Antigen-specific radioimmunoassays for anti-neutrophil cytoplasmic antibodies in the diagnosis of rapidly progressive glomerulonephritis.

Circulating anti-neutrophil cytoplasmic antibodies (ANCA) have been described in most patients with "pauci-immune" necrotizing and crescentic glomerulonephritis. A 29-kDa serine protease (p29 or proteinase 3) and myeloperoxidase are the two best characterized antigens recognized by ANCA. The study presented here was conducted to define the diagnostic value of assays for antibodies against these two antigens in rapidly progressive glomerulonephritis. Radioimmunoassays were developed for anti-p29 and anti-myeloperoxidase antibodies, with purified antigens, and the results of the radioimmunoassays were compared with those obtained by immunofluorescence tests for ANCA. We performed assays on serum samples from 123 patients with the syndrome of rapidly progressive glomerulonephritis, as well as from 200 blood bank donors and from 717 additional control patients. Without knowledge of the results of ANCA tests, the renal pathologic findings in the 123 patients with rapidly progressive glomerulonephritis were analyzed, and 42 were classified as pauci-immune necrotizing and crescentic glomerulonephritis, 18 were classified as anti-glomerular basement membrane nephritis and 63 were classified as other forms of renal disease. We found radioimmunoassays to be more reliable in the diagnosis of pauci-immune necrotizing and crescentic glomerulonephritis than immunofluorescence testing. By radioimmunoassay, ANCA were found in 40 of 42 patients (95% sensitivity) with pauci-immune necrotizing and crescentic glomerulonephritis (14 with anti-p29 and 26 with anti-myeloperoxidase antibodies). The tests for antibodies to p29 and myeloperoxidase were 99.9 and 99.5% specific for pauci-immune necrotizing and crescentic glomerulonephritis, respectively. In the setting of rapidly progressive glomerulonephritis, a positive radioimmunoassay for anti-p29 or anti-myeloperoxidase antibodies (together with a negative test for anti-GBM antibodies) gives a probability of pauci-immune necrotizing and crescentic glomerulonephritis of over 99%.     

Immune complex deposits in ANCA-associated crescentic glomerulonephritis: a study of 126 cases

BACKGROUND: Necrotizing and crescentic glomerulonephritis related to antineutrophil cytoplasmic autoantibodies (ANCA) is typically referred to as "pauci-immune"; however, it is not unusual for renal biopsies in such cases to exhibit some immune complex deposition within glomeruli on immunofluorescence and/or electron microscopic study. The composition and intraglomerular localization of such deposits in ANCA-glomerulonephritis has not been widely studied, and their potential pathologic and clinical significance is not clear, although a possible synergistic effect between immune complexes and ANCA in producing more severe glomerulonephritis is suggested by some human and animal studies. METHODS: Electron micrographs from 126 renal biopsies showing necrotizing/crescentic glomerulonephritis characterized by positive ANCA serology [C-ANCA, anti-proteinase 3 (anti-PR3), or anti-myeloperoxidase (MPO)] or necrotizing arteritis in the absence of known ANCA results were examined for the presence, quantity, and location of electron-dense deposits. The presence or absence of such deposits was correlated with histologic findings (fraction of glomeruli with crescents and segmental necrotizing lesions, mesangial and endocapillary hypercellularity), immunofluorescence findings, and clinical data, including serum creatinine and 24-hour urine protein levels at the time of biopsy. RESULTS: Sixty-eight (54%) of these biopsies showed glomerular immune complex deposits on electron microscopy; 87% of the latter also showed positive immunofluorescence findings for at least one immunoglobulin or complement component, although staining was relatively mild in most instances (< or =2+ on a 0 to 4+ scale in all but eight cases). Nearly half of biopsies negative for deposits by electron microscopy also showed positive immunofluorescence findings, though even more so than in cases with deposits on electron microscopy the intensity of immunofluorescence staining in these biopsies was typically very weak (trace or trace to 1+ in most cases, none >2+). Hypercellularity within the glomerular tuft was seen in 50% of biopsies with deposits on electron microscopy but only 14% of those without deposits; in each group this was usually mild and mesangial. Notably, the presence of deposits on electron microscopy was associated with a higher median level of proteinuria (3.2 versus 1.3 g/24 hours, P < 0.0001) and a higher median percentage of glomeruli with crescents (62.5% versus 44.0%, P= 0.06). CONCLUSION: Immune complex deposits were found on electron microscopy in just over half of renal biopsies with crescentic glomerulonephritis associated with positive ANCA serology and/or necrotizing arteritis. Clinical correlations suggest that these immune complex deposits may somehow potentiate the effect of ANCA in producing glomerulonephritis.     

