Azurocidin is a novel antigen for anti-neutrophil cytoplasmic autoantibodies (ANCA) in systemic vasculitis

Old known and possible new biomarkers of ANCA-associated vasculitis

Antineutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) comprises a group of multisystem disorders involving severe, systemic, small-vessel vasculitis with short- and long term serious and life-threating complications. Despite the simplification of treatment, fundamental aspects concerning assessment of its efficacy and its adaptation to encountered complications or to the relapsing/remitting/subclinical disease course remain still unknown. The pathogenesis of AAV is complex and unique, and despite the progress achieved in the last years, much has not to be learnt. Foremost, there is still no accurate marker enabling us to monitoring disease and guide therapy. Therefore, the disease management relays often on clinical judgment and follows a" trial and error approach". In the recent years, an increasing number of new molecules s have been explored and used for this purpose including genomics, B- and T-cell subpopulations, complement system factors, cytokines, metabolomics, biospectroscopy and components of our microbiome. The aim of this review is to discuss both the role of known historical and clinically established biomarkers of AAV, as well as to highlight potential new ones, which could be used for timely diagnosis and monitoring of this devastating disease, with the goal to improve the effectiveness and ameliorate the complications of its demanding therapy.

Role of Neutrophils in Systemic Vasculitides

Neutrophils and neutrophil extracellular traps (NETs) contribute to the pathogenesis of many autoimmune diseases, including vasculitis. Though neutrophils, and NETs, can break self-tolerance by being a source of autoantigens for autoantibodies in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, playing a key role in driving the autoimmune response, the role of neutrophils and NETs in large vessel vasculitis, including giant cell arteritis (GCA), is not well understood. In this review, we summarize the current insight into molecular mechanisms contributing to neutrophil-mediated pathology in small and medium vessel vasculitis, as well as provide potential translational perspectives on how neutrophils, and NETs, may partake in large vessel vasculitis, a rare disease entity of unclear pathogenesis.

Perinuclear anti-neutrophil cytoplasmic antibody in systemic lupus erythematosus indicates more severe condition

OBJECTIVE

To investigate the clinical significance of perinuclear anti-neutrophil cytoplasmic antibody (p-ANCA) in patients with systemic lupus erythematosus (SLE).

METHODS

This retrospective study included 120 SLE patients. All patients were divided into group p-ANCA+ and group p-ANCA-. Demographic characteristics, clinical symptoms, autoantibodies, laboratory tests and renal pathology were compared between these two groups.

RESULTS

Among 120 patients, 45 (37.5%) patients were p-ANCA+ and 75 (62.5%) patients were p-ANCA-. The occurrence of lupus nephritis was significantly higher in group p-ANCA+ (P = 0.046). For autoantibodies, the occurrences of anti-dsDNA, anti-nucleosome and anti-histone were significantly higher in group p-ANCA+ (P < 0.001, P = 0.004 and P = 0.006, respectively). Titers of anti-dsDNA antibody, erythrocyte sedimentation rate (ESR), serum beta-2-microglobulin (β2-MG) and systemic lupus erythematosus disease activity index (SLEDAI) were higher in group p-ANCA+ (P < 0.001, P = 0.021, P < 0.001 and P = 0.005, respectively), while albumin was significantly lower than p-ANCA- group (P = 0.012). There were no differences in the classification of lupus nephritis, activity index and chronicity index. p-ANCA correlated with lupus nephritis, anti-dsDNA antibody, anti-nucleosome antibody and anti-histone antibody, and also disease activity markers, such as titers of anti-dsDNA antibody, ESR, albumin, serum β2-MG and SLEDAI.

CONCLUSION

The appearance of p-ANCA in SLE indicated high probability of lupus nephritis and more severe condition.

Anti-neutrophil cytoplasmic antibodies (ANCA): Antigen interactions and downstream effects

Neutrophils are the most abundant leukocytes in circulation and are key "first responders" in the immune response to infectious and non-infectious stimuli. Unlike other immune cells, neutrophils can mount a robust response (including a change in surface markers and the production of extracellular traps and reactive oxygen species) just minutes after sensing a disturbance. It has been speculated that, in some individuals, the activation of neutrophils inadvertently leads to the generation of anti-neutrophil cytoplasmic autoantibodies (ANCA) against particular neutrophil proteins (antigens) such as myeloperoxidase (MPO) and proteinase 3 (PR3). In these individuals, continuous ANCA-antigen interactions are thought to drive persistent activation of neutrophils, chronic immune activation, and disease, most notably, small vessel vasculitis. There are significant gaps however in our understanding of the underlying mechanisms and even the pathogenicity of ANCA given that vasculitis can develop in the absence of ANCA, and that ANCA have been found in circulation in other conditions with no apparent contribution to disease. These gaps are particularly evident in the context of human studies. Herein, we review knowledge on neutrophil-derived ANCA antigens PR3 and MPO, ANCA generation, and ANCA-antigen interaction(s) that may promote immune activation and disease.

