New findings in pathogenesis of antineutrophil cytoplasm antibody-associated vasculitis

Giant Cell Arteritis (GCA): Pathogenesis, Clinical Aspects and Treatment Approaches

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Giant Cell Arteritis (GCA), or Horton’s Arteritis, is a chronic form of vasculitis of the large and medium vessels, especially involving the extracranial branches of the carotid arteries, in particular, the temporal artery, with the involvement of the axillary, femoral and iliac arteries too. Arterial wall inflammation leads to luminal occlusion and tissue ischemia, which is responsible for the clinical manifestations of the disease.

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A substantial number of patients affected by GCA present head and neck symptoms, including ocular, neurological and otorhinolaryngological manifestations.

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The aim of this article is to present pathogenesis, clinical aspects and treatment approaches of GCA manifestations.

PR1 peptide vaccine induces specific immunity with clinical responses in myeloid malignancies

PR1, an HLA-A2-restricted peptide derived from both proteinase 3 and neutrophil elastase, is recognized on myeloid leukemia cells by cytotoxic T lymphocytes (CTL) that preferentially kill leukemia and contribute to cytogenetic remission. To evaluate safety, immunogenicity and clinical activity of PR1 vaccination, a phase I/II trial was conducted. Sixty-six HLA-A2+ patients with acute myeloid leukemia (AML: 42), chronic myeloid leukemia (CML: 13) or myelodysplastic syndrome (MDS: 11) received three to six PR1 peptide vaccinations, administered subcutaneously every 3 weeks at dose levels of 0.25, 0.5 or 1.0 mg. Patients were randomized to the 3 dose levels after establishing the safety of the highest dose level. Primary endpoints were safety and immune response, assessed by doubling of PR1/HLA-A2 tetramer-specific CTL, and the secondary endpoint was clinical response. Immune responses were noted in 35 of 66 (53%) patients. Of the 53 evaluable patients with active disease, 12 (24%) had objective clinical responses (complete: 8, partial: 1 and hematological improvement: 3). PR1-specific immune response was seen in 9 of 25 clinical responders vs. 3 of 28 clinical non-responders (p=0.03). In conclusion, PR1 peptide vaccine induces specific immunity that correlates with clinical responses, including molecular remission, in AML, CML and MDS patients.

Granulomatosis with polyangiitis involves sustained mucosal inflammation that is rich in B-cell survival factors and autoantigen

OBJECTIVE

Granulomatosis with polyangiitis (GPA) is a rare chronic autoimmune disease that may be triggered by upper airway infection. ANCAs specific for PR3 that is expressed by activated neutrophils and macrophages are associated with GPA. Our aim was to investigate regional immune mechanisms that might induce or support the autoimmune response in GPA.

METHODS

Biopsy samples from 77 patients including 8 with GPA were studied by immunohistochemistry. B-cell homing subsets in blood samples from 16 patients with GPA and 11 healthy controls were studied by FACS. The distribution of B-cell clones was searched in paired biopsies and blood samples from one patient by analysing immunoglobulin heavy chain gene (IGH) junctional sequences.

RESULTS

Activated B cells were located alongside PR3-expressing cells and B-cell survival factors BAFF and APRIL in mucosa from patients with GPA. We detected APRIL production by the granulomas and giant cells. B cells were proliferating in all cases and persistent for 5 years in biopsies obtained from one patient. However, there was no evidence of B-cell clones from the mucosal biopsies circulating in peripheral blood in GPA or any numerical or proportional change in B-cell subsets expressing markers of regional homing in blood in GPA.

CONCLUSIONS

Our study illustrates chronically activated B cells alongside autoantigens and B-cell survival factors in the mucosa in GPA.

PTU-induced ANCA-positive vasculitis: an innocent or a life-threatening adverse effect?

Antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitides are rare, but they can be triggered by chemicals, infections and drugs; among them, antithyroid drugs are common. Autoimmune disorders, such as vasculitis, are unusual, but serious complications of antithyroid therapy. Both propylthiouracil (PTU) and methimazole may induce ANCA-associated vasculitis. PTU-induced vasculitides may have different organ involvement patterns. Herein, we report four cases with ANCA-associated vasculitis with different clinical manifestations.

Discrimination and variable impact of ANCA binding to different surface epitopes on proteinase 3, the Wegener's autoantigen

Proteinase 3 (PR3)-specific antineutrophil cytoplasmic antibodies (ANCA) are highly specific for the autoimmune small vessel vasculitis, Wegener's granulomatosis (WG). PR3-ANCA have proven diagnostic value but their pathogenic potential and utility as a biomarker for disease activity remain unclear. PR3-ANCA recognize conformational epitopes, and epitope-specific PR3-ANCA subsets with variable impact on biological functions of PR3 have been postulated. The aims of this study were to identify specific PR3 surface epitopes recognized by monoclonal antibodies (moAbs) and to determine whether the findings can be used to measure the functional impact of epitope-specific PR3-ANCA and their potential relationship to disease activity. We used a novel flow cytometry assay based on TALON-beads coated with recombinant human (H) and murine (M) PR3 and 10 custom-designed chimeric human/mouse rPR3-variants (Hm1-5/Mh1-5) identifying 5 separate non-conserved PR3 surface epitopes. Anti-PR3 moAbs recognize 4 major surface epitopes, and we identified the specific surface location of 3 of these with the chimeric rPR3-variants. The ability of PR3-ANCA to inhibit the enzymatic activity of PR3 was measured indirectly using a capture-ELISA system based on the different epitopes recognized by capturing moAbs. Epitope-specific PR3-ANCA capture-ELISA results obtained from patient plasma (n=27) correlated with the inhibition of enzymatic activity of PR3 by paired IgG preparations (r=0.7, P<0.01). The capture-ELISA results also seem to reflect disease activity. In conclusion, insights about epitopes recognized by anti-PR3 moAbs can be applied to separate PR3-ANCA subsets with predictable functional qualities. The ability of PR3-ANCA to inhibit the enzymatic activity of PR3, a property linked to disease activity, can now be gauged using a simple epitope-based capture-ELISA system.

