Antineutrophil cytoplasmic autoantibodies: immunobiological aspects

Pathogenesis of anti-neutrophil cytoplasmic antibody-associated vasculitis: challenges and solutions 2014

Anti-neutrophil cytoplasmic autoantibodies (ANCA) with specificity for proteinase 3 (PR3-ANCA) or myeloperoxidase (MPO-ANCA) are a defining feature of ANCA-associated vasculitides (AAV). They play a pivotal role in disease pathophysiology and have strongly improved early diagnosis and treatment of these infrequent, but potentially fatal diseases. Neutrophils and their products are major players in initiating the autoimmune response and tissue destruction in vasculitic as well as granulomatous inflammation. This review highlights recent findings on old and novel players (ANCA, neutrophils, neutrophil extracellular traps, fibroblasts, immune cells and complement) and puts them into context with the current understanding of disease mechanisms in AAV.

Antineutrophil cytoplasmic antibodies in chronic idiopathic intraocular inflammatory disease

Antineutrophil cytoplasmic antibodies (ANCA) are found in the sera of patients with Wegener's granulomatosis and other systemic necrotising vasculitides. Antibody levels correlate closely with disease activity so that follow-up of ANCA titres might be helpful in guiding therapy. The authors assessed in a cohort of patients with chronic ocular inflammatory disease ANCA titres prospectively over a two-year period, by an indirect immunofluorescent technique. They found that sera from 10/64 patients (15.6%) stained positive for c-ANCA antibodies, and none stained for p-ANCA. Six c-ANCA positive patients had one or more clinical relapses (range one to three) during this study period. Each relapse correlated with a rise in ANCA titre. The remaining four patients who were found to have persistently low titres of c-ANCA had no clinical relapses. The authors conclude that although c-ANCA is only present in a small proportion of patients with idiopathic chronic intraocular inflammatory disease, the ANCA titre may be used to monitor disease activity in this group of patients. Further study to assess the potential of c-ANCA titres in predicting disease relapse is indicated, which in the future may minimise the side effects of currently used immunosuppressive therapies.

Pathways to ANCA production: from differentiation of dendritic cells by proteinase 3 to B lymphocyte maturation in Wegener's granuloma

Wegener's granulomatosis, microscopic polyangiitis, and Churg-Strauss syndrome are idiopathic systemic vasculitides in which circulating anti-neutrophil cytoplasmic antibodies (ANCA) directed against proteinase 3 (PR3) or myeloperoxidase (MPO) are commonly found. Within the last 25 years, these antibodies were subject of intensive studies, and a growing body of evidence arose for a distinct role of ANCA in the pathogenesis of the ANCA-associated vasculitides (AAV). Yet, the evidence derived from clinical observations and in vitro studies remains circumstantial. The various animal models have provided substantial support for a pathogenic role of MPO-ANCA in vivo, but the debate if ANCA play a primary role in the pathogenesis of these diseases is still open. The aim of this review was to update current basic and clinical research on ANCA in the pathophysiology of AAV and to point out and discuss limitations and inconsistencies of the clinical and experimental evidence.

Autoantibodies to early endosome antigen (EEA1) produce a staining pattern resembling cytoplasmic anti-neutrophil cytoplasmic antibodies (C-ANCA)

Autoantibodies to EEA1 have been described in patients with neurological diseases, subacute cutaneous lupus and a variety of other conditions, including a patient with Wegener's granulomatosis (WG). EEA1 is a hydrophilic peripheral membrane protein transiently associated with the cytoplasmic face of early endosomes. Antibodies to EEA1 produce a staining pattern that resembles the C-ANCA pattern produced by anti-proteinase 3 (PR3) antibodies in WG sera. Co-localization studies show incomplete overlap of the staining produced by anti-EEA1 with anti-PR3. We showed that 0/40 unselected sera, from a cohort of WG patients and antibodies to PR3, reacted with EEA1. In addition, 1/15 sera that have a C-ANCA staining pattern but do not react with PR3 in an ELISA, immunoprecipitated the recombinant EEA1 protein. We conclude that although antibodies to EEA1 produce a staining pattern that resembles anti-PR3 and C-ANCA, antibodies to EEA1 in WG are rare. However, some C-ANCA+ sera that do not react with PR3 may contain EEA1 autoantibodies.

Serum autoantibodies in patients with primary sclerosing cholangitis

BACKGROUND/AIM

Primary sclerosing cholangitis is a chronic cholestatic syndrome with a presumed autoimmune basis frequently associated with inflammatory bowel disease. The aim of this study was to determine the profile and significance of serum autoantibodies in patients with primary sclerosing cholangitis.