Microscopic polyangiitis associated with thymic tumor: a case report and review of the literature

Background

Thymic hyperplasia and thymic epithelial tumor (thymoma) have been associated with a variety of autoimmune diseases. Renal involvement has been reported in patients with thymoma. Minimal change disease and membranous nephropathy are frequently observed in glomerular lesions of thymoma patients, but ANCA-associated renal vasculitis is rare. We present a case of thymoma-associated microscopic polyangiitis with positivity for three ANCAs: MPO-ANCA, PR3-ANCA and azurocidin-ANCA.

Case presentation

An 89-year-old Japanese woman was admitted to our hospital following an episode of general fatigue, nausea, muscle weakness of the lower limbs, and ophthalmoplegia. On urinalysis, proteinuria, hematuria, and cellular casts were observed. Elevated levels of serum creatinine and C-reactive protein were also demonstrated, and MPO-, PR3- and azurocidin-ANCA were detected on serological examination. Renal biopsy showed pauci-immune crescentic glomerulonephritis. We therefore diagnosed rapidly progressive glomerulonephritis due to microscopic polyangiitis. Acetylcholine-receptor antibody was also detected. Chest computed tomography and MRI revealed a lobulated tumor in the anterior mediastinum. We thus also diagnosed myasthenia gravis with thymoma.

Conclusion

Considering the patient’s triple-ANCA positivity, thymic diseases may be associated with the pathogenesis of ANCA-associated vasculitis due to central T-cell tolerance. A further accumulation of cases is needed, because thymectomy does not always induce the remission of thymoma-associated autoimmune diseases.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1319-9) contains supplementary material, which is available to authorized users.

Clinical Implications of Excessive Neutrophil Extracellular Trap Formation in Renal Autoimmune Diseases

Neutrophil extracellular traps (NETs) are extracellular DNA structures covered with antimicrobial peptides, danger molecules, and autoantigens that can be released by neutrophils. NETs are an important first-line defense mechanism against bacterial, viral, fungal, and parasitic infections, but they can also play a role in autoimmune diseases. NETs are immunogenic and toxic structures that are recognized by the autoantibodies of patients with antineutrophil cytoplasmic antibodies−associated vasculitis (AAV) (i.e., against myeloperoxidase or proteinase-3) and systemic lupus erythematosus (SLE) (i.e., against double-stranded DNA, histones, or nucleosomes). There is cumulating preclinical and clinical evidence that both excessive formation and impaired degradation of NETs are involved in the pathophysiology of AAV and SLE. These autoimmune diseases give rise to 2 clinically and pathologically distinct forms of glomerulonephritis (GN), respectively, crescentic pauci-immune GN and immune complex−mediated GN. Therefore, it is relevant to understand the different roles NET formation can play in the pathophysiology of these most prevalent renal autoimmune diseases. This review summarizes the current concepts on the role of NET formation in the pathophysiology of AAV and SLE, and provides a translational perspective on the clinical implications of NETs, such as potential therapeutic approaches that target NET formation in these renal autoimmune diseases.

Anca in Dialysis Patients: A Role for Bioincompatibility?

Background

Anti-neutrophil cytoplasmic autoantibodies (ANCA) have been described in patients suffering from systemic vasculitis such as Wegener granulomatosis, microscopic polyangiitis, Churg-Strauss syndrome and other pathological conditions. In this paper we report a greater incidence of ANCA in hemodialysis patients as compared to peritoneal dialysis patients, predialytic uremic patients and non-renal patients; a possible role for dialysis bioincompatibility in ANCA generation was also investigated.

Methods

A total of 335 uremics in substitutive treatment (176 in hemodialytic treatment and 159 in peritoneal dialysis) were examined for ANCA positivity. A total of 189 patients with advanced renal failure in conservative treatment and 100 healthy subjects were used as control. The dialysis techniques were standard hemodialysis (n = 119), low volume hemodiafiltration (n = 26) and hemofiltration (n = 31). ANCA positivity was examined by immunofluorescence (IF): diffuse finely granular staining was considered as classical positive reaction (C-ANCA) and P-ANCA was diagnosed if a perinuclear staining was observed. EIA for proteinase-3 (anti PR-3) and myeloperoxidase-antibodies (anti-MPO) were also performed.

Results

In non-renal patients and in patients with pre-dialytic renal insufficiency none were found ANCA positive. In peritoneal dialysis patients all but one were ANCA negative with IF, with all EIA test resulting negative. In hemodialytic patients, a positive IF test was found in 26 (14.7%) for P-ANCA and in 5 (2.8%) for C-ANCA; using the EIA test 23 (13%) patients were positive for MPO and 12 (6.8%) for PR-3.

