EULAR/ERA-EDTA recommendations for the management of ANCA-associated vasculitis

In this article, the 2009 European League Against Rheumatism (EULAR) recommendations for the management of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) have been updated. The 2009 recommendations were on the management of primary small and medium vessel vasculitis. The 2015 update has been developed by an international task force representing EULAR, the European Renal Association and the European Vasculitis Society (EUVAS). The recommendations are based upon evidence from systematic literature reviews, as well as expert opinion where appropriate. The evidence presented was discussed and summarised by the experts in the course of a consensus-finding and voting process. Levels of evidence and grades of recommendations were derived and levels of agreement (strengths of recommendations) determined. In addition to the voting by the task force members, the relevance of the recommendations was assessed by an online voting survey among members of EUVAS. Fifteen recommendations were developed, covering general aspects, such as attaining remission and the need for shared decision making between clinicians and patients. More specific items relate to starting immunosuppressive therapy in combination with glucocorticoids to induce remission, followed by a period of remission maintenance; for remission induction in life-threatening or organ-threatening AAV, cyclophosphamide and rituximab are considered to have similar efficacy; plasma exchange which is recommended, where licensed, in the setting of rapidly progressive renal failure or severe diffuse pulmonary haemorrhage. These recommendations are intended for use by healthcare professionals, doctors in specialist training, medical students, pharmaceutical industries and drug regulatory organisations.

Plasma exchange induces vitamin D deficiency

BACKGROUND

Plasma exchange is used in the treatment of diseases mediated by pathogenic circulating proteins, or for transplant desensitization. Its non-targeted nature results in the depletion of physiologically important molecules, and it is often complicated by hypocalcaemia.

AIM

To determine the effects of plasma exchange on vitamin D binding protein (DBP) and associated vitamin D metabolites.

DESIGN

Single-centre prospective cohort study of 11 patients.

METHODS

DBP and vitamin D metabolites were measured before and immediately after five plasma exchanges, and 7 and 28 days after discontinuation of plasma exchange.

RESULTS

Plasma exchange reduced plasma DBP concentration from 196.9 ± 53.2 to 98.5 ± 34 μg/ml (P = 0.0001), 1,25-dihydroxyvitamin D from 103 ± 52 to 42 ± 4 pmol/l (P = 0.003) and 25-hydroxyvitamin D from 49.7 ± 29 to 22 ± 9.4 nmol/l (P = 0.0017), through their removal in effluent. After 7 days, DBP and 1,25-dihydroxyvitamin D were not significantly different from baseline, but 25-hydroxyvitamin D remained significantly lower after 7 days (26.4 ± 9.8 nmol/l, P = 0.02) and 28 days (30.8 ± 15.5 nmol/l, P = 0.048). Corrected calcium decreased from 2.23 ± 0.11 to 1.98 ± 0.08 mmol/l (P = 0.0007) immediately after five treatments. Plasma calcium was significantly associated with 1,25-dihydroxyvitamin D (r(2) = 0.79, P < 0.0001).

CONCLUSION

Plasma exchange induced an acute reversible decrease in plasma 1,25-dihydroxyvitamin D, DBP, calcium and a sustained decrease in plasma 25-hydroxyvitamin D.

Increased apoptosis of bone marrow CD34(+) cells and impaired function of bone marrow stromal cells in patients with systemic lupus erythematosus

The changes in bone marrow (BM) stem cell reserve and function and stromal cell function in patients with active systemic lupus erythematosus (SLE) were investigated. The study was carried out on seven SLE patients and 28 healthy controls using flow cytometry and in vitro cell culture assays. We found that patients had low CD34(+) cells, compared with the control group, reflecting the decrease of both CD34(+)/CD38(-) and CD34(+)/CD38(+) cells. Patient CD34(+)/Fas(+) but not CD34(-)/Fas(+) cells were significantly increased. Apoptotic (7AAD(dim)) cells were higher among CD34(+)/Fas(+) than among CD34(+)/Fas(-) cells, and individual values of apoptotic CD34+ cells strongly correlated with the number of CD34(+)/Fas(+) cells. These findings are suggestive of a Fas-mediated apoptosis accounting for the low CD34(+) cells in SLE patients. Moreover, we found that patients had low numbers of granulocyte-macrophage colony-forming units (CFU-GM) and erythroid burst-forming units (BFU-E), compared with the control group, and that the generation of colony-forming cells in long-term BM cultures was significantly reduced. Patient BM stroma failed to support allogeneic progenitor cell growth. In one patient, CD34(+) cells were increased, apoptotic CD34(+)/Fas(+) cells were normalized and defective stromal cell function was restored after autologous stem cell transplantation. We concluded that defective haemopoiesis in SLE patients is probably caused, at least in part, to the presence of autoreactive lymphocytes in BM.