Immunological Aspects of Systemic Vasculitis

Primary vasculitis are commonly multifactorial disorders involving environmental, genetic and immunological factors. Several immune-based effector mechanisms are implicated in the vascular wall damage. These effector mechanisms commonly imply auto-antibodies or immune complexes - mediated cytotoxicity but the contribution of a T-cell mediated immune response has also been described, particularly in large vascular vasculitis. Despite advances in understanding the pathophysiological mechanisms of vasculitis, the triggering events initiating the disease remain largely undefined in most cases. This review highlights the recent advances in the etiopathogenesis of primary vasculitis. A better understanding of the immunological aspects of these disorders may provide insight into the development of novel therapeutical strategies.

Ocular manifestations of ANCA-associated vasculitis

The antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides-Wegener's granulomatosis, microscopic polyangiitis, and Churg-Strauss syndrome-can present with various ophthalmic manifestations. In a subset of patients, these findings may be the earliest indicators of systemic disease. Orbital and anterior segment findings are most common, whereas posterior segment complications such as retinal vasculitis and optic neuropathy occur much less frequently. This article describes the distinguishing features of associated ophthalmic disease, focusing on the manifestations clinicians are most likely to encounter and those with the most significant ocular morbidity. Although the ANCA-associated vasculitides require systemic workup and treatment, this article discusses diagnostic and therapeutic modalities often used concurrently for ophthalmic disease.

ANCA-associated vasculitis: is there a role for neutrophil apoptosis in autoimmunity?

The primary small vessel systemic vasculitides are disorders that target small blood vessels, inducing vessel wall inflammation, and are associated with the development of antineutrophil cytoplasmic antibodies. Multiple organs are attacked including the lungs and kidneys. Increasing knowledge of pathogenesis suggests that the antibodies activate neutrophils inappropriately, leading to endothelial and vascular damage. Cytokines, such as tumor necrosis factor, can facilitate damage by priming neutrophils and activating endothelial cells. Apoptosis of infiltrating neutrophils is also disrupted by antineutrophil cytoplasmic antibody activation. Removal of these effete cells occurs in a proinflammatory manner, promoting persistent inflammation. The autoimmune response may be promoted by aberrant phagocytosis of apoptotic neutrophils by dendritic cells. Understanding pathogenesis can help to rationalize existing therapies and indicate new approaches to therapy.

Epitope-specific anti-neutrophil cytoplasmic antibodies: do they matter? Can they be detected?

Proteinase 3 (PR3)-anti-neutrophil cytoplasmic antibodies (ANCA) and myeloperoxidase (MPO)-ANCA are suggested to play a pathogenic role as they are closely related to the small-vessel vasculitis syndromes, Wegener's granulomatosis and microscopic polyangiitis. A large body of in vitro and animal experiments supports this concept. The mechanisms of action involve a direct interaction between ANCA and its antigen. The epitope specificity of ANCA may therefore influence the functional effects of ANCA and/or may reflect the mechanisms behind different disease manifestations or disease courses.

Analysis of Wegener's granulomatosis responses to rituximab: current evidence and therapeutic prospects

Available data on small numbers of patients with refractory and/or relapsing Wegener's granulomatosis support very good overall outcomes with rituximab, an anti-CD20 biotherapy targeting B cells, in combination with ongoing immunosuppressants, apparently independently of antineutrophil cytoplasm antibody (ANCA) status. However, clearly dissociated responses were observed, with constitutional and vasculitis-related symptoms often achieving complete responses within days or weeks, and granulomatous-related manifestations regressing more slowly over a few weeks to several months or not at all, particularly for orbital pseudotumors. Tolerance was good with few side effects, and when relapses occurred, more often after 12 months, a second or even a third rituximab cycle was almost always able to obtain another complete remission. Randomized trials are needed to define rituximab's best place, compared to cyclophosphamide, in initial and maintenance regimens; to determine optimally combined drugs, considering the various responses of granulomatous-related manifestations; and to delineate the role of circulating B-cell monitoring for pre-emptive management decisions. This promising biotherapy opens the way for other therapeutic agents targeting B lymphocytes and to improve our understanding of the pathophysiology of ANCA-associated vasculitis.