Conclusions

No correlation with age, primary renal diseases, dialytic age, dialysis membrane materials was found; regarding the different extracorporeal dialytic techniques a higher incidence (p < 0.02) was detected in patients undergoing HDF. Backfiltration of contaminated dialysate may induce ANCA via an increased cytokine generation. (Int J Artif Organs 2000; 23: 97–103)

Variability in Testing for Antineutrophil Cytoplasmic Antibodies: A Survey of Participants in the College of American Pathologists Proficiency Testing Program

CONTEXT

-Variability in testing for antineutrophil cytoplasmic antibodies (ANCAs) contributes to confusion and controversy related to testing for vasculitis and other ANCA-associated diseases.

OBJECTIVES

-To survey laboratory testing practices regarding ANCA testing and to investigate differences in testing algorithms.

DESIGN

-Supplemental questions were sent to the 333 laboratories participating in the College of American Pathologists proficiency testing program for ANCA as part of the Special Immunology S2 Survey.

RESULTS

-A total of 315 laboratories submitted responses to the supplemental questions. Only 88 of 315 participants (28%) reported using a combination of indirect immunofluorescence (IFA) and enzyme immunoassay (EIA) techniques as recommended by current guidelines, with a few additional labs using IFA and multiplex bead assay as an acceptable alternative to EIA. Other labs reported using only IFA, EIA, or multiplex bead assays.

CONCLUSIONS

-A wide variety of testing algorithms are in use for ANCA testing despite evidence to suggest that a combination of IFA and EIA testing provides the most comprehensive information. Laboratories should inform clinicians clearly about testing practices and utility of testing in specific disease states.

Glomerular disease in patients with infectious processes developing antineutrophil cytoplasmic antibodies

To identify differences in treatment and outcome of various types of glomerulonephritis developing in the course of infections triggering antineutrophil cytoplasmic antibody (ANCA) formation, we analyzed published reports of 50 patients. Immunosuppressives were added to antibiotics in 22 of 23 patients with pauci-immune glomerulonephritis. Improvement was noted in 85% of 20 patients with information on outcomes. Death rate was 13%. Corticosteroids were added to antibiotics in about 50% of 19 patients with postinfectious glomerulonephritis. Improvement rate was 74%, and death rate was 26%. Two patients with mixed histological features were analyzed under both pauci-immune and post-infectious glomerulonephritis categories. In 9 patients with other renal histology, treatment consisted of antibiotics alone (7 patients), antibiotics plus immunosuppressives (1 patient), or immunosuppressives alone (1 patient). Improvement rate was 67%, permanent renal failure rate was 22%, and death rate was 11%. One patient with antiglomerular basement disease glomerulonephritis required maintenance hemodialysis. Glomerulonephritis developing in patients who became ANCA-positive during the course of an infection is associated with significant mortality. The histological type of the glomerulonephritis guides the choice of treatment. Pauci-immune glomerulonephritis is usually treated with addition of immunosuppressives to antibiotics.

Pathogenesis of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) represents a chronic cholestatic liver disease with fibroobliterative sclerosis of intra- and/or extrahepatic bile ducts, eventually leading to biliary cirrhosis. The association with human leukocyte antigen (HLA) and non-HLA haplotypes and the presence of autoantibodies in sera of PSC patients support a crucial role for immune-mediated mechanisms in the initiation and progression of PSC. The strong clinical association between PSC and inflammatory bowel diseases led to intriguing pathogenetic concepts, in which the inflamed gut with translocation of bacterial products and homing of gut-primed memory T lymphocytes via aberrantly expressed adhesion molecules plays a fundamental role. Genetically or chemically modified bile composition was shown to induce sclerosing cholangitis and liver fibrosis in a number of animal models ("toxic bile concept"). The potential role of vascular injury with ischemia of bile duct epithelium cells in the development of sclerosing cholangitis is supported by animal models of endothelial cell injury showing close morphological similarities with human PSC.

Atypical p-ANCA in PSC and AIH: a hint toward a "leaky gut"?

Primary sclerosing cholangitis (PSC) and autoimmune hepatitis (AIH) are enigmatic chronic inflammatory diseases of the liver, which are frequently associated with chronic inflammatory bowel diseases. Both types of liver disease share various distinct autoantibodies such as atypical perinuclear antineutrophil cytoplasmic antibodies (p-ANCA), and thus are considered autoimmune disorders with atypical features. The discovery that atypical p-ANCA recognize both tubulin beta isoform 5 in human neutrophils and the bacterial cell division protein FtsZ has renewed the discussion on the potential role of microorganisms in the pathogenesis of both diseases. In this paper, we review the evidence for microbial infection in PSC and AIH and discuss new concepts how cross-recognition between microbial antigens in the gut and host components by the immune system along with stimulation of pattern recognition receptors might give rise to chronic hepatic inflammatory disorders with features of autoimmunity.

