Expression of recombinant proteinase 3, the autoantigen in Wegener's granulomatosis, in insect cells

Proteinase 3 (PR3) is the major autoantigen for anti-neutrophil cytoplasmic antibodies (ANCA) in patients with Wegener's granulomatosis. Little is known about the major antigenic sites on PR3. To facilitate epitope mapping, PR3 was cloned in insect cells using a baculovirus expression system. Four different sequences of the PR3 cDNA were amplified by PCR: two clones containing the pro-peptide of PR3 with or without a His-tag (rproPR3-his and rproPR3, respectively) and two clones without the pro-peptide and with or without a His-tag (rPR3-his and rPR3, respectively). The PR3 sequences were cloned behind the polyhedrin promoter and the honeybee melittin signal peptide enabling secretion of rPR3. Plasmids were transposed into the genome of baculovirus, and wild types as well as PR3-containing virus genomes were transfected into Sf21 insect cells. All four rPR3 variants were secreted into the medium and were recognized by anti-neutrophil PR3 rabbit serum and by at least two anti-PR3 monoclonal antibodies. Mature forms of PR3 were recognized by almost all patient sera, whereas the pro-forms of PR3 were recognized by 14 of 18 PR3-ANCA sera tested. On SDS-PAGE, the four rPR3 forms migrated at approximately 32 kDa. RPR3-his and rproPR3-his could be purified by means of this His-tag. In conclusion, especially the mature rPR3s are well recognized by PR3-ANCA sera. The presence of a C-terminal His-tag facilitated purification of His-tagged rPR3. Thus, rPR3 expressed in insect cells can be used as a tool for diagnostic tests as well as for epitope mapping studies.

In vitro T lymphocyte responses to proteinase 3 (PR3) and linear peptides of PR3 in patients with Wegener's granulomatosis (WG)

T cell-mediated immunity is thought to play an important role in the pathogenesis of WG. In previous studies a minority of WG patients as well as some healthy controls showed in vitro proliferation of their peripheral blood mononuclear cells (PBMC) to PR3, the main autoantigen in WG. The relevant peptides responsible for this in vitro proliferation have not been identified. In order to define immunogenic peptides, PBMC of 13 WG patients in remission and 10 healthy controls were tested for proliferation to linear peptides of PR3 and to whole PR3. Fifty overlapping peptides spanning the whole PR3 sequence were synthesized. Peptides were tested in pools of five peptides and as single peptide. PBMC of two WG patients and one healthy control proliferated to whole PR3 and to peptide pools. In addition, 10 WG patients and eight healthy controls that did not proliferate to whole PR3 did proliferate to pools of PR3 peptides. Although more WG patients tended to react to particular peptide pools, no significant difference was seen between lymphocyte proliferation to PR3 peptides of WG patients and that of healthy controls. The pools of peptides recognized were mainly located at the N- and C-terminus of PR3. No correlation was observed between HLA type and proliferation on particular peptide pools. No proliferation of PBMC was observed to single peptides. In conclusion, T cells of WG patients proliferate in vitro more frequently to PR3 peptides than to the whole PR3 protein. Peptides derived from the signal sequence, the propeptide or peptides located at the C-terminus of PR3 induce highest levels of proliferation. No specific PR3 sequence could be identified that was preferentially recognized by PBMC of WG patients compared with controls.

Antimyeloperoxidase-associated lung disease. An experimental model

The lung is a common target in systemic vasculitides associated with antineutrophil cytoplasmic antibodies (ANCA). In the present study, we tested the hypothesis that the presence of antibodies directed against myeloperoxidase (MPO) induces pulmonary (vasculitic) lesions when neutrophils release lysosomal enzymes. Brown Norway (BN) rats were immunized with human MPO in complete Freund's adjuvant (CFA) or with CFA alone. Two weeks after immunization, rats had developed antibodies to human and rat MPO. Next, isolated single left lung perfusion was performed with human neutrophil lysosomal extract containing MPO and proteolytic enzymes. Rats were killed at 15 min, 4 h, and 10 d after perfusion. Tissue samples from the left and right lung were examined for vasculitic lesions and inflammatory cell infiltrates. At 15 min and 4 h, left lungs from control and MPO-immunized rats showed a mild influx of polymorphonuclear cells. At 10 d, patchy inflammatory cell infiltrates, consisting predominantly of polymorphonuclear leukocytes (PMNs) and monocytes, were observed throughout the parenchyma of the left lung in MPO-immunized rats. Occasionally, granuloma-like lesions, giant cells, and foci of alveolar hemorrhage were observed as well. Far less severe lesions were seen in control immunized rats. Strikingly, at 10 d after perfusion, severe pulmonary tissue injury was observed also in right lungs from MPO-immunized rats whereas right lungs from control immunized rats appeared normal. The lesions were characterized by influx of PMNs and monocytes and, in some rats, foci of alveolar hemorrhage. These studies suggest that the presence of an anti-MPO directed autoimmune response contributes to generalized pulmonary tissue injury after local release of products of activated neutrophils, which supports a pathogenic role of MPO-ANCA.

