New pathophysiological insights and treatment of ANCA-associated vasculitis

T1 and T2 mapping for evaluation of myocardial involvement in patients with ANCA-associated vasculitides

BACKGROUND

Myocardial involvement in AAV patients might be silent, presenting with no or nonspecific symptoms, normal ECG, and preserved left-ventricular ejection fraction (LV-EF). Since up to 50% of deaths in these patients may be due to myocardial involvement, a reliable diagnostic tool is warranted. In contrast to LGE-CMR, which has its strengths in detecting focal inflammatory or fibrotic processes, recent mapping techniques are able to detect even subtle, diffuse inflammatory or fibrotic processes. Our study sought to investigate ANCA (antineutrophil cytoplasmic antibody) associated vasculitides (AAV) patients for myocardial involvement by a cardiovascular magnetic resonance (CMR) protocol, including late gadolinium enhancement (LGE) and mapping sequences.

METHODS

Thirty seven AAV patients were prospectively enrolled and underwent CMR imaging. Twenty healthy volunteers served as controls.

RESULTS

Mean LV-EF was 64%; LGE prevalence of the AAV patients was 43%. AAV patients had higher median native T1 (988 vs. 952 ms, p < 0.001), lower post-contrast T1 (488 vs. 524 ms, p = 0.03), expanded extracellular volume (ECV) (27.5 vs. 24.5%, p < 0.001), and higher T2 (53 vs. 49 ms, p < 0.001) compared to controls, with most parameters independent of the LGE status. Native T1 and T2 in AAV patients showed the highest prevalence of abnormally increased values beyond the 95% percentile of controls.

CONCLUSION

AAV patients demonstrated increased T1, ECV, and T2 values, with native T1 and T2 showing the highest prevalence of values beyond the 95% percentile of normal. Since these findings seem to be independent of LGE, mapping techniques may provide complementary information to LGE-CMR in the assessment of myocardial involvement in patients with AAV.

Possible intrinsic association of anti-neutrophil cytoplasmic antibody-associated vasculitis coexisting with multiple myeloma

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a life-threatening condition that causes renal failure. Multiple myeloma (MM) is a malignant proliferation of monoclonal plasma cells in the blood that can also cause renal failure. The two diseases have high morbidity and mortality rates in the elderly, with a poor prognosis. A 64-year-old female presented to Xinqiao Hospital (Chonqing, China) with fatigue and a poor appetite that had been apparent for 6 weeks. Laboratory tests revealed a serum creatinine level of 10.31 mg/dl, a cytoplasmic ANCA titer of 1:10, a positive result for myeloperoxidase and a serum globulin level of 3.96 g/dl. A renal biopsy revealed crescent glomerulonephritis, combined with the rapid progression of renal function. Based on these observations (ANCA titer, crescent glomerulonephritis and rapid progression of renal function) a diagnosis of AAV was established. MM was confirmed by serum immunofixation electrophoresis combined with bone marrow aspiration. The present study discusses what is, to the best of our knowledge, the first case of AAV coexisting with MM in order to highlight it as a clinical concern.

Endothelial progenitor cells are differentially impaired in ANCA-associated vasculitis compared to healthy controls

Background

Endothelial progenitor cells (EPC) are of major importance in vascular repair under healthy circumstances. Vascular injury in need of repair occurs frequently in ANCA-associated vasculitis (AAV). A specialized T cell subset enhancing EPC function and differentiation has recently been described. These angiogenic T cells (T_ang) may have an important impact on the vascular repair process. Therefore, the aim of our study was to investigate EPC and T_ang in AAV.

Methods

Fifty-three patients suffering from AAV and 29 healthy controls (HC) were enrolled in our study. Forty-four patients were in remission, nine patients were in active state of disease. Patients were either untreated or were under monotherapy with low-dose steroids (max. 5 mg/day) at the time of sampling. Circulating EPC and T_ang were determined by flow cytometry (FACS). The functional capacity of EPC was assessed by established cell culture methods.

Results

Circulating EPC were significantly decreased in AAV as compared to HC. The capacity of EPC to differentiate and proliferate was differentially impaired in patients as compared to HC. The outgrowth of endothelial colony-forming cells (ECFC) was severely decreased in patients whereas colony-forming units-endothelial cell (CFU-EC) outgrowth was unaffected. ECFC and CFU-EC differentiation was strictly T cell-dependent. Patients with a relapsing disease course had an impaired ECFC outgrowth and expansion of T_ang as compared to patients with a stable, nonrelapsing disease.

Conclusions

The differentiation process of EPC is impaired in AAV. This may favor insufficient vascular repair promoting a relapsing disease course. Finally, these factors may explain a higher cardiovascular morbidity as has been previously documented in AAV.