Treatment of systemic lupus erythematosus with mycophenolate mofetil

Mycophenolate mofetil is an immunosuppressive drug that is of established efficacy in renal transplantation. It inhibits the de novo pathway of purine synthesis and therefore lymphocyte proliferation. Mycophenylate mofetil has been shown to ameliorate the severity of renal injury in murine models of lupus nephritis. Recent studies suggest that it may also be effective in the treatment of patients with lupus nephritis when used in conjunction with steroids. These observations need to be confirmed in adequately sized randomised-controlled studies.

Intravenous immunoglobulin for ANCA-associated systemic vasculitis with persistent disease activity

Intravenous immunoglobulin (IVIg) is a potential alternative treatment for anti-neutrophil cytoplasm antibody (ANCA)-associated systemic vasculitis (AASV) with less toxicity than conventional immunosuppressive agents. This randomized, placebo-controlled trial aimed to investigate the efficacy of a single course of IVIg (total dose 2 g/kg) in previously-treated AASV with persistent disease activity in whom there was an intention to escalate therapy. Vasculitic activity was monitored by the Birmingham vasculitis activity score (BVAS), C-reactive protein (CRP) and ANCA levels. Treatment response was defined as a reduction in BVAS of more than 50% after 3 months, and there was an intention to keep doses of concurrent immunosuppressive drugs unchanged during this period; follow-up continued to 12 months. Seventeen patients were randomized to receive IVIg and 17 to receive placebo. Treatment responses were found in 14/17 and 6/17 of the IVIg and placebo groups, respectively (p=0.015, OR 8.56, 95%CI 1.74-42.2). Following infusion of trial medication, greater falls in CRP were seen at 2 weeks (p=0.02) and 1 month (p=0.04) in the IVIg group. No differences were observed between ANCA levels or cumulative exposure to immunosuppressive drugs, and after 3 months there were no differences in CRP levels or disease activity between the IVIg and placebo groups. Seventeen adverse effects occurred after IVIg and six after placebo: they were mostly mild, although reversible rises in serum creatinine occurred in four from the IVIg group. A single course of IVIg reduced disease activity in persistent AASV, but this effect was not maintained beyond 3 months; mild, reversible side-effects following IVIg were frequent. IVIg is an alternative treatment for AASV with persistent disease activity after standard therapy.

Immunotherapy for autoimmune and inflammatory renal diseases

New treatments for autoimmune renal disease are required, and a developing knowledge of its underlying immunopathogenesis has identified sites where immunotherapy is likely to be effective. Experience with intravenous immunoglobulin and lymphocyte depletion by monoclonal antibodies in systemic vasculitis and systemic lupus erythematosus is awaiting confirmation by randomized trials. Treatments at or near clinical testing include monoclonal antibody blockade of leucocyte-endothelial interactions and CD40 mediated B-cell activation, and immunoablation with autologous stem-cell transplantation for more severe multisystem autoimmune disease.

Treatment of antineutrophil cytoplasm autoantibody-associated systemic vasculitis: initiatives of the European Community Systemic Vasculitis Clinical Trials Study Group

The diagnosis, treatment, and monitoring of the primary systemic vasculitides associated with circulating antineutrophil cytoplasm autoantibodies (ANCA) have formed the focus of a multicenter collaborative study. Consensus has been reached on criteria for classification, clinical subgroupings by extent and severity of disease, and "standard" and "best alternative" therapeutic regimens. Two series of randomized controlled trials have been designed; their aims are (1) to harmonize current approaches to treatment and (2) to test the value of newer therapeutic agents. In support of these trials, semiobjective scoring systems have been created and validated, and previous standardization of ANCA serologic and histologic analysis has been adopted. The systems of classification and clinical management described herein represent the recommendations of a multidisciplinary study group that hopes to improve the outcome of patients with primary systemic vasculitis by wide dissemination of the collective experience from interested centers.

