Antineutrophil cytoplasmic autoantibodies: the nephrologist's perspective

Serologic tests for antineutrophil cytoplasmic autoantibodies (ANCA) provide diagnostic and prognostic information in patients with nephritis and systemic vasculitis. Four case histories are discussed that illustrate ANCA positivity in patients with renal impairment caused by interstitial, rather than glomerular, nephritis. Renal biopsy should continue to be used to diagnose the cause of renal impairment in ANCA-positive patients.     

Antineutrophil cytoplasmic autoantibodies and associated diseases: a review

Antineutrophil cytoplasmic autoantibodies (ANCA) are specific for constituents of neutrophil primary granules and monocyte lysosomes. There are different types of ANCA with different specificities. By indirect immunofluorescence microscopy using alcohol-fixed neutrophils as substrate, two major categories of ANCA can be recognized, one with cytoplasmic staining (C-ANCA) and the other with artifactual perinuclear staining (P-ANCA). Some C-ANCA have specificity for proteinase 3 (PR3-ANCA) and some P-ANCA have specificity for myeloperoxidase (MPO-ANCA), but there are additional C-ANCA and P-ANCA specificities. ANCA are found in the blood of patients with necrotizing systemic vasculitis, such as Wegener's granulomatosis and polyarteritis nodosa, and patients with idiopathic crescentic glomerulonephritis. The glomerular lesion in patients with systemic and renal-limited ANCA-associated diseases is the same, ie, a pauci-immune necrotizing and crescentic glomerulonephritis. No matter where the vascular lesions of ANCA-associated disease are (eg, kidney, lung, gut, muscle, skin), they are characterized by necrotizing inflammation and a paucity of immune deposits. The distribution of disease correlates to a degree with the ANCA specificity, although there is substantial overlap. For example, patients with Wegener's granulomatosis most often have C-ANCA and patients with renal-limited disease most often have P-ANCA. In patients with P-ANCA-associated glomerulonephritis, approximately 90% of the P-ANCA have specificity for MPO. The clinical manifestations of ANCA-associated diseases often begin following a flu-like illness. The onset is most often in the winter and least often in the summer. The renal disease usually presents as rapidly progressive renal failure with nephritis. One of the most life-threatening components of the systemic involvement is pulmonary hemorrhage caused by a necrotizing alveolar capillaritis. Intravenous cyclophosphamide plus steroids is as effective as oral cyclophosphamide plus steroids for controlling ANCA-associated diseases. Using life-table analysis, the 2-year patient and renal survival rate in both patients with renal-limited and systemic disease is greater than 70%. There is evidence that in addition to being a useful serologic marker, ANCA are directly involved in the pathogenesis of the vascular injury in patients with ANCA-associated diseases. Although ANCA antigens are normally in the cytoplasm of neutrophils and monocytes, priming of these cells, as occurs following exposure to certain cytokines, results in the release of small amounts of ANCA antigens at the cell surface. In vitro, ANCA-IgG causes cytokine-primed neutrophils to undergo a respiratory burst and degranulation.(ABSTRACT TRUNCATED AT 400 WORDS)     

Antineutrophil cytoplasmic autoantibodies in patients with systemic lupus erythematosus recognize a novel 69 kDa target antigen of neutrophil granules

