Angiotensin II Type 2 Receptor Antibodies in Glomerular Diseases.

We evaluated the concentration of AT2R antibodies in 136 patients with primary and secondary glomerular diseases: membranous nephropathy (n = 18), focal and segmental glomerulosclerosis (n = 25), systemic lupus erythematosus (n = 17), immunoglobulin A (IgA) nephropathy (n = 14), mesangial (non-IgA) proliferative nephropathy (n = 6), c-ANCA vasculitis (n = 40), perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCA) vasculitis (n = 16), and compared it with a healthy control group (22 patients). Serum creatinine levels, proteinuria, serum albumin, and total protein concentrations were prospectively recorded for 2 years. The mean levels of AT2R antibodies in the lupus nephropathy group were significantly higher compared to the control group, 64.12 ± 26.95 units/mL and 9.72 ± 11.88 units/mL, respectively. There was no association between this level and the clinical course of the disease. The AT2R levels in other kinds of glomerular disease were no different from the control group. We found significant correlations between AT1R and AT2R in patients with membranous nephropathy (r = 0.66), IgA nephropathy (r = 0.61), and c-ANCA vasculitis (r = 0.63). Levels of AT2R antibodies in systemic lupus erythematosus are higher compared to other types of glomerulonephritis, vasculitis, and a healthy control group. Levels of AT2R antibodies correlate with AT1R antibodies in the groups of patients with membranous nephropathy, IgA nephropathy, and c-ANCA vasculitis. These kinds of AT2R antibodies have a stimulative effect on AT2R, but we have not found the influence of these antibodies on the clinical course of glomerular diseases.

Profiles of cytokines in patients with antineutrophil cytoplasmic antibody-associated vasculitis.

Objective: This study aimed to identify plasma biomarkers that are significantly altered in patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and are closely associated with AAV disease activity, as well as to explore their role in the pathogenesis of AAV. Methods: Cytokines were measured using Human Immune Response Panel 80-Plex in plasma from 59 patients with AAV and 20 healthy controls (HCs). The differentially expressed cytokines between the two groups and the possible signaling pathway involved in the pathogenesis of AAV were analyzed by bioinformatics. Relationship analysis was performed between these cytokines and clinical parameters to identify the biomarkers that can effectively indicate disease activity. Results: We identified 65 differentially expressed cytokines between the two groups. Among them, 43 cytokines significantly affected the risk of AAV. Bioinformatic analysis showed that the 43 cytokines were primarily enriched in signaling pathways such as cytokine-cytokine receptor interaction, viral protein interaction with cytokine and cytokine receptor, chemokine signaling pathway, and IL-17 signaling pathway. The levels of 25 cytokines were significantly positively correlated with Birmingham Vasculitis Activity Score (BVAS), and the levels of 2 cytokines were significantly negatively correlated with BVAS. Receiver operating characteristic analysis showed that 9 cytokines can distinguish between disease relapse and remission (PTX3: area under curve (AUC)=0.932, IL34: AUC=0.856, IL2RA: AUC=0.833, CCL23: AUC=0.826, VEGFA: AUC=0.811, TNFSF13: AUC=0.795, Granzyme A: AUC=0.788, CSF3: AUC=0.773 and IL1A: AUC=0.765). The elevated levels of these 9 cytokines suggested a risk of disease relapse. The AUC of CCL11 in disease relapse and remission was 0.811 (p=0.0116). Unlike the other 9 cytokines, a negatively association existed between CCL11 level and the risk of disease relapse. Conclusion: A group of cytokines that may be involved in AAV pathogenesis was identified. Increased PTX3, IL34, IL2RA, CCL23, and VEGFA levels correlate with active disease in AAV and may be used as biomarkers to identify the disease relapse of AAV.

Cathepsin C inhibition reduces neutrophil serine protease activity and improves activated neutrophil-mediated disorders.

