Is PR3-ANCA formation initiated in Wegener's granulomatosis lesions? Granulomas as potential lymphoid tissue maintaining autoantibody production

Granulomatosis With Polyangiitis (Wegener's Granulomatosis) Nasal Reconstruction: Improved Outcomes With No Delay

BACKGROUND

Granulomatosis with polyangiitis (Wegener's granulomatosis) causes progressive nasal collapse, nasal obstruction, and central face deformity. It is not known whether cartilaginous nasal reconstruction should be performed immediately or delayed until after disease "burnout."

OBJECTIVES

The aims of this research regarding nasal collapse due to Wegener's granulomatosis were to (1) assess the functional and aesthetic outcomes following immediate vs delayed nasal reconstruction; and (2) measure the impact of psychosocial well-being (anxiety, depression, social isolation) in immediate vs delayed nasal reconstruction.

METHODS

Wegener's patients with either immediate or delayed nasal surgery (n = 61) were compared. Functional and aesthetic severity were compared with the validated Standard Cosmesis and Health Nasal Outcome Survey (SCHNOS) score (t test). In addition, Patient-Reported Outcomes Measurement Information System (PROMIS) perioperative and 1-year follow-up surveys were analyzed.

RESULTS

At initial consultation, SCHNOS score severity types were similar for both groups (immediate vs delayed): mild 15% vs 15%; moderate 59% vs 60%, and severe 26% vs 25%. Over a 30 ± 4 month period, delayed surgery patients' conditions deteriorated, with a shift from mild to more severe SCHNOS scores, from 25% severe at initial consultation to 85% before surgery. PROMIS scores at presentation were high compared to the general public; by the time of delayed surgery, patients had significantly worsened: anxiety from 28 to 73; depression from 18 to 62; and social isolation from 20 to 80. Although both immediate and delayed groups improved after surgery in functional and psychosocial scores, the immediate surgery group's improvement was superior.

CONCLUSIONS

Data showed superior functional and aesthetic scores and superior psychosocial indicators with immediate cartilaginous nasal reconstruction, compared with waiting until disease burnout to undergo surgery.

LEVEL OF EVIDENCE: 4

Combination Treatment of Locoregionally Aggressive Granulomatosis with Polyangiitis and Cranial Base Infiltration

OBJECTIVES

To present a personalized approach in three cases of treatment-resistant, locoregionally aggressive forms of cANCA-positive granulomatosis with polyangiitis (GPA) and skull base involvement.

METHODS

Three patients with GPA and skull base involvement were described alongside a critical review of the current literature.

RESULTS

All presented patients suffered from GPA with an inflammatory tumor at the skull base, alongside cerebellopontine angle involvement, cranial nerve palsies, cerebellar disorders, concomitant hearing loss, and severe otalgia. Symptoms were associated with progressive granulomatous destruction of the temporal bone, laryngopharynx, and central nervous system infiltration. Treatment with cyclophosphamide and high doses of glucocorticoid steroids were ineffective but subsequent therapy with rituximab was successful in the presented cases. The literature review showed that the course of the disease with skull base involvement is associated with poorer clinical and radiological responses to standard pharmacotherapies.

CONCLUSION

Granulomatous inflammation localized in the skull base is associated with a more aggressive disease progression and is less likely to respond to pharmacotherapy. Standard induction therapy with cyclophosphamide and glucocorticoid steroids may be ineffective. A better response may be achieved by using rituximab and concomitant local treatment with glucocorticoid steroid injections.

Translational implications of humoral and cellular immune dysfunction in granulomatosis with polyangiitis

Granulomatosis with polyangiitis (GPA) is a rare systemic ANCA (Anti-neutrophil cytoplasmic antibodies) associated vasculitis (AAV). In the last couple of decades, GPA has emerged as a disease of concern due to rapid increase in the prevalence and incidence especially in developing countries. Unknown aetiology and rapid progression have made GPA a critical disease. Thus, establishing specific tools to facilitate early and faster disease diagnosis and efficient disease management has immense importance. GPA may develop in genetically predisposed individuals on receiving the external stimulus (i.e. microbial pathogen, pollutant etc.) that triggers the immune response. B-cell activating factor (BAFF) produced by the neutrophils, promotes the B-cell maturation and survival which leads to increased ANCA production. Abnormal B-cell and T-cell proliferation and their cytokine response plays a major role in disease pathogenesis and granuloma formation. ANCA interacts with neutrophils and induces the neutrophil extracellular traps (NETs) formation and reactive oxygen species (ROS) production which leads to the endothelial cell injury. This review article summarizes the critical pathological events and how cytokines and immune cells shape the GPA pathogenesis. Decoding this complex network would facilitate in developing tools for diagnosis, prognosis and disease management. Recently developed specific monoclonal antibodies (MAbs) targeting cytokines and immune cells are being used for safer treatment and achieving longer remission.

[Pathogenesis of ANCA-associated vasculitides in 2021: An update]

Anticytoplasmic neutrophil antibodies (ANCA)-associated vasculitis (AAV) are rare systemic immune-mediated diseases characterized by small vessel necrotizing vasculitis and/or respiratory tract inflammation. Over the last 2 decades, anti-MPO vasculitis mouse model has enlightened the role of ANCA, neutrophils, complement activation, T helper cells (Th1, Th17) and microbial agents. In humans, CD4T cells have been extensively studied, while the dramatic efficacy of rituximab demonstrated the key role of B cells. Many areas of uncertainty remain, such as the driving force of GPA extra-vascular granulomatous inflammation and the relapse risk of anti-PR3 AAV pathogenesis. Animal models eventually led to identify complement activation as a promising therapeutic target. New investigation tools, which permit in depth immune profiling of human blood and tissues, may open a new era for the studying of AAV pathogenesis.

Circulating autoreactive proteinase 3+ B cells and tolerance checkpoints in ANCA-associated vasculitis

BACKGROUND

Little is known about the autoreactive B cells in antineutrophil cytoplasmic antibody–associated (ANCA-associated) vasculitis (AAV). We aimed to investigate tolerance checkpoints of circulating antigen-specific proteinase 3–reactive (PR3⁺) B cells.

METHODS

Multicolor flow cytometry in combination with bioinformatics and functional in vitro studies were performed on baseline samples of PBMCs from 154 well-characterized participants of the RAVE trial (NCT00104299) with severely active PR3-AAV and myeloperoxidase-AAV (MPO-AAV) and 27 healthy controls (HCs). Clinical data and outcomes from the trial were correlated with PR3⁺ B cells (total and subsets).

