasculitis and 4 healthy volunteers were enrolled in this study. Serum levels of myeloperoxidase (MPO)-DNA complex, a fragment derived from NETs, were determined by enzyme-linked immunosorbent assay (ELISA), and the association between MPO-DNA complex levels and clinical parameters was examined. The presence of the ANCA was also assessed by ELISA specific for MPO and proteinase 3 (PR3) and indirect immunofluorescence (IIF), followed by assessing the differences in clinical parameters with and without the ANCA.

RESULTS

Serum MPO-DNA complex levels were significantly higher in patients with IgA vasculitis than those in healthy controls. A significant positive correlation between the serum MPO-DNA complex and IgA levels was noted. Interestingly, 63.6% of IgA vasculitis patients were ANCA-positive in IIF with an atypical pattern, whereas neither MPO-ANCA nor PR3-ANCA was detected by ELISA. These findings indicated that some IgA vasculitis patients possessed the so called minor ANCA. Serum IgA and MPO-DNA complex levels and the frequency of hematuria in the minor ANCA-positive group were significantly higher than in the minor ANCA-negative group.

CONCLUSION

The collective findings suggested that NETs are certainly involved in the pathogenesis of IgA vasculitis.

Clinicopathologic Characteristics and Outcomes of Lupus Nephritis With Antineutrophil Cytoplasmic Antibody: A Retrospective Study

Few studies have analyzed the clinicopathologic characteristics and outcomes of lupus nephritis (LN) patients with antineutrophil cytoplasmic antibody (ANCA). The clinical and renal histopathologic data of 154 patients with biopsy-proven LN from 2011 to 2013 were analyzed retrospectively. The patients were followed up for a median period of 16.8 ± 9.4 months, and their outcomes were analyzed. Multivariate Cox analysis was used to evaluate the independent factors for poor outcomes. Among the 154 LN patients, 26 (16.88%) were seropositive for ANCA. The incidences of alopecia, oral ulcer, photosensitivity and skin lesion, and psychosomatic manifestations in the ANCA-positive group were significantly higher than in the ANCA-negative group (P = 0.007, 0.02, 0.02, and 0.03, respectively). Compared with the ANCA-negative group, the ANCA-positive group had significantly lower levels of complement C3 (P = 0.03). Additionally, the positive rate of antinucleosome antibodies, antihistone antibodies, antimitochondrial antibody M2, and anticardiolipin antibodies were higher significantly in the ANCA-positive patients than in the ANCA-negative patients (P = 0.001, 0.001, 0.03, 0.005, respectively). The ANCA-positive group had a notably higher chronic index than the ANCA-negative group (P = 0.01). During the follow-up, the complete remission rate in the ANCA-negative group was higher than that in the ANCA-positive group (P = 0.01). The cumulative renal survival rate in the ANCA-positive group was significantly lower than in the ANCA-negative group (log-rank = 6.59, P = 0.01). Multivariate Cox analysis revealed that the reduced estimated glomerular filtration rate (HR, 1.02; 95% confidence interval, 1.01 to 1.03; P = 0.005), NLR (HR, 1.20; 95% confidence interval, 1.02 to 1.40; P = 0.03), and ANCA (HR, 3.37; 95% confidence interval, 1.12 to 10.09; P = 0.03) were independent risk factors for patients' renal survival after adjusting for age, sex, crescent formation, and glomerulosclerosis. The study found ANCA in LN patients is not rare, and patients with ANCA present with more severe clinicopathologic injuries. Thus, ANCA is an independent risk factor for poor renal outcomes in LN patients.