CD4-Positive Effector Memory T Cells Participate in Disease Expression in ANCA-Associated Vasculitis

Although the cause of ANCA-associated vasculitis (AAV) remains undetermined, the presence of lymphocytic infiltrates in inflammatory lesions of patients suggests that vascular damage is immune mediated. Studies over the past decade have implicated a role for T cells in the pathogenesis of AAV as altered T cell phenotype has been observed in this disorder. The distribution of T cell subpopulations has been analyzed most intensely in Wegener's granulomatosis (WG), where an expanded population of circulating CD4(+) effector memory T cells (CD4(+)T(EM)) was demonstrated. CD4(+)T(EM) cells play a major role in the pathogenesis of several autoimmune diseases. Specific suppression of CD4(+)T(EM) cells inhibits delayed-type hypersensitivity (DTH) and has therapeutic potential in autoimmune disease. Thus, CD4(+)T(EM) cells may act as inducers of tissue injury and participate in the development of AAV. Therapies that target CD4(+)T(EM), without impairing the activity of other lymphocyte subsets, may hold therapeutic promise for AAV.

ANCA-associated vasculitis: new options beyond steroids and cytotoxic drugs

Small vessel vasculitic syndromes--Wegener's granulomatosis, microscopic polyangiitis and renal limited vasculitis (which are associated with circulating antineutrophil cytoplasmic autoantibodies)--are an important cause of renal failure. Present immunosuppressive regimens that are based on cyclophosphamide have significantly increased survival rates. However, these treatments are toxic, increase the risk of infection and do not cure disease. Therefore, newer approaches are required. Understanding disease pathogenesis has allowed rational use for newer therapies such as rituximab, which depletes B cells. Unfortunately, blockade of promising targets such as TNF-alpha, which was thought to be a pivotal cytokine in inflammation, has not shown benefit in a randomised controlled trial. Better understanding of the pathogenesis of the disease is the key to the development of novel targeted therapies, which are urgently required to improve patient prognosis. Gene therapy with targeted delivery of specific proteins is an exciting future prospect.

Follow-up of avidity and titre of anti-myeloperoxidase antibodies in sera from patients with propylthiouracil-induced vasculitis

OBJECTIVE

Propylthiouracil (PTU) has been known to induce myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) positive vasculitis. Our previous study indicated that the increase of avidity of MPO-ANCA might be associated with the occurrence of clinical vasculitis in patients with PTU-induced ANCA. The current study aimed to follow-up the avidity and titre of anti-MPO antibodies in sequential sera from patients with PTU-induced ANCA-associated systemic vasculitis (AASV).

METHODS

Six patients with PTU-induced vasculitis were enrolled in the current study. Serial sera in both active phase and in remission were collected. MPO-ANCA avidity was assessed by antigen-inhibition enzyme-linked immunosorbent assays (ELISAs), and avidity constant (aK) was determined as the reciprocal value of the MPO molar concentration in the liquid phase resulting in 50% inhibition of anti-MPO antibody binding to MPO in solid phase ELISA. Titres of MPO-ANCA were determined by using serial serum dilutions in MPO-ELISA.

RESULTS

After cessation of PTU and initiation of immunosuppressive therapy, the avidity and titre of MPO-ANCA decreased significantly during follow-up in sera from all the patients, and the avidity decreased much more quickly than the titres.

CONCLUSION

Our study indicates that avidity of anti-MPO antibodies might be more closely associated with clinical vasculitis than titre.

Quantitation of autoantibodies in systemic autoimmune diseases: clinically useful?

Serial assessment of levels of autoantibodies has been proposed as being clinically useful in certain systemic autoimmune diseases. In particular, attention has been given to anti-dsDNA antibodies in systemic lupus erythematosus (SLE) and ANCA in the ANCA-associated vasculitides (AAV). Much controversy exists, however, concerning the value of serial testing in these diseases. We here review the various tests available for quantitation of anti-dsDNA and ANCA, and their capacity to detect changes in autoantibody levels that are associated with changes in clinical disease activity of the respective diseases. It is concluded that changes in anti-dsDNA as measured by the Farr assay and changes in ANCA as assessed by ELISA have predictive value for the occurrence of disease relapses, although this relationship is far from absolute. Consequently, treatment based on changes in levels of the respective autoantibodies only seems at present not justified, in view of the toxicity of currently available immunosuppressive regimens.

What's new in the aetiopathogenesis of vasculitis?

The cause of the majority of childhood vasculitides is unknown although it is likely that a complex interaction between environmental factors and inherited host responses trigger the disease and determine the vasculitis phenotype. Epidemiological clues continue to implicate infectious triggers in Kawasaki syndrome (KS) and Henoch Schonlein purpura (HSP). Several genetic polymorphisms have now been described in KS and HSP which predispose to disease or predict disease severity. Anti-neutrophil cytoplasmic antibodies (ANCA) are now known to be directly involved in the pathogenesis of vascular injury in ANCA-associated vasculitides, although why some individuals develop ANCA in the first instance is not yet understood. Endothelial injury and repair are active areas of research in vasculitis. It is now possible to track endothelial injury non-invasively in children with vasculitis using surrogate markers of endothelial injury. The vasculogenic pathways involved in vascular repair following vasculitis, including endothelial progenitor cells, are beginning to be studied. It is anticipated that an improved understanding of the aetiopathogenesis of vasculitis in the young will ultimately shape future novel diagnostic and therapeutic approaches and will help us predict which children may develop premature arteriosclerosis in later life.

Failure to detect human herpes simplex virus, cytomegalovirus, and Epstein–Barr virus viral genomes in giant cell arteritis biopsy specimens by real-time quantitative polymerase chain reaction

A study provided evidence of human herpes simplex virus (HSV) DNA in giant cell arteritis (GCA) biopsy specimens. This prompted us to study our own GCA biopsy specimens using real-time quantitative polymerase chain reaction for the detection of HSV1, cytomegalovirus, and Epstein-Barr virus DNAs. Our study failed to confirm an association between HSV1 and GCA, revealing no viral genome in 35 biopsy specimens of histologically positive temporal arteries.