In vitro neutrophil activation by antibodies to proteinase 3 and myeloperoxidase from patients with crescentic glomerulonephritis

Previously, it was found that patients with necrotizing crescentic glomerulonephritis (NCGN) and anti-neutrophil cytoplasmic autoantibodies (ANCA) directed against proteinase 3 (anti-PR3) had a faster deterioration of renal function and more active renal vasculitic lesions than patients with ANCA directed against myeloperoxidase (anti-MPO). Because ANCA-mediated neutrophil activation is thought to play an important role in the pathophysiology of this form of glomerulonephritis, this study was conducted to determine whether anti-PR3 are capable of inducing a more pronounced activation of neutrophils in vitro than anti-MPO. To test this hypothesis, the release of reactive oxygen radicals, as assessed by ferricytochrome c reduction and by dihydrorhodamine 123 oxidation, and the release of granule constituents from healthy donor neutrophils upon stimulation with IgG fractions were measured from 17 anti-PR3- and 14 anti-MPO-positive patients with active NCGN. Patients with anti-PR3 had a higher renal activity index (P < 0.05) compared with patients with anti-MPO. IgG fractions from anti-PR3-positive patients induced more oxygen radical release from tumor necrosis factor-alpha-primed neutrophils compared with IgG fractions from anti-MPO-positive patients, as assessed by ferricytochrome c reduction (P < 0.05) and dihydrorhodamine 123 oxidation (P < 0.01). In addition, IgG fractions from anti-PR3-positive patients generated more neutrophil degranulation of beta-glucuronidase (P < 0.01) than IgG fractions from anti-MPO-positive patients. In conclusion, IgG fractions from anti-PR3-positive patients with NCGN are more potent activators of the respiratory burst and degranulation in vitro than IgG fractions from anti-MPO-positive patients. These observations may be relevant in view of the clinical differences between anti-PR3- and anti-MPO-positive patients with NCGN.

Expression of iNOS, eNOS, and peroxynitrite-modified proteins in experimental anti-myeloperoxidase associated crescentic glomerulonephritis

Nitric oxide radicals are recognized as important mediators in various physiological and pathophysiological processes. During inflammation, increased amounts of nitric oxide (NO) are produced, but it is unclear whether NO radicals are either protective or harmful. To obtain more insight into the role of NO in glomerular inflammation, we studied the temporal expression of endothelial NO synthase (eNOS) and inducible NOS (iNOS) in conjunction with platelet aggregation, inflammatory cell influx, superoxide anion production cells, and nitrotyrosine formation in an experimental model of anti-myeloperoxidase (MPO) associated necrotizing crescentic glomerulonephritis (NCGN). Brown Norway rats were immunized with MPO in complete Freund's adjuvant (CFA) or CFA alone. After two weeks, the left kidney was perfused with a neutrophil lysosomal extract and H2O2. Rats were sacrificed at 24 hours, four days, and 10 days after perfusion. Kidney sections were stained by immunohistochemistry for eNOS, iNOS, platelets, nitrotyrosines, polymorphonuclear cells (PMN), monocytes, and T-cells. Superoxide anion producing cells were identified by enzyme cytochemistry using diaminobenzidine. Strong staining for eNOS was found in glomerular capillaries and interstitial tubular capillaries and larger vessels from non-perfused kidneys. At 24 hours after perfusion, glomerular and interstitial eNOS staining was greatly reduced, which was associated with massive platelet aggregation. At later time points, eNOS expression was absent in severely damaged glomeruli. Inducible NOS expression was found at all time points in infiltrating inflammatory cells, which by double labeling studies were identified as PMNs and monocytes. The peak in iNOS expression was observed at four days after perfusion but declined thereafter. Superoxide anion and nitrotyrosine generating cells were also found at all time points, but were most abundantly present at four days after perfusion, coinciding with the peak in iNOS expression. Double labeling experiments revealed that most nitrotyrosine generating cells also produced superoxide anions and expressed iNOS. In conclusion, these studies suggest that during the course of anti-MPO associated NCGN, loss of NO production by eNOS in conjunction with NO radical production by iNOS contribute to tissue injury. This is compatible with a protective role for eNOS contrasting with the possibly harmful effects of iNOS in anti-MPO associated NCGN.