Cathepsin C (CatC) is an enzyme which regulates the maturation of neutrophil serine proteases (NSPs) essential for neutrophil activation. Activated neutrophils are key players in the innate immune system, and are also implicated in the etiology of various inflammatory diseases. This study aims to demonstrate a therapeutic potential for CatC inhibitors against disorders in which activated neutrophil-derived neutrophil extracellular traps (NETs) play a significant role. We demonstrate that a CatC inhibitor, MOD06051, dose-dependently suppresses the cellular activity of NSPs, including neutrophil elastase (NE), in vitro. Neutrophils derived from MOD06051-administered rats exhibit significantly lower NE activity and NET-forming ability than controls. Furthermore, MOD06051 dose-dependently ameliorates vasculitis and significantly decreases NETs when administered to a rat model of myeloperoxidase (MPO)-antineutrophil cytoplasmic antibody-associated vasculitis (AAV). These findings suggest that CatC inhibition is a promising strategy to reduce neutrophil activation and improve activated neutrophil-mediated diseases such as MPO-AAV.

Causal relationship between immune cells and the risk of myeloperoxidase antineutrophil cytoplasmic antibody-associated vasculitis: A Mendelian randomization study.

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare inflammatory disease categorized as antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. The majority of patients are ANCA-positive, predominantly against myeloperoxidase (MPO). Previous studies have predominantly concentrated on the association between EGPA and neutrophils, but recent research has emphasized the role of lymphocytes in the development of EGPA. The objective of our research was to examine the causal association between immune cells and MPO + ANCA EGPA. A two-sample bidirectional Mendelian randomization (MR) analysis was performed, which included 159 MPO + ANCA EGPA cases and 6688 controls and utilized Genome-Wind Associaton Studies (GWAS) summary statistics of immune traits from approximately 3757 individuals, encompassing around 22 million single nucleotide polymorphisms (SNPs). Our findings revealed that 23 immunophenotypes were associated with MPO + ANCA EGPA. Furthermore, the reverse MR analysis showed that MPO + ANCA EGPA had significant causal effects on three immunophenotypes within the Treg panel. By integrating existing research, our study unveiled the contributions of Tregs, B cells, and monocytes to the development of EGPA. Subgroup analysis specifically examined the roles of lymphocyte subtypes, cytokines, and their surface molecules in the pathogenic mechanisms of the disease. This comprehensive approach provides a novel perspective on the biological mechanisms and early intervention strategies for MPO + ANCA EGPA by focusing on immune cells.

The role of tobacco smoking in anti-neutrophil cytoplasmic antibody-associated vasculitis: a systematic review.

OBJECTIVES: Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV) are a group of systemic pauci-immune necrotising vasculitides involving small vessels, characterised by the presence of specific ANCA autoantibodies directed to leukocyte proteinase 3 (PR3-ANCA) or myeloperoxidase (MPO-ANCA) and subdivided into three clinical entities: granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (EGPA). The aetiology of AAV is unknown and many genetic, epigenetic and environmental factors have been reported to be involved in pathogenesis. Smoking is widely recognised as a risk factor for the development of many autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus. This systematic review will analyse known data about the role of smoking in the development, clinical presentation and outcome of AAV. METHODS: Articles that examined interactions between tobacco smoking and AAV (GPA, MPA, EGPA) were included. All articles selected were in English. No limitation on publication date was established. Case reports were excluded. The systematic search was performed using PubMed/Medline and Cochrane Library databases. RESULTS: The search provided a total of 131 articles. Three studies were added, obtained from the review of the reference lists of articles. 70 were removed because they were duplicated or written in languages other than English. The title and abstract of 64 articles were screened. Of these, 30 were excluded as the title and/or abstract did not meet the inclusion criteria. Thus, 34 remained for full-text review, of which 8 were excluded. 26 articles were therefore included in this review. The role of smoking in AAV development is unclear. AAV patients current smoking appear appear to be younger and more frequently males, with a lower prevalence of EGPA and MPA than GPA. Ever smokers show higher relapse rate. Smoking seems to be associated with a higher risk of cardiovascular events during follow-up. Smokers incur an increased risk of infections. Finally, many data support smoking as a risk factor for end stage renal disease and mortality in AAV patients. CONCLUSIONS: Current data support the hypothesis that smoking influences prevalence, clinical phenotype and prognosis of ANCA-associated vasculitis. However, further studies are required to fully determine its role.