Persistent expansion of CD4+ effector memory T cells in Wegener's granulomatosis

In order to test the hypothesis that Wegener's granulomatosis (WG) is associated with an ongoing immune effector response, even in remission, we examined the distribution of peripheral naive and memory T-lymphocytes in this disease, and analyzed the function-related phenotypes of the memory T-cell population. Peripheral blood mononuclear cells (PBMCs) were freshly isolated from WG-patients in remission (R-WG, n=40), active WG-patients (A-WG, n=17), and age-matched healthy controls (HCs, n=21). Expression of CD4, CD8, CD45RO, CCR7, interleukin (IL)-18Ralpha, ST2L, and FoxP3 were determined by four-color flow cytometric analysis. CD45RO and CCR7 were used for distinction between naive and memory T cells, IL-18Ralpha, ST2L, and FoxP3 for the assessment of Type1, Type2, and regulatory T-cells, respectively. In R-WG, the CD4+CD45RO+CCR7- effector memory T-cell subpopulation (TEM) was relatively increased, whereas the CD4+CD45RO-CCR7+ naive T-cell population (TNaive) was decreased as compared to HC. The distribution of naive and memory CD8+T cells did not differ between R-WG, A-WG, and HC, nor did CD4+CD45RO+CCR7+ central memory T cells (TCM). In contrast to HC, the percentage of CD4+TNaive cells in R-WG correlated negatively with age, whereas CD4+TEM cells showed a positive correlation. In R-WG, a skewing towards Type2 T cells was observed in CD4+TEM cells. No differences were detected in FoxP3+CD4+TEM cells between R-WG and A-WG, whereas the FoxP3-CD4+TEM cells were increased in R-WG and decreased in A-WG as compared to HC. Collectively, peripheral blood homeostasis of CD4+T cells is disturbed in R-WG with the persistent expansion of non-regulatory CD4+TEM cells. These cells might be involved in relapse and may constitute a target for therapy.

Activation, apoptosis, and clearance of neutrophils in Wegener's granulomatosis

Wegener's granulomatosis (WG) is strongly associated with the presence of antineutrophil cytoplasmic autoantibodies (ANCAs). Within WG these ANCAs are usually (80-90%) directed against the azurophilic enzyme proteinase 3, the so called PR3-ANCA. A pathophysiological role for these autoantibodies, supported by numerous in vitro and in vivo studies, is specifically based on their capacity to bind and activate neutrophils and potentially may damage vessels. In this review, the pathogenic potential of different developmental stages of the neutrophil in the pathogenesis of WG is discussed. After release from the bone marrow into the circulation, neutrophils can be primed by TNFalpha and become attached to locally activated endothelium. Once attached to the endothelium, ANCAs can fully activate these primed neutrophils. In this activation process, the degree of activation after stimulation with PR3-ANCAs associates with the level of PR3 expression on the membrane of the neutrophil. Following activation, infiltrated neutrophils become apoptotic with further membrane expression of PR3. In WG patients, clearance of apoptotic neutrophils can be disturbed due to the opsonization of PR3-expressing apoptotic neutrophils with PR3-ANCAs, thereby perpetuating inflammation by the release of proinflammatory cytokines during clearance; or it may favor autoimmunity by PR3 presentation in an inflammatory environment. Furthermore, the presence of ANCAs and the release of the vessel-related pentraxin PTX3 may lead to the persistence of late apoptotic neutrophils in tissues, thereby inducing leukocytoclastic lesions that are characteristic in patients with WG. All together, alive neutrophils as well as apoptotic neutrophils play a key role in different inflammatory phenomena seen in patients suffering from WG.

Anti-myeloperoxidase antibodies enhance phagocytosis, IL-8 production, and glucose uptake of polymorphonuclear neutrophils rather than anti-proteinase 3 antibodies leading to activation-induced cell death of the neutrophils

Anti-neutrophil cytoplasmic antibodies (ANCA) not only are triggered by target protein myeloperoxidase (MPO) and proteinase 3 (PR3) of polymorphonuclear neutrophil (PMN) but also react with primed PMN to exert the inflammatory process in vasculitis syndrome. To clarify the crucial role of PMN in ANCA-associated vasculitis and the related mechanism, PMN was cultured with monoclonal antibody MPO-ANCA and PR3-ANCA to determine the function of phagocytosis, Interleukin- 8 (IL-8) production, glucose uptake, and TNF-related apoptosis induced ligand (TRAIL) production. The spontaneous membrane expression of MPO and PR3 on PMN could be significantly increased by lipopolysaccharide (LPS) and TNF-alpha, but not by IL-8 or GRO-alpha. The PMN-stimulating activity of ANCA was demonstrated by enhancing phagocytosis, IL-8 production, and glucose uptake that was more prominent by MPO-ANCA. The PMN stimulation by ANCA was not through protein kinase, H2O2, or superoxide anion radicals as their inhibitors exerted no effect on ANCA-mediated activation. On the other hand, ANCA also accelerated PMN apoptosis and increased TRAIL production. These results demonstrate that activation-induced cell death (AICD) mechanism could be initiated in PMN with existence of ANCA. In conclusion, MPO-ANCA is more potent in stimulating PMN than PR3-ANCA. ANCA-activated PMN is not only responsible for the amplified inflammatory process in blood vessel but also initiates immune circuit via triggered macrophage/monocyte by apoptotic PMN through the mechanism of AICD elicited by ANCA.