OBJECTIVE: Antineutrophil cytoplasmic autoantibodies (ANCA) were found in patients with systemic lupus erythematosus (SLE). Cathepsin G and lactoferrin were the major target antigens. However, some ANCA-positive sera did not recognize either of them. The present study was to investigate the unknown target antigens of ANCA in patients with SLE and their clinical significance. METHODS: Sera were collected from 72 patients with SLE. ANCA were detected in both indirect immunofluorescence and antigen-specific enzyme-linked immunosorbent assay (ELISA). Mixed neutrophil granules were separated from normal human peripheral neutrophils; soluble acid extracts in non-reducing conditions were used as antigens in western blot analysis to detect ANCA. RESULTS: SLE sera could blot a few bands. Interestingly, 14/72 (19.4%) sera recognized a novel 69 kDa protein band and 10/72 (13.9%) sera recognized the 55 kDa protein band, which might be bactericidal/permeability-increasing protein (BPI). The 69 kDa target antigen was different from the known target ANCA antigens such as cathepsin G and lactoferrin. Further study revealed that the percentages of patients with photosensitivity and oral ulcer in the anti-69 kDa autoantibodies-positive group were significantly higher than those in the anti-69 kDa autoantibodies-negative group (57.1%vs 10.3%, P < 0.005 and 50.0%vs 12.1%, P < 0.05, respectively). CONCLUSIONS: A 69 kDa protein in human neutrophil granules was identified as a novel target antigen of ANCA in patients with SLE. The anti-69 kDa autoantibodies might be associated with photosensitivity and oral ulcer in patients with SLE.     

Antineutrophil cytoplasmic antibody-associated vasculitides

The identification of antineutrophil cytoplasmic antibodies (ANCA) proved a major breakthrough in the classification, diagnosis, monitoring, and understanding of vasculitides. Vasculitides associated with ANCA selectively affect the small vessels; they include Wegener granulomatosis, microscopic polyangiitis, and Churg-Strauss syndrome. Evidence supporting a direct pathogenic role for ANCA has accumulated over the years. The clinical, laboratory, and histological findings vary across diseases; they are discussed here based on a review of published data from over 1600 patients. The course and prognosis also vary according to the disease. New treatment strategies tailored to the type and extent of the vascular disease have improved survival and treatment safety. Induction therapy, which should be given on an emergency basis in a specialized unit, consists of glucocorticoid therapy and cyclophosphamide in Wegener granulomatosis; microscopic polyangiitis and Churg-Strauss syndrome, without poor prognostic factors, can be managed with glucocorticoid therapy alone as the first-line treatment. A full recovery or complete remission is now achieved in over 80% of patients. Maintenance therapy is mandatory to reduce the relapse rate, which varies across diseases. Among patients with Wegener granulomatosis, up to 50% relapse within the first 5 years. Azathioprine is the main maintenance drug, although methotrexate, mycophenolate mofetil, or leflunomide may be used as second-line drugs. Biotherapies such as rituximab and TNFalpha antagonists are currently under evaluation as promising rescue agents for patients with refractory disease.     

Antineutrophil cytoplasmic autoantibody-associated glomerulonephritis in children.

Aretrospective investigation was conducted by members of the Japanese Society for Pediatric Nephrology from 1990 to 1997 to define the clinical features and outcome of antineutrophil cytoplasmic autoantibody (ANCA)-associated glomerulonephritis in children. Thirty-four ANCA-seropositive Japanese pediatric patients with biopsy-proven pauci-immune necrotizing crescentic glomerulonephritis were identified. Of these, 3 cases associated with Wegener's granulomatosis were excluded because of the small sample size. Among the 31 patients studied, 10 had a diagnosis of necrotizing crescentic glomerulonephritis alone and 21 had microscopic polyangiitis. Females predominated (87%), and the median age at onset was 12 yr. Twenty-six patients received treatment with cyclophosphamide and corticosteroids, and five patients received treatment with corticosteroids alone; 84% of patients achieved remission, and 39% of responders relapsed in a median of 24 mo. ANCA titers correlated with response to treatment and disease activity, with some exceptions. Patients were followed for a median of 42 mo (range, 3 to 96 mo). Nine of 31 patients (29.0%) progressed to end-stage renal disease, 6 (19.4%) had reduced renal function, and 15 (48.4%) had normal renal function at the last observation. One patient (3.2%) died from cytomegalovirus infection 3 mo after initiation of therapy. Life-table analysis showed 75% renal survival at 39 mo. Patients who subsequently developed end-stage renal disease (n = 9) had significantly higher average peak serum creatinine levels and more chronic pathologic lesions at diagnosis compared with patients with favorable renal outcome (n = 15). In conclusion, our clinical experience suggests that the clinical disease spectrum of ANCA-associated glomerulonephritis is similar in pediatric and adult patients, but there is a female predominance in children.     