Cerebral vasculitis--recognition, diagnosis and management

Cerebral vasculitis is a serious but uncommon condition which presents considerable difficulties in recognition, diagnosis and treatment. We studied eight consecutive patients in whom this diagnosis was made. Despite the great diversity of symptoms and signs, we noted three clinical patterns: (i) acute or sub-acute encephalopathy, (ii) a picture with some similarities to multiple sclerosis ('MS-plus'), and (iii) features of a rapidly progressive space-occupying lesion. The identification of these patterns may help recognition of cerebral vasculitis. The diagnostic value of four investigative procedures not previously studied in cerebral vasculitis was assessed: ophthalmological examination using low-dose fluorescein angiography with slit-lamp video microscopy of the anterior segment (abnormal in 4/5 patients); spinal fluid oligoclonal band analysis (abnormal in 3/6 patients); anti-neutrophil cytoplasmic antibody assay (abnormal in 3/8 patients); and indium-labelled white-cell cerebral imaging (positive in only one patient). Treatment was with steroid alone (n = 2) or steroid with cyclophosphamide (n = 6). Seven patients responded clinically.

Intravenous immunoglobulin as sole therapy for systemic vasculitis

High-dose, pooled, i.v. immunoglobulin (IVIg) is a potential, alternative treatment for Wegener's granulomatosis (WG) and microscopic polyangiitis (MPA) which has shown promise in the treatment of refractory disease when administered with continuing immunosuppression. This study of six new patients with antineutrophil cytoplasmic antibody (ANCA)-positive vasculitis and early disease, without threatened vital organ function, examined the therapeutic response to treatment with IVIg alone. IVIg was well tolerated and all six patients had early reductions in disease activity. Four entered full, clinical remission which lasted for at least 1 yr, while in two the responses were partial and transient, and they subsequently required conventional treatment. After 16-48 months of follow-up, two of the four patients in full remission relapsed, but the other two have remained well.

Autoantibodies against bactericidal/permeability-increasing protein in patients with cystic fibrosis

Cystic fibrosis (CF), a genetic disorder, is characterized by chronic pulmonary infection/inflammation which leads to respiratory failure. The presence of anti-neutrophil cytoplasmic autoantibodies (ANCA) has previously been observed in the sera of patients with CF. In view of the known relationship of ANCA with primary vasculitis and of their putative pathogenetic role in these disorders, we studied the presence, specificity and isotype of ANCA and their clinical associations in 66 adult CF patients. None of the 66 CF samples had autoantibodies to the major ANCA antigens, proteinase 3 or myeloperoxidase. However, 60/66 (91%) CF samples contained IgG, and 55/66 (83%) IgA, autoantibodies to bactericidal/permeability-increasing protein (BPI), a recently-characterized ANCA specificity. All the IgA anti-BPI-positive samples were also IgG anti-BPI-positive. The autoantibody specificity was confirmed by inhibition assay and immunoblotting of CF sera against a neutrophil granule preparation. Furthermore, in this cross-sectional study, anti-BPI levels were inversely correlated with the observed reductions in FEV1 and FVC (IgA anti-BPI & FEV1: r = -0.508, p < 0.0001), and both IgG and IgA anti-BPI levels were higher in CF patients with secondary vasculitis (n = 6) than in those without (p < 0.05). ANCA with specificity for BPI were present in the majority of CF sera in this study and autoimmune processes may be associated with the development of pulmonary injury in CF.

ANCA and predicting relapse in systemic vasculitis

We studied 60 patients with ANCA-positive systemic vasculitis (SV) to assess the prognostic significance of clinical and serological features at presentation, and the value of sequential monitoring of ANCA, C-reactive protein (CRP) and ESR levels as predictors of disease relapse. Patients were recruited at the time of diagnosis, treated with a standard protocol, and assessed monthly for one year. Clinical remission was achieved in 56/60 (93%), and ANCA became undetectable in 50/60 (83%) after treatment. During the one year follow-up period, disease relapses were seen in 23 (38%) patients. No specific associations were observed between initial disease presentation, initial ANCA level or ANCA antigenic specificity and relapse. However, 13/23 (57%) of relapses were preceded by a rise in ANCA a mean of 7.8 weeks earlier, while at the time of relapse 19/23 (83%) were ANCA-positive. Rises in CRP and ESR occurred in 23/60 (38%) and 14/43 (33%), respectively, but were less closely associated with relapse than ANCA. A sustained rise in ANCA was seen in six patients without relapse while clinical relapse occurred with a negative ANCA in four. Sequential ANCA monitoring at monthly intervals during disease remission is of value, at least during the first year, in the prediction and diagnosis of relapse in SV, and is superior to measurement of CRP or ESR.