Anti-neutrophil cytoplasmic autoantibodies in a child with pauci-immune necrotizing and crescentic glomerulonephritis

We report a case of pauci-immune, necrotizing and crescentic glomerulonephritis in a 10-year-old child initially thought to have Henoch-Schönlein purpura. The diagnosis of a Wegener's granulomatosis-microscopic polyarteritis disorder was made on the basis of clinical presentation and a positive anti-neutrophil cytoplasmic auto-antibody (ANCA). This case illustrates the usefulness of the ANCA in the diagnosis and management of childhood vasculitides.     

Hydralazine-Induced ANCA-Positive Pauci-immune Glomerulonephritis: A Case Report and Literature Review

We report a case of hydralazine-induced alveolar hemorrhage and anti-neutrophil cytoplasmic antibody (ANCA)-positive pauci-immune glomerulonephritis, with serum anti-histone antibodies present, features not previously described in the literature with this drug. A 50-year-old Caucasian female had hypertension treated with hydralazine 75mg TID for three years, and a lung nodule followed up periodically with chest-computed tomographies. She was admitted to the hospital for hemoptysis and newly discovered diffuse pulmonary ground-glass opacities. Transbronchial lung biopsy showed alveolar hemorrhage. Serum creatinine was 3.5 mg/dL and urinalysis showed 2+blood, 30-50RBC/hpf and red blood cell casts. ANCA against myeloperoxidase were present. Anti-double-stranded DNA, ANA, and anti-histone antibodies were positive. Serum complements were normal. Renal biopsy revealed focal crescentic necrotizing glomerulonephritis with negative immunofluorescence, consistent with pauci-immune ANCA-positive vasculitis. Serum creatinine returned to baseline three days after hydralazine was discontinued, and the hemoptysis resolved after treatment with cyclophosphamide and prednisone was started. We concluded that this case represents a hydralazine-induced small vessel vasculitis rather than an idiopathic one. The possibility of hydralazine-induced vasculitis should be considered when patients treated with hydralazine develop a pulmonary-renal syndrome. Anti-histone antibodies may be present in the absence of full classification criteria of drug-induced lupus.     

MPO-ANCA-positive crescentic necrotizing glomerulonephritis and tubulointerstitial nephritis with renal eosinophilic infiltration and peripheral blood eosinophilia

We present the case of a 67-year-old woman with myeloperoxidase (MPO)-antineutrophil cytoplasmic antibody (ANCA)-positive pauci-immune crescentic necrotizing glomerulonephritis and tubulointerstitial nephritis with renal eosinophilic infiltration and peripheral blood eosinophilia. Staining for eosinophil cationic protein indicated that activated eosinophils were involved in the tubulitis, as well as in the glomerular injury. Marked peripheral blood eosinophilia is uncommon in ANCA-positive crescentic necrotizing glomerulonephritis associated with tubulointerstitial nephritis, except in Churg-Strauss syndrome. However, our patient had no clinical history or signs of asthma, no other signs suggestive of allergic diseases, and no histologic findings of granulomas in the kidney, thus failing to fulfill the criteria for Churg-Strauss syndrome.     

A case of a 6-year-old girl with anti-neutrophil cytoplasmic autoantibody-negative pauci-immune crescentic glomerulonephritis

A 6-year-old girl was admitted to our hospital with proteinuria, hematuria, skin rash and joint pain of the lower limbs. Due to rapid progression of renal insufficiency, hemodialysis and peritoneal dialysis were performed. She was diagnosed with rapidly progressive glomerulonephritis. Kidney biopsy showed severe crescent formation (50% of glomeruli) and no deposition of any immunoglobulins or complements. Serologically, anti-neutrophil cytoplasmic autoantibody (ANCA) was negative not only by ELISA against proteinase-3 and myeloperoxidase-ANCA but also by indirect immunofluorescent assay against cytoplasmic and perinuclear ANCA. Anti-glomerular basement membrane antibody was also negative. In the acute phase, proinflammatory cytokines such as soluble tumor necrosis factor receptor 1 (sTNFR1), soluble interleukin (IL)-2 receptor (sIL2R), IL-6 and chemokine IL-8 were elevated. The patient was diagnosed with ANCA-negative pauci-immune crescentic glomerulonephritis (CrGN). Intensive treatment with methylprednisolone pulse therapy, plasma exchange, and multiple drug therapy including prednisolone and cyclophosphamide resulted in histopathological improvement and complete remission of proteinuria. There was a possibility that sTNFR1, sIL2R, IL-6 and IL-8 might be involved in the initiation and progression of ANCA-negative pauci-immune CrGN, and to remove and suppress these cytokines might be an effective way to treat ANCA-negative pauci-immune CrGN.     