Coexistence of double seropositivity for MPO antibody and anti-GBM antibody in ANCA-associated vasculitis concurrent with multiple myeloma: A case report.

RATIONALE: Immune-mediated vasculitis with 2 or more autoantibodies, for example, anti-proteinase-3, combined with anti-myeloperoxidase (MPO) or anti-glomerular basement membrane (GBM) antibodies, is extremely unusual. Furthermore, the coexistence of autoimmune vasculitis and hematological malignancies is uncommon. Herein, we describe a case of double-seropositive anti-neutrophil cytoplasmic antibody (ANCA) vasculitis with multiple myeloma. PATIENT CONCERNS: A 79-year-old Asian man presented with persistent leg edema and kidney dysfunction. His kidney function rapidly decreased, and serologic test results showed higher titers of the anti-MPO antibody (54.7 IU/mL) and anti-GBM antibodies (>200 IU/mL). Additionally, the clinical features showed the possibility of monoclonal gammopathy with anemia and hyperglobulinemia. We performed kidney and bone marrow biopsy. Serum protein electrophoresis and immunofixation revealed no significant differences, but the results of the bone marrow smear were compatible with those of myeloma with 15% plasmacytosis. However, kidney biopsy showed diffuse crescentic glomerulonephritis without deposition of the immune complex or kappa/lambda chain. DIAGNOSES AND INTERVENTIONS: Finally, the patient was diagnosed with double-seropositive ANCA-associated glomerulonephritis and multiple myeloma. Given the patient's performance status, we initiated low-dose steroid pulse therapy, followed by conservative management. OUTCOMES: While the pulmonary lesions showed improvement, the kidney function did not regain its previous state, prompting the initiation of kidney replacement therapy by hemodialysis. There has been a decrease in the levels of anti-GBM and anti-MPO antibodies since the initial diagnosis. LESSONS: This case elucidates the complex interplay between ANCA-associated glomerulonephritis and hematologic malignancy and emphasizes the need for a nuanced treatment strategy considering its multifaceted clinical presentation.

Clinical characteristics and outcome of double-seropositive patients with anti-glomerular basement membrane antibodies and anti-neutrophil cytoplasmic antibodies.

OBJECTIVE: To explore the clinical characteristics of double-seropositive patients (DPPs) with anti-glomerular basement membrane (Anti-GBM) antibodies and anti-neutrophil cytoplasmic antibodies (ANCA). METHODS: We collected patients with both ANCA and anti-GBM positive glomerulonephritis who were hospitalized in the Department of Nephrology at the First Affiliated Hospital of Nanjing Medical University from January 2010 to August 2022. Retrospective analysis of the baseline clinical characteristics of patients and follow-up to explore relevant factors affecting renal and patient survival. RESULTS: A total of 386 patients, including 69 ANCA negative anti-GBM glomerulonephritis patients, 296 anti-GBM negative ANCA associated vasculitis (AAV) patients, and 21 DPPs were enrolled in this study. Among the 21 DPPs aged 68.0 years (59.5, 74.0), there were 11 males and 10 females. The median serum creatinine at diagnosis was 629.0 (343.85, 788.75) µmol/L, and the median eGFR (CKD-EPI) was 7.58 (4.74, 13.77) mL/min. Fifteen cases (71.4 %) underwent initial RRT. After a follow-up of 40.0 (11.0, 73.0) months, 13 out of 21 DPPs (61.9 %) received maintenance RRT, while 49 out of 69 (71.0 %) ANCA negative anti-GBM-GN patients and 124 out of 296 (41.9 %) anti-GBM negative AAV patients received maintenance RRT (P < 0.001). Kaplan-Meier survival analysis showed that DPPs and ANCA negative anti-GBM-GN patients were more likely to progress to ESRD than anti-GBM negative AAV patients (P = 0.001). Among the 21 patients with DPPs, renal survival was significantly better in patients with better initial renal function, including those who did not receive initial RRT (P = 0.003), with lower serum creatinine levels (Cr < 629.0 µmol/L, P = 0.004) and higher eGFR levels (eGFR ≥ 7.60 ml/min, P = 0.005) than those with poor initial renal function. At the end of follow-up, 14 out of 21 DPPs (66.7 %) survived. Survival analysis showed no significant difference among patients in DPPs group, ANCA negative anti-GBM-GN group, and anti-GBM negative AAV group. CONCLUSIONS: DPPs and ANCA negative anti-GBM-GN patients were more likely to progress to ESRD than anti-GBM negative AAV patients. In DPPs, the poor renal function at diagnosis might be a risk factor associated with poor renal survival.