Distribution of MHC class II alleles in primary systemic vasculitis

Previous studies have shown a number of different associations between major histocompatibility complex (MHC) alleles and primary systemic vasculitis. Disease heterogeneity and the lack of specificity of certain MHC typing techniques may have contributed to the lack of consistency in those studies. We therefore studied a relatively homogeneous group of 94 patients with Wegener's granulomatosis, microscopic polyangiitis, or renal-limited vasculitis using molecular techniques that allow more precise assignment of MHC genotype. DNA was prepared from peripheral blood and DRB1 genotype determined by Taq restriction fragment length polymorphism. DQB1 and DPB1 genotype were assigned by polymerase chain reaction amplification followed by probing with allele-specific oligonucleotides. Specificity of associated anti-neutrophil cytoplasm antibodies (ANCA) was determined where possible by solid phase immunoassays using purified proteinase 3 (PR3) and myeloperoxidase (MPO). After correction for multiple comparisons there were no significant differences in the distribution of DRB1, DQB1 and DPB1 alleles between a local control group (N = 90 for DRB1, N = 50 for DQB1 and DPB1) and the patient group as a whole (N = 94) or two a priori defined subgroups (anti-PR3 positive, N = 35; anti-MPO positive, N = 22). We have therefore found no significant association between primary systemic vasculitis and any MHC class II allele. This, together with the fact that previous smaller studies have shown no consistent association, suggests that any such association is very weak, if it exists at all.

Clinical significance of anti-endothelial cell antibodies in systemic vasculitis: a longitudinal study comparing anti-endothelial cell antibodies and anti-neutrophil cytoplasm antibodies

Ten patients with systemic vasculitis, all positive for anti-neutrophil cytoplasm antibody (ANCA), were followed for a mean of 36 weeks to determine the prevalence of anti-endothelial cell antibodies (AECAs) and the relationship between AECAs, ANCAs, and disease activity. Anti-endothelial cell antibodies were detected in eight (80%) patients at some time during the study. The levels of both AECAs and ANCAs changed with time, and these autoantibodies were present in 48% and 63% of the total 100 serum samples, respectively. Eighteen clinical remissions were observed; in 16 (88.9%) cases the level of ANCAs dropped. Fifteen (83.3%) of the 18 remissions were among the AECA-positive patients and the level of AECAs decreased in 13 (86.7%) instances (P = not significant). There were 11 episodes of disease relapse; all were associated with an increase in the level of ANCAs. Nine (81.8%) of the 11 relapses were among AECA-positive patients, and the level of AECAs increased in eight (88.9%) cases (P = not significant). Serum levels of AECAs appeared less suppressible by cyclophosphamide therapy compared with ANCAs, and patients who were persistently positive for AECAs despite being ANCA-negative during remissions were at risk of subsequent relapse. Disease recrudescense was not observed in patients persistently tested negative for both AECAs and ANCAs. Intravenous immunoglobulin therapy was used in four patients and resulted in clinical improvement in all cases, but with variable changes in the levels of AECAs and ANCAs. We conclude that AECAs are commonly detected in patients with systemic vasculitis and their levels show a relationship to disease activity similar to that for ANCAs.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-idiotype antibodies to anti-myeloperoxidase autoantibodies in patients with systemic vasculitis

The presence of anti-idiotype antibody (anti-id) activity to anti-myeloperoxidase autoantibodies (anti-MPO) was measured by assessing binding of IgG in patients' sera to F(ab')2 fragments of polyclonal heterologous anti-MPO antiserum. Thirteen paired acute and remission sera and three groups of sequential sera from patients with systemic vasculitis were studied. The levels of anti-MPO fell as disease activity subsided with treatment. However, levels of anti-id activity against these anti-MPO rose as patients entered remission. This effect was still seen after controlling for binding to F(ab')2 constant regions and after polyethylene glycol precipitation of immune complexes. In the sequential studies, levels of anti-MPO and anti-MPO anti-id tended towards a reciprocal relationship. These observations point to dynamic interactions between autoantibody and complementary anti-idiotype antibodies in this system and a role for idiotypic networks in the regulation of anti-neutrophil cytoplasm antibodies.

Association of ANCA isotype and affinity with disease expression

The association of ANCA isotype and affinity with disease expression is reviewed and new data on IgA ANCA levels and affinity in relation to disease activity are presented. Differences in the IgG ANCA subclass distribution exist between active disease and remission, with high affinity IgG3 ANCA present at the onset of disease. IgM ANCA, with or without associated IgG ANCA, correlates with pulmonary haemorrhage and disappears at remission. IgA ANCA are mainly found in patients presenting with Henoch-Schönlein purpura (HSP), and are directed against a distinct autoantigen of approximately 50 kD. The level and affinity of IgA ANCA also correlate with disease activity in HSP. Isotype as well as antibody specificity appear to be major determinants of disease expression.