100例新月体肾炎的免疫病理分型及临床病理分析

目的：了解新月体性肾炎的免疫病理分型及其临床病理特点。方法：对我科近10年来经肾活检确诊的100例新月体性肾炎进行回顾性分析,对患者血清进行抗中性粒细胞胞浆抗体（ANCA）和抗肾小球基底膜（GBM）抗体的检测。结果：100例患者中21％为抗GBM抗体型,其中6／21例同时合并ANCA阳性;47％为免疫复合物型,其中9／47型ANCA阳性;32％为少免疫沉积型,其中17／32例为ANCA阳性小血管炎。3种类型相比,抗GBM抗体型以青年男性为主,多有少尿或无尿（P＜0．05）,肾小球受累受为广泛（P＜0．001）,预后差（P＜0．001）。免疫复合物型以中青年为主,多表现为肾病综合征（P＜0．01）,强化免疫抑制治疗有效。少免疫沉积型以中老年为主,有多系统受累（P＜0．05）,治疗效果相对较好。结论：我国新月体肾炎中虽仍以免疫复合物型为主,但抗GBM抗体型和ANCA阳性小血管炎并不少见。肾活检免疫病理和血清自身抗体的联合应用对新月体肾炎进行分类更接近病因学诊断。     

ANCA-positive crescentic glomerulonephritis associated with minocycline therapy

Minocycline is an oral antibiotic widely used for the long-term treatment of acne and rheumatoid arthritis. A few patients develop antineutrophil cytoplasmic antibodies (ANCAs) during minocycline therapy. In this report, the authors describe a case of severe pauci-immune crescentic and necrotizing glomerulonephritis associated with positive cytoplasmic ANCA (C-ANCA) titers and proteinase 3 (PR3) levels after minocycline therapy. Discontinuation of minocycline and initiation of immunosuppressive treatment resulted in improvement of renal function and decline in C-ANCA titers and PR3 levels. A high degree of suspicion, testing for ANCA titers, prompt discontinuation of the drug, and initiation of immunosuppressive treatment are crucial to the diagnosis and treatment of drug-induced ANCA-associated glomerulonephritis.     

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.     

Pauci-immune necrotizing and crescentic glomerulonephritis in a patient with systemic lupus erythematosus

We report a case of pauci-immune proliferative necrotizing and crescentic glomerulonephritis in a patient with systemic lupus erythematosus (SLE) who presented with a nephrotic syndrome, while SLE was clinically and serologically quiescent. Immunofluorescence and electron microscopy examination of the kidney biopsy failed to reveal any significant deposit of immunoglobulins as well as of complement C3 and C1q, excluding lupus nephritis as the determinant of crescentic glomerulonephritis. Anti-myeloperoxydase (MPO) as well as anti-proteinase 3 (PR3) antibodies were absent in the serum. An immunosuppressive regimen including corticosteroids and IV cyclophosphamide led to a dramatic decrease of proteinuria. We conclude that necrotizing glomerulonephritis unrelated to lupus nephritis may occur in a patient with quiescent SLE. An underlying dysfunction of cell-mediated immunity might explain the association of pauci-immune crescentic glomerulonephritis and SLE.     

Antineutrophil cytoplasmic antibody-negative pauci-immune crescentic glomerulonephritis associated with rheumatoid arthritis: An unusual case report

Clinically relevant renal lesions in rheumatoid arthritis (RA) are not common. More often renal involvement is related to complications of therapy than the disease itself. The most common forms of primary renal disease in RA are membranous glomerulonephropathy and a pure mesangial proliferative glomerulonephritis. Some studies have described the association between crescentic glomerulonephritis (crescentic GN) and RA, but they were all found to be perinuclear antineutrophil cytoplasmic antibody (p-ANCA) positive. However, RA associated with ANCA negative pauci-immue crescentic GN has not been reported. This is a case report of a 37-year-old female with RA who initially presented with general oedema and acute deterioration of renal function. The renal biopsy revealed ANCA negative pauci-immune crescentic GN. The patient was treated with steroid pulse and plasmapheresis, but not cyclophosphamide because of severe urosepsis. Despite the use of aggressive therapy, her renal function was not improved and she underwent maintenance haemodialysis thereafter. Because ANCA negative crescentic GN may occur in RA patients without frank systemic vasculitis, but with severe clinical manifestation, a heightened suspicion for a relatively 'silent' crescentic GN would have led to the correct diagnosis and appropriate treatment.     