Update on antineutrophil cytoplasmic autoantibody vasculitis in children.

PURPOSE OF REVIEW: Antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) is often organ- or life-threatening in children and impacts them during important periods of psychosocial and physical development. This review covers recent advances in the pathophysiology, diagnosis, management, and outcomes of AAV in children and highlights the ongoing need for funding and increased research collaboration. RECENT FINDINGS: Recent work has improved our understanding of AAV disease pathogenesis, potentially identifying new biomarkers and therapeutic targets. Collaborative clinical studies have also highlighted the variable manifestations in children and identified potential factors associated with poorer outcomes. Consensus-based treatment guidelines are also appearing, but clinical trials are still essential to better understanding treatment efficacy and safety in children affected by AAV. New, validated outcome measures, including those that are patient-reported, will facilitate these much-needed clinical trials in pediatric AAV. SUMMARY: There is a continued need for more rigorous study in pediatric AAV, however, there is certainly excitement with the increase in recent research relevant to the pediatric population.

Co-existence of ANCA-associated vasculitides with immune-mediated diseases: a single-center observational study.

BACKGROUND: Antineutrophil cytoplasmic antibody-associated vasculitides (AAV) is a group of systemic necrotizing small vessel autoimmune diseases, with microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA) being the two most common. The co-existence of AAV with different immune-mediated diseases (autoimmune disesases - AID) might affect the clinical presentation of the primary disease. The purpose of the study was to assess the co-existence of AAV with AID and to investigate whether it affects the characteristics and the course of AAV. METHODS: A retrospective single-center study was performed to identify patients with a diagnosis of MPA or GPA and concomitant AID, and to investigate their clinical features and characteristics. The group consisted of consecutive unselected AAV patients treated at a large university-based hospital, since 1988 with follow-up until 2022. RESULTS: Among 284 patients diagnosed either with GPA (232) or MPA (52), 40 (14,1%) had co-existing AIDs. The most frequent were: Hashimoto thyroiditis (16 cases), rheumatoid arthritis (8 cases), followed by psoriasis (6 cases), pernicious anemia (3 cases), and alopecia (3 cases). Patients with autoimmune comorbidities had a significantly longer time between the onset of symptoms and the diagnosis (26 vs. 11 months, p < 0.001). Laryngeal involvement (20.0% vs. 9.0%, p = 0,05), peripheral nervous system disorders (35.0% vs. 13.9%, p < 0.001), and neoplasms (20.0% vs. 8.6%, p = 0,044) were more common in patients with AID comorbidities, compared to subjects without AID. In contrast, renal involvement (45.0% vs. 70.9%, p = 0.001) and nodular lung lesions (27.5% vs. 47.5%, p = 0.044) were significantly less frequent in patients with co-morbidities. Following EUVAS criteria, patients with autoimmune co-morbidities had a generalized form of the disease without organ involvement (52.5% vs. 27.2%, p = 0.007), while the others had a higher percentage of generalized form with organ involvement (38.3% vs. 20.0%, p = 0.007). CONCLUSIONS: The coexistence of AAV with different autoimmune diseases is not common, but it might affect the clinical course of the disease. Polyautoimmunity prolonged the time to diagnosis, but the AAV course seemed to be milder. Particular attention should be paid to the increased risk of cancer in these patients. It also seems reasonable that AAV patients should receive a serological screening to exclude the development of overlapping diseases.