RESULTS

The frequency of PR3⁺ B cells among circulating B cells was higher in participants with PR3-AAV (4.77% median [IQR, 3.98%–6.01%]) than in participants with MPO-AAV (3.16% median [IQR, 2.51%–5.22%]) and participants with AAV compared with HCs (1.67% median [IQR, 1.27%–2.16%], P < 0.001 for all comparisons), implying a defective central tolerance checkpoint in patients with AAV. Only PBMCs from participants with PR3-AAV contained PR3⁺ B cells capable of secreting PR3-ANCA IgG in vitro, proving they were functionally distinct from those of participants with MPO-AAV and HCs. Unsupervised clustering identified subtle subsets of atypical autoreactive PR3⁺ memory B cells accumulating through the maturation process in patients with PR3-AAV. PR3⁺ B cells were enriched in the memory B cell compartment of participants with PR3-AAV and were associated with higher serum CXCL13 levels, suggesting an increased germinal center activity. PR3⁺ B cells correlated with systemic inflammation (C-reactive protein and erythrocyte sedimentation rate, P < 0.05) and complete remission (P < 0.001).

CONCLUSION

This study suggests the presence of defective central antigen-independent and peripheral antigen-dependent checkpoints in patients with PR3-AAV, elucidating the selection process of autoreactive B cells.

Trial registration

ClinicalTrials.gov NCT00104299.

Funding

The Vasculitis Foundation, the National Institute of Allergy and Infectious Diseases of the NIH, and the Mayo Foundation for Education and Research.

Classification of ANCA-associated vasculitis: differences based on ANCA specificity and clinicopathologic phenotype

The classification of vasculitis according to a schema with universal acceptance is challenging, given the heterogeneous and protean nature of these diseases. Formal nomenclature and classification criteria for anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) have suffered several changes since their first description; none provides comprehensive diagnostic and classification criteria. Different factors account for the difficulties in the classification of vasculitis, including the incomplete understanding of the pathogenesis, the multisystemic nature of the disease, the non-specific patterns of vascular involvement, the overlap between entities, and the presence of various classification systems. The present article reviews the classification of AAV considering different points of view, including clinical, serologic, pathogenetic, organ predilection, therapeutic, and prognostic factors, and provides perspectives on future challenges in the understanding of AAV. There is an unmet need for a unifying view of the disease spectrum that considers the constantly evolving paradigms.

Granulomatous Inflammation in ANCA-Associated Vasculitis

ANCA-associated vasculitis (AAV) comprises granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). While systemic vasculitis is a hallmark of all AAV, GPA is characterized by extravascular granulomatous inflammation, preferentially affecting the respiratory tract. The mechanisms underlying the emergence of neutrophilic microabscesses; the appearance of multinucleated giant cells; and subsequent granuloma formation, finally leading to scarred or destroyed tissue in GPA, are still incompletely understood. This review summarizes findings describing the presence and function of molecules and cells contributing to granulomatous inflammation in the respiratory tract and to renal inflammation observed in GPA. In addition, factors affecting or promoting the development of granulomatous inflammation such as microbial infections, the nasal microbiome, and the release of damage-associated molecular patterns (DAMP) are discussed. Further, on the basis of numerous results, we argue that, in situ, various ways of exposure linked with a high number of infiltrating proteinase 3 (PR3)- and myeloperoxidase (MPO)-expressing leukocytes lower the threshold for the presentation of an altered PR3 and possibly also of MPO, provoking the local development of ANCA autoimmune responses, aided by the formation of ectopic lymphoid structures. Although extravascular granulomatous inflammation is unique to GPA, similar molecular and cellular patterns can be found in both the respiratory tract and kidney tissue of GPA and MPA patients; for example, the antimicrobial peptide LL37, CD163⁺ macrophages, or regulatory T cells. Therefore, we postulate that granulomatous inflammation in GPA or PR3-AAV is intertwined with autoimmune and destructive mechanisms also seen at other sites.

Effect of Reduced-Dose vs High-Dose Glucocorticoids Added to Rituximab on Remission Induction in ANCA-Associated Vasculitis: A Randomized Clinical Trial

IMPORTANCE

The current standard induction therapy for antineutrophil cytoplasm antibody (ANCA)-associated vasculitis is the combination of high-dose glucocorticoids and cyclophosphamide or rituximab. Although these regimens have high remission rates, they are associated with considerable adverse events presumably due to high-dose glucocorticoids.

OBJECTIVE

To compare efficacy and adverse events between a reduced-dose glucocorticoid plus rituximab regimen and the standard high-dose glucocorticoid plus rituximab regimen in remission induction of ANCA-associated vasculitis.

DESIGN, SETTING, AND PARTICIPANTS

This was a phase 4, multicenter, open-label, randomized, noninferiority trial. A total of 140 patients with newly diagnosed ANCA-associated vasculitis without severe glomerulonephritis or alveolar hemorrhage were enrolled between November 2014 and June 2019 at 21 hospitals in Japan. Follow-up ended in December 2019.

INTERVENTIONS

Patients were randomized to receive reduced-dose prednisolone (0.5 mg/kg/d) plus rituximab (375 mg/m2/wk, 4 doses) (n = 70) or high-dose prednisolone (1 mg/kg/d) plus rituximab (n = 70).

MAIN OUTCOMES AND MEASURES

The primary end point was the remission rate at 6 months, and the prespecified noninferiority margin was -20 percentage points. There were 8 secondary efficacy outcomes and 6 secondary safety outcomes, including serious adverse events and infections.

RESULTS

Among 140 patients who were randomized (median age, 73 years; 81 women [57.8%]), 134 (95.7%) completed the trial. At 6 months, 49 of 69 patients (71.0%) in the reduced-dose group and 45 of 65 patients (69.2%) in the high-dose group achieved remission with the protocolized treatments. The treatment difference of 1.8 percentage points (1-sided 97.5% CI, -13.7 to ∞) between the groups met the noninferiority criterion (P = .003 for noninferiority). Twenty-one serious adverse events occurred in 13 patients in the reduced-dose group (18.8%), while 41 occurred in 24 patients in the high-dose group (36.9%) (difference, -18.1% [95% CI, -33.0% to -3.2%]; P = .02). Seven serious infections occurred in 5 patients in the reduced-dose group (7.2%), while 20 occurred in 13 patients in the high-dose group (20.0%) (difference, -12.8% [95% CI, -24.2% to -1.3%]; P = .04).

