IgM and IgG autoantibodies from microscopic polyangiitis patients but not those with other small- and medium-sized vessel vasculitides recognize multiple endothelial cell antigens

Evaluation of subclinical ocular involvement in patients with deficiency of adenosine deaminase 2 (DADA2)

PURPOSE

To evaluate changes in the peripapillary, macular, and choroidal microvasculature in the eyes of patients with deficiency of adenosine deaminase 2 (DADA2) and no clinical signs of ocular involvement.

METHODS

The study included 12 eyes of 12 patients with DADA2 and 24 eyes of 24 healthy subjects. The foveal avascular zone (FAZ), macular vessel densities (VDs) in the superficial and deep retinal capillary plexuses, peripapillary VDs, and choroidal thickness were evaluated by optical coherence tomography angiography (OCTA). Measurements were compared between DADA2 patients and healthy controls.

RESULTS

The median age was 17 (8-25) years in DADA2 patients and 17.5 (7-23) years in control group at the OCTA visit (p = 0.934). FAZ area did not differ between the groups (p = 0.224). In the superficial capillary plexus, whole-image, foveal, and parafoveal VD values were slightly lower in DADA2 patients than in controls (p = 0.054, p = 0.052, p = 0.117). In the deep capillary plexus, whole-image and parafoveal VD values were significantly lower in DADA2 patients than controls (p = 0.010, p = 0.001). VD in the radial peripapillary capillary plexus was also lower in DADA2 patients, with significantly lower peripapillary VD (p = 0.002). Subfoveal choroidal thickness was significantly higher in patients with DADA2 (p < 0.001).

CONCLUSIONS

This OCTA study demonstrates that both retinal and choroidal involvement may occur in DADA2 patients before the emergence of evident clinical findings.

Choroidal vascularity index as a biomarker of systemic inflammation in childhood Polyarteritis Nodosa and adenosine deaminase-2 deficiency

BACKGROUND/PURPOSE

To assess EDI-OCT (enhanced depth imaging optical coherence tomography) of choroid for inflammatory signs in children with polyarteritis nodosa (PAN) and adenosine deaminase-2 deficiency (DADA-2).

METHODS

In this cross-sectional study conducted between June 2017 and September 2018, we evaluated children diagnosed with PAN (n = 11) and DADA-2 (n = 4) and an age- and sex-matched control group (n = 15). Demographic and laboratory data were retrospectively analyzed from patient charts. Disease activity was assessed using the pediatric vasculitis activity score (PVAS). Choroidal images were obtained with spectral domain-OCT to measure choroidal thickness (ChT) at 5 points (750 and 1500 μm from the foveal center in the temporal and nasal quadrants and beneath the fovea), and to calculate the total subfoveal choroidal area (TCA), luminal area (LA), stromal area (SA), and the choroidal vascularity index (CVI).

RESULTS

The median (min-max) age was 8 (4-16) years in PAN patients, 6 (5-16) years in DADA-2 patients and 8 (8-10) years in control group at the OCT visit (p = 0.214). The ChT at 3 points and the TCA, LA, and SA were higher in children with both PAN and DADA-2 patients compared to those of the control group (p < 0.0001, p = 0.049, p = 0.007, p = 0.007, p = 0.006, p = 0.033, respectively). The CVI was similar in both groups. No association was observed between the OCT findings, PVAS, and the erythrocyte sedimentation rate, and serum leukocyte and C-reactive protein levels.

CONCLUSION

Similar CVI scores were obtained from PAN and DADA2 patients under treatment and from healthy controls. Increased subfoveal ChT without any other signs of ocular involvement may suggest choroidal thickening as a sign of mild subclinical inflammation.