ANCA anti-idiotype antibodies and the treatment of systemic vasculitis with intravenous immunoglobulin

The presence of anti-idiotype antibodies (anti-id) to anti-neutrophil cytoplasm autoantibodies (ANCA) in intravenous immunoglobulin (IVIg) and remission sera from patients with systemic vasculitis, and the use of IVIg as an alternative therapeutic agent in open studies, has suggested a role for idiotypic regulation in the normal control of these disorders. Clinical benefit with IVIg has been reported in 15/16 patients, with sustained remission in eight. The ability of IVIg to produce lasting remission has been associated with a fall in ANCA levels and stimulation of endogenous immunoglobulin production. IVIg has the potential to influence the pathogenetic process in patients with vasculitis at several stages, and an influence on the idiotypic regulation of ANCA may explain the observed clinical responses and point to possible targets for more specific immunotherapy in the future.

Anti-idiotype antibodies to anti-mitochondrial antibodies in the sera of patients with primary biliary cirrhosis

Idiotype-anti-idiotype interactions were investigated in the sera of patients with primary biliary cirrhosis (PBC), which is characterized by the presence of circulating anti-mitochondrial antibodies (AMA). A mouse monoclonal antibody, CPZ674, has been raised to the E2 component of the pyruvate dehydrogenase complex (PDC), which is the target antigen of AMA. CPZ674 recognizes one of the epitopes recognizable by AMA, as demonstrated by competitive Western blotting. Anti-idiotypic antibodies in PBC sera were detected either by their specific binding to CPZ674 in an ELISA or by the formation of idiotype-anti-idiotype complexes with CPZ674, detected using chromatography on a Sephacryl-300 column and by a polyethylene glycol precipitation method. The specificity of the anti-idiotypic antibodies to AMA was shown by their ability to inhibit the binding of AMA to PDC, but not the binding of other autoantibodies to their relevant autoantigens. We have therefore produced evidence for the existence of idiotype-anti-idiotype interactions in PBC, but whether these anti-idiotypic antibodies are involved in the control of AMA is unknown.

Influence of immunoadsorption on the removal of immunoglobulin G autoantibodies in crescentic glomerulonephritis

We report the treatment of 5 patients with crescentic glomerulonephritis by immunoadsorption using a protein A column. Two had systemic vasculitis, 2 antiglomerular basement membrane disease and 1 systemic lupus erythematosus (SLE). In the patients with systemic vasculitis and SLE, there was successful removal of autoantibodies and rapid control of disease; remission was maintained over a mean follow-up of 2 years. Clinical improvement was not seen in 2 patients with anti-glomerular basement membrane (GBM) disease who presented with dialysis-dependent renal failure. There were no apparent clinical side-effects related to the immunoadsorption procedure. Protein A immunoadsorption offers a semiselective alternative to plasma exchange and appears to be safe and efficient in removing pathogenic autoantibodies in crescentic glomerulonephritis without anti-GBM antibodies.

Pooled intravenous immunoglobulin in the management of systemic vasculitis

Investigation into the therapeutic use of intravenous immunoglobulin (IVIg) in systemic vasculitis was prompted by the detection of anti-idiotype antibodies reactive with ANCA in IVIg and the proven ability of IVIg to reduce the incidence of coronary artery aneurysms in Kawasaki disease. The efficacy and safety of IVIg (Sandoglobulin) was assessed in an open study of 26 patients with active systemic vasculitis. Eight weeks after IVIg 13 patients were in full and 13 in partial remission, clinical benefit was maintained in 18 twelve months later and was reflected by changes in C-reactive protein and ANCA.

Analysis of anti-idiotypic antibodies against anti-microsomal antibodies in patients with thyroid autoimmunity

Anti-microsomal antibody (AMA) activity was inhibited in 14 of 16 sera and in all 12 IgG preparations from patients with postpartum thyroiditis following incubation with F(ab')2 fragments from normal polyspecific immunoglobulin for therapeutic use (ivIg). Similar results were observed with sera from seven of seven patients with Graves' disease and five of six patients with autoimmune hypothyroidism. Results of these competitive binding assays and affinity chromatography of AMA IgG on Sepharose-bound F(ab'), fragments from ivIg indicated that AMA antibodies reacted with ivIg through idiotypic-anti-idiotypic interactions. Eight out of 10 IgG preparations from patients with autoimmune thyroid disease also showed inhibition of AMA activity when coincubated with autologous IgM at various IgG:IgM molar ratios. These observations suggest that ivIg can inhibit anti-microsomal antibodies through idiotype-anti-idiotype interactions and that such interactions occur with IgM anti-idiotype antibodies in vivo, providing evidence of a role for idiotypic network regulation in the control of thyroid autoimmunity.