Antineutrophil cytoplasmic autoantibodies (ANCA) and their target antigens in Chinese patients with lupus nephritis

Background: ANCA have been found in patients with systemic lupus erythematosus (SLE); however, the prevalence of ANCA and their target antigens is still not certain. This study is to investigate the prevalence of ANCA and their target antigens in Chinese patients with lupus nephritis. Methods: Ninety-five serum samples were collected from 95 renal-biopsy-proven lupus nephritis patients. Indirect immunofluorescence using ethanol-fixed leukocytes as substrate and ELISA using six highly purified known ANCA antigens as solid-phase ligands were performed. The specific ANCA antigens included proteinase 3, myeloperoxidase, bactericidal/permeability-increasing protein, human leukocyte elastase, cathepsin G, and lactoferrin. The prevalence of ANCA in patients with (n=65) and without (n=30) active renal pathological lesions was also compared to reveal whether ANCA correlates with disease activity. Results: (i) None of the sera recognized proteinase 3, myeloperoxidase, and human leukocyte elastase, and only one serum recognized bactericidal/permeability-increasing protein. The striking finding was that 59/95 (62.1%) sera recognized cathepsin G and the titres of some sera reached 1/3200. Eight of 95 sera (8.4%) recognized lactoferrin. (ii) The percentage of anticathepsin G antibody positive samples in patients with active renal lesions was significantly higher than in patients without active lesions (73.4 vs 36.7%, P<0.0001), whereas, anti-lactoferrin antibodies had no correlation with active renal lesions. (iii) By indirect immunofluorescence, only 22% of the 95 sera were ANCA positive. Conclusions: Our results suggest that the majority of lupus nephritis patients have ANCA and that the major target antigens is cathepsin G. Anti-cathepsin G antibodies seem to be correlated with renal disease activity. Key words: ANCA; autoantibodies; autoantigen; autoimmune disease; cathepsin G; lupus nephritis; SLE; vasculitis      

Antineutrophil cytoplasmic antibody-associated glomerulonephritis in Taiwanese

AIMS: This retrospective study defined the clinical features and outcome of antineutrophil cytoplasmic antibody-associated glomerulonephritis in 18 seropositive Taiwanese patients (11 male, seven female; median age 64 years; range 21-82 years) with biopsy-proven pauci-immune necrotizing crescentic glomerulonephritis. RESULTS: Fourteen patients had a diagnosis of systemic vasculitis including 10 with microscopic polyangiitis and four with Wegener's granulomatosis; the remaining four had only glomerulonephritis. At onset, 100% of the systemic vasculitis patients had pulmonary lesions with or without haemoptysis, and 29% presented with seizure in the absence of a defined brain lesion. Median serum creatinine concentration was 362.4 micromol/L (range 61.9-857.5 micromol/L) and dialysis therapy was needed in six patients. During follow up (median 16.5 months; range 2-72 months), treatment included cyclophosphamide and corticosteroids (n = 8) or corticosteroids alone (n = 7). In some patients, treatment improved (n = 4) or stabilized (n = 4) renal function. But chronic dialysis was needed in the other 10 patients. Follow-up death occurred because of sepsis (n = 3) and haemorrhage (n = 2). Patient survival rates were 78% (1 year) and 72% (5 years). Renal survival rates were 56 and 39% at 1 and 5 years, respectively. Of the candidate clinical and pathological parameters, chronic glomerular lesions in renal biopsy were the only determinant of poor renal outcome (P = 0.006). CONCLUSION: Antineutrophil cytoplasmic antibody-associated glomerulonephritis should be considered in nephritic patients with extrarenal manifestations, especially pulmonary infiltrate, unexplained seizure, and fever of an unknown origin in Taiwanese patients. Renal biopsy should be performed before initiating immunosuppressive therapy because the most common cause of mortality was sepsis.     