Polyarteritis nodosa: A contemporary overview

Polyarteritis nodosa (PAN) is a systemic necrotizing vasculitis predominantly targeting medium-sized arteries. PAN is a rare form of vasculitis, and the precise frequency of this disease is difficult to determine. The major environmental factor associated with PAN is HBV infection. The pathogenesis of "idiopathic PAN" remains enigmatic, although the clinical responses to immunosuppressive therapy support the concept that immunological mechanisms play an active pathogenic role. The spectrum of disease ranges from involving a single organ to polyvisceral failure. Any organ might be affected; however, for reasons that are not understood, PAN does not affect the lungs. In addition to the systemic idiopathic form, called "idiopathic generalized PAN," there are 2 clinical variants of this disease: "cutaneous PAN" and "hepatitis B virus (HBV)-associated PAN". Diagnosis requires the integration of clinical, angiographic, and biopsy findings. The overall prognosis of this disease has been improved in recent decades, primarily reflecting early diagnosis and more effective treatments. Idiopathic generalized PAN should be treated with a combination of glucocorticoids and cyclophosphamide. The treatment of HBV-associated PAN involves a different approach, centered on the use of an antiviral agent to control the infection. The therapy for cutaneous PAN requires a less aggressive approach based on the administration of non-steroidal anti-inflammatory drugs over short periods of time.

Vasculitis related to viral and other microbial agents

Vasculitis due to infection may occur as a consequence of the inflammation of vessel walls due to direct or contiguous infection, type II or immune complex-mediated reaction, cell-mediated hypersensitivity, or inflammation due to immune dysregulation triggered by bacterial toxin and/or superantigen production. As immunosuppressive therapy administered in the absence of antimicrobial therapy may increase morbidity and fail to effect the resolution of infection-associated vascular inflammation, it is important to consider infectious entities as potential inciting factors in vasculitis syndromes. The causality between infection and vasculitis has been established in hepatitis B-associated polyarteritis nodosa (HBV-PAN) and hepatitis C-associated (cryoglobulinemic) vasculitis (HCV-CV). The review summarizes the recent literature on the pathophysiological mechanisms and the approaches to the management of HBV-PAN and HCV-CV. Roles of other viral and microbial infections, which either manifest as vasculitic syndromes or are implicated in the pathogenesis of primary vasculitides, are also discussed.

IgG from patients with systemic sclerosis bind to DNA antitopoisomerase 1 in normal human fibroblasts extracts

By using a semi-quantitative immunoblotting technique, we have analyzed serum immunoglobulin G (IgG) reactivities of patients with limited cutaneous systemic sclerosis and anticentromere antibodies, patients with diffuse systemic sclerosis and antitopoisomerase 1 antibodies, patients with diffuse systemic sclerosis without antitopoisomerase 1 or anticentromere antibodies and age- and gender-matched healthy controls with normal human skin fibroblasts and HEp-2 cells antigens. Serum IgG reactivities of patients with diffuse systemic sclerosis and antitopoisomerase 1 antibodies differed significantly from those of healthy controls or systemic sclerosis patients in other groups for reactivity with fibroblast proteins. IgG from patients with antitopoisomerase 1 antibodies bound to a 90 kDa fibroblast band and to a 100 kDa protein band in a HEp-2 cell protein extract. These two bands were further identified as DNA topoisomerase 1. Our results indicate that IgG from patients with diffuse systemic sclerosis bind DNA topoisomerase 1 in normal human fibroblasts extracts.

Identification of target antigens of anti-endothelial cell and anti-vascular smooth muscle cell antibodies in patients with giant cell arteritis: a proteomic approach

Introduction

Immunological studies of giant cell arteritis (GCA) suggest that a triggering antigen of unknown nature could generate a specific immune response. We thus decided to detect autoantibodies directed against endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) in the serum of GCA patients and to identify their target antigens.

Methods

Sera from 15 GCA patients were tested in 5 pools of 3 patients' sera and compared to a sera pool from 12 healthy controls (HCs). Serum immunoglobulin G (IgG) reactivity was analysed by 2-D electrophoresis and immunoblotting with antigens from human umbilical vein ECs (HUVECs) and mammary artery VSMCs. Target antigens were identified by mass spectrometry.

Results

Serum IgG from GCA patients recognised 162 ± 3 (mean ± SD) and 100 ± 17 (mean ± SD) protein spots from HUVECs and VSMCs, respectively, and that from HCs recognised 79 and 94 protein spots, respectively. In total, 30 spots from HUVECs and 19 from VSMCs were recognised by at least two-thirds and three-fifths, respectively, of the pools of sera from GCA patients and not by sera from HCs. Among identified proteins, we found vinculin, lamin A/C, voltage-dependent anion-selective channel protein 2, annexin V and other proteins involved in cell energy metabolism and key cellular pathways. Ingenuity pathway analysis revealed that most identified target antigens interacted with growth factor receptor-bound protein 2.