Association of IgM with IgG ANCA in patients presenting with pulmonary hemorrhage

ANCA are markers for systemic vasculitis such as Wegener's granulomatosis (WG) and microscopic polyarteritis (MPA) and are usually of the IgG isotype. However, IgM ANCA may rarely occur in isolation, and in these circumstances, we have found that they are associated clinically with a syndrome of pulmonary hemorrhage and systemic vasculitis. How frequently IgM ANCA may occur in conjunction with IgG has not previously been investigated. We report here a study of 24 consecutive patients with IgG ANCA-positive systemic vasculitis (14 WG, 10 MPA) in whom we determined whether IgM ANCA occurred in association with IgG ANCA, and if so, whether this had clinical importance. Eight patients were found to have IgM ANCA as well as IgG ANCA, and of these, seven presented with severe pulmonary hemorrhage. None of the IgM ANCA-negative patients presented with pulmonary hemorrhage. Although the occurrence of pulmonary hemorrhage in ANCA positive vasculitis was closely correlated with the presence of IgM ANCA, the antigen specificity of these IgM autoantibodies was variable, since both myeloperoxidase (4 patients), PR3 (3 patients), and an unknown ANCA antigen (1 patient) were found to be targets. We conclude that knowledge of ANCA isotype may have important clinical and therapeutic implications for the management of patients with systemic vasculitis.

Anti-mitochondrial antibody IgG subclass distribution and affinity in primary biliary cirrhosis

We have studied the total IgG subclass and anti-mitochondrial antibody (AMA) specific IgG subclass distribution in primary biliary cirrhosis (PBC) sera. In order to solve the problems caused by the differing affinities of subclass specific monoclonals and the competitive inhibition of antibodies in a whole serum assay, six sera were separated into subclass-specific fractions by affinity-depletion chromatography. AMA subclass distribution of 20 further sera from patients with PBC was assessed using conventional methods and the results were calibrated against one of the fractionated sera. Light chain distribution and AMA functional affinity were also assessed for the fractionated subclasses. Total amounts of IgG3 were significantly increased compared with normal controls. AMA were found in all IgG subclasses and not restricted predominantly to IgG3 as previously described. The functional affinity of IgG3 AMA is generally lower as compared with that of other subclasses. No light chain restriction was found.

IgG subclass distribution and relative functional affinity of anti-myeloperoxidase antibodies in systemic vasculitis at presentation and during follow-up

Circulating IgG autoantibodies to myeloperoxidase (MPO) are associated with renal vasculitis and have been implicated in its pathogenesis. However, raised levels of these autoantibodies may persist during clinical remission. We tested whether this paradox could be explained by immunoglobulin subclass switching during disease evolution, since different subclasses have different immunological and biochemical properties. Sera with anti-myeloperoxidase (anti-MPO) activity from 33 patients with active disease and 20 anti-MPO positive follow-up sera were studied by an ELISA using a panel of anti-human IgG subclass monoclonal reagents previously calibrated on human myeloma proteins. Anti-MPO subclass distribution in initial sera was: IgG1, 31 (94%); IgG2, 10 (30%); IgG3, 24 (73%); and IgG4, 22 (67%). IgG3 anti-MPO decreased during follow-up (P less than 0.02), with no change in IgG1 and IgG4. Relative functional affinity of anti-MPO antibodies in purified IgG subclasses was studied by the diethylamine method. IgG3 fractions consistently had a greater affinity for MPO than the other subclasses. Sequential studies in four patients demonstrated an affinity maturation for IgG1 and IgG4 anti-MPO as IgG3 anti-MPO disappeared. We conclude that dynamic changes of subclass distribution and affinity may explain discrepancies between anti-MPO antibody titre and disease expression.