The avidity of PR3-ANCA in patients with granulomatosis with polyangiitis during follow-up

The objective of this study is to investigate whether the avidity of proteinase-3-anti-neutrophil cytoplasmic antibody (PR3-ANCA) changes during follow-up in different subgroups of patients with granulomatosis with polyangiitis (GPA). We selected 10 patients with renal relapsing GPA, 10 patients with renal non-relapsing GPA and 10 patients with non-renal relapsing GPA. In all patients, an ANCA rise occurred during remission. The avidity was measured using a chaotropic approach at the time of an ANCA rise and at the time of a relapse in relapsing patients or time-matched during remission in non-relapsing patients. No difference was observed in the avidity at the ANCA rise between renal relapsing patients [26·2% (15·5-47·5)], renal patients without a relapse [39·6% (21·2-63·4)] and non-renal relapsing patients [34·2% (21·6-59·5)]. In renal relapsing patients, the avidity increased significantly from the moment of the ANCA rise to the relapse [difference 6·4% (0·0-17·1), P = 0·0273]. The avidity did not increase after an ANCA rise in renal non-relapsing patients [difference 3·5 (-6·0 to 10·1), P = 0·6250] or in non-renal relapsing patients [difference -3·1% (-8·0 to 5·0), P = 0·5703]. The avidity of PR3-ANCA increases after an ANCA rise during follow-up in renal relapsing patients, but not after an ANCA rise in renal patients who remain in remission or in non-renal relapsing patients.

IFI27 Is a Useful Genetic Marker for Diagnosis of Immunoglobulin A Nephropathy and Membranous Nephropathy Using Peripheral Blood

Diagnosis of chronic glomerulonephritis (CGN) depends primarily on renal biopsy, which is expensive and requires hospitalization, creating a demand for noninvasive diagnostic method for this disease. We used DNA microarray analysis to search for genes whose expression levels in peripheral blood mononuclear cells (PBMCs) could distinguish between patients with CGN and healthy volunteers (HVs). We selected immunoglobulin A nephropathy (IgAN) and membranous nephropathy (MN) as typical forms of CGN. The mRNA level of the gene encoding interferon (IFN)-alpha-inducible protein 27, IFI27, which is preferentially expressed in podocytes of glomeruli, was lower in PBMCs of IgAN and MN patients than in those of HVs. This result was confirmed by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). Moreover, qRT-PCR analysis revealed that the IFI27 mRNA level was reduced in PBMCs of patients with other types of chronic glomerulonephritis. IFI27 immunohistochemical staining of biopsied specimens also confirmed reduced expression of IFI27 protein in IgAN and MN patients. Based on these results, we propose that IFI27 could serve as a noninvasive diagnostic marker for CGNs using peripheral blood.

Long-term Prognosis of Anti-Neutrophil Cytoplasmic Antibody-Negative Renal Vasculitis: Cohort Study in Korea

Few studies have reported on the long-term prognosis of anti-neutrophil cytoplasmic antibody (ANCA)-negative renal vasculitis. Between April 2003 and December 2013, 48 patients were diagnosed with renal vasculitis. Their ANCA status was tested using indirect immunofluorescence and enzyme-linked immunosorbent assays. During a median (interquartile range) follow-up duration of 933.5 (257.5-2,079.0) days, 41.7% of patients progressed to end stage renal disease (ESRD) and 43.8% died from any cause. Of 48 patients, 6 and 42 were ANCA-negative and positive, respectively. The rate of ESRD within 3 months was higher in ANCA-negative patients than in ANCA-positive patients (P = 0.038). In Kaplan-Meier survival analysis, ANCA-negative patients showed shorter renal survival than did ANCA-positive patients (log-rank P = 0.033). In univariate Cox-proportional hazard regression analysis, ANCA-negative patients showed increased risk of ESRD, with a hazard ratio 3.190 (95% confidence interval, 1.028-9.895, P = 0.045). However, the effect of ANCA status on renal survival was not statistically significant in multivariate analysis. Finally, ANCA status did not significantly affect patient survival. In conclusion, long-term patient and renal survival of ANCA-negative renal vasculitis patients did not differ from those of ANCA-positive renal vasculitis patients. Therefore, different treatment strategy depending on ANCA status might be unnecessary.

Aortic ¹⁸F-FDG uptake in patients suffering from granulomatosis with polyangiitis

PURPOSE

The objective of the study was to systematically assess aortic inflammation in patients with granulomatosis with polyangiitis (GPA) using (18)F-2-deoxy-2-[(18)F]fluoro-D-glucose (FDG) positron emission tomography (PET)/CT.

METHODS

Aortic inflammation was studied in PET/CT scans obtained from 21 patients with GPA; 14 patients with sarcoidosis were included as disease controls, 7 patients with stage I or II head and neck carcinoma ascertained during routine clinical practice were used as healthy controls (HC) and 5 patients with large vessel vasculitis (LVV) were used as positive controls. Aortic (18)F-FDG uptake was expressed as the blood-normalized maximum standardized uptake value (SUVmax), known as the target to background ratio (mean TBRmax).