Predictive utility of ANCA positivity and antigen specificity in the assessment of kidney disease in paediatric-onset small vessel vasculitis.

OBJECTIVES: The objective of this study is to evaluate whether anti-neutrophil cytoplasmic antibody (ANCA) seropositivity and antigen specificity at diagnosis have predictive utility in paediatric-onset small vessel vasculitis. METHODS: Children and adolescents with small vessel vasculitis (n=406) stratified according to the absence (n=41) or presence of ANCA for myeloperoxidase (MPO) (n=129) and proteinase-3 (PR3) (n=236) were compared for overall and kidney-specific disease activity at diagnosis and outcomes between 1 and 2 years using retrospective clinical data from the ARChiVe/Paediatric Vasculitis Initiative registry to fit generalised linear models. RESULTS: Overall disease activity at diagnosis was higher in PR3-ANCA and MPO-ANCA-seropositive individuals compared with ANCA-negative vasculitis. By 1 year, there were no significant differences, based on ANCA positivity or specificity, in the likelihood of achieving inactive disease (~68%), experiencing improvement (≥87%) or acquiring damage (~58%). Similarly, and in contrast to adult-onset ANCA-associated vasculitis, there were no significant differences in the likelihood of having a relapse (~11%) between 1 and 2 years after diagnosis. Relative to PR3-ANCA, MPO-ANCA seropositivity was associated with a higher likelihood of kidney involvement (OR 2.4, 95% CI 1.3 to 4.7, p=0.008) and severe kidney dysfunction (Kidney Disease Improving Global Outcomes (KDIGO) stages 4-5; OR 6.04, 95% CI 2.77 to 13.57, p<0.001) at onset. Nonetheless, MPO-ANCA seropositive individuals were more likely to demonstrate improvement in kidney function (improved KDIGO category) within 1 year of diagnosis than PR3-ANCA seropositive individuals with similarly severe kidney disease at onset (p<0.001). CONCLUSIONS: The results of this study suggest important paediatric-specific differences in the predictive value of ANCA compared with adult patients that should be considered when making treatment decisions in this population.

Clinicopathological characteristics of pediatric ANCA-associated glomerulonephritis.

BACKGROUND: Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis and glomerulonephritis is uncommon in children. We sought to characterize the histological and clinical features of the disease and report on risk factors for adverse outcomes in a pediatric cohort. METHODS: Retrospective single-center cohort of all pediatric (< 20 years) patients diagnosed with ANCA-associated glomerulonephritis (AAGN) by kidney biopsy between 2002 and 2022 at Johns Hopkins University. Histological and clinical features were extracted from the medical record. Clinical, laboratory, and histological findings were analyzed to determine the association with kidney failure (KF) and/or death. RESULTS: A total of 17 patients were identified (GPA n = 7, MPA = 10) with a median age of 15 years (IQR 12-17) at presentation, a slight female predominance (59%), with seven patients reaching the composite outcome of death (n = 1) or kidney failure (n = 6). There was no difference in presenting clinical symptoms or extra-renal manifestations between the two groups. Univariable Cox regression identified several factors associated with an increased hazard of endpoint including the degree of global or segmental sclerosis, interstitial fibrosis and tubular atrophy (IFTA), C3 and C1q staining, presence of subendothelial deposits, and proteinuria. Multivariable regression was not performed due to the small sample size. We saw a trend towards increased utilization of plasma exchange and a decrease in cyclophosphamide utilization in the more recent era. There was no association between treatment modality and outcome. CONCLUSIONS: Pediatric AAGN is a rare disease associated with significant morbidity. We identified glomerulosclerosis and IFTA on histology, and proteinuria on initial presentation as risk factors for KF/death.