IgG subclass distribution of autoantibodies to neutrophil cytoplasmic antigens in systemic vasculitis

The IgG subclass distribution for both ANCA-specific, and total IgG subclasses, of sera from 48 patients with active systemic vasculitis was determined by solid-phase assay using monoclonal anti-human subclass reagents. To control for varying performance of the subclass reagents, the assays were calibrated with sera affinity-depleted into subclass specific fractions, whose ANCA IgG subclass distribution was determined by a common reagent. In 10 patients whose ANCA persisted during clinical remission, the ANCA IgG subclass distributions between active and remission phases of disease were compared. The total IgG subclass distribution of sera from patients with active vasculitis was similar to that found in a normal population. The ANCA IgG subclass distribution of the same sera showed relative enrichment for IgG3 and depletion of IgG2 (P less than 0.05). When the active and clinical remission ANCA IgG subclass distributions were compared, ANCA IgG3 levels had fallen and ANCA IgG2 levels were increased during remission (P less than 0.01).

Treatment of systemic vasculitis with pooled intravenous immunoglobulin

The therapeutic effect of a course of high-dose, pooled, intravenous immunoglobulin (IVIg) on disease activity and circulating antineutrophil cytoplasm antibodies (ANCA) was investigated in 7 patients with systemic vasculitis. 5 had active disease despite conventional immunosuppression, and 2 had not received any treatment. All 7 had clinical improvement, which was sustained in 6 and transient in 1. The fall in ANCA concentrations to a mean of 51% of the pre-treatment values was maintained during follow-up. C-reactive protein concentration also dropped considerably. IVIg seemed to confer a useful therapeutic effect without adverse reaction.

Anti-idiotypes against anti-neutrophil cytoplasmic antigen autoantibodies in normal human polyspecific IgG for therapeutic use and in the remission sera of patients with systemic vasculitis

Anti-neutrophil cytoplasmic antigen (ANCA) activity was inhibited in 15 out of 21 sera from patients with acute systemic vasculitis following incubation with normal polyspecific IgG for therapeutic use (IVIg). ANCA antibodies reacted with IVIg through idiotypic-anti-idiotypic interactions, as shown in competitive binding assays using F(ab')2 fragments from IVIg and affinity chromatography of ANCA IgG on Sepharose-bound F(ab')2 fragments from IVIg. Co-incubation of sera from patients with acute systemic vasculitis with paired autologous remission stage sera also resulted in inhibition of ANCA activity in acute sera. Remission sera contain IgM and IgG capable of interacting with beta and or alpha idiotypes of ANCA IgG from acute sera. Anti-idiotypic IgM may account for the lack of expression of ANCA activity in whole serum from patients in remission from systemic vasculitis, which were found to contain high titres of ANCA IgG. These observations suggest that remission of systemic vasculitis is associated with the generation of anti-idiotypes against autoantibodies rather than the suppression of production of ANCA autoantibodies. IVIg may modulate the activity of systemic vasculitis in vivo.

The specificity of anti-neutrophil cytoplasm autoantibodies in systemic vasculitides

Autoantibodies to neutrophil cytoplasmic antigens are found in patients with small or medium-size vessel systemic vasculitis such as Wegener's granulomatosis and microscopic polyarteritis. We studied the specificity of anti-neutrophil cytoplasm autoantibodies (ANCA) by examining the binding of sera from patients with different forms of systemic vasculitis, to neutrophil extract size-fractionated by gel filtration for high performance liquid chromatography. Sequential fractions were collected for solid-phase radioimmunoassay. Patients with Wegener's granulomatosis showed two peaks of activity over fractions of 12 and 2 kD. Patients with microscopic polyarteritis had two different peaks of activity over fractions of 100 and 25 kD. Patients with Takayasu's arteritis and dermal lymphocytic vasculitis were studied as controls (all were ANCA negative by indirect immunofluorescence studies and solid-phase radioimmunoassay). However, the patient with lymphocytic vasculitis showed a distinct peak of activity over 22 kD and patients with Takayasu's arteritis had a single peak of activity over 200 kD. These results suggest the binding pattern of sera to fractionated neutrophil extract could be useful in differentiating between different diseases within the spectrum of systemic vasculitis. Cryptic antigen recognition in certain vasculitides may only be revealed by this procedure. We conclude that the association of ANCA and systemic vasculitis may not be limited to diseases of small or medium-size vessels, but could also include large vessel disease such as Takayasu's arteritis.