RESULTS

The mean TBRmax (interquartile range) of the aorta in patients with GPA, sarcoidosis, HC and LVV were 1.75 (1.32-2.05), 1.62 (1.54-1.74), 1.29 (1.22-1.52) and 2.03 (1.67-2.45), respectively. The mean TBRmax was significantly higher in patients suffering from GPA or LVV compared to HC (p < 0.05 and p < 0.005, respectively) and tended to be higher in patients suffering from sarcoidosis, but this did not reach statistical significance (p = 0.098). The mean TBRmax of the most diseased segment was significantly higher compared to HC [1.57 (1.39-1.81)] in LVV patients [2.55 (2.22-2.82), p < 0.005], GPA patients [2.17 (1.89-2.83), p < 0.005] and patients suffering from sarcoidosis [2.04 (1.88-2.20), p < 0.05]. In GPA patients, the mean TBRmax of the aorta was significantly higher in patients with previous renal involvement [2.01 (1.69-2.53)] compared to patients without renal involvement in the past [1.60 (1.51-1.80), p < 0.05]. Interrater reproducibility with a second reader was high (all intraclass correlation coefficients >0.9).

CONCLUSION

Patients suffering from GPA show marked aortic FDG uptake.

From the nephrologist's point of view: diversity of causes and clinical features of acute kidney injury

Acute kidney injury (AKI) is a clinical syndrome with multiple entities. Although AKI implies renal damage, functional impairment or both, diagnosis is solely based on the functional parameters of serum creatinine and urine output. The latest definition was provided by the Kidney Disease Improving Global Outcomes (KDIGO) working group in 2012. Independent of the underlying disease, and even in the case of full recovery, AKI is associated with an increased morbidity and mortality. Awareness of the patient's individual risk profile and the diversity of causes and clinical features of AKI is pivotal for optimization of prophylaxes, diagnosis and therapy of each form of AKI. A differentiated and individualized approach is required to improve patient mortality, morbidity, long-term kidney function and eventually the quality of life. In this review, we provide an overview of the different clinical settings in which specific forms of AKI may occur and point out possible diagnostic as well as therapeutic approaches. Secifically AKI is discussed in the context of non-kidney organ failure, organ transplantation, sepsis, malignancy and autoimmune disease.

Phosphorylcholine antibodies are diminished in ANCA-associated vasculitis

BACKGROUND/AIM

ANCA-associated (AAV) vasculitis is an autoimmune small-vessel vasculitis and may be associated with accelerated atherosclerosis as suggested by current literature. Antibodies against oxidized lipoproteins (OxLDL) and phosphorylcholine (Pc) protect from atherosclerosis. This study characterizes these antibodies in AAV.

METHODS

Pc- and anti-OxLDL antibodies were determined in sera of 39 AAV patients and 44 healthy controls (HC). Intima-media thickness (IMT, carotids) and pulse wave velocity (PWV, A. femoralis) were measured.

RESULTS

Pc-/OxLDL IgM antibodies were significantly reduced in AAV. IMT and PWV were negatively associated with anti-Pc antibodies in HC only.

CONCLUSION

Atheroprotective anti-Pc/anti-OxLDL antibodies are significantly reduced in AAV possibly explaining accelerated atherosclerosis in vasculitis patients.

Neutrophil serine proteases exert proteolytic activity on endothelial cells

Neutrophil serine proteases (NSPs) are released from activated neutrophils during inflammation. Here we studied the transfer of the three major NSPs, namely proteinase 3, human neutrophil elastase, and cathepsin G, from neutrophils to endothelial cells and used an unbiased approach to identify novel endothelial NSP substrates. Enzymatically active NSPs were released from stimulated neutrophils and internalized by endothelial cells in a dose- and time-dependent manner as shown by immunoblotting, flow cytometry, and the Boc-Ala substrate assay. Using terminal-amine isotopic labeling of substrates in endothelial cells, we identified 121 peptides from 82 different proteins consisting of 36 substrates for proteinase 3, 30 for neutrophil elastase, and 28 for cathepsin G, respectively. We characterized the extended cleavage pattern and provide corresponding IceLogos. Gene ontology analysis showed significant cytoskeletal substrate enrichment and confirmed several cytoskeletal protein substrates by immunoblotting. Finally, ANCA-stimulated neutrophils released all three active NSPs into the supernatant. Supernatants increased endothelial albumin flux and disturbed the endothelial cell cytoskeletal architecture. Serine protease inhibition abrogated this effect. Longer exposure to NSPs reduced endothelial cell viability and increased apoptosis. Thus, we identified novel NSP substrates and suggest NSP inhibition as a therapeutic measure to inhibit neutrophil-mediated inflammatory vascular diseases.

Proteinase 3-ANCA Vasculitis versus Myeloperoxidase-ANCA Vasculitis

In patients with GN or vasculitis, ANCAs are directed against proteinase 3 (PR3) or myeloperoxidase (MPO). The differences between PR3-ANCA-associated vasculitis (AAV) and MPO-AAV described in the past have been supplemented during the last decade. In this review, we discuss the differences between these two small-vessel vasculitides, focusing especially on possible etiologic and pathophysiologic differences. PR3-AAV is more common in northern parts of the world, whereas MPO-AAV is more common in southern regions of Europe, Asia, and the Pacific, with the exception of New Zealand and Australia. A genetic contribution has been extensively studied, and there is a high prevalence of the HLA-DPB1*04:01 allele in patients with PR3-AAV as opposed to patients with MPO-AAV and/or healthy controls. Histologically, MPO-AAV and PR3-AAV are similar but show qualitative differences when analyzed carefully. Clinically, both serotypes are difficult to distinguish, but quantitative differences are present. More organs are affected in PR3-AAV, whereas renal limited vasculitis occurs more often in patients with MPO-AAV. For future clinical trials, we advocate classifying patients by ANCA serotype as opposed to the traditional disease type classification.