Antineutrophil cytoplasmic autoantibodies: how should the biologist manage them?

Antineutrophil cytoplasmic antibodies (ANCA) are directed against enzymes found in the granules of the polymorphonuclear (PMN) leukocytes. They are detected by indirect immunofluorescence microscopy assays on human ethanol fixed neutrophils. Three different fluorescence patterns can be distinguished: a cytoplasmic pattern (cANCA), a perinuclear pattern (pANCA), and an atypical pattern (aANCA). The use of other fixatives, e.g., formalin and methanol, allows differentiation between the pANCA and the antinuclear antibodies. ANCA specificity is determined by solid phase assays (ELISA, immunodot, and multiplex assay). ANCA with high titres and defined specificities (antiproteinase 3 [PR 3] or antimyeloperoxidase [MPO]) are proven to be good serological markers of active primary systemic vasculitis: c/PR 3-ANCA for Wegener's granulomatosis and p/MPO-ANCA for microscopic polyangiitis. The former have higher sensitivity and specificity for Wegener's granulomatosis than the latter for microscopic polyangiitis. ANCA with low titres and unknown specificity have been detected in a wide range of inflammatory and infectious diseases leading to a critical reappraisal of the diagnostic significance of ANCA testing. Physicians must keep in mind the possible occurrence of infectious diseases like subacute endocarditis that could be dramatically worsened by irrelevant immunosuppressive therapy. ANCA findings in certain manifestations, such as the pulmonary-renal syndrome in which massive pulmonary hemorrhage can quickly be life-threatening, warrant ANCA testing as an emergency test for patient care.

The target antigens of antineutrophil cytoplasmic antibodies (ANCA) induced by propylthiouracil

OBJECTIVE

Antineutrophil cytoplasmic antibody (ANCA) has been well documented in association with propylthiouracil (PTU), and some patients with PTU-induced ANCA also develop clinical vasculitis. The aim of the current study was to detect ANCA specificities in sera from patients with PTU-induced ANCA with and without clinical vasculitis.

METHODS

Sera from 65 patients with PTU-induced ANCA were collected, and 27 of these patients were diagnosed with PTU-induced ANCA associated systemic vasculitis (AASV). Indirect immunofluorescence assay and antigen-specific ELISAs were used to detect ANCA and their antigen specificities. The seven known target antigens included myeloperoxidase (MPO), proteinase 3, human leukocyte elastase, lactoferrin, cathepsin G, azurocidin and bactericidal/permeability-increasing protein (BPI).

RESULTS

In IIF assay, P-ANCA was found in 58/65 (89.2%) sera, C-ANCA in two, both P-ANCA and C-ANCA in five, respectively. MPO (60%) and lactoferrin (63.1%) were the two most common target antigens detected in sera from all the patients. 25/27 sera from patients with PTU-induced AASV recognized multiple target antigens, which was significantly higher than those (13/38) from patients without (P<0.001). Except anti-BPI antibodies, the prevalence of antibodies against the other six target antigens was significantly higher in patients with clinical vasculitis than that in patients without (P<0.05, respectively).

CONCLUSION

Antibodies against multiple ANCA specific antigens, especially the antigens rather than MPO and PR3, might be the characteristic of PTU-induced ANCA. Patients with antibodies against more ANCA specific antigens might be at increased risk of developing overt clinical vasculitis. The mechanism of ANCA production in PTU-induced cases was different from that in primary AASV.

Role of auto-antibodies for the diagnosis of chronic cholestatic liver diseases

Auto-antibodies are an integral part of the diagnostic armentarium in chronic cholestatic liver disorders, such as primary sclerosing cholangitis (PSC), primary biliary cirrhosis (PBC),auto-immune cholangitis, or overlap syndromes among these disorders. However, care should be taken not to overestimate the diagnostic specificity. Auto-antibodies to mitochondrial antigens(AMAs) with reactivity to the E2 subunit of the pyruvate dehydrogenase complex represent the hallmark antibody for the diagnosis of PBC, whereas antinuclear antibodies (ANAs)with low disease specificity are found in up to 50% of these sera. Antibodies that recognize nuclear envelope proteins exert a similarly high diagnostic specificity as AMA in PBC but occur at a rather low prevalence. The role of auto-antibodies is less well-studied for patients with PSC, but there is growing evidence that only antineutrophil cytoplasmic antibodies(ANCAs) are of relevant diagnostic significance. In contrast, auto-antibodies-particularlyAMAs-do not contribute to the diagnosis of auto-immune cholangitis, whereas ANCAs,ANAs, smooth muscle antibodies, and AMAs are of varying significance in PBC-auto-immune hepatitis (AIH) or PSC-AIH overlap syndromes. It has been widely accepted that the course of the auto-antibody serum end point titers are not suited for the clinical management of patients with chronic cholestatic liver disorders. Additionally, auto-antibodies in these disorders usually do not contribute to the immunopathogenesis of the disease.