Recombinant proteinase 3 (Wegener's antigen) expressed in Pichia pastoris is functionally active and is recognized by patient sera

The open reading frame of human proteinase 3 (PR3) without the prepro-peptide was cloned and expressed in Escherichia coli (rcPR3) and in Pichia pastoris (rpPR3). The 6-histidine tagged rpPR3 was efficiently secreted into culture supernatant from which it could be purified by immobilized metal chelate chromatography. Purified rpPR3 migrated as a single 32-kD band on SDS-PAGE and harboured protease activity that could be inhibited with inhibitors specific for serine-proteases. By indirect antigen-capture ELISA using rpPR3, 60% of sera from patients with Wegener's granulomatosis bound to the recombinant product, although it was not recognized in ELISA with directly coated rpPR3.

Systemic injection of products of activated neutrophils and H2O2 in myeloperoxidase-immunized rats leads to necrotizing vasculitis in the lungs and gut

The strong association of anti-neutrophil cytoplasmic antibodies with various forms of systemic vasculitis suggests a role for these autoantibodies in the pathophysiology of systemic vasculitis. In the present study, we tested the hypothesis that release of neutrophil lysosomal enzymes in the presence of an anti-myeloperoxidase (anti-MPO) immune response may underlie the development of systemic vasculitis. Brown Norway rats were immunized with MPO in complete Freund's adjuvant or complete Freund's adjuvant alone. Two weeks after immunization, rats bad developed antibodies to human and rat MPO as measured by enzyme-linked immunosorbent assay. Next, rats were intravenously infused with 400 micrograms of a human neutrophil lysosomal extract containing 200 micrograms of MPO followed by 0.5 ml of a 1 mmol/L solution of H2O2 through a cannula inserted into the right jugular vein. Rats were sacrificed at 4 hours, 24 hours, 7 days, or 14 days, and several organs (lungs, heart, liver, spleen, gut, and kidneys) were examined for vasculitic lesions and inflammatory cell infiltrates. Macroscopically, patchy hemorrhagic spots were observed in the lungs and gut of MPO-immunized rats at days 7 and 14 after systemic infection of the neutrophil lysosomal extract and H2O2. Such changes were not observed at earlier time points or in control immunized rats. Histologically, the lungs of MPO-immunized rats sacrificed at days 7 and 14 showed patchy inflammatory cell infiltrates associated with vasculitis, granuloma formation, giant cells, and foci of hemorrhage. At 14 days, early signs of fibrosis were found with deposition of collagen and proliferation of fibroblasts. Furthermore, a prominent leukocytoclastic vasculitis was found in the small intestine of these rats characterized by fibrinoid necrosis and an extensive neutrophilic infiltrate. No inflammatory changes were found in the other organs studied (heart, liver, spleen, and kidneys). Control immunized rats, sacrificed at days 7 and 14 showed only some small foci of inflammatory infiltrates in the lungs whereas no inflammatory changes were found in the gastrointestinal tract. These studies show that release of products from activated neutrophils in the presence of anti-MPO autoantibodies may be relevant to the pathogenesis of anti-MPO-associated vasculitides.

Autoantibodies to myeloperoxidase aggravate mild anti-glomerular-basement-membrane-mediated glomerular injury in the rat

Autoantibodies to myeloperoxidase (MPO) are present in sera from patients with various forms of vasculitis-associated glomerulonephritis. Evidence for a pathogenic role of anti-MPO antibodies has been provided mainly by in vitro studies. We studied the pathogenic role of autoantibodies to MPO in a rat model of mild immune-mediated glomerular injury. Brown Norway rats were immunized with human MPO in complete Freund's adjuvant or with complete Freund's adjuvant alone. At 2 weeks after immunization, rats had developed antibodies to human and rat MPO as detected by indirect immunofluorescence, enzyme-linked immunosorbent assay, and immunoprecipitation. At this time point, rats were intravenously injected with a subnephritogenic dose of 150 micrograms of rabbit anti-rat GBM. Rats were sacrificed at 4 hours, 24 hours, 4 days, and 10 days after antibody administration. Control immunized rats developed mild glomerulonephritis characterized by slight proteinuria at day 10 (14.8 +/- 8.1 mg/24 hours) and moderate intraglomerular accumulation of ED1+ macrophages. Crescent formation, tuft necrosis, and tubular atrophy were not observed in those rats. In contrast, rats immunized with MPO developed severe glomerulonephritis characterized by the early occurrence of severe hematuria, marked proteinuria at day 10 (76.2 +/- 18.2 mg/24 hours), and massive glomerular deposition of fibrin. Complement and rat IgG were present in insudative lesions, but no linear pattern along the glomerular capillary wall was observed. By light microscopy, severe glomerular lesions were found at day 10 consisting of crescent formation and fibrinoid necrosis of capillary loops. In the interstitium, tubular necrosis and atrophy and marked interstitial mononuclear infiltration were found in conclusion, autoantibodies to MPO severely aggravate subclinical anti-GBM disease demonstrating their in vivo pathogenic potential.