Positron emission tomography scanning in anti-neutrophil cytoplasmic antibodies-associated vasculitis

Tools for evaluation of disease activity in patients with anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) include scoring clinical manifestations, determination of biochemical parameters of inflammation, and obtaining tissue biopsies. These tools, however, are sometimes inconclusive. 2-deoxy-2-[F]-fluoro-D-glucose (FDG) positron emission tomography (PET) scans are commonly used to detect inflammatory or malignant lesions. Our objective is to explore the ability of PET scanning to assess the extent of disease activity in patients with AAV.Consecutive PET scans made between December 2006 and March 2014 in Maastricht (MUMC) and between July 2008 and June 2013 in Brussels (EUH) to assess disease activity in patients with AAV were retrospectively included. Scans were re-examined and quantitatively scored using maximum standard uptake values (SUVmax). PET findings were compared with C-reactive protein (CRP) and ANCA positivity at the time of scanning.Forty-four scans were performed in 33 patients during a period of suspected active disease. All but 2 scans showed PET-positive sites, most commonly the nasopharynx (n = 22) and the lung (n = 22). Forty-one clinically occult lesions were found, including the thyroid gland (n = 4 patients), aorta (n = 8), and bone marrow (n = 7). The amount of hotspots, but not the highest observed SUVmax value, was higher if CRP levels were elevated. Seventeen follow-up scans were made in 13 patients and showed decreased SUVmax values.FDG PET scans in AAV patients with active disease show positive findings in multiple sites of the body even when biochemical parameters are inconclusive, including sites clinically unsuspected and difficult to assess otherwise.

Clinical characteristics and outcomes of childhood-onset ANCA-associated vasculitis: a French nationwide study

BACKGROUND

Data on anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis are scarce in children. The current study is aimed at describing the clinical features and outcomes of childhood-onset ANCA-associated vasculitis (AAV).

METHODS

We conducted a retrospective French multicentre study involving patients in whom AAV was diagnosed before the age of 18 years. Inclusion criteria were (i) granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA) according to classification criteria of the European League Against Rheumatism/Paediatric Rheumatology European Society, and (ii) ANCA positivity. Patient and renal survival were analysed.

RESULTS

Among 66 children included, 80% were female, 42% had GPA and 58% MPA including renal-limited vasculitis, 67% were pANCA+ and 33% cANCA+. The mean incidence of reported cases increased to 0.45 per million children/year in the period 2006-10. Median age at diagnosis was 11.5 years, and median time to diagnosis was 1 month. Initial symptoms included fever and fatigue (79%), skin lesions (41%), arthritis (42%), pulmonary (45%) and renal involvement (88%). Clinical features were similar between GPA and MPA with the exception of upper airway impairment (28%) specific of GPA. Ninety percent of the patients achieved remission after induction treatment. After a median follow-up of 5.2 years, 4 patients (6%) died, corresponding to a mortality rate of 1.2 per 100 person-years, and 22 patients (34%) developed end-stage renal disease (ESRD). Renal survival was 74, 70 and 59% at 1, 5 and 10 years, respectively. In a multivariable Cox regression model, baseline glomerular filtration rate, ethnic origin, histopathological classification and era of treatment were associated with the occurrence of ESRD. Relapse-free survival was 57% at 5 years and 34% at 10 years of follow-up. Patient and renal outcome did not significantly differ between GPA and MPA.

CONCLUSION

Childhood-onset AAV is a rare disease characterized by female predominance, delayed diagnosis, frequent renal impairment and a high remission rate. Baseline GFR and new histopathological classification system are strong predictors of ESRD. Renal survival in childhood AAV has improved over time.

Autoantibodies 2015: From diagnostic biomarkers toward prediction, prognosis and prevention

At the 12th International Workshop on Autoantibodies and Autoimmunity (IWAA), organized in August 2014 in Sao Paulo, Brazil, more than 300 autoimmunologists gathered to discuss the status of many novel autoantibodies in clinical practice, and to envisage additional value of autoantibodies in terms of prediction, prognosis and prevention of autoimmune diseases. Two separate workshops were dedicated to standardization and harmonization of autoantibody testing and nomenclature: International Autoantibody Standardization (IAS) and International Consensus on ANA Patterns (ICAP). It was apparent to all in attendance that the discovery and elucidation of novel autoantibodies did not slow down, but that multiple challenges lay ahead of us in order to apply these discoveries to effective and efficient clinical practice. Importantly, this requires optimal bidirectional communication between clinicians and laboratory specialists, as well as close collaboration with the diagnostic industry. This paper is a report on the 12th IWAA in combination with a review of the recent developments in the field of autoantibodies.