Conclusions

IgG antibodies to proteins in the proteome of ECs and VSMCs are present in the sera of GCA patients and recognise cellular targets that play key roles in cell biology and maintenance of homeostasis. Their potential pathogenic role remains to be determined.

Antiendothelial cells autoantibodies in vasculitis-associated systemic diseases

Antiendothelial cell antibodies (AECA) have been detected in healthy individuals, as well as in autoimmune and systemic inflammatory diseases, including systemic vasculitides. AECA have been reported in large vessel vasculitides such as giant cell arteritis and Takayasu arteritis; medium-sized vessel vasculitides, such as polyarteritis nodosa related to hepatitis B virus infection and Kawasaki disease; and small-sized vessel vasculitides, such as Wegener's granulomatosis, microscopic polyangiitis, and Henoch-Schonlein purpura. In Takayasu arteritis and antineutrophil cytoplasm antibody-positive vasculitides, AECA have been reported to correlate with disease activity. A cell-based enzyme-linked immunosorbent assay (ELISA) using cultured human umbilical vein endothelial cells (HUVEC) represent one of the reference techniques for AECA detection, although flow cytometry and immunobloting have also been proposed. AECA might contribute to the pathogenesis of systemic vasculitides and vasculitis-associated diseases through (1) activation of endothelial cells (EC), (2) direct cytotoxic effect due to complement-dependent cytotoxicity or indirect cytotoxic effect secondary to antibody-dependent cytotoxicity, (3) induction of coagulation, (4) induction of apoptosis through the binding of phospholipids or heat-shock protein 60, and (5) induction of EC activation. None of the identified target antigens of AECA is specific for EC, and EC-specific target antigens of AECA remain to be identified in systemic vasculitides.

Pivotal role of glutathione depletion in plasma-induced endothelial oxidative stress during sepsis

OBJECTIVE

Plasma from septic shock patients can induce production of reactive oxygen species (ROS) by human umbilical vein endothelial cells (HUVEC) in vitro. How endothelial cells defend themselves against ROS under increased oxidative stress has not yet been examined. This study investigates the antioxidant defenses of HUVEC exposed to plasma obtained from either septic shock patients or healthy volunteers.

DESIGN

Prospective, observational study.

SETTING

Medical intensive care unit in a university hospital.

PATIENTS

Twenty-five patients with septic shock and 10 healthy volunteers.

INTERVENTIONS

Blood samples were collected within the first 24 hrs of septic shock. In vitro HUVEC production of ROS was studied by spectrofluorimetry using 2',7'-dichlorodihydrofluorescein diacetate fluorescent dye. Reactive nitrogen species were also assessed. Intracellular reduced glutathione (GSH) levels were measured using monochlorobimane fluorescent dye. Activity of catalase and superoxide dismutase in HUVEC were also measured. Cell death was assessed using YOPRO fluorescent dye and the MTT assay.

MEASUREMENTS AND RESULTS

On admission, the septic shock population's mean age was 55 yrs old, the mean Sequential Organ Failure Assessment score was 12, mean simplified acute physiology score was 50, and intensive care unit mortality rate was 45%. Evaluation of HUVEC antioxidant defenses showed a significantly decreased GSH level, increased catalase activity, and unchanged superoxide dismutase activity. ROS levels and cell death were significantly reduced when cells were pretreated with N-acetylcysteine or GSH, but no changes in reactive nitrogen species were observed.

CONCLUSION

This study demonstrates that plasma-induced ROS production by HUVEC is associated with an intracellular decrease in reduced GSH. Both ROS levels and cell death decreased when N-acetylcysteine or GSH were added before exposing the cells to plasma. These data suggest a pivotal role of alterations in GSH in damage caused by sepsis-generated ROS in endothelial cell.