Elastase, but not proteinase 3 (PR3), induces proteinuria associated with loss of glomerular basement membrane heparan sulphate after in vivo renal perfusion in rats

Elastase, but not PR3, induces proteinuria associated with loss of glomerular basement membrane (GBM) heparan sulphate after in vivo renal perfusion in rats. PR3 and elastase are cationic neutral serine proteinases present in the azurophilic granules of polymorphonuclear leucocytes. Release of these proteolytic enzymes along the glomerular capillary wall may induce glomerular injury. Here, we investigated the effects of PR3 and elastase on the induction of proteinuria and glomerular injury after renal perfusion of these enzymes in Brown-Norway rats. Perfusion of active elastase induced a dose-dependent proteinuria 24h after perfusion, while inactivated elastase did not. Perfusion of comparable amounts of active PR3 did not induce proteinuria. Light and electron microscopy showed no morphological abnormalities in any experimental group. However, immunohistology revealed that proteinuria occurring after perfusion of active elastase was associated with a strong reduction in intraglomerular expression of the heparan sulphate side chain and, to a lesser extent, of the protein core of heparan sulphate proteoglycans (HSPG). In vitro, both elastase and PR3 digested HSPG. However, PR3 bound to a lesser extent to HSPG than elastase. We conclude that elastase, but not PR3, induces proteinuria after in vivo renal perfusion. This differential effect probably relates to different binding to the GBM of those enzymes due to differences in their isoelectric points. Degradation of heparan sulfate proteoglycans, leading to the disappearance of their side chains that contribute to the polyanionic structure of the GBM, appears to be involved in the induction of proteinuria after perfusion of elastase.

Antineutrophil cytoplasmic antibodies in systemic lupus erythematosus

Antineutrophil cytoplasmic antibodies (ANCA) with specificity for proteinase-3 (PR3) are associated with Wegener's granulomatosis, and ANCA directed to myeloperoxidase (MPO) with other idiopathic vasculitides. Inflammation of small-sized blood vessels is a hallmark of systemic lupus erythematosus (SLE). We evaluated the prevalence of ANCA in SLE, their antigenic specificities, and their possible relation to clinical disease patterns and activity. Plasma samples from 84 patients with SLE were tested for ANCA during remission. Plasma samples from the 25 patients who relapsed during a follow-up of 32 months were serially analysed for ANCA in a 6 month period preceding and including the relapse. The presence of ANCA was assessed by indirect immunofluorescence (IIF) and ELISA for antibodies to PR3, MPO, lactoferrin (LF), elastase (HLE) and cathepsin-G (CG). We related the presence of ANCA to disease patterns, activity and duration. ANCA by IIF were difficult to interpret dut to the presence of antinuclear antibodies (ANA). By ELISA, we found no anti-PR3 or anti-HLE. Anti-MPO (n = 7), anti-LF (n = 13) and anti-CG (n = 10) were detected, generally in low titres. The presence of ANCA of defined specificity was not associated with specific clinical subsets. The prevalence of ANCA was higher in patients who developed relapses than in those who did not (P < 0.01). However, levels of ANCA did not fluctuate in the period preceding the relapse. ANCA of various specificities occur in SLE. Their presence is not associated with specific clinical disease entities. The higher frequency of ANCA in relapsing patients compared to those who do not relapse may suggest that ANCA are involved in disease expression. Their diagnostic significance is limited.

Renal ischemia/reperfusion injury contributes to renal damage in experimental anti-myeloperoxidase-associated proliferative glomerulonephritis

The occurrence of focal fibrinoid necrosis of capillary loops in the very early stages of ANCA-associated necrotizing crescentic glomerulonephritis (NCGN) and the increased prevalence of this disease at older age suggest that renal ischemia may play an additional role in its pathophysiology. In the present study we investigated the contribution of renal ischemia to the induction of anti-myeloperoxidase (MPO) associated NCGN in a previously described rat model of this disease. The development of renal lesions is dependent on the presence of an anti-MPO immune response and the localization of a lysosomal extract containing lytic enzymes and MPO in combination with hydrogen peroxide (H2O2) along the glomerular basement membrane (GBM). The hypothesis tested whether perfusion of hydrogen peroxide (H2O2) could be replaced by ischemia/reperfusion (I/R) injury, as I/R injury activates endothelial cells to produce oxygen metabolites. I/R was induced by clamping the renal artery for 20 minutes in kidneys in which the circulation had been restored several minutes after perfusion with the lysosomal extract in MPO immunized rats. Rats developed lesions characterized by intra- and extracapillary cell proliferation, periglomerular infiltration, ruptures in Bowman's capsule, ischemic tubuli, and interstitial mononuclear infiltrate. Immune deposits, however, persisted for a longer time along the GBM after perfusion of lytic enzymes followed by I/R injury compared to previous studies in which H2O2 in conjunction with lytic enzymes were perfused in MPO-immunized rats.(ABSTRACT TRUNCATED AT 250 WORDS)

T cell reactivity to proteinase 3 and myeloperoxidase in patients with Wegener's granulomatosis (WG)