Autoantibodies to endothelial cells and neutrophil cytoplasmic antigens in systemic vasculitis

The interaction of circulating autoantibodies with the endothelium may be an important mechanism in the pathogenesis of systemic vasculitis. In a prospective study, we looked for circulating antiendothelial cell autoantibodies (AECA) and anti-neutrophil cytoplasm autoantibodies (ANCA) in 80 patients with suspected systemic vasculitis. AECA were measured using an isotype-specific cellular ELISA incorporating human umbilical vein endothelial cells. ANCA activity was determined by indirect immunofluorescence and radioimmunoassay. Sequential studies were performed on sera from four cases with dual positivity, where autoantibody binding was compared with von Willebrand factor (vWF) concentration and disease activity. IgG AECA were significantly higher in the 27 ANCA-positive sera as compared with normal controls (P = 0.027) with IgG (P = 0.009) and IgA (P = 0.046) AECA isotypes correlating with ANCA positivity; in contrast, no differences were found between AECA levels in the ANCA-negative sera and the normal controls. Cross-inhibition studies pointed to the co-existence of two autoantibody populations. An association between autoantibody binding, disease activity and vWF concentration was found for both ANCA and AECA. Some patients with systemic vasculitis have detectable AECA that recognize different epitopes to ANCA and like ANCA, their titre correlates with disease activity and thus they may have a pathogenetic role in these conditions.

Anti-neutrophil cytoplasm antibodies in patients with monoclonal gammopathies

Anti-neutrophil cytoplasm antibodies (ANCA) are specific markers for systemic vasculitis. In view of the autoreactivity to other autoantigens reported in patients with monoclonal immunoglobulins (MIg), the reactivity of 150 sera from 125 patients with MIg was tested for ANCA by radioimmunoassay (RIA) with inhibition stage and indirect immunofluorescence (IIF). Seven were positive for IgG ANCA, all with IgG MIg and 5 were positive for IgM ANCA, 4 with IgM MIg and 1 with IgG MIg. No IgA ANCA were found. The patterns seen on IIF were identical to those seen with sera from patients with systemic vasculitis and were cytoplasmic in 6 and peri-nuclear in 6. The restriction of the ANCA activity to the MIg was studied in six sera by light chain specific RIA, and anion exchange fractionation of the sera. The ANCA activity appeared to be polyclonal in at least three sera and could be found in the monoclonal fraction in only three patients. Associated autoimmune diseases were found in some of these ANCA positive patients including Sjögren's syndrome, MacDuffie hypocomplementemic vasculitis and rheumatoid polyarthritis but the classical vasculitic features normally associated with ANCA were not observed. We conclude that ANCA is a further autoreactivity present in some sera with MIg and discuss the relation between monoclonal gammopathies and autoimmunity.

Autoantibodies to GBM and neutrophil cytoplasm in rapidly progressive glomerulonephritis

The incidence of autoantibodies to glomerular basement membrane (AGBMA) and neutrophil cytoplasmic antigens (ANCA) in the initial sera of 889 consecutive patients with a suspected diagnosis of rapidly progressive glomerulonephritis, was determined by prospective study. Forty-seven (5%) were positive for AGBMA alone, 246 (28%) were positive for ANCA alone, 576 (65%) had neither autoantibodies while 20 (2%) had both. Clinical and pathological data collected from patients with both autoantibodies suggested the coexistence of anti-glomerular basement membrane disease and systemic vasculitis. Together, assays for AGBMA and ANCA are important in the diagnosis and management of rapidly progressive glomerulonephritis and may help its further classification.

New strategies for plasma exchange in systemic vasculitis

The use of plasma exchange in the treatment of systemic vasculitis has been controversial and poorly defined. Since the discovery of anti-neutrophil cytoplasm antibodies (ANCA) and the demonstration of their specificity for systemic vasculitis, there has been a reassessment of the use of plasma exchange along the same lines as its use in anti-glomerular basement membrane disease. ANCA has also contributed to the diagnosis and classification of rapidly progressive glomerulonephritis, in which there is now firmer evidence to support the use of plasma exchange. Current work into the immunoregulation of ANCA by idiotype/anti-idiotype interactions is leading to new approaches to therapy and plasma exchange alone appears capable of inducing prolonged remission in some patients with vasculitis, possibly through an effect on these interactions.

Severe pulmonary hemorrhage and systemic vasculitis in association with circulating anti-neutrophil cytoplasm antibodies of IgM class only

We report an association of severe pulmonary hemorrhage with circulating autoantibodies to neutrophil cytoplasmic antigens (ANCA) restricted to IgM class in three patients with systemic vasculitis. ANCA were detected by indirect immunofluorescence and isotype specific solid phase radioimmunoassay (SPRIA). Institution of immunosuppressive therapy was accompanied by an isotype switch to IgG ANCA and recovery in all three patients. In an associated study, ANCA activity was found in eluates from the washed glomeruli of two postmortem cases, with the same isotype distribution as was present in the sera.