PR3-ANCA: a promising biomarker in primary sclerosing cholangitis (PSC)

Background and Aims

The only recognized biomarker for primary sclerosing cholangitis (PSC) is atypical anti-neutrophil cytoplasmic antibodies (aANCA), which, in addition to having low sensitivity and specificity, is an indirect immunofluorescence (IIF) test lacking the advantages of high throughput and objectivity. Recent reports have shown that antibodies to proteinase-3 (PR3-ANCA) might add diagnostic value in inflammatory bowel disease (IBD), specifically in ulcerative colitis (UC). As PSC is associated with IBD, the objective of this study was to evaluate the frequency and clinical significance of PR3-ANCA in a large cohort of patients.

Methods

A total of 244 PSC and 254 control [autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC), hepatitis C viral infection (HCV), hepatitis B viral infection (HBV), and healthy controls] sera and their clinical correlations were retrospectively analyzed for PR3-ANCA determined by ELISA and a new chemiluminescence immunoassay (CIA). Testing was also performed for aANCA by IIF.

Results

When measured by CIA, PR3-ANCA was detected in 38.5% (94/244) of PSC patients compared to 10.6% (27/254) controls (p<0.0001). By ELISA, PR3-ANCA was detected in 23.4% (57/244) of PSC patients compared to 2.7% (6/254) controls (p<0.0001). PR3-ANCA in PSC patients was not associated with the presence or type of underlying IBD, and, in fact, it was more frequent in Crohn's disease (CD) patients with PSC than previously reported in CD alone. PR3-ANCA in PSC measured by CIA correlated with higher liver enzymes.

Conclusion

PR3-ANCA is detected in a significant proportion of PSC patients compared to other liver diseases including PBC and AIH. PR3-ANCA is associated with higher liver enzyme levels in PSC, and is not solely related to underlying IBD.

Novel clinical and diagnostic aspects of antineutrophil cytoplasmic antibodies

Antineutrophil cytoplasmic antibodies (ANCA) are the serological hallmark of some idiopathic systemic vasculitides. Besides the investigation of ANCA-associated vasculitis (AAV) and constant effort for a standardized nomenclature and classification of the AAV, a main focus of research during the last few years has been to constantly improve the performance of enzyme immunoassays. With the latest so called third generation ELISA, this goal seemed to be fulfilled. The International Consensus Statement on Testing and Reporting of ANCA gave recommendations for standardized strategies for the serological diagnosis of ANCA. New developments now target the system immanent drawbacks of the respective diagnostic methods, be it the need for batching and the long time to result for ELISA, or the high likelihood of error and subjectivity of indirect immunofluorescence (IIF). Random access technology and multiplexing for solid phase assays as well as digital imaging for IIF are tools which may help to expedite and simplify routine diagnostics in the lab and in emergency settings. Recent findings indicate that PR3-ANCA have clinical utility beyond the diagnosis of AAV. PR3-ANCA can also serve as an aid for the differentiation between ulcerative colitis (UC) and Crohn's disease (CrD) and the stratification of UC patients. This review provides a detailed review of what is known about ANCA and highlights the latest research and state-of-the-art developments in this area.

Utility of immunologic testing in suspected rheumatologic disease

The use of diagnostic testing in the clinical practice of medicine has been a shifting landscape from the time that the first blood test was utilized. This is no different in the field of immunology and in particular rheumatology. As the field of immunology is relatively young, the clinical tests are not well established and therefore guidelines for use are still under debate. In this review, we seek to look at some of the key autoantibodies, as well as other tests that are available to diagnose suspected rheumatologic disease, and examine how to best use these tests in the clinic. In particular, we will focus on the anti-nuclear antibodies, anti-neutrophil cytoplasmic antibodies, complement, cryoglobulins, rheumatoid factor, and anti-citrullinated protein antibodies.

Diagnostic value of distinguishing and reporting different perinuclear ANCA (P-ANCA) immunofluorescence patterns: a prospective study

OBJECTIVES

To investigate whether discriminating the classic perinuclear antineutrophil cytoplasmic antibody (P-ANCA) pattern from atypical P-ANCA and uninterpretable patterns improves the diagnostic utility of ANCA testing.