Antineutrophil cytoplasmic autoantibody-negative Pauci-immune crescentic glomerulonephritis

Pauci-immune crescentic glomerulonephritis (CrGN) is one of the most common causes of rapidly progressive glomerulonephritis. The majority of patients with pauci-immune CrGN had circulating antineutrophil cytoplasmic autoantibody (ANCA). However, patients with ANCA-negative pauci-immune CrGN were not investigated fully. This study aimed to analyze the characteristics of this subgroup of patients. Patients whose pauci-immune CrGN was diagnosed from 1997 to 2006 in one center were studied retrospectively. The criteria of pauci-immune was defined as "the intensity of glomerular immunoglobulins staining by direct immunofluorescence assay in renal sections was negative to 1+ staining on a scale of 0 to 4+." Clinical and pathologic characteristics were compared between patients with and without ANCA. Among the 85 patients with pauci-immune CrGN, 28 (32.9%) were ANCA negative. Compared with the 57 ANCA-positive patients, the ANCA-negative patients were much younger (39.7 +/- 17.0 versus 57.6 +/- 14.0 yr; P < 0.001). The level of urinary protein and the prevalence of nephrotic syndrome were significantly higher in ANCA-negative patients than that in ANCA-positive patients (P < 0.01 and P < 0.001, respectively). However, the prevalence of extrarenal involvement was significantly lower in ANCA-negative patients than that in ANCA-positive patients. The renal survival was poorer in ANCA-negative patients than that in ANCA-positive ones (P < 0.05). ANCA-negative pauci-immune CrGN was not rare and might represent an independent disease entity from ANCA-positive vasculitis.     

Prognostic implication of anti-neutrophil cytoplasmic autoantibodies with myeloperoxidase specificity in anti-glomerular basement membrane disease.

Anti-neutrophil cytoplasmic autoantibodies (ANCA) were detected in 12 out of 37 (32%) serum samples from patients with anti-glomerular basement membrane (GMB) disease by an indirect immunofluorescence assay. In 11 cases, ANCA were directed against myeloperoxidase, as revealed employing neutrophils devoid of this enzyme as the test substrate. Patients having both ANCA and anti-GBM antibodies (AGBMA) were considerably older (mean age 59 years) than patients with AGBMA alone (mean age 33 years). In addition, patients with both antibodies had some clinical and pathologic data that suggested an associated systemic vasculitis. This was supported by the fact that among these patients, those with highest ANCA titres recovered renal function despite being initially on hemodialysis, as opposed to those with lowest ANCA titres or AGBMA alone. In patients with both antibodies, there was an inverse relationship between AGBMA and ANCA values (p = 0.02). Moreover, the mean AGBMA level tended to be higher for patients with AGBMA alone than for those with both ANCA and AGBMA. These results suggest that, at least in some cases, there may be a contribution of an ANCA-related mechanism in the pathogenesis of anti-GBM disease. Although the exact role of ANCA in this and other diseases remains to be clarified, there is important clinical evidence that in anti-GBM disease ANCA may represent a serologic marker of good prognosis identifying a subset of patients who may recover renal function.     

Antineutrophil cytoplasmic autoantibody-associated vasculitis in Chinese patients

Antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) is a common autoimmune disease in China. AAVs in the majority of Chinese patients are microscopic polyangiitis with antigenicity to myeloperoxidase. Propylthiouracil is the leading cause of drug-induced AAV. The genetic background and immunological characteristics of ANCA, such as the epitope, IgG subclass and avidity, might contribute to various clinical phenotypes of AAV.     

Antineutrophil cytoplasmic antibody-associated glomerulonephritis with immunoglobulin deposition

Background

Antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis is commonly classified as pauci-immune glomerulonephritis; however, some cases have granular immunoglobulin deposition along the glomerular capillary. The pathogenesis of immune deposits is poorly studied.