Anti-neutrophil cytoplasmatic antibodies and lung disease in cystic fibrosis

BACKGROUND

Bactericidal-permeability-increasing protein (BPI) is a potent anti-microbial protein produced by neutrophil granulocytes. Anti-neutrophil cytoplasmatic antibodies (ANCA) directed against BPI have been detected in up to 91% in patients with cystic fibrosis (CF). We aimed to evaluate the prevalence of BPI-ANCA in our CF patients and to determine whether presence of BPI-ANCA is correlated with organ damage.

METHODS

Twenty-four patients performed respiratory function testing and pulmonary high-resolution computed tomography (HRCT). HRCT was scored by using a modified Bhalla method. Serum samples were analysed by direct binding enzyme-linked immunosorbent assay for BPI-ANCA.

RESULTS

The prevalence of anti-BPI-IgG was 71% and anti-BPI-IgA 33%. Twenty-nine percent of our patients were positive for both BPI-ANCA isotypes. Mean HRCT score was 8.0 ranging from 0 to 22, bronchiectasis presented the most common finding (79%). There was a significant correlation between BPI-ANCA and both HRCT score and FEV(1) (p < 0.01). High levels of BPI-ANCA were correlated to chronic Pseudomonas aeruginosa lung infection (p < 0.01).

CONCLUSIONS

BPI-ANCA was common in our study group. Highly significant correlations between BPI-ANCA and parameters to evaluate lung disease in CF may be a consequence of the inflammation process, or it may indicate a pathogenic role of BPI-ANCA levels in the development of lung disease. More research is needed and the clinical significance of our findings needs further evaluation.

Detection rate and antigenic specificities of antineutrophil cytoplasmic antibodies in chinese patients with clinically suspected vasculitis

The detection rate of antineutrophil cytoplasmic antibodies (ANCA) in Chinese patients with clinically suspected small vessel vasculitis was investigated, and their antigen specificity and demographic features were analyzed. A number of sera (n = 5,604) sent to our referral laboratory for ANCA screening were tested by indirect immunofluorescence (IIF), enzyme-linked immunosorbent assays (ELISAs) for myeloperoxidase (MPO)- and proteinase 3 (PR3)-ANCA. Then the IIF-ANCA-positive sera that were negative for MPO- and PR3-ANCA were further tested by antigen-specific ELISA by using other five highly purified known ANCA antigens as solid-phase ligands. The known antigens included bactericidal/permeability-increasing protein (BPI), human leukocyte elastase (HLE), lactoferrin, cathepsin G, and azurocidins. Of the 5,604 sera, 267 (4.76%) sera were IIF-ANCA positive and 390 (7%) were antinuclear antibody (ANA) positive in the IIF assay. Of the IIF-positive samples, 213 were anti-MPO positive, 32 were anti-PR3 positive, and five cases were positive for both. Of the 48 sera positive for IIF-ANCA but negative for MPO- and PR3-ANCA, 13 sera (27%) recognized other target antigens, 7 sera recognized BPI, 5 recognized HLE, 1 recognize cathepsin G, and 1 recognized azurocidin. None of the sera recognized lactoferrin, and one serum sample recognized both BPI and HLE. The majority of ANCA-positive patients presented in summer or winter. There was no difference in gender (male/female ratio, 1:1.12) in ANCA-positive patients with a mean age of 53.1 years. The male/female ratio was 1.17:1 for patients over 60 years of age; however, it was 1:4 for patients under 20 years of age. We conclude that ANCA-related diseases are not rare in China, and the major antigens are MPO and PR3. When the IIF technique is used to detect ANCA, ANA should be carefully distinguished.

Antimicrobial proteins and peptides: anti-infective molecules of mammalian leukocytes

Phagocytic leukocytes are a central cellular element of innate-immune defense in mammals. Over the past few decades, substantial progress has been made in defining the means by which phagocytes kill and dispose of microbes. In addition to the generation of toxic oxygen radicals and nitric oxide, leukocytes deploy a broad array of antimicrobial proteins and peptides (APP). The majority of APP includes cationic, granule-associated (poly)peptides with affinity for components of the negatively charged microbial cell wall. Over the past few years, the range of cells expressing APP and the potential roles of these agents have further expanded. Recent advances include the discovery of two novel families of mammalian APP (peptidoglycan recognition proteins and neutrophil gelatinase-associated lipocalin), that the oxygen-dependent and oxygen-independent systems are inextricably linked, that APP can be deployed in the context of novel subcellular organelles, and APP and the Toll-like receptor system interact. From a clinical perspective, congeners of several of the APP have been developed as potential therapeutic agents and have entered clinical trials with some evidence of benefit.