METHODS

All ANCA requests (n = 3,544) referred to Pathology Queensland were analyzed prospectively over 4 months for P-ANCA pattern subtypes and myeloperoxidase (MPO)-ANCA/PR3-ANCA results and correlated with clinical, laboratory, and radiologic evidence of necrotizing small vessel vasculitis.

RESULTS

Of the 436 perinuclear immunofluorescence-positive samples, 45 were classic P-ANCA, 163 were atypical P-ANCA, and 228 were antinuclear antibodies/uninterpretable. The classic P-ANCA pattern had a significantly stronger association with vasculitis (30/45) than atypical P-ANCA (2/163) (P <.0001) or ANA/uninterpretable patterns (8/228) (P <.0001). The combination of a classic P-ANCA pattern and positive MPO-ANCA/PR3-ANCA result was also more strongly associated with vasculitis than a positive MPO-ANCA/PR3-ANCA result in isolation (P = .003).

CONCLUSIONS

This study demonstrates that reporting different P-ANCA patterns (including ANA/uninterpretable patterns) provides additional diagnostic information to MPO-ANCA/PR3-ANCA results.

Diffuse alveolar haemorrhage in granulomatosis with polyangitis (Wegener's) with coexistent rheumatoid arthritis

Diffuse alveolar haemorrhage is a serious manifestation of granulomatosis with polyangitis (Wegener's) with high morbidity and mortality. It is defined by the clinical triad of haemoptysis, anaemia and progressive hypoxaemia. The diagnosis of granulomatosis with polyangitis is confirmed in an appropriate clinical setting by bronchoalveolar lavage, lung biopsy or detection of C-antineutrophil cytoplasmic antibodies. In this report, the patient was a known case of rheumatoid arthritis and presented with diffuse alveolar haemorrhage on CT scan; the underlying cause was found to be granulomatosis with polyangitis (Wegener's) with positive C-antineutrophil cytoplasmic antibodies. Despite aggressive treatment with immunosuppressants and steroids the patient died within a few days.

Multidimensional degradomics identifies systemic autoantigens and intracellular matrix proteins as novel gelatinase B/MMP-9 substrates

The action radius of matrix metalloproteinases or MMPs is not restricted to massive extracellular matrix (ECM) degradation, it extends to the proteolysis of numerous secreted and membrane-bound proteins. Although many instances exist in which cells disintegrate, often in conjunction with induction of MMPs, the intracellular MMP substrate repertoire or degradome remains relatively unexplored. We started an unbiased exploration of the proteolytic modification of intracellular proteins by MMPs, using gelatinase B/MMP-9 as a model enzyme. To this end, multidimensional degradomics technology was developed by the integration of broadly available biotechniques. In this way, 100-200 MMP-9 candidate substrates were isolated, of which 69 were identified. Integration of these results with the known biological functions of the substrates revealed many novel MMP-9 substrates from the intracellular matrix (ICM), such as actin, tubulin, gelsolin, moesin, ezrin, Arp2/3 complex subunits, filamin B and stathmin. About 2/3 of the identified candidates were autoantigens described in multiple autoimmune conditions and in cancer (e.g. annexin I, nucleolin, citrate synthase, HMGB1, alpha-enolase, histidyl-tRNA synthetase, HSP27, HSC70, HSP90, snRNP D3). These findings led to the insight that MMPs and other proteases may have novel (immuno)regulatory properties by the clearance of toxic and immunogenic burdens of abundant ICM proteins released after extensive necrosis. In line with the extracellular processing of organ-specific autoantigens, proteolysis might also assist in the generation of immunodominant 'neo-epitopes' from systemic autoantigens. The study of proteolysis of ICM molecules, autoantigens, alarmins and other crucial intracellular molecules may result in the discovery of novel roles for proteolytic modification.