Identification of target antigens of antiendothelial cell antibodies in healthy individuals: A proteomic approach

In order to identify target antigens of anti-endothelial cell (anti-EC) antibodies (AECA) in healthy individuals, we have used a proteomic approach combining 2-DE and immunoblotting. Whole cell protein extracts obtained from human umbilical vein EC (HUVEC) cultures were used as a source of antigens. Serum IgG from 12 healthy blood donors were tested at a concentration of 200 microg/mL. Targeted spots were identified by MS. The HUVEC proteome was composed of 884 protein spots. Among these, 61 +/- 25.8 (mean +/- SD) spots were recognized by serum IgG from healthy individuals, with marked differences from one individual to another. Among these spots, 11 were recognized by serum IgG from all healthy individuals tested. These spots corresponded to six different proteins with several spots corresponding to different isoforms of the same protein. Target antigens were: cytoskeletal proteins (beta-actin, alpha-tubulin, and vimentin); glycolytic enzymes (glucose-3-phosphate-deshydrogenase and alpha-enolase); and prolyl-4-hydroxylase beta subunit, a member of the disulfide isomerase family. This study shows that the repertoire of IgG AECA is heterogeneous among healthy individuals. IgG from all of the healthy individuals tested recognized a restricted set of highly conserved ubiquitous proteins playing key roles in cell biology and maintenance of homeostasis.

Natural anti-endothelial cell antibodies

Anti-endothelial cell antibodies (AECA) are detectable in a heterogenous group of autoimmune and inflammatory conditions. These antibodies have also been detected in healthy individuals. Nevertheless, most of the literature focuses on AECA in pathological conditions and their targets and functions in healthy individuals remain to be clarified. Recently, proteome-based technologies have been successfully used for the identification of antigens targeted by natural AECA. Thus, it has been shown that IgG AECA can be detected in sera from healthy individuals that recognize a restricted set of proteins among a whole protein extract of umbilical vein endothelial cells. These proteins correspond to ubiquitous proteins belonging to highly conserved protein families and exerting pivotal roles in cell physiology, including cytoskeletal proteins (beta actin, vimentin, alpha tubulin) and glycolytic enzymes (glyceraldehyde-3-phosphate-deshydrogenase and alpha-enolase). As reported for other types of natural autoantibodies, natural AECA could exert anti-inflammatory and anti-thrombotic functions. In addition, they could play a role in the control of EC activation.

Polyangéite microscopique

Microscopic polyangiitis was initially considered a "microscopic" form of polyarteritis nodosa and was not definitively distinguished from it until the Chapel Hill nomenclature (1994). Microscopic polyangiitis is a systemic necrotizing vasculitis of small vessels. Its typical clinical manifestations are rapidly progressive glomerulonephritis and alveolar hemorrhage. Other possible symptoms resemble those encountered in polyarteritis nodosa. Microscopic polyangiitis belongs to the group of ANCA-associated vasculitides, and 75-80% of patients have pANCA to myeloperoxidase (MPO). Anti-MPO ANCA pathogenicity has been established in animal models, and a recent report describes transplacental transfer of these antibodies in humans, resulting in pulmonary hemorrhage and renal involvement in the newborn. Patients with no poor prognostic factors, as defined by a five-factor score, can be treated with corticosteroids alone, with immunosuppressants added only in case of treatment failure. Patients with one or more poor prognostic factors must receive a combination of corticosteroids and immunosuppressants, mainly intravenous pulsed cyclophosphamide, with plasma exchange as an adjuvant therapy for those with severe renal involvement. Once remission is achieved, maintenance therapy can replace cyclophosphamide by azathioprine or methotrexate. Biological therapies are under evaluation. The remission rate is above 80% with these regimens, and the relapse rate is around 30% at 5 years, lower than for Wegener's granulomatosis.

Immunoblotting on HEp-2 cells increases the detection of antitopoisomerase 1 antibodies in patients with systemic sclerosis

In order to improve the detection of antitopoisomerase 1 antibodies in a cohort of 111 systemic sclerosis patients, we have performed immunoblots on protein extracts of HEp-2 cells. Using indirect immunofluorescence and ELISA, 27 patients (24.3%) had antitopoisomerase 1 antibodies, 32 (28.8%) had anticentromere antibodies, 31 (27.9%) had antinuclear antibodies with none of these two antibodies and 21 (18.9%) had no antinuclear antibody. IgG from 24/27 (88.9%) patients with antitopoisomerase 1 antibodies bound to 2 protein bands of 63 and 100 kDa identified as topoisomerase 1 by N-terminal sequencing. Antitopoisomerase 1 antibodies were detected in 9 (8.1%) patients who had no antitopoisomerase 1 antibody as determined by ELISA. Patients with antitopoisomerase 1 antibodies had an almost similar phenotype without distinction between ELISA or immunoblot approaches. Our results provide evidence for the use of a combination of ELISA and immunoblot approaches for the detection of antitopoisomerase 1 antibodies.