Mediation of endothelial cell damage by serine proteases, but not superoxide, released from antineutrophil cytoplasmic antibody–stimulated neutrophils

OBJECTIVE

To evaluate potential mediators of endothelial cell injury in systemic vasculitis associated with antineutrophil cytoplasmic antibodies (ANCAs), we investigated the factors controlling the neutrophil respiratory burst and endothelial release of von Willebrand factor (vWF) during neutrophil-endothelial cell interactions.

METHODS

Superoxide release from neutrophils binding to purified P-selectin or to tumor necrosis factor-activated endothelial cells was measured under flow or static conditions using the superoxide dismutase (SOD)-inhibitable reduction of ferricytochrome c. Neutrophils were activated with fMLP, normal IgG, or ANCA IgG. Enzyme-linked immunosorbent assay was used to measure vWF. Serine protease activity was measured enzymatically.

RESULTS

ANCA IgG or fMLP induced superoxide release when perfused over neutrophils that were rolling over P-selectin, but not those that were binding to endothelial cells. In static assays, endothelial cells inhibited superoxide production by neutrophils. Adenosine inhibited the respiratory burst, and, in cocultures, adenosine deaminase overcame the inhibitory effects of endothelial cells. Serine proteases were released during activated neutrophil-endothelial cell coculture. There was enhanced release of vWF during activated neutrophil-endothelial cell coculture; this was not inhibited by diphenyleneiodonium or by SOD plus catalase, but was inhibited by diisopropylfluorophosphate.

CONCLUSION

Endothelial cells inhibit superoxide generation by fMLP and ANCA-activated neutrophils. The release of vWF occurs during coculture and is sensitive to serine protease, but not NADPH oxidase inhibition. Serine proteases may play a more important role than reactive oxygen species as mediators of endothelial injury during ANCA-associated systemic vasculitis.

A novel capture-ELISA for detection of anti-neutrophil cytoplasmic antibodies (ANCA) based on c-myc peptide recognition in carboxy-terminally tagged recombinant neutrophil serine proteases

Testing for antineutrophil cytoplasmic antibodies (ANCA) reacting with proteinase 3 (PR3) is part of the routine diagnostic evaluation of patients with small vessel vasculitis. For PR3-ANCA detection, capture ELISAs are reported to be superior to direct ELISAs. Standard capture ELISAs, in which PR3 is anchored by anti-PR3 monoclonal antibodies (moAB), have two potential disadvantages. First, the capturing moAB may compete for epitopes recognized by some PR3-ANCA, causing occasional false-negative results. Second, the capture of recombinant PR3 mutant molecules becomes unpredictable as modifications of specific conformational epitopes may not only affect the binding of PR3-ANCA, but also the affinity of the capturing anti-PR3 moAB. Here, we describe a new capture ELISA, and its application for PR3-ANCA detection. This new assay is based on the standardized capture of a variety of different carboxy-terminally c-myc tagged recombinant ANCA target antigens using anti-c-myc coated ELISA plates. Antigen used include c-myc tagged human rPR3 variants (mature and pro-form conformations), mouse mature rPR3 and human recombinant neutrophil elastase. This new anti-c-myc-capture ELISA for PR3-ANCA detection has an intra- and inter-assay coefficient of variation of 3.6% to 7.7%, and 15.8% to 18.4%, respectively. The analytical sensitivity and specificity for PR3-ANCA positive serum samples were 93% and 100%, respectively when rPR3 with mature conformation was used as target antigen, and 83% and 100% when the pro-enzyme conformation was employed. In conclusion, this new anti-c-myc capture ELISA compares favorably to our standard capture ELISA for PR3-ANCA detection, enables the unified capture of different ANCA target antigens through binding to a c-myc tag, and allows capture of rPR3 mutants necessary for PR3-ANCA epitope mapping studies.

Differences between human proteinase 3 and neutrophil elastase and their murine homologues are relevant for murine model experiments

Direct comparisons of human (h) and murine (m) neutrophil elastase (NE) and proteinase 3 (PR3) are important for the understanding and interpretation of inflammatory and PR3-related autoimmune processes investigated in wild-type-, mNE- and mPR3/mNE knockout mice. To this end, we purified recombinant mPR3 and mNE expressed in HMC1 and 293 cells and compared their biophysical properties, proteolytic activities and susceptibility to inhibitors with those of their human homologues, hPR3 and hNE. Significant species differences in physico-chemical properties, substrate specificities and enzyme kinetics towards synthetic peptide substrates, oxidized insulin B chain, and fibrinogen were detected. MeOSuc-AAPV-pNA and Suc-AAPV-pNA were hydrolyzed more efficiently by mPR3 than hPR3, but enzymatic activities of mNE and hNE were very similar. Fibrinogen was cleaved much more efficiently by mPR3 than by hPR3. All four proteases were inhibited by alpha(1)-antitrypsin and elafin. Eglin C inihibited mNE, hNE, mPR3, but not hPR3. SLPI inhibited both NEs, but neither PR3. The custom-designed hNE inhibitor, Val(15)-aprotinin, is a poor inhibitor for mNE. In conclusion, appropriate interpretation of experiments in murine models requires individual species-specific assessment of neutrophil protease function and inhibition.