Kidney Failure in Pauci-immune Crescentic Glomerulonephritis: Rationale for Immunosuppression to Improve Kidney Outcome.

PURPOSE OF REVIEW: Pauci-immune crescentic glomerulonephritis is the hallmark finding in ANCA-associated vasculitis (AAV) when the kidneys are affected. The rationale for immunosuppression in AAV is based on the underlying autoimmune nature of the disease. Overall remission rates, kidney outcomes, and the burden of disease have greatly improved since the discovery of various immunosuppressive therapies, but relapses remain common, and a significant proportion of patients continue to progress to end-stage kidney disease. Here, we review the role of immunosuppressive therapies for the treatment of pauci-immune crescentic glomerulonephritis. RECENT FINDINGS: Besides the recognized role of B and T cells in the pathogenies of AAV, the focus on the contribution of inflammatory cytokines, neutrophil extracellular traps (NETs), and the complement system allowed the discovery of new therapies. Specifically, the C5a receptor blocker (avacopan) has been approved as a glucocorticoid-sparing agent. Additionally, based on observational data, more clinicians are now using combination therapies during the induction phase. There is also an evolving understanding of the role of plasma exchange in removing ANCA antibodies. Furthermore, the recent development of risk score systems provides physicians with valuable prognostic information that can influence decisions on immunosuppression, although future validation from larger cohorts is needed. The over-activation of various immune pathways plays a significant role in the pathogenesis of pauci-immune crescentic glomerulonephritis in AAV. Immunosuppression is, therefore, an important strategy to halt disease progression and improve overall outcomes. Relapse prevention while minimizing adverse events of immunosuppression is a major long-term goal in AAV management.

Antineutrophil cytoplasmic antibody-associated vasculitis.

PURPOSE OF REVIEW: This review focuses on latest developments in managing antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV), a systemic autoimmune condition characterized by inflammation and necrosis of small blood vessels due to circulating autoantibodies that target neutrophilic granules. RECENT FINDINGS: Our understanding of AAV pathogenesis has evolved in the past decades highlighting the central pathogenic roles of autoantibodies and complement activation. In parallel, the appreciation for glucocorticoid toxicity has led the research on crucial steroid-sparing therapeutic alternatives. Complement inhibitors (like avacopan) that have emerged are associated with better preservation of kidney function in AAV patients with severe kidney impairment. The role of plasma-exchange (PLEX) was revisited in updated guidelines that recommended its potential use in the context of diffuse alveolar hemorrhage associated hypoxia and severe kidney involvement, particularly with a serum creatinine level above 3.4 mg/dl. The ANCA Kidney Risk Score risk prediction and Glucocorticoid Toxicity Index score aid in identifying high-risk patients and individualizing management plans. SUMMARY: Kidney involvement in AAV requires prompt diagnosis and initiation of immunosuppression to prevent irreversible nephron loss. Newer therapeutic targets are on the horizon and offer hope for personalized treatment strategies.

Pathogenesis of Pulmonary Manifestations in ANCA-Associated Vasculitis and Goodpasture Syndrome.

Pulmonary manifestations of vasculitis are associated with significant morbidity and mortality in affected individuals. They result from a complex interplay between immune dysregulation, which leads to vascular inflammation and tissue damage. This review explored the underlying pathogenesis of pulmonary involvement in vasculitis, encompassing various forms such as granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), eosinophilic granulomatosis with polyangiitis (EGPA), and anti-GBM disease. Mechanisms involving ANCA and anti-GBM autoantibodies, neutrophil activation, and neutrophil extracellular trap (NETs) formation are discussed, along with the role of the complement system in inducing pulmonary injury. Furthermore, the impact of genetic predisposition and environmental factors on disease susceptibility and severity was considered, and the current treatment options were presented. Understanding the mechanisms involved in the pathogenesis of pulmonary vasculitis is crucial for developing targeted therapies and improving clinical outcomes in affected individuals.