Radical oxygen species production induced by advanced oxidation protein products predicts clinical evolution and response to treatment in systemic sclerosis

OBJECTIVES

To investigate the role of reactive oxygen species (ROS) in the development of the various patterns of systemic sclerosis (SSc) and the mechanisms of ROS production by endothelial cells and fibroblasts.

METHODS

Production of hydrogen peroxide (H(2)O(2)), nitric oxide (NO) and cellular proliferation were determined following incubation of endothelial cells and fibroblasts with 56 SSc and 30 healthy sera. Correlations were established between those markers, the type and the severity of the clinical involvements, and the response to treatment. The factors leading to ROS production were determined.

RESULTS

H(2)O(2) production by endothelial cells and fibroblasts was higher after incubation with SSc sera than with normal sera (p<0.001) and with sera from SSc patients with severe complications than sera from other patients (p<0.05). Sera from patients with lung fibrosis triggered the proliferation of fibroblasts more than other SSc sera (p<0.001), whereas sera from patients with vascular complications exerted no proliferative effect on fibroblasts, but inhibited endothelial cell growth (p<0.05) and induced NO overproduction (p<0.05). Bosentan reduced NO release by 32%, whereas N-acetylcystein potentiated 5-fluorouracil (5FU) to inhibit fibroblast proliferation by 78%. Those serum-mediated effects did not involve antibodies but advanced oxidation protein products that selectively triggered cells to produce H(2)O(2) or NO.

CONCLUSIONS

SSc sera induce the production of different types of ROS that selectively activate endothelial cells or fibroblasts, leading to vascular or fibrotic complications. Assaying serum-induced ROS production allows clinical activity of the disease to be followed and appropriate treatments to be selected.

[New insights into the pathogenesis of ANCA-positive vasculitides]

Recent studies provided new insights into the pathogenesis of vasculitides associated with antineutrophil cytoplasm antibodies (ANCA). They yield more information about the pathogenic role of ANCA, the initiation of the immune response against proteinase 3, the expression of ANCA target antigens on neutrophil surfaces, endothelial damage and the mechanisms of vasculitis associated with propylthiouracil. The pathogenic role of antimyeloperoxidase antibodies has been established in vitro and in vivo in animal models and in human. A pathogenic role for antiproteinase 3 antibodies has not yet been clearly established in vivo although it is well documented in vitro.

Anti-endothelial cell antibodies from patients with limited cutaneous systemic sclerosis bind to centromeric protein B (CENP-B)

By using a quantitative immunoblotting technique on protein extracts of human macrovascular and microvascular endothelial cells, we have analyzed the self-reactive repertoires of IgG from 20 patients with limited cutaneous SSc, 40 patients with diffuse SSc and 60 age- and sex-matched healthy controls. Serum IgG from 15/20 patients with limited cutaneous SSc and anti-centromere antibodies bound to at least one of the two 75- and 85-kDa protein bands in the different endothelial cell extracts, whereas IgG from healthy controls or patients with diffuse SSc did not. N-terminal sequencing of the 75- and 85-kDa bands identified CENP-B as the sole antigen in both bands. Moreover, IgG from all of the SSc patients who recognized the 75- and/or 85-kDa bands bound to a full-length recombinant CENP-B protein as assessed by ELISA, whereas IgG from other SSc patients did not. The main target of anti-endothelial cell antibodies in patients with limited cutaneous SSc is the nuclear and ubiquitous protein CENP-B.

Cutaneous Vasculitis Update: Diagnostic Criteria, Classification, Epidemiology, Etiology, Pathogenesis, Evaluation and Prognosis