An unusual endocarditis-induced crescentic glomerulonephritis treated by plasmapheresis

A 58-year-old man presented with fever and a rapidly progressive glomerulonephritis. An infective endocarditis due to Streptococcus parasanguis was diagnosed. A renal biopsy revealed type III pauci-immune crescentic glomerulonephritis. As first-line therapy, antibiotics were administered alone. Faced to the unsuccessful anti-infective approach, corticosteroid therapy was added as a second-line therapy. Finally, plasmapheresis introduced as the third-line therapy, significantly improved renal function. This case is an original type III rapidly progressive glomerulonephritis, since ANCA were repeatedly found negative. In very few cases, plasmapheresis was successfully used for the treatment of infective endocarditis-induced crescentic glomerulonephritis. The pathophysiology and the potential efficiency of plasmapheresis are discussed.     

Bone marrow-derived cells are sufficient and necessary targets to mediate glomerulonephritis and vasculitis induced by anti-myeloperoxidase antibodies

Clinical and experimental evidence indicate that ANCA cause pauci-immune necrotizing and crescentic glomerulonephritis (NCGN) and systemic small vessel vasculitis in humans. One of the major target antigens for ANCA is myeloperoxidase (MPO). An animal model that closely resembles the human disease is induced by intravenous injection of anti-MPO IgG into mice. The likely primary pathogenic targets for the anti-MPO IgG are circulating neutrophils and monocytes, although other cells have been implicated, including endothelial cells and epithelial cells. Herein is reported a new model for anti-MPO-mediated glomerulonephritis and vasculitis that further documents the pathogenic potential of ANCA and demonstrates that bone marrow (BM)-derived cells are sufficient targets to cause anti-MPO disease in the absence of MPO in other cell type. MPO knockout (Mpo-/-) mice that were immunized with mouse MPO were exposed to irradiation and received a transplant of Mpo+/+ or Mpo-/- BM. Engraftment in mice with circulating anti-MPO resulted in development of pauci-immune NCGN in all mice and pulmonary capillaritis and splenic necrotizing arteritis in some. Anti-MPO IgG also was introduced intravenously into chimeric mice by transplantation of Mpo+/+ BM into irradiated Mpo-/- mice or Mpo-/- BM into irradiated Mpo+/+ mice. Chimeric Mpo-/- mice with circulating MPO-positive neutrophils developed NCGN, whereas chimeric Mpo+/+ mice with circulating MPO-negative neutrophils did not, thereby indicating that BM-derived cells are not only sufficient but also necessary for induction of anti-MPO disease. This novel animal model further documents ANCA IgG interactions with neutrophils as a cause of ANCA-associated glomerulonephritis and vasculitis.     

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.     

Successful renal transplantation in a child with ANCA-associated microscopic polyangiitis

Crescentic glomerulonephritis (CGN) is a clinicopathologic entity which is characterized by severe renal dysfunction of rapid onset with glomerular crescents. Type III CGN is associated with the absence of glomerular immune complex deposition (pauci-immune) and is associated with antineutrophil cytoplasmic antibody (ANCA). Microscopic polyangiitis and idiopathic pauci-immune necrotizing glomerulonephritis (NCGN) are strongly associated with ANCA directed against myeloperoxidase (anti-MPO). We describe here an unusual pediatric patient with MPO-ANCA-associated rapidly progressive glomerulonephritis (RPGN), emphasizing the management and outcome of the disease.     