Methods

Of 66 patients diagnosed with ANCA-associated glomerulonephritis on renal biopsy, cases with immunoglobulin deposition along the glomerular capillary were identified and their clinicopathological characteristics were analyzed. We also performed myeloperoxidase (MPO) and double immunofluorescence (IF) stainings to determine the presence of immune complex antigens.

Results

Granular IgG deposition, IgG plus IgM deposition, and IgM deposition were observed in 15 (22.1%), 8 (11.2%), and 17 (25.0%) cases, respectively. In cases with granular IgG deposition, MPO-IgG double IF staining revealed co-localization of MPO and IgG. In cases with granular IgM deposition, MPO-IgM double IF staining did not co-localize. By electron microscopy, subepithelial deposition as well as intramembranous, subendothelial, and mesangial deposition was detected in the patients with IgG deposition. In addition, renal survival curves were not significantly different between the immunoglobulin deposition and non-deposition groups.

Conclusions

Granular IgG and/or IgM deposition was observed in 60.6% of patients with ANCA-associated glomerulonephritis. In cases with IgG deposition, electron-dense deposits (EDDs) were observed at various sites in the glomerulus, and MPO and IgG immunocomplex deposition was frequently observed along the glomerular capillary. With IgM deposition, EDDs were not obvious in the glomerular basement membrane, and MPO and IgM immunocomplex was not detected. These data suggest differential mechanism between IgG deposition and IgM deposition.

     

Antineutrophil cytoplasmic autoantibody-associated diseases: a pulmonologist's perspective

The development of the antineutrophil cytoplasmic autoantibody (ANCA) test has lent support to the concept of Wegener's granulomatosis as a spectrum that may affect one or more of the major anatomic sites: upper respiratory tract (E), lung (L), or kidney (K). It is C-ANCA that has high specificity for Wegener's granulomatosis (WG). The sensitivity is highest in the fully expressed Wegener's triad, or ELK, and less in local regional disease. It is possible that isolated manifestations such as episcleritis, subglottic stricture, or diffuse alveolar hemorrhage associated with C-ANCA may be considered in the Wegener's spectrum, although traditional histopathologic criteria are lacking. Until specific etiologic agents are uncovered for the various ANCA-associated entities, classification schemes should continue to employ previously established clinicopathologic syndromes such as WG using the ANCA test to better define their clinical spectrums.     

Antineutrophil cytoplasmic autoantibody-associated diseases: a rheumatologist's perspective

Autoantibodies against neutrophil cytoplasmic antigens (ANCA) produce two major immunofluorescence (IF) patterns on ethanol-fixed granulocytes: the "classical" (centrally accentuated) C-ANCA, associated with Wegener's granulomatosis (WG), and P-ANCA (perinuclear), which mainly occur in renal vasculitis. Rheumatic manifestations are an important clinical finding in systemic vasculitis, often preceding a fulminant course and sometimes imitating various rheumatic disorders. We analyzed the incidence of ANCA in rheumatic patients and looked for the frequency of rheumatic symptoms in systemic vasculitis. In WG (n = 186), we found rheumatic symptoms in 55% (myalgia, 45%; arthritis, 21%); in 90%, rheumatic complaints were associated with active vasculitis. In 730 patients with various rheumatic conditions (eg, 268 rheumatoid arthritis, 130 systemic lupus erythematosis [SLE], 32 sharp-S, 50 ankylosing spondylitis, 43 systemic sclerosis) no C-ANCA were found. On the contrary, the P-ANCA pattern was seen in seven of 62 giant cell arteritis, five of 27 Felty's/Still's syndrome, and four of 130 SLE patients in addition to renal vasculitis (21/74). We demonstrated that 95% of C-ANCA-positive sera react with proteinase 3 (PR3 or myeloblastin). Using monoclonal antibodies, we showed that PR3 is expressed on the plasma membrane of neutrophil granulocytes and monocytes; thus, PR3 autoantigens are accessible for circulating antibodies. The detection of ANCA in sera from vasculitis and other rheumatic diseases is of immunodiagnostic value and provides new insight in the pathogenesis of systemic vasculitides.     