Autoantibodies to vascular smooth muscle are pathogenic for vasculitis

We have previously shown that microvascular smooth muscle activates CD4+ T lymphocytes in sterile co-culture, presents antigen, and produces inflammatory cytokines. Adoptive transfer of lymphocytes co-cultured with syngeneic smooth muscle cells to healthy recipient mice results in vasculitic lesions predominantly in postcapillary venules. The present study assessed the pathogenic role of immunoglobulin and B cells in a murine model of vasculitis. Here, we show that transferred B cells, including plasmablast cells, accumulated, persisted, and proliferated in lung and secondary lymphoid organs of recipient mice. The induction of vasculitis was accompanied by production of IgM and IgG2a autoantibodies specific for vascular smooth muscle intracellular antigens. Circulating immunoglobulin had a pathogenic role in this vasculitis model, because the disease could be induced by transfer of serum from vasculitic mice to untreated animals but not by transfer of serum depleted of anti-smooth muscle autoantibodies. Additionally, the pathogenic mechanisms triggered by the transfer of vasculitogenic serum were dependent on T lymphocytes because both wild-type and B cell-deficient mice developed the disease after serum transfer, whereas RAG2-deficient mice did not. Thus, immunoglobulin and cell-mediated pathways work in concert to produce vasculitis in this model.

Development of multiple malignancies after immunosuppression in a patient with Wegener?s granulomatosis

We describe the development of multiple malignancies in a patient with Wegener's granulomatosis treated with glucocorticosteroids, azathioprin and cyclophosphamide over 20 years. His symptoms started with a neurological disease, which is unusual. Less attention was paid to other symptoms that occurred simultaneously and were more typical manifestations of the disease. This resulted in delayed diagnosis. Despite incorrect diagnoses, he received appropriate immunosuppressive therapy. After 2 years of therapy, he developed a spinocellular carcinoma, after 12 years a basal cell carcinoma and after 19 years both a Kaposi sarcoma and a urinary bladder carcinoma. This patient illustrates a difficult therapeutic balance between prolonged treatment and the hazards of therapy. No guidelines are established to manage this clinical dilemma.

Plasmapheresis for diffuse alveolar hemorrhage in a patient with Wegener's granulomatosis: Case report and review of the literature

We present a case of a 20-year-old male with Wegener's Granulomatosis involving the upper respiratory tract, lungs, and kidneys. In his fourth hospital admission, the patient presented with diffuse alveolar hemorrhage and poor pulmonary function: FiO2 of 100% and PEEP of 17cm H2O on intubation. Due to a fast clinical deterioration while receiving drug therapy (cyclophosphamide and methylprednisolone), we performed nine daily 1-volume therapeutic plasma exchanges (TPE) using 5% albumin as replacement fluid. TPE resulted in a decrease in cytoplasmic anti-neutrophil cytoplasm antibodies (c-ANCA) titer from 1:1,024 to 1:16. On the ninth day of plasmapheresis, his pulmonary status was markedly improved with FiO2 of 60% and PEEP of 8 cm H2O. The patient was later extubated and discharged home in stable condition. Wegener's Granulomatosis with pulmonary hemorrhage is not included in the current guidelines for therapeutic apheresis; therefore, we report this case and, if warranted, propose this condition to be included in the guidelines.

Frequency of proteinase 3 (PR3)-specific autoreactive T cells determined by cytokine flow cytometry in Wegener's granulomatosis

OBJECTIVE

Previous studies have shown proliferation to Wegener's autoantigen, proteinase 3 (PR3). We tested immunogenicity of PR3-derived peptides and determined frequencies of PR3-specific T cells using cytokine flow cytometry in Wegener's granulomatois (WG).

METHODS

Peripheral blood T-cell responses were measured after stimulation with previously described PR3-derived peptides. PBMC were stimulated with PR3-derived peptides or control stimuli for up to 10 days. Cells were stained with antibodies against CD4 or CD8, CD69 and intracellular TNF-alpha and analyzed by flow cytometry. PR3-specific T cells were counted as the percentage of CD69(+)TNF-alpha(+)double positive T cells after stimulation.

RESULTS

Frequencies of PR3-specific peripheral blood T cells after short-term stimulation (<or=0.4%) were lower compared to frequencies of PR3-specific CD4(+)T cells (0.64+/-0.09%, mean+/-SEM) and PR3-specific CD8(+)T cells (0.65+/-0.18%) after 10 days of stimulation in WG. There were no differences of the frequency of PR3-specific T cells between WG and healthy controls after stimulation with other peptides. The frequency of PR3-specific CD8(+)T cells stimulated with a preferentially HLA-A*0201 binding PR3-peptide sequence was higher compared to the frequency of T cells stimulated with a HLA-B*0702 binding PR3-peptide in one WG patient whose HLA type was known (A2B7).

CONCLUSION

Low frequencies of TNF-alpha(+)PR3-specific T cells can be detected in individual WG patients and controls using cytokine flow cytometry. The pattern and time course of cytokine production in response to PR3 peptides needs to be further elucidated. Additional factors such as the influence of proinflammatory or regulatory T cells might be important for the induction of autoimmunity in WG.