ANCA as a predictor of relapse: useful in patients with renal involvement but not in patients with nonrenal disease

The value of measuring ANCA during follow-up to predict a relapse is controversial. On the basis of recently obtained pathophysiologic insights, we postulated that measuring ANCA is useful in patients with renal involvement but is less valuable in patients with nonrenal disease. One hundred sixty-six consecutive patients with ANCA-associated vasculitis, positive for either proteinase 3 (PR3)-ANCA or myeloperoxidase (MPO)-ANCA, were included in our study, followed at regular intervals, and tested for PR3-ANCA and MPO-ANCA. In this cohort, 104 patients had renal involvement (72 with PR3-ANCA, 32 with MPO-ANCA) and 62 patients had nonrenal disease (36 with PR3-ANCA, 26 with MPO-ANCA). During an average (±SD) follow-up of 49±33 months and 18±14 ANCA measurements, 89 ANCA rises and 74 relapses were recorded. ANCA rises correlated with relapses in patients who presented with renal involvement (hazard ratio [HR], 11.09; 95% confidence interval [95% CI], 5.01 to 24.55), but in comparison, associated only weakly with relapses in patients who presented with nonrenal disease (HR, 2.79; 95% CI, 1.30 to 5.98). In conclusion, longitudinal ANCA measurements may be useful in patients with renal involvement but is less valuable in patients with nonrenal disease.

Signal tranducers and activators of transcription: expression and function in anti-neutrophil cytoplasmic antibody-associated vasculitis

Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) is an autoimmune small vessel vasculitis. Despite the role of autoantibodies, T cells play an essential role in pathogenesis and are abnormal in AAV. Signal transducers and activators of transcription (STAT) affect immunoregulation and T-cell homeostasis. Therefore, the present study examined the ex vivo basal expression of the activated forms of STAT5 [phosphorylated (p)STAT5] and STAT3 (pSTAT3) in AAV and analyzed the function of two signaling pathways linked to these transcription factors. In total, 31 patients with AAV and 16 age-matched healthy controls (HCs) were enrolled. CD3+ T cells from peripheral blood were analyzed directly ex vivo by a fluorescence-activated cell sorter for basal expression of pSTAT5 and pSTAT3. Expression was also analyzed in T cells following short-term stimulation with interleukin (IL)-2 or -10. The basal expression of pSTAT5/3 in T cells was similar to AAV patients and HC. Following stimulation with IL-2 or -10, expression of pSTAT5/3 increased in AAV subjects compared with HC. Basal expression of pSTAT3 correlated with the relapse rate in AAV. In conclusion, STAT3 and STAT5 mediated signaling pathways were functionally intact in AAV patients and exhibited hyper-responsiveness to IL-2 and -10 stimuli. Thus, T-cell abnormalities in AAV are not promoted by an altered basal expression of pSTAT5/3 or dysfunction of the IL-2/-10 signaling pathways, in which STAT5/3 are essential.

Tissue-specific microvascular endothelial cells show distinct capacity to activate NK cells: implications for the pathophysiology of granulomatosis with polyangiitis

The relevance of tissue specificity of microvascular endothelial cells (MECs) in the response to inflammatory stimuli and sensitivity to immune cell-mediated injury is not well defined. We hypothesized that such MEC characteristics might shape their interaction with NK cells through the use of different adhesion molecules and NK cell receptor ligands or the release of different soluble factors and render them more or less vulnerable to NK cell injury during autoimmune vasculitis, such as granulomatosis with polyangiitis (GPA). To generate a comprehensive expression profile of human MECs of renal, lung, and dermal tissue origin, we characterized, in detail, their response to inflammatory cytokines and to proteinase 3, a major autoantigen in GPA, and analyzed the effects on NK cell activation. In this study, we show that renal MECs were more susceptible than lung and dermal MECs to the effect of inflammatory signals, showing upregulation of ICAM-1 and VCAM-1 on their surface, as well as release of CCL2, soluble fractalkine, and soluble VCAM-1. Proteinase 3-stimulated renal and lung MECs triggered CD107a degranulation in control NK cell. Notably, NK cells from GPA patients expressed markers of recent in vivo activation (CD69, CD107a), degranulated more efficiently than did control NK cells in the presence of renal MECs, and induced direct killing of renal MECs in vitro. These results suggest that, upon inflammatory conditions in GPA, renal MECs may contribute to the recruitment and activation of NK cells in the target vessel wall, which may participate in the necrotizing vasculitis of the kidney during this disease.

Association of low serum complement C3 with reduced patient and renal survival in antimyeloperoxidase-associated small-vessel vasculitis

OBJECTIVE

This study aimed to determine the value of hypocomplementemia in predicting the renal and patient survival of patients with antineutrophil cytoplasmatic antibody-associated vasculitis (AAV).

METHODS

A retrospective analysis of 30 consecutive patients who were diagnosed with AAV and followed at our hospital from 1996 to 2011 was performed. Renal outcome was determined by the Modification of Diet in Renal Disease equation. Disease outcome measures included patient survival and accrual of chronic kidney disease (CKD) defined as an estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m(2) from the date of diagnosis. Logistic regression analysis was used to identify predictors of survival.