CONCLUSIONS AND RELEVANCE

Among patients with newly diagnosed ANCA-associated vasculitis without severe glomerulonephritis or alveolar hemorrhage, a reduced-dose glucocorticoid plus rituximab regimen was noninferior to a high-dose glucocorticoid plus rituximab regimen with regard to induction of disease remission at 6 months.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02198248.

Immunoglobulins G from patients with ANCA-associated vasculitis are atypically glycosylated in both the Fc and Fab regions and the relation to disease activity

Background

Anti-neutrophil cytoplasmic autoantibodies (ANCA) directed against myeloperoxidase (MPO) and proteinase 3 (PR3) are pathogenic in ANCA-associated vasculitis (AAV). The respective role of IgG Fc and Fab glycosylation in mediating ANCA pathogenicity is incompletely understood. Herein we investigate in detail the changes in Fc and Fab glycosylation in MPO-ANCA and Pr3-ANCA and examine the association of glycosylation aberrancies with disease activity.

Methodology

Total IgG was isolated from serum or plasma of a cohort of 30 patients with AAV (14 MPO-ANCA; 16 PR3-ANCA), and 19 healthy control subjects. Anti-MPO specific IgG was affinity-purified from plasma of an additional cohort of 18 MPO-ANCA patients undergoing plasmapheresis. We used lectin binding assays, liquid chromatography, and mass spectrometry-based methods to analyze Fc and Fab glycosylation, the degree of sialylation of Fc and Fab fragments and to determine the exact localization of N-glycans on Fc and Fab fragments.

Principal findings

IgG₁ Fc glycosylation of total IgG was significantly reduced in patients with active AAV compared to controls. Clinical remission was associated with complete glycan normalization for PR3-ANCA patients but not for MPO-ANCA patients. Fc-glycosylation of anti-MPO specific IgG was similar to total IgG purified from plasma. A major fraction of anti-MPO specific IgG harbor extensive glycosylation within the variable domain on the Fab portion.

Conclusions/Significance

Significant differences exist between MPO and PR3-ANCA regarding the changes in amounts and types of glycans on Fc fragment and the association with disease activity. These differences may contribute to significant clinical difference in the disease course observed between the two diseases.

Pathogenesis of ANCA-Associated Pulmonary Vasculitis

Antineutrophil cytoplasmic antibodies (ANCAs) are autoantibodies specific for antigens located in the cytoplasmic granules of neutrophils and lysosomes of monocytes. ANCAs are associated with a spectrum of necrotizing vasculitis that includes granulomatosis with polyangiitis, microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis. Pulmonary vasculitis and related extravascular inflammation and fibrosis are frequent components of ANCA vasculitis. In this review, we detail the factors that have been associated with the origin of the ANCA autoimmune response and summarize the most relevant clinical observations, in vitro evidence, and animal studies strongly indicating the pathogenic potential of ANCA. In addition, we describe the putative sequence of pathogenic mechanisms driven by ANCA-induced activation of neutrophils that result in small vessel necrotizing vasculitis and extravascular granulomatous necrotizing inflammation.

Targeted immunotherapy strategies in ANCA-associated vasculitis

Targeted immunotherapy is substantially improving the management of ANCA-associated vasculitides (AAV), which include granulomatosis with polyangiitis (GPA, Wegener's granulomatosis), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA, Churg-Strauss syndrome). This article reviews the current role for targeted immunotherapy in AAV, its validated indications, and avenues for further development. Rituximab is a validated induction treatment for GPA and severe MPA. Rituximab in these indications is not less effective than cyclophosphamide and is particularly useful in patients with refractory or relapsing disease, women of childbearing potential, and patients previously treated with cyclophosphamide. Rituximab is more effective than cyclophosphamide for treating relapses. For remission maintenance therapy, which is indispensable, rituximab has been proven superior over conventional immunosuppressive treatment. Rituximab is licensed in the USA and in Europe for the induction treatment of severe forms of GPA and MPA. An extension study for remission maintenance therapy is ongoing. In EGPA, although maintenance treatment with the interleukin-5 antagonist mepolizumab is effective in decreasing glucocorticoid requirements and in alleviating asthma and sinonasal symptoms, its efficacy on the vasculitis remains somewhat unclear. Mepolizumab is licensed for use in EGPA, and rituximab is also being evaluated as an induction and maintenance agent. Immunoglobulins can be helpful as an adjuvant treatment for active AAV with severe immunedepression, notably when infections occur. Plasma exchange is indicated in AAV with advanced renal dysfunction and, perhaps, in the event of alveolar hemorrhage, a possibility that will be assessed in 2018 in a large international study.

Proteases and Their Inhibitors in Chronic Obstructive Pulmonary Disease

In the context of respiratory disease, chronic obstructive pulmonary disease (COPD) is the leading cause of mortality worldwide. Despite much development in the area of drug development, currently there are no effective medicines available for the treatment of this disease. An imbalance in the protease: Antiprotease ratio in the COPD lung remains an important aspect of COPD pathophysiology and several studies have shown the efficacy of antiprotease therapy in both in vitro and in vivo COPD models. However more in-depth studies will be required to validate the efficacy of lead drug molecules targeting these proteases. This review discusses the current status of protease-directed drugs used for treating COPD and explores the future prospects of utilizing the potential of antiprotease-based therapeutics as a treatment for this disease.