METHODS

Serum samples taken from 73 untreated patients (32 female and 41 male, median age 45 years) with well-defined primary sclerosing cholangitis, and from 75 healthy age- and sex-matched controls were assayed for 20 different autoantibodies.

RESULTS

Of 73 patients, 71 (97%) were positive for at least 1 autoantibody; whereas 59/73 patients (81%) were positive for > or =3 antibodies. Patients with primary sclerosing cholangitis had a significantly greater rate of positivity than controls for antinuclear, anticardiolipin, antineutrophil cytoplasmic, and antithyroperoxidase antibodies as well as rheumatoid factor. The rate of positivity and serum levels of any of these 20 autoantibodies were not significantly different between patients with primary sclerosing cholangitis and inflammatory bowel disease and those without inflammatory bowel disease. Anticardiolipins were the single group of antibodies that had a significant correlation with the Mayo risk score (r=0.49, p<0.001) and histologic stage of disease (r=0.30, p<0.01).

CONCLUSIONS

Primary sclerosing cholangitis is associated with a high proportion of non-organ specific autoantibodies. Anticardiolipin antibodies appear to be related to the severity of primary sclerosing cholangitis and may be a useful prognostic marker.

ANCA-associated glomerulonephritis: Relationship of main ANCA subtypes to renal outcome, age and sex of the patients

BACKGROUND

Antineutrophil cytoplasmic antibodies (ANCA) have been proven to be useful diagnostic tools in patients with systemic vasculitis and glomerulonephritis. These antibodies exist in two types, a cytoplasmic pattern (cANCA) and a perinuclear pattern (pANCA). The effect of the main ANCA subtypes on renal outcome and its relationship to demographic findings and clinical features of patients with ANCA-associated glomerulonephritis has not been adequately studied.

PATIENTS AND METHOD

In this prospective study, we compared the clinical features at presentation and the renal outcome after 1 year of follow-up between two groups of patients with cANCA (n=22) and pANCA (n=29) consecutively encountered over a one-year period.

RESULT

At presentation, rapidly progressive glomerulonephritis (RPGN), and after 1 year of follow-up, endstage renal disease (ESRD) were seen more commonly in patients with pANCA than cases with cANCA (P=0.001 and P=0.004, respectively). Seropositivity for cANCA was more common in male and pANCA in female patients (P=0.005). Occurrence of the pulmonary-renal syndrome or extra-renal manifestations, such as sinusitis and skin rash, did not differ significantly among the two groups of patients with cANCA and pANCA.

CONCLUSION

Patients with pANCA present more frequently with RPGN, leading to a poorer renal survival compared to cases with cANCA. RPGN and pANCA are more common in females.

The effect of thymectomy on myasthenia gravis, thrombocytopenia, and granulocytopenia associated with thymoma: report of a case

We report the case of a 47-year-old woman with thymoma who developed myasthenia gravis, thrombocytopenia, and granulocytopenia, simultaneously, the concurrent association of these four disorders being extremely rare. Thymectomy was performed, and, during the post-thymectomy course, there were surprising findings concerning the recovery of not only the myasthenia gravis but also of the hematologic disorders. Immediately after thymectomy, the myasthenic symptoms completely disappeared, and the granulocyte and platelet counts recovered to within the normal range within a few days. The laboratory data revealed no difference between pre- and post-thymectomy in the release of cytokines (tumor necrosis factor; TNF, interleukin; IL-2, and IL-6), anti-acetylcholine receptor antibody, or platelet-associated IgG. On the other hand, the serum level of anti-neutrophil cytoplasmic antibody (p-ANCA), against the myeloperoxidase of the granulocytes was dramatically decreased, after thymectomy, showing a significant correlation with the granulocyte count. According to our survey of the literature, this is the first report to show that the removal of a thymoma led to the dramatic resolution not only of myasthenia gravis but also of other associated diseases. It is possible that p-ANCA may be regulated by thymoma, thus causing severe granulocytopenia.