Antineutrophil cytoplasmic autoantibody-associated diseases: a pathologist's perspective

Antineutrophil cytoplasmic autoantibodies (ANCA) are a useful diagnostic serologic marker for the most common forms of necrotizing vasculitis, provide a means of categorizing vasculitides so that diagnostically useful shared pathologic and clinical characteristics can be recognized, and offer insight into the pathogenesis of previously idiopathic diseases. ANCA-associated vasculitides can be categorized into a number of distinctive clinicopathologic categories, eg, Wegener's granulomatosis, Churg-Strauss syndrome, pulmonary renal syndrome, microscopic polyarteritis nodosa, leukocytoclastic angiitis, and necrotizing and crescentic glomerulonephritis. At least the latter four syndromes can also be caused by other ANCA-negative immunopathogenic mechanisms, eg, immune complex deposition. Therefore, thorough diagnostic classification requires both an assessment of clinicopathologic category, as well as an assessment of immunopathologic category. Although different ANCA-associated vasculitic syndromes have distinctive clinical and pathologic features, all ANCA-associated vasculitides share a number of common pathologic features, ie, focal distribution, necrosis, and neutrophil infiltration. ANCA assays have very good sensitivity and specificity for ANCA-associated diseases, but the prevalence of these diseases in the patient population being analyzed must be taken into consideration when determining the predictive value of a test result. As with all serologic tests, ANCA results must be integrated with other clinical and pathologic data in order to reach the most accurate diagnostic conclusion.     

The pathogenic role of antineutrophil cytoplasmic autoantibodies.

Antineutrophil cytoplasmic autoantibodies (ANCA) are found in the sera of patients with systemic necrotizing vasculitis and glomerulonephritis. Their role in the pathogenesis of these diseases is not clearly understood; however, there is a growing body of data that supports a pathogenic function for these antibodies. In vitro they can activate neutrophils and monocytes to produce reactive oxygen species (ROS), degranulate, and damage target cells. The antigens to which they are directed stimulate T lymphocytes from patients with these diseases. The ANCA directed against proteinase 3 (PR3) may also play a role in growth regulation of monocytes by inactivating the enzymatic function of its antigen. The proposed model of ANCA-induced disease takes into account both the in vitro data and the natural history of these diseases.     

Antineutrophil cytoplasmic antibodies in IgA nephropathy and Henoch-Sch?nlein purpura.

The frequency, isotype, and specificity of antineutrophil cytoplasmic antibodies were investigated in a cross-sectional study of 100 patients with IgA nephropathy and 30 children with Henoch-Sch?nlein purpura. Two of the patients with IgA nephropathy had high titres of antineutrophil cytoplasmic antibodies which were of IgG isotype and confirmed as antimyeloperoxidase antibodies in solid-phase ELISA and inhibition experiments. Antineutrophil cytoplasmic antibodies were not detected in the children with Henoch-Sch?nlein purpura and none of the patients in either group had IgA antineutrophil cytoplasmic antibodies. A further 20 IgA nephropathy and 10 Henoch-Sch?nlein purpura patients were studied longitudinally in different clinical phases at 4-monthly intervals over a 2-year period. None of these patients had or developed antineutrophil cytoplasmic antibodies. We conclude that IgA antineutrophil cytoplasmic antibodies are not involved in the vasculitis of Henoch-Sch?nlein purpura or in the pathogenesis of glomerular injury in IgA nephropathy. The detection of IgG antimyeloperoxidase antibodies in a small minority of IgA nephropathy patients extends the spectrum of diseases associated with autoimmunity to this antigen but is of uncertain significance.