In situ detection of PR3-ANCA+ B cells and alterations in the variable region of immunoglobulin genes support a role of inflamed tissue in the emergence of auto-reactivity in granulomatosis with polyangiitis

Circulating anti-neutrophilic cytoplasmic autoantibodies targeting proteinase 3 (PR3-ANCA) are a diagnostic and pathogenic hallmark of granulomatosis with polyangiitis (GPA). It is, however, incompletely understood if inflamed tissue supports presence or emergence of PR3-ANCA⁺ B cells. In search of such cells in inflamed tissue of GPA, immunofluorescence staining for IgG and a common PR3-ANCA idiotype (5/7 Id) was undertaken. Few 5/7 Id⁺/IgG⁺ B cells were detected in respiratory and kidney tissue of GPA. To gain more insight into surrogate markers possibly indicative of an anti-PR3-response, a meta-analysis comprising IGVH and IGVL genes derived from respiratory tract tissue of GPA (231 clones) was performed. Next generation sequencing-based IGHV genes derived from peripheral blood of healthy donors (244.353 clones) and previously published IGLV genes (148 clones) served as controls. Additionally, Ig genes of three murine and five known human monoclonal anti-PR3 antibodies were analyzed. Primary and probably secondary rearrangements led to altered VDJ usage and an extended complementarity determining region 3 (CDR3) of IGHV clones from GPA tissue. Selection against amino acid exchanges was prominent in the framework region of IGHV clones from GPA tissue. The comparison of V(D)J rearrangements and deduced amino acid sequences of the CDR3 yielded no identities and few similarities between clones derived from respiratory tissue of GPA and anti-PR3 antibodies, arguing against a presence of B cells that carry PR3-ANCA-prone Ig genes among the clones. In line with the scarcity of 5/7 Id⁺ B lymphocytes in GPA tissue, the results suggest that with respect to a local anti-PR3 response, methods detecting rare clones are required.

Targeting B Cells and Plasma Cells in Glomerular Diseases: Translational Perspectives

The unique contributions of memory B cells and plasma cells in kidney diseases remain unclear. In this review, we evaluate the clinical experience with treatments directed at B cells, such as rituximab, and at plasma cells, such as proteasome inhibition, to shed light on the role of these two B lineage compartments in glomerular diseases. Specifically, analysis of these targeted interventions in diseases such as ANCA-associated vasculitis, SLE, and antibody-mediated transplant rejection permits insight into the pathogenetic effect of these cells. Notwithstanding the limitations of preclinical models and clinical studies (heterogeneous populations, among others), the data suggest that memory B and plasma cells represent two engines of autoimmunity, with variable involvement in these diseases. Whereas memory B cells and plasma cells appear to be key in ANCA-associated vasculitis and antibody-mediated transplant rejection, respectively, SLE seems likely to be driven by both autoimmune compartments. These conclusions have implications for the future development of targeted therapeutics in immune-mediated renal disease.

Low-dose glucocorticoids plus rituximab versus high-dose glucocorticoids plus rituximab for remission induction in ANCA-associated vasculitis (LoVAS): protocol for a multicentre, open-label, randomised controlled trial

INTRODUCTION

Antineutrophil cytoplasm antibody-associated vasculitis (AAV) is a form of systemic vasculitis. The current standard induction therapy with the combination of high-dose glucocorticoids and cyclophosphamide or rituximab has high remission rates of 80%-90%. However, it is also associated with various side effects, including death due to infection or cardiovascular disease. There is an unmet medical need of a new therapy to reduce side effects.

METHODS AND ANALYSIS

This is a phase IV multicentre, open-label, randomised controlled trial that aims to evaluate the efficacy and safety of a new remission induction regimen with the combination of low-dose glucocorticoids and rituximab. Newly diagnosed patients with AAV will be assessed for eligibility at 34 tertiary rheumatology/nephrology centres in Japan. One hundred and forty patients will be randomised (1:1) to receive low-dose prednisolone (0.5 mg/kg daily) plus rituximab (375 mg/m² weekly) or high-dose prednisolone (1 mg/kg daily) plus rituximab. The trial consists of remission induction and maintenance phases. The primary endpoint of the study is the remission rate at 6 months (induction phase). Relapse and long-term safety profile will also be assessed until 24 months (maintenance phase).

ETHICS AND DISSEMINATION

The protocol was first approved by the Institutional Review Board of Chiba University Hospital (reference number: G25051), and then approved by each participating site. The trial was registered at the University hospital Medical Information Network (UMIN) clinical registry (UMIN000014222) and ClinicalTrials.gov registry (NCT02198248). The Low-dose Glucocorticoid Vasculitis Induction Study (LoVAS) trial is currently ongoing and is due to finish in September 2019. The findings of this trial will be disseminated to participants through peer-reviewed publications and presented at national and international conferences in accordance with the Consolidated Standards of Reporting Trials (CONSORT) Statement.

TRIAL REGISTRATION NUMBER

UMIN000014222; NCT02198248.

Bronchiectasis is highly prevalent in anti-MPO ANCA-associated vasculitis and is associated with a distinct disease presentation

OBJECTIVES

To assess the prevalence of bronchiectasis in a Western cohort with ANCA-positive granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA) and its correlations with disease presentation and outcome.

METHODS

Retrospective study of ANCA-associated vasculitis (AAV) patients followed at Nantes University Hospital (2005-2015). Clinical, biological, and follow-up data were collected through chart review. Two experienced radiologists blinded to the clinical data interpreted chest high-resolution CTs according to the Feischner Society criteria.

RESULTS

Fifty-eight patients were included: 30 had MPA (51.7%) and 28 had GPA (48.3%). The median age at AAV diagnosis was 65.5 years. Anti-MPO-ANCA and anti-PR3-ANCA were present in 39 (67.2%) and 19 (32.8%) patients, respectively. Overall, bronchiectasis was found in 22 patients (37.9%), all of whom had anti-MPO ANCA. In multivariate analysis, bronchiectasis was independently associated with anti-MPO-ANCA, female gender and age at AAV diagnosis. Furthermore, anti-MPO ANCA patients with bronchiectasis had more frequent peripheral nerve involvement (54.5 vs. 17.6%, p = 0.019) and less frequent renal involvement than those without bronchiectasis (40.9% vs. 82.3%, p = 0.009). Disease course, survival and risk of severe pulmonary infection were similar in patients with and without bronchiectasis on chest CT.

CONCLUSIONS

This study shows that bronchiectasis is a highly prevalent pre-existing respiratory condition in Caucasian patients with anti-MPO AAV. This subset of patients exhibits a distinct presentation. Further studies are needed to confirm these findings and clarify the clinical implications of this association. Whether the respiratory tract could be the site of initiation of anti-MPO auto-immunity remains to be investigated.