The prevalence and target antigens of antithyroid drugs induced antineutrophil cytoplasmic antibodies (ANCA) in Chinese patients with hyperthyroidism

OBJECTIVE

Antithyroid drugs such as propylthiouracil (PTU) and methimazole (MMI) are common medications in Chinese patients with hyperthyroidism and PTU-induced antineutrophil cytoplasmic antibody (ANCA) positive vasculitis has been reported. The current cross-sectional study aimed to investigate the prevalence and the target antigens of ANCA in Chinese patients with hyperthyroidism pre- and post-antithyroid medication therapy.

METHODS

Sera from 216 patients with hyperthyroidism in our hospital were collected from January to July in 2002. Patients were divided into four groups: untreated (n = 34); treated with PTU (n = 62); treated with MMI (n = 77); and treated with both PTU and MMI (n = 43). Indirect immunofluorescence (IIF) assay was used to detect ANCA and ANA. Antigen-specific ELISAs were used to detect antigen specificities. The known antigens included myeloperoxidase (MPO), proteinase 3 (PR3), human leukocyte elastase (HLE), lactoferrin, bactericidal/permeability-increasing protein (BPI), cathepsin G and azurocidin.

RESULTS

33/216 sera were IIF positive, 20 of the 33 samples were ANCA positive, 11 samples were ANA positive, and two samples were both P-ANCA and ANA positive. The prevalence of positive ANCA in patients receiving PTU (14/62, 22.6%) was significantly higher than that of untreated patients (1/34, 2.9%) and patients treated with MMI (0/77, 0), P < 0.017. Of the 22 IIF-ANCA positive samples, 12 (54.5%) sera recognized lactoferrin, seven (31.8%) sera recognized HLE, four sera recognized MPO and azurocidin respectively, three sera recognized PR3 and cathepsin G respectively, and one serum recognized BPI. Six of the 22 (27.3%) patients with ANCA positive had clinical evidence of vasculitis. All patients with MPO-ANCA and two of the three patients with PR3-ANCA had clinical vasculitis.

CONCLUSION

PTU is associated with the production of ANCA in patients with hyperthyroidism. PTU-induced ANCA are due to polyclonal activation of B cells. Anti-MPO and anti-PR3 antibodies may associate the occurrence of clinical vasculitis.

Azurocidin-specific-ANCA-related idiopathic necrotizing crescentic glomerulonephritis

An 80-year-old woman who had rapidly progressive glomerulonephritis unaccompanied by systemic vasculitis is described. On renal biopsy, she showed necrotizing crescentic glomerulonephritis by light microscopy and pauci-immune glomerular lesions by immunofluorescent study. No dense deposits were present on electronmicroscopic study. On serum examination, indirect immunofluorescent study showed perinuclear pattern antineutrophil cytoplasmic antibody (ANCA), but myeloperoxidase-ANCA and proteinase 3-ANCA were both negative. Her serum reacted only to azurocidin excluding other ANCA antigens: bactericidal permeability-increasing protein, cathepsin G, elastase, lactoferrin, or lysozyme. Serum creatinine level decreased, and C-reactive protein turned negative after steroid therapy. Azurocidin-ANCA also turned negative. It is suggested that azurocidin-ANCA might have been related to the inflammatory process of pauci-immune necrotizing crescentic glomerulonephritis in this patient.

Histologic and immunohistologic study and clinical presentation of ANCA-associated glomerulonephritis with correlation to ANCA antigen specificity

BACKGROUND

The major antigen specificities of antineutrophil cytoplasmic antibodies (ANCA) are for proteinase 3 (PR3) and myeloperoxidase (MPO). Only a limited number of studies have systematically assessed renal pathology with respect to ANCA antigen specificity.

METHODS

The authors evaluated renal biopsy light microscopy and immunofluorescence findings, clinical presentation, and outcome in 135 patients with ANCA-associated vasculitides.

RESULTS

Patients were divided into 3 groups: PR3-ANCA (n = 55), MPO-ANCA (n = 74), and ANCA of other specificities (n = 6). The mean duration of renal disease at biopsy was significantly longer in patients with MPO-ANCA than in those with PR3-ANCA (6.9 v 3.0 months). Immunofluorescence results showed mostly pauci-immune glomerulonephritis (n = 129) and rarely diffuse granular glomerular immune deposits suggesting immune complex deposition (n = 6). A focal form of crescentic glomerulonephritis was more frequent (P < 0.001), and glomerular necrosis was more prominent (P = 0.013) in the PR3-ANCA group, whereas diffuse crescentic glomerulonephritis, glomerulosclerosis, and interstitial fibrosis predominated in the MPO-ANCA group (P < 0.001). Extraglomerular vasculitis, present in 22.2%, and chronic vascular lesions indicative of previous vasculitis, present in 11.9% of patients, correlated with systemic involvement.