An audit of ANCA in routine clinical practice

We have reviewed the medical records of 301/327 consecutive patients in whom anti-neutrophil cytoplasmic antibodies (ANCA) were detected by the Regional Immunology Laboratory in Northern Ireland between January 1988 and October 1991 (45 months). We have collected data for each patient regarding age, sex, smoking habit, area of residence, and details of any other autoantibody activity. Clinical diagnosis was established, with the number of organ systems involved and the evidence for that involvement (symptomatic, biochemical, radiological, and histological). Diagnoses were divided into four groups according to their recognised vasculitic features and these were related to the pattern of immunofluorescence and maximum ANCA titre detected. The most frequent diagnosis was rheumatoid arthritis (18.2% of patients) and the connective tissue disorders as a whole accounted for 27.9% of patients. ANCA were also detected in a wide range of clinical conditions which are not associated with vasculitis and these patients were an important source of 'false-positives'. The positive predictive value (PPV) of ANCA of all patterns and titres for vasculitic conditions was 27%, however, the detection of a classical ANCA pattern at high titre (> or = 1:640) was associated with an increased PPV of 75%. The coexistence of an antinuclear antibody (ANA) reduces the PPV of both classical and perinuclear ANCA, although perinuclear ANCA with antimyeloperoxidase specificity had an improved PPV. We conclude that ANCA testing should not be used as the only screening investigation for vasculitis but should be included in a rational investigative scheme. The interpretation of a positive ANCA result must take into account the presence of other autoantibodies and the full range of non-vasculitic conditions when the clinical situation is not typical of vasculitis.

Anti-neutrophil cytoplasmic antibody for proteinase 3 in a child with polyarteritis nodosa

We report a case of a 15 year old boy with polyarteritis nodosa associated with antineutrophil cytoplasmic antibody (ANCA) against proteinase 3 (PR3). After months of steroid and immunosuppressant therapy, the symptoms subsided and the polyaneurysms almost disappeared. The levels of anti-PR3 antibody and of cytokines also decreased. The results indicate that ANCA is a good indicator of this disease activity, and may play some pathogenic role in the disease.

[Kidney and vasculitis]

The kidney is affected in a variety of vasculitic syndrome. Vasculitis represent an heterogeneous group of inflammatory disease concerning vessels. They can be considered as secondary in systemic lupus erythematosus, cryoglobulinemia, rheumatoid polyarthritis but also in infectious diseases (Streptococci, hepatitis B) in malignant disease and after drugs. However, in many circumstances, no causes are found. The discovery of autoantibodies directed against components of neutrophil cytoplasm (ANCA) represent a great progress in the understanding of vasculitis. ANCA are autoantibodies directed against neutrophil lysosomial enzymes, preferentially myeloperoxidase and proteinase 3. They are frequently found in patients with idiopathic necrotizing vasculitis, systemic or localized to the kidney (Wegener granulomatosis, microscopic periarteritis, pauci-immune necrotizing glomerulonephritis, Churg and Strauss syndrome and polyarteritis nodosa). Diagnostic and prognostic values are sure, although their presence is unconstant with variable percentage in relation with the type of vasculitis. The increase of ANCA level is not always related with disease relapse. Conversely, a permanent low level means a quiescent disease. At the present time, it is not known if ANCA play a pathogenetic role or if they constitute a marker of the disease.

Activated neutrophils express proteinase 3 on their plasma membrane in vitro and in vivo

Apart from the diagnostic value of anti-neutrophil cytoplasmic antibodies (ANCA), their detailed characterization and that of their corresponding antigens have opened new ways for the exploration of the pathogenesis of primary systemic vasculitis. ANCA are now thought to play an important functional role via activation of phagocytic cells (e.g. polymorphonuclear neutrophils (PMN)). In this study we examined the mechanisms by which ANCA could gain access to proteinase 3 (PR3) in intact PMN, at two levels: ex vivo by analysing the presence of PR3 on the plasma membrane of PMN from patients with ANCA-associated vasculitis, and in vitro by stimulation of PMN using different cytokines, including recombinant tumour necrosis factor-alpha (rhTNF-alpha) and two forms of IL-8 (produced by monocytic and endothelial cells). Using immunocytochemical staining techniques (FACS and immunoelectronmicroscopy) PR3 has been detected on the plasma membrane of PMN from patients with active ANCA-associated vasculitis. However, this phenomenon is also seen in patients with sepsis who do not have ANCA. In addition, TNF-alpha and both forms of IL-8 act synergistically and induce a translocation of PR3 from the intragranular loci to the cell surface of PMN. These results provide strong evidence for the hypothesis that ANCA are directly pathogenic by binding to PR3 which is expressed on the cell surface of primed/activated PMN.

Prognostic factors in Wegener's granulomatosis

We analysed data from 64 patients with Wegener's granulomatosis to determine predictor variables of outcome. The mean period of observation after the diagnosis had been established was 3.2 (range 0.1-11.2) years. At the time of diagnosis, 15 (23%) patients had only local symptoms. The disease was generalized to multiple organs in 49 (77%) patients. Renal biopsies were obtained in 33 patients; 13 (39%) had extracapillary glomerulonephritis, which was the most common renal lesion. All but three patients received immunosuppressive therapy. At time of follow-up, 17 (27%) patients were in complete, and 26 (40%) in partial remission. We employed a Kaplan Meier analysis to identify predictor variables of outcome. Renal involvement, initial creatinine concentration, serum albumin or total protein concentration, leukocyte count and erythrocyturia proved to be predictor variables. These variables may be of value in guiding the intensity of treatment in patients with Wegener's granulomatosis.