Vasculitis, inflammation of the vessel wall, can result in mural destruction with hemorrhage, aneurysm formation, and infarction, or intimal-medial hyperplasia and subsequent stenosis leading to tissue ischemia. The skin, in part due to its large vascular bed, exposure to cold temperatures, and frequent presence of stasis, is involved in many distinct as well as un-named vasculitic syndromes that vary from localized and self-limited to generalized and life-threatening with multi-organ disease. To exclude mimics of vasculitis, diagnosis of cutaneous vasculitis requires biopsy confirmation where its acute signs (fibrinoid necrosis), chronic signs (endarteritis obliterans), or past signs (acellular scar of healed arteritis) must be recognized and presence of extravascular findings such as patterned fibrosis or collagenolytic granulomas noted. Although vasculitis can be classified by etiology, many cases have no identifiable cause, and a single etiologic agent can elicit several distinct clinicopathologic expressions of vasculitis. Therefore, the classification of cutaneous vasculitis is best approached morphologically by determining vessel size and principal inflammatory response. These histologic patterns roughly correlate with pathogenic mechanisms that, when coupled with direct immunofluorescent examination, anti-neutrophil cytoplasmic antibody (ANCA) status, and findings from work-up for systemic disease, allow for specific diagnosis, and ultimately, more effective therapy. Herein, we review cutaneous vasculitis focusing on diagnostic criteria, classification, epidemiology, etiology, pathogenesis, and evaluation of the cutaneous vasculitis patient.

Polyarteritis nodosa revisited

Polyarteritis nodosa (PAN), the prototype of systemic vasculitis, is a rare condition characterized by necrotizing inflammation of medium-sized or small arteries without glomerulonephritis or vasculitis in arterioles, capillaries, or venules. Signs and symptoms of this disease are primarily attributable to diffuse vascular inflammation and ischemia of affected organs. Virtually any organ with the exception of the lungs may be affected, with peripheral neuropathy and symptoms from osteoarticular, renal artery, and gastrointestinal tract involvement being the most frequent clinical manifestations. A clear distinction between limited versus systemic disease and idiopathic versus hepatitis B related PAN should be done because there are differences in the implicated pathogenetic mechanisms, their treatment, and prognosis. Currently, corticosteroids plus cyclophosphamide is the standard of care for idiopathic PAN, in particular for patients with adverse prognostic factors (more severe disease), in whom this combination prolonged survival. In contrast for hepatitis B related PAN treatment consists of schemes that include plasmapheresis and antiviral agents.

Anti-endothelial cell antibodies in idiopathic and systemic sclerosis associated pulmonary arterial hypertension

BACKGROUND

It has previously been shown that IgG antibodies from patients with limited cutaneous systemic sclerosis (SSc) bind to specific microvascular endothelial cell antigens. Since patients with limited cutaneous SSc are prone to develop pulmonary arterial hypertension (PAH), and since endothelial cell activation is involved in the pathogenesis of idiopathic PAH (IPAH), a study was undertaken to examine the presence of anti-endothelial cell antibodies in patients with idiopathic or SSc associated PAH.

METHODS

PAH was confirmed by right heart catheterisation (mean pulmonary artery pressure at rest >25 mm Hg). Serum IgG and IgM reactivities were analysed by immunoblotting on human macrovascular and microvascular lung and dermal endothelial cells from patients with IPAH (n = 35), patients with PAH associated with SSc (n = 10), patients with diffuse (n = 10) or limited cutaneous (n = 10) SSc without PAH, and 65 age and sex matched healthy individuals.

RESULTS

IgG antibodies from patients with IPAH bound to a 36 kDa band in macrovascular endothelial cell extracts with a higher intensity than IgG from other patient groups and controls. IgG antibodies from patients with IPAH bound more strongly to a 58 kDa band in microvascular dermal endothelial cells and to a 53 kDa band in microvascular lung endothelial cells than IgG antibodies from other patients and controls. IgG antibodies from patients with limited cutaneous SSc with or without PAH, but not from other groups or from healthy controls, bound to two major bands (75 kDa and 85 kDa) in microvascular endothelial cells.

CONCLUSION

IgG antibodies from patients with idiopathic or SSc associated PAH express distinct reactivity profiles with macrovascular and microvascular endothelial cell antigens.

Analysis of autoantibody repertoires in small- and medium-sized vessels vasculitides. Evidence for specific perturbations in polyarteritis nodosa, microscopic polyangiitis, Churg-Strauss syndrome and Wegener's granulomatosis