CONCLUSION

The evolution of the pathologic lesions of PR3-ANCA and MPO-ANCA-associated glomerulonephritis seems to be similar. Differences in histopathology could be explained by the observation that in patients with PR3-ANCA, kidney biopsy was performed soon after renal involvement appeared, and focal active lesions were prevalent, whereas in patients with MPO-ANCA, kidney biopsy was done late in the course of the disease, and diffuse chronic sclerotic lesions predominated. Renal extraglomerular small vessel vasculitis appeared to be predictive of systemic involvement.

Contact-system activation in children with vasculitis

BACKGROUND

The contact system triggers the kallikrein-kinin cascade, liberating bradykinin from high-molecular-weight kininogen. Effectors of the contact system have proinflammatory and vasoactive properties. Vasculitis is a condition characterised by inflammation around vessel walls, leading to secondary tissue damage for which the underlying molecular mechanisms are poorly understood. Our aim was to investigate contact-system activation in children with vasculitis.

METHODS

We compared 17 children, aged 4-19 years, with vasculitis, engaging the skin, joints, intestines, or kidneys, with 21 controls, aged 2-18 years. We analysed proteolysis of high-molecular-weight kininogen by immunoblotting. Plasma bradykinin concentrations were quantified by ELISA. Kidney and skin biopsies were stained in situ for kinins. Concentrations of heparin binding protein (HBP) were quantified by ELISA.

FINDINGS

We noted extensive proteolysis of high-molecular-weight kininogen in the plasma of 13 of 17 patients, but in only one of 21 controls (p<0.0001). Bradykinin concentrations were higher in the patients' plasma (median 320 ng/L, range <1-19680) than in plasma from controls (11 ng/L, <1-304; p=0.0004). Patients had local release of kinins at sites of inflammation in kidney and skin biopsies. HBP values were raised in patients (17.4 microg/L, 5.4-237.6) compared with controls (6 microg/L, 2.5-43.4; p=0.008).

INTERPRETATION

Activation of the contact system could play a part in the pathogenesis of vasculitis, and explain the inflammation, pain, vasodilatation, and oedema seen in patients.

Testing for antineutrophil cytoplasmic antibodies

The most common reason to request a test for antineutrophil cytoplasmic antibodies (ANCA) is to diagnose Wegener's granulomatosis and microscopic polyangiitis and to monitor inflammatory activity in these diseases. Several retrospective and prospective studies have suggested that the demonstration of ANCA lacks sensitivity and specificity, but these series have detected ANCA with neutrophil-indirect immunofluorescence alone, have used a disease classification that did not describe microscopic polyangiitis and have included patients with inactive disease. The 'International Consensus Statement on Testing and Reporting ANCA' has been developed to optimize the clinical relevance of ANCA testing by the adoption of standardized testing and reporting procedures. International collaborative efforts continue to focus on improving the tests for ANCA.

Anti-neutrophil antibodies in primary sclerosing cholangitis

Anti-neutrophil specific antibodies are detected in up to 88% of patients with PSC. The labelling pattern of neutrophils produced by these antibodies when examined by indirect immunofluorescence microscopy is distinct from that produced by anti-neutrophil cytoplasmic antibodies (ANCA) in vasculitic diseases. The antigen(s) recognized by anti-neutrophil antibodies in PSC is not yet known but appears to be localized to the periphery of the nucleus. Accordingly, the term peripheral anti-neutrophil nuclear antibodies (p-ANNA) is more appropriate than the frequently used p-ANCA. As the titre of p-ANNA in PSC does not correlate with disease-specific clinical parameters, they are not useful markers for the management of patients. However, the high prevalence of p-ANNA in PSC makes them a reasonable diagnostic marker if used in conjunction with other standard diagnostic tests. The role of anti-neutrophil antibodies in the pathogenesis of PSC, if any, remains to be established.