Expression of cytokines and growth factors in human glomerulonephritides

Numerous experimental studies point to the potential role of cytokines and growth factors in the pathogenesis of renal disease. However, from the various autocrine and paracrine mediators identified in vitro and in animal models, so far only a few have been demonstrated in selected human glomerulopathies. We examined two types of glomerulonephritis (GN): extracapillary GN with anti-neutrophil cytoplasmic autoantibodies (ANCA), an example of an acute form of GN, and mesangial IgA GN, usually a chronic form of GN, with immunocytochemistry, in situ hybridization and the polymerase chain reaction. Normal renal tissue from tumour nephrectomies served as a control. In ANCA-positive GN with active renal lesions (crescents, glomerular and vascular necrosis), infiltrating mononuclear cells in glomeruli and in the interstitium expressed interleukin (IL)-1 beta, tumour necrosis factor (TNF)-alpha, IL-2, interferon (IFN)-gamma, platelet-derived growth factor (PDGF) and transforming growth factor (TGF)-beta. Cytokine expression was also observed in activated resident cells, including endothelial cells, capsular epithelial cells, smooth muscle cells of vessel walls, fibroblasts and some tubular epithelial cells. In addition, we noted an increase in the cytokine and growth factor receptors TNF-R, IL-1R type II, IL-2R, IFN-gamma R and PDGF beta-R. In contrast, in mesangial IgA-GN, IL-1 beta, TNF-alpha, IFN-gamma and IL-2 were usually absent in glomeruli. Mesangial expansion in this disorder was accompanied by an increased expression of PDGF, PDGF beta-R, TGF-beta and IL-6 in mesangial areas. In both conditions a good correlation was observed between cytokine expression at the mRNA (in situ hybridization) and protein level (immunocytochemistry).(ABSTRACT TRUNCATED AT 250 WORDS)

In situ production of TNF-alpha, IL-1 beta and IL-2R in ANCA-positive glomerulonephritis

Humoral and cellular immune mechanisms are thought to be involved in various forms of vasculitis and glomerulonephritis. Recent clinical and experimental results point to a role of cytokines in ANCA-positive vasculitides. We analyzed tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and interleukin-2 receptors (IL-2R) in renal biopsies and in plasma from 22 patients with Wegener's granulomatosis and microscopic polyangiitis. Kidney biopsies were examined by immunocytochemistry, polymerase chain reaction and in situ hybridization. Immunoreactive TNF-alpha, IL-1 beta and/or IL-2R positive infiltrating cells were observed in 21 of 22 biopsies. TNF-alpha, IL-1 beta and IL-2R staining was evident in the interstitium and at periglomerular and perivascular sites. The number of positive cells was markedly increased in biopsies with active lesions. Positive cells were also present in cellular and fibrocellular crescents, surrounding tuft necrosis and in the walls of arteries and arterioles with acute vasculitic lesion. Some tubular epithelial cells stained for TNF-alpha and IL-1 beta. TNF-alpha, IL-1 beta and IL-2R positive infiltrating cells correlated with the presence of histologically active renal lesions. The evaluation of TNF-alpha and IL-1 beta expression at the mRNA level assessed by the polymerase chain reaction demonstrated specific transcripts for TNF-alpha and IL-1 beta in all six cases analyzed. In situ hybridization studies showed an increased expression of mRNA for TNF-alpha and IL-1 beta in infiltrating mononuclear cells, in epithelial cells of Bowman's capsule and in some tubules, predominantly of patients with active renal lesions. The results at the mRNA level correlated with the immunocytochemical findings. Compared to healthy individuals higher TNF-alpha plasma levels were observed in patients with vasculitis (34.4 +/- 16.6 pg/ml (SEM) vs. 1.9 +/- 0.7 pg/ml in controls; P < 0.01). All patients presented a marked increase in sIL-2R plasma levels (3512 +/- 485 U/ml vs. 397 +/- 21 U/ml in healthy controls; P < 0.001). IL-1 beta was not detected in most plasma samples. Elevated TNF-alpha and sIL-2R plasma levels were related to active renal lesions. Our study clearly demonstrates that in ANCA-positive vasculitis TNF-alpha and IL-1 beta are produced in situ by activated infiltrating mononuclear cells and resident renal cells. Intrarenal localization of cytokine producing cells and the correlation between cytokine production and histological signs of activity suggest that TNF-alpha and IL-1 beta are important locally acting mediators in the vasculitic/glomerulonephritic process.