T cell-mediated immunity is hypothesized to play an important role in the pathogenesis of granulomatous inflammation and vasculitis as found in patients with WG. The antigenic specificities of those T cells remain, however, unknown. Anti-neutrophil cytoplasmic antibodies (ANCA) present in patients with WG are directed to proteinase 3 (PR3) and myeloperoxidase (MPO). In the present study we investigated the proliferative capacity of peripheral blood mononuclear cells (PBMC) from patients with WG and age- and sex-matched controls in response to the WG autoantigens PR3 and MPO. Possible mitogenic effects of active PR3 and toxic effects of active MPO were excluded by using heat-inactivated PR3 and MPO. Antigen-specific stimulation induced by these autoantigens was studied by using processed PR3 and MPO in the lymphocyte stimulation test (LST). Proliferation induced by processed antigen correlated with that by heat-inactivated free antigen. The general capacity to proliferate in response to mitogens and recall antigens did not differ between patients and controls. However, patients with WG who were or had been positive for PR3-ANCA (n = 17) responded more strongly to PR3 than to MPO and showed higher responses to PR3 compared with controls (n = 13). Within the PR3-ANCA group T cell proliferation did not correlate with ANCA titre. In a small group of patients with MPO-ANCA (n = 5) no differences were observed compared with controls for MPO-specific proliferation. The data presented demonstrate that autoreactive PR3-specific T cells are present in patients with WG. Their fine specificity and possible role in the pathogenesis of WG have to be defined in further studies.

Levels of soluble VCAM-1, soluble ICAM-1, and soluble E-selectin during disease exacerbations in patients with systemic lupus erythematosus (SLE); a long term prospective study

Active SLE is characterized by immune deposits and subsequent vascular inflammation in many organs. Expression and up-regulation of adhesion molecules is basic to migration of inflammatory cells into the tissues. Recently, soluble isoforms of these molecules have been described which might be an expression of their up-regulation in the tissues and, as such, of disease activity. The purpose of this study was to evaluate whether changes in levels of soluble adhesion molecules reflect disease activity. We analysed serial sera in a 6-month period preceding 22 consecutive exacerbations of SLE for levels of soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble intercellular adhesion molecule-1 (sICAM-1), and sE-selectin. Levels were related to clinical disease activity (SLEDAI), and levels of anti-dsDNA and complement. At the time of maximal disease activity, levels of sVCAM-1 in patients with SLE were higher than those in controls (P < 0.0001), levels in patients with renal involvement being higher than in those without (P < 0.02). Levels of sVCAM-1 correlated with SLEDAI scores (P < 0.05) and, inversely, with levels of C3 (P = 0.01). In addition, in the presence of anti-dsDNA, levels of sVCAM-1 tended to correlate with levels of these autoantibodies (P < 0.1). Levels of sICAM-1 were normal and sE-selectin levels even decreased compared with controls. Levels of sVCAM-1 were higher at the moment of relapse (P = 0.001) than at 6 months before this time point. This rise correlated with the rise in SLEDAI score (P < 0.02). Levels of sICAM-1 and sE-selectin did not rise, and remained in the normal range in all exacerbations studied. In conclusion, in contrast to sICAM-1 and sE-selectin, levels of sVCAM-1 are increased, rise parallel to disease activity during exacerbations in SLE, and are associated with decreasing levels of complement factors. This favours the hypothesis of immune deposit formation, activation of the complement cascade and activation of endothelial cells. Concurrent up-regulation of vascular adhesion molecules may thus result in transmigration of activated inflammatory cells inducing tissue damage.

Serum levels of soluble adhesion molecules intercellular adhesion molecule 1, vascular cell adhesion molecule 1, and E-selectin in patients with Wegener's granulomatosis. Relationship to disease activity and relevance during followup

OBJECTIVE

To assess the value of measuring serum levels of soluble intercellular adhesion molecule 1 (sICAM-1), soluble vascular cell adhesion molecule 1 (sVCAMP-1), and soluble E-selectin for monitoring disease activity in Wegener's granulomatosis (WG).

METHODS

A sandwich enzyme-linked immunosorbent assay was used to measure levels of soluble adhesion molecules at the time of diagnosis in 22 consecutive patients with WG, in 12 WG patients studied serially prior to disease relapse, at the time of upper airways infection in 18 patients with inactive WG, and in 57 controls. Disease activity was assessed by disease activity score and C-reactive protein levels.

RESULTS

At diagnosis of WG, sICAM-1 and sVCAM-1 levels were significantly elevated and correlated with disease activity. At the time of relapse, a significant increase in all 3 soluble adhesion molecules was found compared with levels at 6 months prior to relapse, but only sVCAM-1 levels were significantly elevated compared with those in controls. Levels of soluble adhesion molecules at the time of relapse did not differ from those measured during an upper airways infection without disease activity.