RESULTS

At presentation, 6 (20%) patients had a low C3 level, which was significantly associated with older age (p = 0.009), higher C-reactive protein (p = 0.02), a lower eGFR (p = 0.03), and anti-MPO antibody positivity (p = 0.03). A low C3 level at presentation was significantly associated with a reduced eGFR at the last study visit (p = 0.015, OR = 11; 95% CI 1.27-95.15). During a mean follow-up of 9.0 ± 6.2 years, 8 (26.6%) patients had accrued CKD that was significantly associated with low C3 levels at presentation (p = 0.002, OR = 22; 95% CI 2.36-204.7). Mortality was significantly associated with low serum C3 levels at presentation (p = 0.02).

CONCLUSION

We found that a low serum C3 level at the time of diagnosis was significantly associated with reduced renal and patient survival in patients with anti-MPO AAV. Our results suggest a role for complement activation in the pathogenesis of AAV.

Abnormal expression pattern of the IL-2 receptor β-chain on CD4+ T cells in ANCA-associated vasculitis

BACKGROUND/AIM

ANCA-associated vasculitis (AAV) is a small-vessel vasculitis of autoimmune origin. In addition to autoantibodies, T cells have a pivotal pathophysiological role in this disease. T-cell homeostasis and immune tolerance critically depend on IL-2 and its receptor expressed by T cells. In this study, we investigated the IL-2 receptor (IL-2r) expression on CD4(+) T cells in AAV.

METHODS

Thirty patients with AAV and 15 age-matched healthy controls (HC) were enrolled. T cells from peripheral blood were analysed by flow cytometry for expression of the IL-2r α - and β-chain.

RESULTS

The IL-2r α-chain was overexpressed in AAV as compared to HC (36 ± 16% versus 20 ± 9%, P < 0.005). The IL-2r-β-chain expression was significantly reduced on CD25(+) CD4(+) T-cells and CD4(+)CD25(+)FoxP3(pos) regulatory T-cells (Tregs; AAV versus HC: 48 ± 14% versus 62 ± 9%, P = 0.002 and 38 ± 18% versus 68 ± 5%, P = 0.002). Low β -chain expression in AAV was associated with relapsing disease and systemic vasculitis with renal involvement.

CONCLUSION

The IL-2r expression pattern is abnormal in AAV. To our knowledge, we are the first to show that the β -chain expression is drastically diminished on T cells in AAV and related to a less favorable disease course. Given the indispensable function of the β -chain in IL-2 signaling of T cells, diminished expression may contribute to disturbed immune homeostasis in AAV.

Vasculitis of anti-neutrophil cytoplasmic antibody after liver transplantation

OBJECTIVE

We reported a case of vasculitis of anti-neutrophil cytoplasmic antibody after liver transplantation. A 56-year-old male patient underwent orthotopic liver transplantation of the classic style on February 25, 2010 because of alcoholic cirrhosis.

METHODS

Pathology analysis showed it was nodular cirrhosis. The patient was given conventional treatment programs of FK (tacrolimus) + mycophenolate mofetil + hormone; hormone was suspended at the third month. He began to cough and spit, and there was blood in the sputum in September. Lung CT scanning images showed that there was a visible multiple low-density patchy shadow in both lungs; however, a number of other detecting results were negative.

RESULTS

Considering the patient with contact suspected mold, we improved the inspection and switched to experimental treatment (itraconazole), and the patient improved and was then discharged. Two months later, he complained about appearing hemoptysis. Final diagnostic results showed it was anti-neutrophil cytoplasmic antibody-associated vasculitis after liver transplantation. Then we stopped medication with itraconazole. Treatment with methylprednisolone was continued, and the patient gradually stopped coughing and had no expectoration and hemoptysis.

CONCLUSIONS

Reviewing CT respectively showed significant improvement at the 7th and 24th days of hormone therapy; thus, we confirmed it was anti-neutrophil cytoplasmic antibody-associated vasculitis after liver transplantation.

Patients with antineutrophil cytoplasmic antibodies associated vasculitis in remission are hypercoagulable

OBJECTIVES

The risk of venous thromboembolism (VTE) is increased in patients with antineutrophil cytoplasmic antibodies (ANCA) associated vasculitides (AAV) as compared to healthy subjects. The mechanisms underlying this increased occurrence of VTE are not completely understood. We hypothesize that AAV patients in remission are more procoagulant than healthy controls.

METHODS

Patients with AAV in remission and no VTE for the last 6 months were included. Patients with severe renal impairment (serum creatinine > 250 μmol/l) were excluded. Age and sex matched healthy controls were included. The endogenous thrombin potential (ETP) was determined together with hemostatic variables: fibrinogen, D-dimers, factor VIII (FVIII), tissue factor pathway inhibitor (TFPI), protein C, and free protein S.