Investigational drugs in systemic vasculitis

INTRODUCTION

Treatment of systemic vasculitis is based on glucocorticoids (GC) in association with immunosuppressive therapy. There are still unmet needs, including earlier onset of response, more targeted therapies, reduction of relapse-risk and decrease of long-term GC and classic immunosuppressants toxicities. Areas covered: In this review, we discuss investigational drugs in early phase clinical trials for induction of remission in vasculitis. We focus on ANCA-associated vasculitis, Behçet's disease, giant cell arteritis, Takayasu arteritis, and cryoglobulinemic vasculitis. We performed a comprehensive review of articles published on pubmed and a review of clinical trials registered online ( https://clinicaltrials.gov ) for each vasculitis. Expert opinion: Recent progress in the pathogenesis identifies new therapeutic targets. Some of these therapies are promising in GC sparing effects, in reducing relapse rate, and for their safety profile. These results need to be confirmed in large-scale phase III studies.

Updates in ANCA-associated vasculitis

Antineutrophil cytoplasm antibody (ANCA)-associated vasculitides are small-vessel vasculitides that include granulomatosis with polyangiitis (formerly Wegener's granulomatosis), microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome). Renal-limited ANCA-associated vasculitides can be considered the fourth entity. Despite their rarity and still unknown cause(s), research pertaining to ANCA-associated vasculitides has been very active over the past decades. The pathogenic role of antimyeloperoxidase ANCA (MPO-ANCA) has been supported using several animal models, but that of antiproteinase 3 ANCA (PR3-ANCA) has not been as strongly demonstrated. Moreover, some MPO-ANCA subsets, which are directed against a few specific MPO epitopes, have recently been found to be better associated with disease activity, but a different method than the one presently used in routine detection is required to detect them. B cells possibly play a major role in the pathogenesis because they produce ANCAs, as well as neutrophil abnormalities and imbalances in different T-cell subtypes [T helper (Th)1, Th2, Th17, regulatory cluster of differentiation (CD)4+ CD25+ forkhead box P3 (FoxP3)+ T cells] and/or cytokine-chemokine networks. The alternative complement pathway is also involved, and its blockade has been shown to prevent renal disease in an MPO-ANCA murine model. Other recent studies suggested strongest genetic associations by ANCA type rather than by clinical diagnosis. The induction treatment for severe granulomatosis with polyangiitis and microscopic polyangiitis is relatively well codified but does not (yet) really differ by precise diagnosis or ANCA type. It comprises glucocorticoids combined with another immunosuppressant, cyclophosphamide or rituximab. The choice between the two immunosuppressants must consider the comorbidities, past exposure to cyclophosphamide for relapsers, plans for pregnancy, and also the cost of rituximab. Once remission is achieved, maintenance strategy following cyclophosphamide-based induction relies on less toxic agents such as azathioprine or methotrexate. The optimal maintenance strategy following rituximab-based induction therapy remains to be determined. Preliminary results on rituximab for maintenance therapy appear promising. Efforts are still under way to determine the optimal duration of maintenance therapy, ideally tailored according to the characteristics of each patient and the previous treatment received.

Spotlight on rituximab in the treatment of antineutrophil cytoplasmic antibody-associated vasculitis: current perspectives

A 54-year-old patient presented to his general practitioner because of strong muscle pain in both thighs. Inflammatory parameters (CRP 16.3 mg/dL) and white blood cells (15 g/L) were elevated. The patient reported a weight loss of 10 kg in 4 weeks. There was no fever or any other specific symptoms. Urine dipstick examination and computed tomography of the chest were unremarkable. Because of increasing symptoms, the patient was referred to our department. Magnetic resonance tomography showed diffuse inflammatory changes of the muscles of both thighs. Neurological examination and electrophysiology revealed axonal sensorimotor neuropathy and ground-glass opacities of both lungs had occurred. Serum creatinine increased to 229 μmol/L within a few days, with proteinuria of 3.3 g/g creatinine. Kidney biopsy showed diffuse pauci-immune proliferative glomerulonephritis. Proteinase 3-specific antineutrophil cytoplasmic antibodies were markedly increased. Birmingham Vasculitis Activity Score was 35. Within 2 days, serum creatinine further increased to 495 μmol/L. Plasma exchange, high-dose glucocorticosteroids, and hemodialysis were started. The patient received cyclophosphamide 1 g twice and rituximab 375 mg/m² four times according to the RITUXVAS protocol. Despite ongoing therapy, hemodialysis could not be withdrawn and had to be continued over 3 weeks until diuresis normalized. Glucocorticosteroids were tapered to 20 mg after 2 months, and serum creatinine was 133 μmol/L. However, nephritic urinary sediment reappeared. Another dose of 1 g cyclophosphamide was given, and glucocorticosteroids were raised for another 4 weeks. After 6 months, the daily prednisolone dose was able to be tapered to 5 mg. Serum creatinine was 124 μmol/L, proteinuria further decreased to 382 mg/g creatinine, and the Birmingham Vasculitis Activity Score was 0. Maintenance therapy with rituximab 375 mg/m² every 6 months was started. At the last visit after 8 months, the patient was still in remission, with only minor persistent dysesthesia of the left foot and a persistent serum creatinine of 133 μmol/L.

Current and emerging treatment options for ANCA-associated vasculitis: potential role of belimumab and other BAFF/APRIL targeting agents

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) comprises several clinical entities with diverse clinical presentations, outcomes, and nonunifying pathogenesis. AAV has a clear potential for relapses, and shows unpredictable response to treatment. Cyclophosphamide-based therapies have remained the hallmark of induction therapy protocols for more than four decades. Recently, B-cell depleting therapy with the anti-CD20 antibody rituximab has proved beneficial in AAV, leading to Food and Drug Administration approval of rituximab in combination with corticosteroids for the treatment of AAV in adults. Rituximab for ANCA-associated vasculitis and other clinical trials provided clear evidence that rituximab was not inferior to cyclophosphamide for remission induction, and rituximab appeared even more beneficial in patients with relapsing disease. This raised hopes that other B-cell-targeted therapies directed either against CD19, CD20, CD22, or B-cell survival factors, B-cell activating factor of the tumor necrosis factor family (BAFF) and a proliferation-inducing ligand could also be beneficial for the management of AAV. BAFF neutralization with the fully humanized monoclonal antibody belimumab has already shown success in human systemic lupus erythematosus and, along with another anti-BAFF reagent blisibimod, is currently undergoing Phase II and III clinical trials in AAV. Local production of BAFF in granulomatous lesions and elevated levels of serum BAFF in AAV provide a rationale for BAFF-targeted therapies not only in AAV but also in other forms of vasculitis such as Behcet’s disease, large-vessel vasculitis, or cryoglobulinemic vasculitis secondary to chronic hepatitis C infection. BAFF-targeted therapies have a very solid safety profile, and may have an additional benefit of preferentially targeting newly arising autoreactive B cells over non-self-reactive B cells.