CONCLUSION

Elevated serum levels of sICAM-1 and sVCAM-1 can be found in active WG and correlate with disease activity. However, their clinical relevance for followup is limited due to lack of sensitivity and specificity for WG disease activity.

Changes in levels of soluble T-cell activation markers, sIL-2R, sCD4 and sCD8, in relation to disease exacerbations in patients with systemic lupus erythematosus: a prospective study

OBJECTIVES

To assess serial activation of T-cell subsets in relation to auto-antibody production and the occurrence of disease exacerbations in patients with systemic lupus erythematosus (SLE).

METHODS

To study the possible role of T-cells in the pathophysiology of the disease, 16 consecutive exacerbations were prospectively studied in a cohort of patients with SLE, and serial plasma levels of sIL-2R, sCD4, and sCD8 preceding and during these exacerbations were determined. Levels of these molecules were related to total IgM and IgG, and anti-dsDNA.

RESULTS

During major disease exacerbations (n = 6), levels of sIL-2R increased significantly (p < 0.001). Levels of sCD4 were predominantly in the normal range, whereas levels of sCD8 were frequently increased. No change in levels of both molecules could be detected in the period before the exacerbation. During minor exacerbations (n = 10), levels of sIL-2R remained stable. Levels of sCD4, however, tended to drop, whereas levels of sCD8 tended to rise. No correlations were found between sIL-2R, sCD4 or sCD8 on the one hand, and total IgM, IgG, or anti-dsDNA on the other.

CONCLUSIONS

Levels of sIL-2R are increased, and rise before major exacerbations of SLE. Levels of sCD4 and sCD8, however, are not related to levels of sIL-2R, and do not reflect B-cell activation, nor disease activity during exacerbations of SLE. Thus for the clinical follow up of SLE measurement of levels of sCD4 or sCD8 is of limited value.

Neutrophil activation in vitro and in vivo in Wegener's granulomatosis

The mechanisms underlying glomerular capillary wall injury in Wegener's granulomatosis (WG) are not well understood. Anti-neutrophil cytoplasmic antibodies (ANCA), present in sera from patients with WG, are known to stimulate respiratory burst and degranulation of primed polymorphonuclear neutrophils (PMN) in vitro. Experimental studies have shown that oxygen radical production and lysosomal enzymes are important mediators of glomerular capillary wall injury. In the present study we investigated the presence of activated PMN and the extracellular localization of lysosomal enzymes in 28 consecutive renal biopsies from patients with WG. The presence of activated PMN within the renal biopsies was compared with the capacity of ANCA, isolated from simultaneously drawn serum samples, to activate primed PMN obtained from a normal donor. Both parameters were also related to renal function. Renal biopsies were obtained from newly diagnosed WG patients before therapy had started. Activation of PMN in the biopsies was assessed by measuring hydrogen peroxide production in situ. The number of activated PMN in the biopsy correlated with the extent of impairment of renal function. Proteinase 3, myeloperoxidase, and elastase, all targets of ANCA, were localized extracellularly in renal tissue and were also found within tubular epithelial cells. All ANCA positive samples were capable of activating primed PMN. The amount of activation correlated with the ANCA titer in those samples. No correlation, however, was found between the in vitro capacity of ANCA-positive IgG fractions to activate primed PMN and the number of activated PMN present in the renal biopsy. We conclude that activated PMN producing toxic oxygen metabolites and releasing lysosomal enzymes, are present in renal biopsies from patients with WG. The amount of activated PMN present within the kidney, and not the capacity of the corresponding ANCA to activate PMN, correlates with renal tissue damage as assessed by serum creatinine levels.

Antimyeloperoxidase-associated proliferative glomerulonephritis: an animal model

To develop an animal model for antimyeloperoxidase (MPO)-associated necrotizing crescentic glomerulonephritis (NCGN), we immunized Brown Norway rats with MPO and localized a neutrophil lysosomal enzyme extract, primarily consisting of MPO and elastinolytic enzymes, plus H2O2, the substrate of MPO, to the glomerular basement membrane (GBM). Upon immunization rats developed antibodies and positive skin tests to MPO. After unilateral perfusion of the left kidney with the lysosomal enzyme extract and H2O2, MPO and immunoglobulin (Ig)G localized transiently along the GMB. At the time of maximal inflammation, at 4 and 10 d after perfusion, MPO, IgG, and C3 could not be detected anymore. MPO-immunized rats perfused with the lysosomal enzyme extract and H2O2, in contrast to control-immunized and/or control-perfused rats, developed a proliferative GN characterized by intra- and extracapillary cell proliferation, ruptured Bowman's capsule, periglomerular granulomatous inflammation, and formation of giant cells. Monocytes, polymorphonuclear leukocytes (PMN), and to a far lesser extent T cells were found in the glomeruli. Interstitial infiltrates consisted of monocytes, PMN, and T cells. Granulomatous vasculitis of small vessels was found at 10 d after perfusion. The proliferative NCGN in this rat model closely resembles human anti-MPO-associated pauci-immune NCGN, and enables the study of the pathophysiology of anti-MPO-associated NCGN.