Autoantibodies to neutrophil cytoplasmic antigens (ANCA) do not bind to polymorphonuclear neutrophils in blood

BACKGROUND

Autoantibodies to neutrophil cytoplasmic antigens (ANCA), particularly to proteinase 3 (PR3), are found in the majority of patients with systemic Wegener's granulomatosis. The autoantibodies are widely used as diagnostic markers. Their role in the development and progression of the disease, however, is still under investigation. The primary target of ANCA, PR3, is located in the cytoplasm of polymorphonuclear neutrophils (PMN) or monocytes and is translocated to the cell surface upon stimulation. In patients with Wegener's granulomatosis PR3 is up-regulated most prominently during active disease. Despite the fact that both autoantibodies to PR3 and PMN expressing PR3 are present in patients with Wegener's granulomatosis, there is no evidence for binding of the autoantibodies to PMN. The present study was designed to analyze binding characteristics of autoantibodies to PR3 on PMN.

METHODS AND RESULTS

PMN of patients with active Wegener's granulomatosis (N= 10) were tested for autoantibody binding. Despite high autoantibody titer and PR3 expression on the PMN, no surface-bound IgG was found on PMN ex vivo. When ANCA-containing plasma from patients was incubated with isolated PMN, stimulated to express PR3, again no specific binding of the autoantibody could be detected. Also keeping the samples on ice did not allow surface detection of IgG, ruling out degradation or internalization of the autoantibodies. Only when purified IgG fractions were used, binding to PMN was seen in 14 of 25 patients. Already 1% of plasma, however, was sufficient to greatly reduce the IgG binding. Reduced binding of the IgG fraction was also seen when a larger reaction volume was used.

CONCLUSION

Our data indicate that autoantibodies to PR3 have a rather low affinity for surface-associated PR3 on PMN. This, in turn, argues against the hypothesis that ANCA contributes to the pathogenesis of the disease by stimulating viable PMN in whole blood.

The antineutrophil cytoplasmic antibody-associated vasculitides

Wegener's granulomatosis, microscopic polyangiitis, and Churg-Strauss syndrome are small- to medium-vessel vasculitides linked by overlapping pathology and the presence of antineutrophil cytoplasmic antibodies (ANCA). Commonly referred to as the ANCA-associated vasculitides, these diseases are challenging to diagnose and to treat. Distinguishing the ANCA-associated vasculitides from other forms of vasculitis or nonvasculitic processes (such as infection) can be particularly difficult. This review describes the clinical and pathologic hallmarks of the ANCA-associated vasculitides, discusses the role of ANCA assays in diagnosis and treatment, and outlines an approach to the evaluation and management of these diseases.

Site-specific glycosylation of an aglycosylated human IgG1-Fc antibody protein generates neoglycoproteins with enhanced function

A range of well-defined IgG glycoforms was prepared by employing a combination of synthetic carbohydrate chemistry and genetic engineering. The key aspect of this methodology is the coupling of thioaldoses with cysteine-containing proteins to give disulfide-linked neoglycoproteins. This technology was applied to the synthesis of a series of synthetic N-glycan thioaldoses which were coupled to an aglycosylated IgG1-Fc fragment, engineered to have Cys-297 in place of glycan-linked Asn (Deltah-Fc N297C). Analysis of the resulting Fc neoglycoproteins by mass spectrometry and trypsin digestion showed that the saccharides were site-selectively incorporated at Cys-297 to full occupancy without affecting other Fc protein disulfides. The neoglycoproteins were tested for their ability to interact with human FcgammaRI by inhibiting superoxide production by gamma-interferon-stimulated U937 cells. The neoglycoproteins displayed enhanced superoxide inhibition relative to aglycosylated Deltah-Fc N297C, where increased glycan size correlated positively with increased inhibition.

Myeloperoxidase in kidney disease

In glomerular and tubulointerstitial disease, polymorphonuclear- and monocyte-derived reactive oxygen species may contribute to oxidative modification of proteins, lipids, and nucleic acids. In part, the processes instigated by reactive oxygen species parallel events that lead to the development of atherosclerosis. Myeloperoxidase (MPO), a heme protein and catalyst for (lipo)protein oxidation is present in these mononuclear cells. The ability of MPO to generate hypochlorous acid/hypochlorite (HOCl/OCl-) from hydrogen peroxide in the presence of chloride ions is a unique and defining activity for this enzyme. The MPO-hydrogen peroxide-chloride system leads to a variety of chlorinated protein and lipid adducts that in turn may cause dysfunction of cells in different compartments of the kidney. The aim of this article is to cover and interpret some experimental and clinical aspects in glomerular and tubulointerstitial diseases in which the MPO-hydrogen peroxide-chloride system has been considered an important pathophysiologic factor in the progression but also the attenuation of experimental renal disease. The colocalization of MPO and HOCl-modified proteins in glomerular peripheral basement membranes and podocytes in human membranous glomerulonephritis, the presence of HOCl-modified proteins in mononuclear cells of the interstitium and in damaged human tubular epithelia, the inflammation induced and exacerbated by MPO antibody complexes in necrotizing glomerulonephritis, and the presence of HOCl-modified epitopes in urine following hyperlipidemia-induced renal damage in rodents suggest that MPO is an important pathogenic factor in glomerular and tubulointerstitial diseases. Specifically, the interaction of MPO with nitric oxide metabolism adds to the complexity of actions of oxidants and may help to explain bimodal partly detrimental partly beneficial effects of the MPO-hydrogen peroxide-chloride system in redox-modulated renal diseases.