T cell-macrophage interactions and granuloma formation in vasculitis

Granuloma formation, bringing into close proximity highly activated macrophages and T cells, is a typical event in inflammatory blood vessel diseases, and is noted in the name of several of the vasculitides. It is not known whether specific properties of the microenvironment in the blood vessel wall or the immediate surroundings of blood vessels contribute to granuloma formation and, in some cases, generation of multinucleated giant cells. Granulomas provide a specialized niche to optimize macrophage-T cell interactions, strongly activating both cell types. This is mirrored by the intensity of the systemic inflammation encountered in patients with vasculitis, often presenting with malaise, weight loss, fever, and strongly upregulated acute phase responses. As a sophisticated and highly organized structure, granulomas can serve as an ideal site to induce differentiation and maturation of T cells. The granulomas possibly seed aberrant Th1 and Th17 cells into the circulation, which are known to be the main pathogenic cells in vasculitis. Through the induction of memory T cells, aberrant innate immune responses can imprint the host immune system for decades to come and promote chronicity of the disease process. Improved understanding of T cell-macrophage interactions will redefine pathogenic models in the vasculitides and provide new avenues for immunomodulatory therapy.

Single-dose rituximab for remission induction and maintenance therapy in ANCA-associated vasculitis: a retrospective analysis of 17 patients

OBJECTIVES

The aim of this study was to evaluate the efficacy of a repeated single-dose rituximab (RTX) regimen for remission induction and maintenance in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV).

METHOD

We performed a retrospective analysis of all patients with an established diagnosis of AAV who were treated with single-dose RTX infusions at our institution. Clinical outcome data were assessed over a period of 24 months.

RESULTS

Sixteen patients were treated for remission induction and maintenance and one patient was treated for only maintenance therapy. Remission (absence of disease activity during the past 3 months and a prednisolone dose of ≤ 7.5 mg) was achieved in 11 patients (68%) with a mean time to remission of 9.4 (range 3-24) months. At 6 months, six patients (37.5%) were in remission and the mean prednisolone dose of all responding patients was 8.2 mg. Five patients had treatment failure due to early relapsing (n = 4) or persistently active (n = 1) disease. At 24 months, nine of the 11 responding patients (82%) were in remission. All patients still had concomitant steroid and/or disease-modifying anti-rheumatic drug (DMARD) therapy at 24 months. Overall, 11 relapses were seen in nine patients (five non-responders and four responders) with a mean time to relapse of 5.3 (range 4-24) months. No major relapses were observed in the responding patients. Severe infections were only seen in patients who had been previously treated with cyclophosphamide (CYC).

CONCLUSIONS

The combination of single-dose RTX with other immunosuppressants seems less effective than the standard RTX regimen for the induction of remission of AAV.

Emerging therapies in antineutrophil cytoplasm antibody-associated vasculitis

PURPOSE OF REVIEW

The current standard therapy for antineutrophil cytoplasm antibody-associated vasculitis (AAV), high-dose glucocorticoid and cyclophosphamide followed by azathioprine, has improved the disease prognosis. However, there are still unmet needs. For example, reducing relapse risk and glucocorticoid toxicity. Newer therapies are needed.

RECENT FINDINGS

Potential newer drugs are emerging following a better understanding of disease mechanisms and the availability of targeted therapies to B cells, T cells, proinflammatory cytokines and complement. Rituximab, an anti-CD20 monoclonal antibody, has proven efficacy in remission induction therapy for AAV, and two trials with rituximab as remission maintenance therapy are ongoing. Clinical trials evaluating mycophenolate mofetil as remission induction therapy, gusperimus, belimumab and complement factor C5a inhibition are also ongoing, and many other potential candidates are being investigated both clinically and experimentally.

SUMMARY

B-cell therapy is now an established treatment in AAV and several other therapies are under evaluation. However, the unmet need in vasculitis therapy remains large and newer therapies either alone or in combination will need to both improve efficacy and permit reductions in glucocorticoid and immunosuppressive exposure.

Pathogenesis of antineutrophil cytoplasmic autoantibody-mediated disease

Antineutrophil cytoplasmic autoantibodies (ANCAs) are the probable cause of a distinct form of vasculitis that can be accompanied by necrotizing granulomatosis. Clinical and experimental evidence supports a pathogenesis that is driven by ANCA-induced activation of neutrophils and monocytes, producing destructive necrotizing vascular and extravascular inflammation. Pathogenic ANCAs can originate from precursor natural autoantibodies. Pathogenic transformation might be initiated by commensal or pathogenic microbes, legal or illegal drugs, exogenous or endogenous autoantigen complementary peptides, or dysregulated autoantigen expression. The ANCA autoimmune response is facilitated by insufficient T-cell and B-cell regulation. A putative pathogenic mechanism for vascular inflammation begins with ANCA-induced activation of primed neutrophils and monocytes leading to activation of the alternative complement pathway, which sets in motion an inflammatory amplification loop in the vessel wall that attracts and activates neutrophils with resultant respiratory burst, degranulation, extrusion of neutrophil extracellular traps, apoptosis and necrosis. The pathogenesis of extravascular granulomatosis is less clear, but a feasible scenario proposes that a prodromal infectious or allergic condition positions primed neutrophils in extravascular tissue in which they can be activated by ANCAs in interstitial fluid to produce extravascular necrotizing injury that would initiate an innate granulomatous inflammatory response to wall off the necrotic debris.

Plasmacytoid Dendritic Cells: Neglected Regulators of the Immune Response to Staphylococcus aureus

Plasmacytoid dendritic cells (pDC) are a rare subset of leukocytes equipped with Fcγ and Fcε receptors, which exert contrary effects on sensing of microbial nucleic acids by endosomal Toll-like receptors. In this article, we explain how pDC contribute to the immune response to Staphylococcus aureus. Under normal circumstances the pDC participates in the memory response to the pathogen: pDC activation is initiated by uptake of staphylococcal immune complexes with IgG or IgE. However, protein A-expressing S. aureus strains additionally trigger pDC activation in the absence of immunoglobulin. In this context, staphylococci exploit the pDC to induce antigen-independent differentiation of IL-10 producing plasmablasts, an elegant means to propagate immune evasion. We further discuss the role of type I interferons in infection with S. aureus and the implications of these findings for the development of immune based therapies and vaccination.