Serum markers of T cell activation in relapses of Wegener's granulomatosis

Levels of soluble IL-2 receptor (sIL-2R), soluble CD4 (sCD4) and CD8 (sCD8) were measured by sandwich ELISA as markers for T cell activation in serial serum samples from 16 patients showing 18 histologically proven relapses of Wegener's granulomatosis (WG). Levels of sIL-2R increased from 1065 U/ml (median, range 373-2345 U/ml) 6 months before the relapse to 1684 U/ml (median, range 486-3404 U/ml) at the moment of relapse for the whole group (P = 0.10). The eight major relapses showed a profound rise in sIL-2R levels, from 1008 U/ml (median, range 686-1553 U/ml) 6 months before the relapse, to 1994 U/ml (median, range 1469-3404 U/ml) at the moment of relapse (P < 0.01). The levels of sIL-2R at the moment of relapse were significantly higher at the eight major relapses than at the time of the 10 minor relapses (P < 0.05). Minor relapses were not accompanied by a significant rise in sIL-2R levels. Titres of antineutrophil cytoplasmic antibodies (ANCA) rose by two or more titresteps or from negative to positive in 15/18 patients during the 6 months period before the relapse. In all seven cases with both a rise of the ANCA titre and an at least 25% increase in sIL-2R levels, the rise in ANCA preceded the rise in sIL-2R by at least 1 month. The level of sIL-2R at the moment of relapse correlated with the level of C-reactive protein (r = 0.488, P < 0.05) and with the disease activity score (r = 0.824, P < 0.002). There were no significant changes in levels of sCD4 or sCD8, although the levels of sCD4 tended to be higher at the time of major relapses. We conclude that major relapses of Wegener's granulomatosis are accompanied by systemic T cell activation. T cell activation, however, does not appear to precede the rise in ANCA titre.

Induction of an humoral and cellular (auto) immune response to human and rat myeloperoxidase(MPO) in Brown-Norway(BN), Lewis and Wistar Kyoto(WKY) rat strains

Anti-MPO and anti-proteinase 3 antibodies are strongly associated with certain forms of vasculitis and glomerulonephritis and a pathophysiological role for the antibodies has been hypothesized (Kallenberg et al. 1991). To test this hypothesis WKY, Lewis and BN rats were immunized with human MPO. BN rats developed a strong humoral response, cross reacting with autologous MPO, and Lewis rats a strong cellular response to human MPO.

Serum markers of T-cell activation in relapses of Wegener's granulomatosis

Levels of soluble IL-2 receptor (sIL-2R), soluble CD4 (sCD4) and CD8 (sCD8) were measured by sandwich ELISA as markers for T-cell activation in serial serum samples drawn monthly from 16 patients showing 18 histologically proven relapses of Wegener's granulomatosis (WG). Levels of sIL-2R increased from 1162 U/ml (median, 95% CI 843 to 1814 U/ml) at three months before the relapse to 1684 U/ml (95% CI 1254 to 2202 U/ml) at the time of relapse for the whole group (P = 0.10). The 8 major relapses showed a profound rise in sIL-2R levels (P < 0.01). The level of sIL-2R at the moment of relapse correlated with the level of C-reactive protein (r = 0.547, P < 0.05) and with the disease activity score (r = 0.814, P < 0.001). There were no significant changes in levels of sCD4 or sCD8.

Detection of autoantibodies against myeloid lysosomal enzymes: a useful adjunct to classification of patients with biopsy-proven necrotizing arteritis

PURPOSE

Assessment of the value of determination of antineutrophil cytoplasmic antibodies (ANCA) and its specificities for classification of patients with biopsy-proven necrotizing arteritis.

PATIENTS AND METHODS

The serum samples of 28 consecutive patients with biopsy-proven vasculitis involving medium- and/or small-sized arteries were tested for ANCA by an indirect immunofluorescence technique, by neutrophil extract enzyme-linked immunosorbent assay (ELISA), and by catching ELISA.

RESULTS

Eight patients had Churg-Strauss syndrome; six had myeloperoxidase (MPO) antibodies, and in the other two patients, ANCA were not detected. Six patients had polyarteritis nodosa (PAN) limited to the skin and the musculoskeletal system; ANCA were not detected in these patients. Two patients had systemic PAN and both had MPO antibodies. The remaining 12 patients had overlapping clinical features of the different forms of vasculitis. Five patients had polyarteritis in combination with chronic nasal inflammation and glomerulonephritis compatible with Wegener's granulomatosis (WG) but without granulomas in the respiratory tract. All five patients had 29-kd serine protease antibodies. Two patients had polyarteritis in combination with nasal polyposis and asthma compatible with Churg-Strauss syndrome, but eosinophilia was not detected. Both patients had MPO antibodies. Three patients with unclassified granulomatous arteritis had either elastase antibodies or ANCA of unknown specificity. One patient with unclassified systemic vasculitis had 29-kd serine protease antibodies, and one patient with necrotizing arteritis of the bowel in combination with Schönlein-Henoch purpura was negative for ANCA.