Antibodies to selected minor target antigens in patients with anti-neutrophil cytoplasmic antibodies (ANCA)

In patients with anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis, indirect immunofluorescence (IF) distinguishes between cytoplasmic (C-ANCA) and perinuclear (P-ANCA) neutrophil staining patterns. In patients with primary systemic vasculitis such as Wegener's granulomatosis, microscopic polyangiitis and Churg-Strauss syndrome, these IF staining patterns correspond broadly with antibodies to the two major antigens: the C-ANCA pattern is associated generally with antibodies to serine protease 3 (PR3) and the P-ANCA pattern with antibodies to myeloperoxidase (MPO). However, some sera positive for ANCA by IF are negative for anti-PR3 and anti-MPO antibodies, suggesting the presence of antibodies to minor antigens of PMN granules. We tested sera from a previously well-defined clinical cohort of patients for antibodies to four possible minor antigens: bactericidal permeability increasing protein, elastase, cathepsin G and lactoferrin. IF-positive (+) sera had significantly higher antibody frequencies to the minor antigens than did the IF-negative (-) sera (P < 0.01). Patients with IF(+) PR3(-)MPO(-) sera showed the most varied reactivity to the minor antigens. Among the IF(+) groups, the IF(+) PR3(+)/MPO(-) sera showed the lowest reactivity to the minor antigens. Patients with well-defined ANCA specificities, e.g. the PR3-ANCA response associated with Wegener's granulomatosis, are less likely than are other patient subsets to have antibodies to minor antigen targets. Autoantibodies to these minor antigens contribute to the overall pattern of ANCA identified by IF and help to explain why the correlation between IF and enzyme immunoassays show discrepancies. While the pathophysiological significance of antibodies to minor target antigens needs further evaluation, they may be markers of inflammation associated with disease processes.

Small vessel vasculitis

BACKGROUND

Vasculitis is a primary inflammatory process of large, medium-sized, and small blood vessels. There are multiple entities particularly among small vessel vasculitides. Some are life threatening and require treatment with toxic agents. Diagnostic challenges are posed by low prevalence, controversial classification, inconsistency of clinical and pathological features, and the existence of clinical and pathological "look-alikes". Also, patients may present to a variety of medical specialists, and the diagnosis is often unexpected. The cause often is unknown.

REVIEW

Classification is by vessel size and then on an immunopathologic basis. Generalised and "organ-limited" forms occur. The principal clinical and pathological features are outlined for each of antibasement membrane disease, immune complex disorders including Henoch-Schönlein purpura and cryoglobulinemic vasculitis and the pauci-immune group, which is often associated with antineutrophil cytoplasmic antibody (ANCA), comprising microscopic polyangiitis, Wegener's granulomatosis, and Churg-Strauss syndrome. A brief account is given of "look-alikes" including microthrombotic conditions, which can confound the diagnosis of small vessel vasculitis.

CONCLUSION

Requirements for diagnosis include full disclosure of the past and present medical history with review of laboratory results, especially diagnostic immunology. Histology should be of targeted biopsies of recent active lesions in preference to blind biopsies. Sampling should be extensive using high-quality thin sections. Systematic microscopic evaluation of architectural features and cellular detail is necessary. Tissue immunofluorescence is a useful adjunct. The final opinion must take all available information into account but may ultimately depend on a critical judgement by the pathologist.

Synovial fluid exoglycosidases are predictors of rheumatoid arthritis and are effective in cartilage glycosaminoglycan depletion

OBJECTIVE

To analyze enzymes involved in joint damage by simultaneous investigation of glycosidases and matrix metalloproteinases (MMPs) in patients with various joint diseases.

METHODS

Activities of glycosidases (beta-D-glucuronidase, beta-D-N-acetyl-glucosaminidase, beta-D-N-acetyl-galactosaminidase, beta-D-galactosidase, and alpha-D-mannosidase) were tested at an acidic pH as well as at the original pH of the synovial fluid (SF) samples in parallel with activities of MMP-1 and MMP-9.