RESULTS

Thirty-one patients were included. In 27 patients not taking anticoagulants, ETP was measured and found to be elevated: 137.1% as compared to a median of 90.0% for healthy controls (p < 0.01). Fibrinogen and D-dimer levels were not elevated in patients (median 3.5 g/l and 279 μg/l, respectively). FVIII and TFPI levels were also significantly increased in patients as compared to healthy controls (159% vs 137%; 122.5% vs 101%, respectively), whereas protein C and free protein S levels were not elevated (126.5% vs 118.6% and 124.6% vs 118.3%, respectively).

CONCLUSION

Patients with AAV in remission are more procoagulant than healthy controls, as indicated by an increased ETP. The increased FVIII level measured in these patients suggests persistence of endothelial activation and/or dysfunction. This endothelial dysfunction may cause a continuous low-grade procoagulant state.

Impact of rituximab trials on the treatment of ANCA-associated vasculitis

ANCA-associated vasculitis (AAV) is a subgrouping of autoimmune disorders characterized by a chronic relapsing course. Induction therapy is usually effective, but 70% of patients will relapse and 20% develop refractory disease. In the relapsing and refractory subgroups, treatment is complicated by the cumulative exposure to toxic drugs that contribute to poor long-term outcomes. The anti-CD20 monoclonal antibody rituximab (RTX) depletes B cells, and the success of this targeted therapy has contributed to the evidence supporting a central role for B cells in AAV pathogenesis. Initial proof of RTX effectiveness originated from small, prospective trials and retrospective surveys conducted in AAV patients with relapsing and refractory disease; high remission rates permitted the reduction of glucocorticoids (GCS) doses and withdrawal of immunosuppressives. There has been controversy over the effectiveness of RTX in patients with predominantly granulomatous manifestations, where response rates have varied between studies, in part due to different RTX dosing regimens. These studies were followed by comparison of RTX against cyclophosphamide (CYC) for remission induction of new or relapsing AAV in two randomized trials, which led to the licensing of RTX for this indication. Subsequent attention has been turned to the use of RTX as a relapse prevention agent, to the potential for GCS sparing and to RTX-associated toxicity. We will discuss the impact that the results of RTX clinical trials have had on the management of AAV patients.

Antineutrophil cytoplasmic autoantibodies: how are they detected and what is their use for diagnosis, classification and follow-up?

Antineutrophil cytoplasmic antibodies (ANCA) are traditionally detected by an indirect immunofluorescence technique. According to the international consensus on ANCA testing, ANCA should also be tested by antigen-specific tests for myeloperoxidase-ANCA and proteinase 3-ANCA. The direct noncompetitive enzyme-linked immunosorbent assay (ELISA) used to be the method of choice. Nowadays, these assays are called "first-generation" assays. Second-generation tests (capture ELISA) or third-generation tests (anchor ELISA) are more sensitive and specific for ANCA testing. We postulate that ANCA as detected by these newer ANCA tests may replace the need to perform indirect immunofluorescence-based assays. For classification of patients, ANCA serotype seems more important than classifying patients according to their clinical subtype, since genetics, clinical manifestations and response to therapy are more related to ANCA serotype than to clinical subtype. Detection of ANCA to monitor disease activity is still a controversial issue. Treatment based on ANCA levels is at present only experimentally performed in those patients who are treated with B-cell depletion therapy with rituximab. Future studies are needed to establish whether this way of monitoring patients is warranted.

C1q-targeted monoclonal antibody prevents complement-dependent cytotoxicity and neuropathology in in vitro and mouse models of neuromyelitis optica

Neuromyelitis optica (NMO) is an autoimmune disorder with inflammatory demyelinating lesions in the central nervous system, particularly in the spinal cord and optic nerve. NMO pathogenesis is thought to involve binding of anti-aquaporin-4 (AQP4) autoantibodies to astrocytes, which causes complement-dependent cytotoxicity (CDC) and downstream inflammation leading to oligodendrocyte and neuronal injury. Vasculocentric deposition of activated complement is a prominent feature of NMO pathology. Here, we show that a neutralizing monoclonal antibody against the C1q protein in the classical complement pathway prevents AQP4 autoantibody-dependent CDC in cell cultures and NMO lesions in ex vivo spinal cord slice cultures and in mice. A monoclonal antibody against human C1q with 11 nM binding affinity prevented CDC caused by NMO patient serum in AQP4-transfected cells and primary astrocyte cultures, and prevented complement-dependent cell-mediated cytotoxicity (CDCC) produced by natural killer cells. The anti-C1q antibody prevented astrocyte damage and demyelination in mouse spinal cord slice cultures exposed to AQP4 autoantibody and human complement. In a mouse model of NMO produced by intracerebral injection of AQP4 autoantibody and human complement, the inflammatory demyelinating lesions were greatly reduced by intracerebral administration of the anti-C1q antibody. These results provide proof-of-concept for C1q-targeted monoclonal antibody therapy in NMO. Targeting of C1q inhibits the classical complement pathway directly and causes secondary inhibition of CDCC and the alternative complement pathway. As C1q-targeted therapy leaves the lectin complement activation pathway largely intact, its side-effect profile is predicted to differ from that of therapies targeting downstream complement proteins.