Vasculitis syndromes: RAVE about rituximab in ANCA vasculitis?

Follow-up data from the RAVE trial have shown that rituximab is as effective as immunosuppression with cyclophosphamide followed by azathioprine in antineutrophil cytoplasmic antibody (ANCA) associated vasculitis. Rituximab is likely to become the standard of care for many patients with ANCA disease. However, an individualized approach is needed to identify those who require more-intense or prolonged therapy.

Kinin system activation in vasculitis

Vasculitis is a systemic autoimmune inflammatory disease, characterized by inflammation in and around vessel walls leading to perturbed vessel patency and tissue damage. Many different organs may be involved. In this review, pathogenetic mechanisms of vasculitis are discussed, with special reference to activation of the kinin system. Mechanisms of kinin system activation are described, ultimately leading to release of kinins from high molecular weight kininogen. These vasoactive peptides promote inflammation.

CONCLUSION

  Kinin system activation during vasculitis promotes inflammation.

Nasal surgery in patients with systemic disorders

Multisystemic disorders represent a heterogenous group of diseases which can primarily manifest at the nose and paranasal sinuses as limited disease or secondarily as part of systemic involvement. Rhinologists therefore play an important role in the diagnostic but also therapeutic process. Although therapy of multisystemic disorders is primary systemic, additional rhinosurgery may become necessary. The spectrum of procedures consists of sinus surgery, surgery of the orbit and lacrimal duct, septorhinoplasty and closure of nasal septal perforation. Since the prevalence of most systemic diseases is very rare, recommendations are based on the analysis of single case reports and case series with a limited number of patients only. Although data is still limited, experiences published so far have shown that autologous cartilage or bone grafts can be used in nasal reconstruction of deformities caused by tuberculosis, leprosy, Wegener’s granulomatosis, sarcoidosis and relapsing polychondritis. Experiences gained from these diseases support the concept that well-established techniques of septorhinoplasty can be used in systemic diseases as well. However, a state of remission is an essential condition before considering any rhinosurgery in these patients. Even under these circumstances revision surgery has to be expected more frequently compared to the typical collective of patients undergoing septorhinoplasty. In addition, experiences gained from saddle nose reconstruction may in part be of value for the treatment of nasal septal perforations since implantation of cartilage grafts often represents an essential step in multilayer techniques of closure of nasal septal perforations. Aside from the treatment of orbital complications sinus surgery has been proven beneficial in reducing nasal symptoms and increasing quality of life in patients refractory to systemic treatment.

Therapeutic targeting of B cells for rheumatic autoimmune diseases

Autoreactive B cells are characterized by their ability to secrete autoantibodies directed against self-peptides. During the last decade, it has become increasingly apparent that B lymphocytes not only produce autoantibodies but also exert important regulatory roles independent of their function as antibody-producing cells. This is especially relevant in the context of autoimmunity, because autoreactive B cells have been shown to possess the ability to activate pathogenic T cells, to produce pro-inflammatory cytokines, and to promote the formation of tertiary lymphoid tissue in target organs. The production of monoclonal antibodies against B-cell-surface molecules has facilitated the characterization of several distinct B lymphocyte subsets. These cell-surface molecules have not only served as useful cell differentiation markers but have also helped to unravel the important biological functions of these cells. Some of these molecules, all of which are expressed on the cell surface, have proven to be effective therapeutic targets. In both animal models and in clinical assays, the efficient elimination of B lymphocytes has been shown to be useful in the treatment of rheumatoid arthritis and other autoimmune diseases. The treatment of most rheumatic autoimmune diseases relies mainly on the use of cytotoxic immunosuppressants and corticosteroids. Although this has resulted in improved disease survival, patients may nonetheless suffer severe adverse events and, in some cases, their relapse rate remains high. The increasing need for safer and more effective drugs along with burgeoning new insights into the pathogenesis of these disorders has fueled interest in biological agents; clinical trials involving the B-cell depletion agent rituximab have been especially promising. This article reviews the current knowledge of B-cell biology and pathogenesis as well as the modern therapeutic approaches for rheumatic autoimmune diseases focusing in particular on the targeting of B-cell-specific surface molecules and on the blocking of B-cell activation and survival.

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.

High-mobility group box-1 protein (HMGB1) is increased in antineutrophilic cytoplasmatic antibody (ANCA)-associated vasculitis with renal manifestations

High-mobility group box 1 (HMGB1) is a nuclear and cytosolic protein that is increasingly recognized as an important proinflammatory mediator actively secreted from monocytes and macrophages and passively released from necrotic cells. In antineutrophilic cytoplasmatic antibody (ANCA)-associated vasculitis (AAV), the kidneys are commonly affected vital organs, characterized by focal necrotizing and/or crescentic pauci-immune glomerulonephritis. The aim of the study was to determine whether HMGB1 serum levels are elevated in AAV with renal manifestations. A total of 30 AAV patients (16 female and 14 male; median age 59 years, range 17-82) with Wegener granulomatosis, microscopic polyangiitis and Churg-Strauss syndrome with available renal biopsies and serum samples were included. In seven cases, serum was also obtained at rebiopsy in remission. HMGB1 was analyzed with Western blot. Birmingham Vasculitis Activity Score (BVAS, version 2003), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), urinanalysis, creatinine, estimated glomerular filtration rate, sex and age were included in the analysis. Twenty-five episodes of biopsy-proven active disease with BVAS 17.9 ± 4.6 and 13 cases with inactive biopsies and BVAS 2.3 ± 3.7 (P = 0.0001) were identified. CRP, ESR, hematuria and proteinuria were significantly higher in active cases. HMGB1 was significantly elevated (P = 0.01) comparing active with inactive cases (120 ± 48 versus 78 ± 46 ng/mL) and significantly lower in the seven control patients (P = 0.03) at rebiopsy in remission. HMGB1 remained higher in inactive cases compared with historic healthy controls (10.9 ± 10.5 ng/mL). HMGB1 levels did not differ significantly between AAV subgroups. CRP and ESR did not correlate with HMGB1. HMGB1 is significantly increased in AAV with renal involvement. Residual HMGB1 elevation in remission could possibly reflect low-grade inflammatory activity or tissue damage. Future studies may further reveal whether HMGB1 is useful as a marker of disease activity and a predictor of outcome in AAV.