RESULTS

Patients with rheumatoid arthritis (RA) were characterized by significantly elevated activities of beta-D-glucuronidase and beta-D-N-acetyl-glucosaminidase in SF compared with patients with osteoarthritis, seronegative spondylarthritis, or acute sports injury. To select the best predictor for distinguishing among patient groups, a stepwise logistic regression analysis was performed; the strongest association was found to be between RA and beta-D-glucuronidase/beta-D-N-acetyl-glucosaminidase activities (measured at the pH of the SF). Further, a significant correlation was observed between the activity of SF beta-D-N-acetyl-glucosaminidase and the level of rheumatoid factor. In vitro digestion of human hyaline cartilage samples revealed that the dominant glycosidases, alone or in combination with MMPs, proved to be effective in depleting glycosaminoglycans (GAGs) from cartilage.

CONCLUSION

These results suggest that exoglycosidases, which are present in the SF of RA patients, may contribute to the depletion of GAGs from cartilage and thereby facilitate the invasion of synovial cells and their attachment to cartilage in RA.

Periodontitis and anti-neutrophil cytoplasmic antibodies in systemic lupus erythematosus and rheumatoid arthritis: a comparative study

BACKGROUND

This investigation was designed to determine and compare the distribution pattern of anti-neutrophil cytoplasmic antibodies (ANCA) in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) in the presence or absence of periodontal disease.

METHODS

Sera of 30 patients with SLE and 30 with RA were tested for ANCA utilizing an indirect enzyme immunosorbent assay (ELISA) directed to a neutrophil granular extract and 6 neutrophil granule proteins. A control group of 20 healthy individuals showing neither evidence of periodontal disease nor systemic compromise was also included in this study.

RESULTS

For RA, the number of ANCA-positive sera was very low but was evenly distributed among patients with and without periodontitis. Conversely, a high number of ANCA-positive sera in SLE was found mostly in individuals presenting periodontal compromise. A statistically significant association between ANCA and periodontitis in SLE patients was found (P <0.005, chi square test).

CONCLUSIONS

A marked difference in the number and distribution of ANCA with respect to periodontitis between RA and SLE was found. Hyperresponsiveness of B cells and polyclonal B activation to periodontopathic bacteria in SLE might be accountable for the high numbers of ANCA and the close association observed between those autoantibodies and periodontitis in SLE.

Serum levels of interleukins 8 and 10, interferon gamma, granulocyte-macrophage colony stimulating factor and soluble CD23 in patients with primary sclerosing cholangitis

The presence of auto-antibodies and hypergammaglobulinaemia in patients with primary sclerosing cholangitis (PSC) suggest an overactive humoral immune system. Serum cytokines, measured using in-house double monoclonal sandwich ELISA, were used to assess the state of cellular and humoral immunity in this condition by comparison with sex and age matched normal controls and patients with alcoholic cirrhosis (AC). Soluble CD23 (sCD23) as a marker of humoral immunity was significantly elevated in PSC (N = 31) relative to patients with AC (N = 12) and the control group (N = 20) (P < 0.0001 and P < 0.001 respectively). Serum interleukin (IL) 10, as an anti-inflammatory cytokine and IL8, as a marker of neutrophil activation were significantly elevated in patients with PSC relative to those with AC and the controls (P < 0.001 and P < 0.05 respectively). Interferon gamma, as a marker of cellular immunity, and granulocyte-macrophage colony stimulating factor, a marker of monocyte/macrophage function were similar in all the groups. Cytokines and sCD23 were no different between patients with AC and the control group. While more than two thirds of the patients with PSC were positive for ANCA, there was no correlation between the presence of ANCA or ANCA titre and serum levels of either IL8, IL10 and sCD23. These results suggest exaggerated humoral immunity in PSC. The raised levels of IL10 and IL8 in PSC are discussed in the context of inflammatory bowel disease and liver dysfunction.