[Rapidly progressive glomerulonephritis:classification, pathogenesis and clinical management]

Rapidly progressive glomerulonephritides (RPGN) belong to a heterogeneous group of inflammatory kidney diseases which are commonly associated with systemic vasculitic syndromes. Renal histology is characterized by necrotizing lesions within the glomerual tuft and extracapillary proliferation, in most cases leading rapidly to renal failure. The etiology and pathogenesis are only partly elucidated. Since irreversible renal scaring develops within days to weeks, RPGN represent a nephrological emergency necessitating urgent diagnostic evaluation and rapid institution of effective therapy. New onset nephritic sediment combined with concomitantly deteriorating excretory renal function should lead to immediate nephrological consultation. Autoimmune serology and particularly renal biopsy are of the utmost importance for rapid diagnosis. Most forms of RPGN are treated with immunosuppressive regimens which generally consist of high dose steroids in combination with the alkylating agent cyclophosphamide. Some forms also require the use of plasma exchange therapy. Rapid diagnosis and early therapy improves both renal and overall outcome in the affected patients.

Accommodation in ABO-incompatible kidney allografts, a novel mechanism of self-protection against antibody-mediated injury

To elucidate the mechanism of self-protection against anti-donor blood-group antibody known as accommodation, we studied 16 human ABO-incompatible living-donor kidney transplant recipients at 3 and 12 months post transplantation. Both circulating anti-blood-group antibody and the target blood-group antigen in the graft were demonstrable in all patients after transplantation. Thirteen of 16 grafts had normal renal function and histology, while three grafts with prior humoral rejection demonstrated significant glomerulopathy and thus did not meet the criterion for accommodation. Using microarrays, we compared five 1-year protocol ABO-compatible renal graft biopsies to four accommodated ABO-incompatible graft biopsies. Significant alterations in gene expression in 440 probe sets, including SMADs, protein tyrosine kinases, TNF-alpha and Mucin 1 were identified. We verified these changes in gene expression using RT-PCR and immunohistochemistry. Heme oxygenase-1, Bcl-2 and Bcl-xl were not increased in ABO-incompatible grafts at any time-point. We conclude that accommodation is always present in well-functioning, long-surviving ABO-incompatible kidney transplants. This self-protection against antibody-mediated damage may involve several novel mechanisms including the disruption of normal signal transduction, attenuation of cellular adhesion and the prevention of apoptosis.

ANCA and anti-GBM antibodies in diagnosis and follow-up of vasculitic disease

In the last decade, serological detection of anti-neutrophil cytoplasmic antibodies (ANCA) and of anti-glomerular basement membrane (GBM) antibodies has tremendously facilitated the diagnosis of small vessel vasculitides. Once diagnosed, these diseases have proven to be treatable. However, in contrast to anti-GBM disease, ANCA-associated vasculitides are chronic diseases with a high relapse rate. Since morbidity in ANCA-associated vasculitides is dictated by the frequency and severity of relapses, much health benefit would be achieved if a relapse could be prevented or early treatment started. Increases in ANCA titers and persistently high ANCA levels indicate a high risk of relapse and warrant clinical evaluation of the patient for signs of relapse. This review will focus on the value of ANCA and anti-GBM antibody testing in diagnosis and on the importance of these tests in follow-up of disease.

Neutrophil-activating potential of antineutrophil cytoplasm autoantibodies

Accumulating in vivo and in vitro evidence supports the hypothesis that antineutrophil cytoplasm autoantibodies (ANCA) with specificity for proteinase 3 (PR3) and myeloperoxidase (MPO) are involved in the pathophysiology of small-vessel vasculitis. The best-described effector function of these autoantibodies is stimulation of neutrophils to produce reactive oxygen species and to release proteolytic enzymes. Neutrophil activation requires interaction of monomeric ANCA with PR3/MPO and Fcgamma receptors, but also other mechanisms--for instance, stimulation by ANCA-containing immune complexes--cannot be excluded. This review focuses on the mechanisms of neutrophil activation by ANCA. We discuss the molecules involved in ANCA binding to the neutrophil surface and in triggering the functional responses. We summarize current knowledge on the signal-transduction pathways initiated by ANCA and on the factors determining susceptibility of neutrophils to activation by these autoantibodies.

Differences in CCR5 expression on peripheral blood CD4+CD28- T-cells and in granulomatous lesions between localized and generalized Wegener's granulomatosis

Wegener's granulomatosis (WG) is an autoimmune disease characterized by granulomatous lesions and a necrotizing vasculitis. Th1-type-cells lacking CD28 are expanded independent of age and immunosuppressive therapy in WG. To address their migratory properties of CD4(+)CD28(-) T-cells we studied the expression of the inducible inflammatory Th1-type chemokine receptor CCR5 in localized WG and generalized WG. Expansion of CD4(+)CD28(-) T-cells was more prominent in generalized WG compared to localized WG. In localized WG a larger fraction of CD4(+)CD28(-) T-cells displayed CCR5 expression compared to generalized WG. CCR5 expression was also higher in granulomatous lesions in localized WG. Higher levels of CCR5 expression on CD4(+)CD28(-) T-cells in localized WG may favor stronger CCR5-mediated recruitment of this T-cell subset into granulomatous lesions in localized WG. Expansion of Th-1-type CD4(+)CD28(-)CCR5(+) effector memory T-cells might contribute to disease progression and autoreactivity, either directly, by maintaining the inflammatory response, or as a result of bystander activation.