In order to identify new antibody reactivities, we have used a quantitative immunoblotting technique on extracts of normal human tissues to analyze the repertoires of serum IgM, serum IgG and purified IgG autoantibodies of patients with systemic vasculitides. Patients fulfilled the American College of Rheumatology and Chapel Hill criteria for the diagnosis of polyarteritis nodosa (PAN) (n=8), PAN related to hepatitis B virus (HBV) infection (n=5), Wegener's granulomatosis (WG) (n=6), microscopic polyangiitis (MPA) (n=18) or Churg-Strauss syndrome (CSS) (n=8). Sera from patients with chronic HBV infection without PAN (n=5) and age- and gender-matched healthy individuals (n=45) were used as controls. In the lung extract, IgM from 12/18 MPA patients reacted with high intensity with a 50 kDa band and serum IgG from 3/8 CSS patients bound to a 70 kDa protein band. In the artery extract, serum IgG from 6/18 MPA patients bound to an 85 kDa antigen, whereas purified IgG from all WG patients tested bound to a 28 kDa protein band and IgM from CSS patients bound to 2 main antigens of 38 and 60 kDa. These results provide evidence for the specificity of autoantibody repertoires from patients with PAN, WG, CSS and MPA.

Pathogénie des vascularites systémiques primitives (I) : vascularites ANCA-positives

The pathogenesis of different types of systemic vasculitis positive for antineutrophil cytoplasmic antibodies (ANCA) remains incompletely understood. ANCA constitute a heterogeneous group of antibodies that are associated with different types of small-vessel vasculitis, including Wegener's granulomatosis (WG), microscopic polyangiitis (MPA) and Churg-Strauss syndrome (CSS). Anti-proteinase 3 ANCA are present in more than 90% of patients with systemic WG, and anti-myeloperoxidase (MPO) ANCA in 50-75% of those with MPA and 40-60 % of those with CSS. The pathogenic role of ANCA has been well documented in vivo: passive transfer of anti-MPO ANCA in an MPO knockout mouse model immunized with MPO is sufficient to induce the disease. In vitro, mouse and human anti-proteinase 3 ANCA can activate neutrophils primed with TNF-a and contribute to vasculitic lesions. T-cells are also involved: type 1 helper cytokines have been detected in tissue lesions of limited forms of WG, while type 2 helper cytokines have been identified in its systemic forms. Eosinophils may play a key role in the development of vasculitic lesions in CSS, although this remains to be proved.

Hepatitis B virus replication in damaged endothelial tissues of patients with extrahepatic disease

Hepatitis B virus (HBV) infection may be complicated by extrahepatic manifestations such as polyarteritis nodosa (PAN), glomerulonephritis, polymyositis, and dermatitis, but the etiology of these processes is not yet clear. HBV replication has been demonstrated in a variety of extrahepatic tissues and cell types, but the possible pathogenetic role of extrahepatic HBV replication has not been fully explored in patients with extrahepatic manifestations of HBV infection. In this case series, immunohistochemistry and in situ hybridization studies were performed on extrahepatic tissues from one HBsAg-positive patient with PAN and another HBsAg-positive patient with polymyositis, using HBsAg-seronegative control subjects with the same vasculitic disorders as controls. Tissue samples from the two study patients had detectable HBV RNA, replicative intermediates of HBV DNA, as well as HBsAg and HBcAg localized to vascular endothelium. In contrast, HBsAg-negative control patients had no tissue reactivity. Our results suggest that patients with HBV-related extrahepatic disease have evidence of viral replication in damaged extrahepatic endothelial tissues. While further studies would be required to support a hypothesis of causality, these findings suggest a role for both immune complex deposition and viral replication within diseased endothelial tissue in the pathogenesis of these poorly understood extrahepatic disorders.

Endothelial cells, antineutrophil cytoplasmic antibodies, and cytokines in the pathogenesis of systemic vasculitis

Endothelial cells play a pivotal role in the pathogenesis of systemic vasculitis. Endothelial cells have significant proinflammatory activities, amplifying and perpetuating the inflammatory process and contributing to vessel regeneration and repair. Significant contributions have improved the understanding of additional ways through which antineutrophil cytoplasmic antibodies (ANCA) may potentiate neutrophil- and monocyte-mediated endothelial cell activation and damage. Signaling pathways mediating ANCA effects have been delineated, and new animal models have demonstrated the pathogenic role of ANCA in the development of systemic vasculitis. Significant efforts have identified anti-endothelial cell antibody specificities and elucidated mechanisms through which these antibodies may promote endothelial cell activation and injury. New ways to assess in vivo endothelial cell damage and dysfunction also have been developed. In addition, besides being a relevant compensatory mechanism for ischemia, angiogenesis may have important proinflammatory functions in vasculitis. The potential relevance of bone-marrow-derived endothelial cell precursors in neovascularization has begun to be appreciated.