Antineutrophil cytoplasmic antibodies and associated diseases: a review of the clinical and laboratory features

There have been a number of recent advances in this field. First, the "International Consensus Statement on Testing and Reporting of Antineutrophil Cytoplasmic Antibodies (ANCA)" has been developed to optimize ANCA testing. It requires that all sera are tested by indirect immunofluorescent (IIF) examination of normal peripheral blood neutrophils and, where there is positive fluorescence, in enzyme-linked immunosorbent assays (ELISAs) for antibodies against both proteinase 3 (PR3) and myeloperoxidase (MPO). Testing will be further improved when international standards and common ELISA units are available. Second, new diagnostic criteria for the small vessel vasculitides that take into account ANCA-positivity and target antigen specificity as well as histologic features are currently being produced. Third, we understand that the complications associated with treatment of the ANCA-associated vasculitides are often more hazardous than the underlying disease, and regimens that use effective but less toxic agents are being evaluated. The factors associated with increased risk of relapse, however, remain incompletely understood. Finally, ANCA with specificities other than PR3 and MPO are present in many nonvasculitic autoimmune diseases. Their clinical significance is still largely unclear, and some of the target antigens are present in other cells as well as neutrophils and thus are not strictly "ANCA."

Pulmonary vasculitis

Pulmonary vascular inflammation may be seen in a variety of primary lung diseases and in the setting of numerous systemic illnesses. This article reviews those entities in which pulmonary vasculitis represents a central feature of the pathologic process (Wegener's granulomatosis, Churg-Strauss syndrome, and pulmonary capillaritis). In addition, features of pulmonary involvement in other systemic vasculitides (Giant Cell Arteritis, Takayasu's Arteritis, and Behçet's disease) are described. Finally, general principles for the treatment of vasculitis are reviewed.

Anti-phagocyte antibodies and infection

Autoantibodies specific to the cytoplasmic components of neutrophils and monocytes are associated with vasculitis and other idiopathic inflammatory disorders. In this study, using enzyme-linked immunosorbent assay (ELISA) and immunofluorescence assays, sera from patients with acute and chronic infection were examined for the presence of anti-neutrophil and anti-monocyte antibodies: cystic fibrosis (n = 23), acute appendicitis (n = 22), tuberculosis (n = 26), acute gastroenteritis (n = 38), bronchiectasis (n = 9) and chronic granulomatous disease (n = 6). Sera from patients with Wegener's granulomatosis (n = 14), rheumatoid factor positive (n = 15) and healthy volunteers (n = 20) were used as positive and negative controls. In patients with chronic infection, using an ELISA assay, antibodies reactive with neutrophil or monocyte components (% reacting with monocyte components in parenthesis) were found in: 70% (39%) of patients with cystic fibrosis, 4% (38%) of patients with tuberculosis, 0% (33%) of patients with bronchiectasis and 0% (17%) of patients with chronic granulomatous disease. When these sera were examined using an immunofluorescence assay, all of the positive samples were found to react with the cytoplasmic component of neutrophils or monocytes. In patients with acute infection no antibodies (either IgG or IgM) were detected against neutrophils or monocytes. These findings imply that antibodies directed against neutrophil cytoplasmic components are predominantly associated with chronic pyogenic infection and antibodies specific to monocyte cytoplasmic components are predominantly associated with chronic granulomatous infection. This mirrors the findings in idiopathic inflammatory disease where anti-monocyte antibodies are associated with granulomatous disorders such as sarcoidosis, and anti-neutrophil antibodies are associated with neutrophilic disorders such as ulcerative colitis. These results suggest that chronic stimulation of phagocytes by infectious agents may result in the generation of a humoral response against phagocyte cytoplasmic components. This furthers our understanding of humoral immune responses against phagocytic cell components during infection.

Atypical antineutrophil cytoplasmic antibodies with perinuclear fluorescence in chronic inflammatory bowel diseases and hepatobiliary disorders colocalize with nuclear lamina proteins

Antineutrophil cytoplasmic antibodies (ANCA) are frequently associated with chronic inflammatory bowel diseases (IBD) and hepatobiliary disorders. However, their target antigens have not been identified yet. Recently, we observed an atypical perinuclear ANCA fluorescence (p-ANCA) together with an intranuclear staining using ANCA-positive sera from patients with IBD and hepatobiliary disorders. This observation suggests that the target antigens are localized within the nucleus of neutrophilic granulocytes. To further investigate this hypothesis, we examined sera from patients with ulcerative colitis, primary sclerosing cholangitis, autoimmune hepatitis or systemic vasculitis on ethanol or formaldehyde-fixed neutrophils using confocal laser scanning microscopy and immunoelectron microscopy. Counterstaining with propidium iodide, a DNA-specific dye, showed that ANCA-positive sera in IBD and heptobiliary disorders react with intranuclear antigens at the nuclear periphery of the neutrophils. Double immunolabeling techniques revealed that nuclear lamina proteins, lamins A, C and B1, and lamin B receptor were colocalized with the antigen(s) recognized by atypical p-ANCA. No colocalization was observed with classical p-ANCA and antibodies against histones (H1-H4). Our study showed that atypical p-ANCA are antinuclear antibodies reactive with granulocyte-specific antigens present in the nuclear lamina.