Limited prognostic value of changes in antineutrophil cytoplasmic antibody titer in patients with Wegener's granulomatosis

OBJECTIVE

To assess the correlation and prognostic value of antineutrophil cytoplasmic antibody (cANCA) titers with disease activity in patients with Wegener's granulomatosis (WG).

METHODS

One hundred six patients with WG had serum ANCA determinations; 72 had serial titers obtained routinely at 1-3-month intervals. One hundred twelve subjects (19 of whom were healthy donors) served as controls. All serum samples were tested for cANCA by an indirect immunofluorescence technique. A prospective analysis of disease activity and cANCA values was performed. Disease activity was assessed according to clinical, laboratory, radiographic, and histopathologic findings.

RESULTS

Positivity for cANCA was a sensitive (88%) marker of active WG. However, changes in serial titers temporally correlated with a change in disease status in only 64% of patients. Furthermore, an increase in the cANCA titer preceded clinical exacerbation of disease in only 24% of patients who had been in remission or had low-grade, smoldering disease.

CONCLUSION

A rise in cANCA titer alone should not be considered adequate evidence of an impending clinical exacerbation, and therefore does not justify initiating or increasing immunosuppressive therapy.

Autoantibodies directed against lysozyme: a new target antigen for anti-neutrophil cytoplasmic antibodies (ANCA)

ANCA-positive sera from 1138 patients and ANCA-negative sera from 90 patients were screened for autoantibodies directed against lysozyme (LZ) by ELISA. Sera from 120 patients did react with LZ. 99 sera bound to LZ only, whereas 56 sera bound to further granule proteins, especially cathepsin G and lactoferrin. In the routine ANCA screening, most of the anti-LZ-positive sera showed a pANCA fluorescence. In total, 8% of 674 pANCA-positive sera did react with LZ. Clinically, anti-LZ antibodies were associated inflammatory rheumatologic, -renal and -bowel diseases.

ANCA and associated diseases: immunodiagnostic and pathogenetic aspects

The past decade has seen an explosion of data on the new group of autoantibodies known collectively as ANCA (anti-neutrophil cytoplasmic antibodies). ANCA are specific for granule proteins of granulocytes and monocytes and induce distinct fluorescence patterns, e.g. the cytoplasmic (classic) cANCA and the perinuclear pANCA. cANCA is induced by antibodies directed against Proteinase 3 (PR3; PR3-ANCA) in about 90% of all ANCA-positive sera, and pANCA is induced by antibodies against myeloperoxidase (MPO; MPO-ANCA) in about 40%. A further staining pattern, which does not have a clear cut association with a distinct granule protein, is sometimes seen in chronic inflammatory bowel diseases. PR3-ANCA are serological markers for Wegener's granulomatosis (WG) and MPO-ANCA are associated with certain subtypes of primary vasculitides. Evidence exists that both the autoantigen and ANCA participate in the pathogenesis of at least the group of 'ANCA-associated vasculitides'.

Pro- and anti-inflammatory cytokines in primary systemic vasculitis

The expression of cytokines that are potentially involved in the pathogenesis of vasculitis was studied in patients with primary systemic vasculitis (PSV). In extension of earlier reports, we detected an overexpression of transforming growth factor beta (TGF beta), interleukin 6 (IL6), and interleukin 8 (IL8), indicating that the whole cytokine cascade is activated to a significant extent in PSV.

Elevated serum levels of soluble interleukin-2 receptor in patients with Wegener's granulomatosis. Association with disease activity

OBJECTIVE

To investigate whether soluble interleukin-2 receptor (sIL-2R), a marker of T cell activation, could be a useful marker of disease activity in Wegener's granulomatosis (WG).

METHODS

Soluble IL-2R levels were determined by enzyme-linked immunosorbent assay. WG disease activity in 102 patients was assessed according to clinical features and levels of classic antineutrophil cytoplasmic antibody (c-ANCA) and C-reactive protein (CRP).

RESULTS

Soluble IL-2R levels were higher in patients with generalized and active disease than in those with limited and inactive disease. In 25 patients with complete clinical remission, sIL-2R levels were significantly elevated, although levels of CRP and c-ANCA were normal. Eight of these 25 patients had disease relapses within 6 months. Levels of sIL-2R were significantly higher in patients who had relapses than in those who did not. Patients with clinically active WG but low c-ANCA or CRP levels had elevated levels of sIL-2R.

CONCLUSION

Levels of sIL-2R correlate with disease activity in patients with WG, and may indicate imminent relapse.