CONCLUSION

Determination of ANCA and its specificities is a useful adjunct to the classification of patients with biopsy-proven necrotizing arteritis. Within the spectrum of idiopathic vasculitides, 29-kd serine protease antibodies are associated with WG, MPO antibodies are associated with Churg-Strauss syndrome and systemic PAN, and PAN limited to the skin and the musculoskeletal system is not associated with ANCA.

Predominance of IgG1 and IgG4 subclasses of anti-neutrophil cytoplasmic autoantibodies (ANCA) in patients with Wegener's granulomatosis and clinically related disorders

In view of the supposed hypersensitivity, the elevated levels of IgE, and the occurrence of eosinophilia reported in Wegener's granulomatosis and related conditions, we studied the IgG subclass distribution of ANCA directed against a 29-kD serine protease and myeloperoxidase (MPO) in 41 untreated ANCA-positive patients with several forms of active vasculitis and/or glomerulonephritis. We found that both 29-kD ANCA and MPO ANCA were predominantly of the IgG1 and IgG4 subclass in all groups of patients. The additional presence of IgG3 subclass was associated with renal involvement. We compared the subclass distribution of ANCA with that of total IgG subclass levels, and with the IgG subclass distribution of antibodies to cytomegalovirus (CMV) as a persistent endogenous antigen and antibodies to tetanus toxoid (TT) as an exogenous recall antigen. Total levels of IgG4 were elevated in the majority of the patients together with elevated IgG1 levels. Antibodies to CMV and TT, however, had the same subclass distribution as found in normals and did not show enhanced IgG4 expression. ANCA belong predominantly to the IgG1 and IgG4 subclass, which may suggest that the production of ANCA is related to recurrent exposition to the antigen(s) involved, possibly as part of a hypersensitivity reaction.

Prevention of relapses in Wegener's granulomatosis by treatment based on antineutrophil cytoplasmic antibody titre

58 patients with biopsy-proven Wegener's granulomatosis (WG) were prospectively screened for clinical evidence of the disease 3-monthly, with antineutrophil cytoplasmic antibody (ANCA) measurements every month. Over 24 months, ANCA rose in 20 patients, 9 of whom were randomly assigned to receive combined 9 and 3 month courses of cyclophosphamide and prednisolone, respectively, at the time of ANCA rise; and 11 patients who were untreated except if there was a clinical relapse. 6 of 11 untreated patients relapsed within 3 months of ANCA rise. 3 of the remaining 5 patients relapsed after 3 months. There were no early or late relapses in patients randomised to treatment. Patients receiving no treatment at the time of ANCA rise took more cyclophosphamide and prednisolone than patients who were treated. Side-effects did not significantly differ between the two groups.

Association of autoantibodies to myeloperoxidase with different forms of vasculitis

Antineutrophil cytoplasmic autoantibodies with specificity for myeloperoxidase (MPO) were found in 53 patient sera that were routinely submitted for antineutrophil cytoplasmic antibody determination. Based on clinical and histologic criteria, 15 of these 53 patients were classified as having systemic necrotizing vasculitis of the polyarteritis group, 11 patients were classified as having Wegener's granulomatosis (WG), and 14 were classified as having idiopathic crescentic glomerulonephritis. The remaining 13 patients did not fulfill the diagnostic criteria for these disorders, although most of these patients had clinical symptoms compatible with these disorders. While all patients with WG had renal involvement, only 4 of the 15 patients with systemic necrotizing vasculitis of the polyarteritis group had glomerulonephritis. The sensitivity of autoantibodies to MPO for either systemic necrotizing vasculitis of the polyarteritis group, WG, or idiopathic crescentic glomerulonephritis was further tested in all our patients with these disorders (n = 104). Twenty-seven of 104 patients had autoantibodies to MPO. Furthermore, 69 of the remaining 77 patients had autoantibodies specific for the 29-kd serine protease, which has been reported to be specifically associated with WG. Sera from 8 patients were negative for either of these antibodies (92% sensitivity of autoantibodies to MPO and/or the 29-kd serine protease). The specificity of autoantibodies to MPO for either systemic necrotizing vasculitis of the polyarteritis group, WG, or idiopathic crescentic glomerulonephritis was also tested in selected groups of patients who had closely related diseases. Two of 144 patients had autoantibodies to MPO (specificity 99%).(ABSTRACT TRUNCATED AT 250 WORDS)