Rituximab versus cyclophosphamide in ANCA-associated renal vasculitis

BACKGROUND

Cyclophosphamide induction regimens for antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis are effective in 70 to 90% of patients, but they are associated with high rates of death and adverse events. Treatment with rituximab has led to remission rates of 80 to 90% among patients with refractory ANCA-associated vasculitis and may be safer than cyclophosphamide regimens.

METHODS

We compared rituximab with cyclophosphamide as induction therapy in ANCA-associated vasculitis. We randomly assigned, in a 3:1 ratio, 44 patients with newly diagnosed ANCA-associated vasculitis and renal involvement to a standard glucocorticoid regimen plus either rituximab at a dose of 375 mg per square meter of body-surface area per week for 4 weeks, with two intravenous cyclophosphamide pulses (33 patients, the rituximab group), or intravenous cyclophosphamide for 3 to 6 months followed by azathioprine (11 patients, the control group). Primary end points were sustained remission rates at 12 months and severe adverse events.

RESULTS

The median age was 68 years, and the glomerular filtration rate (GFR) was 18 ml per minute per 1.73 m(2) of body-surface area. A total of 25 patients in the rituximab group (76%) and 9 patients in the control group (82%) had a sustained remission (P=0.68). Severe adverse events occurred in 14 patients in the rituximab group (42%) and 4 patients in the control group (36%) (P=0.77). Six of the 33 patients in the rituximab group (18%) and 2 of the 11 patients in the control group (18%) died (P=1.00). The median increase in the GFR between 0 and 12 months was 19 ml per minute in the rituximab group and 15 ml per minute in the control group (P=0.14).

CONCLUSIONS

A rituximab-based regimen was not superior to standard intravenous cyclophosphamide for severe ANCA-associated vasculitis. Sustained-remission rates were high in both groups, and the rituximab-based regimen was not associated with reductions in early severe adverse events. (Funded by Cambridge University Hospitals National Health Service Foundation Trust and F. Hoffmann-La Roche; Current Controlled Trials number, ISRCTN28528813.)

T cells in ANCA-associated vasculitis: what can we learn from lesional versus circulating T cells?

Anti-neutrophil cytoplasmic antibody (ANCA) - associated vasculitis (AAV) is a life-threatening autoimmune disease characterized by an antibody-mediated glomerulonephritis and necrotizing vasculitis. Apart from antibodies, T cells are also involved in disease pathogenesis. This review stresses the hallmarks of T cell-mediated pathology in AAV and highlights the characteristics of lesional and circulating T cells in the immune response in AAV. Circulating effector T-cell populations are expanded and are in a persistent state of activation. Circulating regulatory T-cell subsets are less well characterized but seem to be impaired in function. Lesional effector T cells are present in granulomas, vasculitic lesions, and nephritis. Lesional T cells usually show pro-inflammatory properties and promote granuloma formation. Apart from T cells, dendritic cells are abundantly present at the sites of inflammation and locally orchestrate the immune response. Targeting the above-mentioned T cell-mediated disease mechanisms will potentially provide powerful therapeutic tools for AAV.

Wegener's Granulomatosis vasculitis and granuloma

Wegener's Granulomatosis (WG) is an autoimmune disease with manifestations in different organ systems. The hallmark of WG is a necrotizing granulomatous inflammation of the upper and/or lower respiratory tract and systemic small vessel vasculitis which can involve multiple organ systems. The treatment of WG has evolved over the last decades. Steroid, cytotoxic and biologic therapies have been used leading to great improvements in outcome. However, still mortality is high and relapses are a major cause of mortality and morbidity. Despite intensified maintenance regimens and new possibilities of biologic therapies in WG the relapse rate is high. Even patients treated with high dose cytotoxic therapies in autologous stem cell treatment protocols have shown relapses in the course of disease. Increasing knowledge of the pathophysiology of granuloma in WG and new biologic therapies might be of great importance for future treatment of WG.

Neutrophils and B lymphocytes in ANCA-associated vasculitis

The pathogenesis of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is unknown but is most consistent with a primary role for neutrophils in the acute injury. Thus, neutrophils are cardinal cells in the pathophysiological process in AAV because they are both effector cells responsible for endothelial damage and targets of autoimmunity. In addition, because of their capacity to synthesize a wide variety of cytokines and chemokines, neutrophils can be considered as important modulators of the inflammatory and potentially of the autoimmune process. ANCA directed against two main autoantigens, namely proteinase 3 and myeloperoxidase, are likely to play a modulatory role in the inflammatory process. Interestingly, neutrophils are an important source of lymphocyte stimulator (BLy), a cytokine that plays a fundamental role in B-cell physiology, including differentiation, proliferation and immunoglobulin production. The issue of B-cell activation and/or dysregulation in vasculitis will be discussed.

Ectopic lymphoid tissues and local immunity

Ectopic or tertiary lymphoid tissues develop at sites of inflammation or infection in peripheral, non-lymphoid organs. These tissues are architecturally similar to conventional secondary lymphoid organs, with separated B and T cell areas, specialized populations of dendritic cells, well-differentiated stromal cells and high endothelial venules. Ectopic lymphoid tissues are often associated with the local pathology that results from chronic infection or chronic inflammation. However, there are also examples in which ectopic lymphoid tissues appear to contribute to local protective immune responses. Here we review how ectopic lymphoid structures develop and function in the context of local immunity and pathology.

Hypotheses on the etiology of antineutrophil cytoplasmic autoantibody associated vasculitis: the cause is hidden, but the result is known

The first description of what is now known as antineutrophil cytoplasmic autoantibody-associated necrotizing vasculitis appeared more than 140 yr ago. Since then, many aspects of the pathogenic pathway have been elucidated, indicating the involvement of antineutrophil cytoplasmic autoantibodies, but why antineutrophil cytoplasmic autoantibodies are produced in the first place remains unknown. Over the years, many hypotheses have emerged addressing the etiology of antineutrophil cytoplasmic antibody production, but no exclusive factor or set of factors can so far be held responsible. Herein is reviewed the most influential hypotheses regarding the causes of antineutrophil cytoplasmic antibody-associated vasculitis with the aim of placing in an epidemiologic background the different hypotheses that are centered on environmental and genetic influences.