Proteinase 3-specific antineutrophil cytoplasmic antibody-associated vasculitis.

Proteinase 3 (PR3)-specific antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis is one of two major ANCA-associated vasculitis variants and is pathogenically linked to granulomatosis with polyangiitis (GPA). GPA is characterised by necrotising granulomatous inflammation that preferentially affects the respiratory tract. The small vessel vasculitis features of GPA are shared with microscopic polyangiitis. Necrotising granulomatous inflammation of GPA can lead to PR3-ANCA and small vessel vasculitis via activation of neutrophils and monocytes. B cells are central to the pathogenesis of PR3-ANCA-associated vasculitis. They are targeted successfully by remission induction and maintenance therapy with rituximab. Relapses of PR3-ANCA-associated vasculitis and toxicities associated with current standard therapy contribute substantially to remaining mortality and damage-associated morbidity. More effective and less toxic treatments are sought to address this unmet need. Advances with cellular and novel antigen-specific immunotherapies hold promise for application in autoimmune disease, including PR3-ANCA-associated vasculitis. This Series paper describes the inter-related histopathological and clinical features, pathophysiology, as well as current and future targeted treatments for PR3-ANCA-associated vasculitis.

Myeloperoxidase-specific antineutrophil cytoplasmic antibody-associated vasculitis.

Myeloperoxidase (MPO)-specific antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (MPO-ANCA-associated vasculitis) is one of two major ANCA-associated vasculitis variants characterised by systemic necrotising vasculitis with few or no immune deposits. MPO-ANCA-associated vasculitis predominantly affects small blood vessels and, in contrast to its counterpart proteinase 3-ANCA-associated vasculitis, is generally not associated with granulomatous inflammation. The kidneys and lungs are the most commonly affected organs. The pathogenesis of MPO-ANCA-associated vasculitis is characterised by loss of tolerance to the neutrophil enzyme MPO. This loss of tolerance leads to a chronic immunopathological response where neutrophils become both the target and effector of autoimmunity. MPO-ANCA drives neutrophil activation, leading in turn to tissue and organ damage. Clinical trials have improved the therapeutic approach to MPO-ANCA-associated vasculitis. However, there remains substantial unmet need regarding relapse frequency, toxicity of current treatment, and long-term morbidity. In this Series paper, we present the current state of research regarding pathogenesis, diagnosis, and treatment of MPO-ANCA-associated vasculitis.

Neutrophil Extracellular Trap Formation and Deoxyribonuclease I Activity in Patients with Otitis Media with Antineutrophil Cytoplasmic Antibody-Associated Vasculitis.

INTRODUCTION: No previous studies have evaluated the levels of neutrophil extracellular trap (NET) remnants or the importance of deoxyribonuclease (DNase) I activity based on the disease activity of otitis media with antineutrophil cytoplasmic antibody-associated vasculitis (OMAAV). The aim of this study was to explore the formation of NETs in the middle ear of patients with OMAAV during the onset and remission phases of the disease, with a particular focus on the relationships between the quantifiable levels of NET remnants and DNase I activity. METHODS: OMAAV patients were eligible for inclusion. Patients with otitis media with effusion (OME) were examined as controls. The levels of cell-free deoxyribonucleic acid (DNA), citrullinated-histone H3 (cit-H3)-DNA complex, and myeloperoxidase (MPO)-DNA complex were quantified using an enzyme-linked immunosorbent assay. DNase I activity was measured using a fluorometric method. RESULTS: The quantifiable levels of cell-free DNA, cit-H3-DNA complex, and MPO-DNA complex in the middle ear lavage of patients with OMAAV at onset were significantly higher than those in patients with OMAAV at remission and in patients with OME. DNase I activity in the patients with OMAAV at onset was significantly lower than those in patients with OMAAV at remission and OME and was negatively correlated with the level of MPO-DNA complex. CONCLUSIONS: This study suggests that NET remnants and DNase I activity may be potentially useful biomarkers for the diagnosis and disease activity of OMAAV.