Two cases of ANCA-associated vasculitis in post-transplant kidney: relapse and de novo

Abstract:  Two cases of anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitis (ANCA-V) occurred in the transplanted kidney were reported. Case 1 was a 57 yr-old female whose original disease was MPO-ANCA-V. A relapse of necrotizing crescentic glomerulonephritis occurred one year after transplantation with positive serum reaction for MPO-ANCA. In spite of several immunosuppressive treatments, the disease progressed and she returned to hemodialysis treatment three yr and seven months after transplantation. Case 2 was a 34 yr-old female whose original disease was IgA nephropathy. She had a stable clinical condition during 13 yr after transplantation; however, de novo onset of necrotizing crescentic glomerulonephritis occurred at 14 yr 10 months after transplantation with positive serum reaction for MPO-ANCA. She returned to hemodialysis treatment five yr after the onset of ANCA-V. Urinary abnormities such as microhematuria and proteinuria were useful diagnostic findings but the titers of serum MPO-ANCA were relatively low in both patients. Concerning the treatment, steroid pulse therapy was effective in some extents but the disease progressed to graft failure in both cases. ANCA-V is a severe glomerulonephritis which can occur in kidney allograft in the manner of relapse and de novo . Detection of urinary abnormalities and positive serum ANCA combined with histological confirmation of necrotizing crescentic glomerulonephritis and/or vasculitis is required for early diagnosis and effective treatment of ANCA-V in renal transplant patients.     

Antineutrophil cytoplasmic antibodies (ANCA) in Chinese patients with anti-GBM crescentic glomerulonephritis

OBJECTIVE: To study the prevalence of ANCA and their target antigen in Chinese patients with anti-GBM crescentic glomerulonephritis (CGN), and to evaluate the possible role of ANCA in Chinese anti-GBM CGN patients with coexisting serum ANCA by studying clinicopathologic features of this disease. MATERIAL AND METHODS: Twenty-three sera were collected from 23 renal biopsy-proven anti-GBM CGN patients. According to the standardized procedures, all of the sera were determined by both, indirect immunofluorescence (IIF) ANCA, and enzyme-linked immunosorbent assay (ELISA) MPO-ANCA, PR3-ANCA and BPI-ANCA. The patients were divided into two groups according to serum ANCA positivity (Group A) or negativity (Group B). Thirty-three ANCA-associated pauci-immune CGN patients were regarded as control group (Group C). Their clinicopathologic features were compared to reveal whether ANCA correlated with disease activity. RESULTS: There were 11 (47.8%) cases with positive serum ANCA in 23 anti-GBM glomerulonephritis patients. There were 4/11 MPO-ANCA (one with positive PR3-ANCA and C-ANCA, three with negative IIF-ANCA), 1/11 PR3-ANCA (with positive MPO-ANCA and C-ANCA), 3/11 P-ANCA (with negative ELISA-ANCA) and 5/11 C-ANCA (one with positive PR3-ANCA and MPO-ANCA, and the other four with negative ELISA-ANCA). No BPI-ANCA was detected. No different clinicopathologic features were found between Groups A and B. Both were different from Group C in age, sex ratio, frequence of anuria and ESRD, variety of crescents, glomerular sclerosis, vessel lesion and prognosis. CONCLUSION: Our data demonstrate that ANCA in Chinese patients with anti-GBM CGN is not rare. The major target antigen of ANCA is MPO. ANCA seems not to be correlated with disease activity.     

Temporal arteritis with pauci-immune glomerulonephritis: a systemic disease

Temporal arteritis is easily diagnosed and responds gratifyingly to treatment. Renal complications are unusual, but nevertheless occur. Earlier, an association between pauci-immune glomerulonephritis and temporal arteritis was shown. We present a patient who clearly had temporal arteritis but also developed cerebral hemorrhage, pulmonary infiltrates related to granulomatous pulmonary vasculitis, and pauci-immune glomerulonephritis. We suggest that temporal arteritis is neither always localized nor temporal. Instead, the condition can be a lethal, systemic disease. Renal involvement in patients with temporal arteritis is not common and the presence of glomerulonephritis is rare [Jennette and Falk 1994]. Lenz et al. [1998] described a patient who developed vision loss, optic nerve atrophy, elevated erythrocyte sedimentation rate, a positive rheumatoid factor and terminal glomerulonephritis. The renal biopsy showed focal and segmental necrotizing glomerulonephritis, despite negative antineutrophil cytoplasmatic antibodies (ANCA), antinuclear antibodies and antiglomerular basement membrane antibodies. Giant cells were identified in the necrotic vessel walls within the kidney. Immunofluorescence was negative and a diagnosis of ANCA-negative pauci-immune glomerulonephritis was made. The patient did not respond to immunosuppression and developed end-stage renal disease. Although the clinical attributes were consistent with temporal arteritis, no temporal artery biopsy was done in that patient. We recently treated a patient with temporal arteritis and pauci-immune glomerulonephritis. Our patient's course was somewhat different in comparison to the patient described by Lenz et al. [1998].     

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)