Antineutrophil cytoplasmic antibody-associated vasculitides: is it time to split up the group?

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides are a heterogeneous group of diseases corresponding to necrotising inflammation of small vessels with a wide range of clinical presentations. At least two of the diseases are believed to exhibit a common ground of pathophysiological mechanisms. These are granulomatosis with polyangiitis (GPA, formerly known as Wegener's granulomatosis) and microscopic polyangiitis (MPA). ANCA directed against proteinase 3 (PR3) are preferentially associated with GPA, and anti-myeloperoxidase (MPO) ANCA are associated mainly with MPA and eosinophilic GPA (formerly known as Churg-Strauss syndrome). Anti-MPO and anti-PR3 antibodies can activate neutrophils in vitro. In vivo data are available for humans and mice on the pathogenicity of anti-MPO but it is more controversial for PR3-ANCA. A recent genome-wide association study of patients with ANCA-associated vasculitides confirmed the genetic contribution to the pathogenesis of these conditions, with significant association of PR3-ANCA and human leukocyte antigen-DP and the genes encoding α1-antitrypsin and PR3. MPO-ANCA were significantly associated with human leukocyte antigen-DQ. Thus, recent results from epidemiological studies, genome-wide association study and therapeutic trials have suggested that these entities are, in fact, distinct. We have summarised these results and discuss the idea that these two entities should be studied separately as the nature of the two auto-antigens suggests at a molecular level despite shared ANCA involvement.

Genetics of toll like receptor 9 in ANCA associated vasculitides

OBJECTIVES

To investigate the contribution of genetic polymorphisms of toll like receptor (TLR) 9 and related genes on the susceptibility and clinical manifestation of anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitides (AAV).

METHODS

Four single nucleotide polymorphisms (SNPs) in TLR9 were genotyped in 863 German AAV cases and 1344 healthy controls. Significant results were replicated in a cohort of 426 Dutch and British AAV cases. 11 polymorphisms in TLR9 related genes were studied concomitantly.

RESULTS

A strong association of TLR9 genotypes and haplotypes with granulomatosis with polyangiitis was observed as well as a contrariwise association with microscopic polyangiitis. The association was confirmed when cases were compared according to ANCA status rather than to clinical entity. This was partly replicated in the second cohort leading to a striking overall difference in TLR9 allele/haplotype frequencies between proteinase 3 (PR3) ANCA+ and myeloperoxidase (MPO) ANCA+ cases (p=0.00000398, pc=0.000016, OR 1.68 (95% CI 1.35 to 2.1) for rs352140; p=0.000011, pc=0.000044, OR 1.64 (95% CI 1.31 to 2.04) for a 3-SNP haplotype). No significant association or epistatic effect was detected for TLR9 related genes: interleukin 6, interleukin 23 receptor, myeloid differentiation primary response 88, TNF receptor-associated factor 6, interleukin-1 receptor-associated kinase 4, discs large homolog 5 and nucleotide-binding oligomerisation domain containing 2.

CONCLUSIONS

We provide further evidence that PR3-ANCA+ AAV differs genetically from MPO-ANCA+ AAV. TLR9 signalling may be involved in disease pathology, favouring models of infectious agents triggering AAV development.

Validation of the 2010 histopathological classification of ANCA-associated glomerulonephritis in a Japanese single-center cohort

OBJECTIVES: To validate the 2010 histopathological classification system of anti-neutrophil cytoplasmic antibodies (ANCA)-associated glomerulonephritis (GN) in a Japanese single-center cohort. METHODS: We retrospectively studied 54 patients (28 renally limited pauci-immune GN, 25 microscopic polyangiitis, and one Churg-Strauss syndrome). RESULTS: There were 17 patients with focal GN, eight patients with crescentic GN, 19 patients with mixed GN, and 10 patients with sclerotic GN. Detailed information regarding treatment was available in 39 patients. All these patients were treated with steroids with or without immunosuppressive agents. Hemodialysis was introduced in two patients with crescentic GN and three patients with sclerotic GN. During the follow-up period, 27 of 54 patients died. The major cause of death was pneumonia. Significant differences were observed in estimated glomerular filtration rate among patients with focal, crescentic, mixed, and sclerotic GN at entry and 1- and 5-year follow-up. Patients with focal GN had preserved renal function and favorable outcome. CONCLUSIONS: Our validation study suggests that the 2010 histopathological classification of ANCA-associated GN might aid in prognostication of patients at the time of diagnosis and in therapy selection.

Central nervous system vasculitis

OPINION STATEMENT

A patient presenting with suspected primary central nervous system (CNS) vasculitis is often difficult to manage. Once the diagnosis is suspected, the clinical course may already be severe and warrant timely aggressive treatment with potentially toxic drugs. Definitive diagnosis is often delayed, requiring specialized tests that are only possible in certain centers and sometimes prove to be inconclusive. The need to make a confident diagnosis before starting powerful and potentially toxic immunosuppression, often conflicts with the desire to initiate timely treatment aimed at preventing irreversible neurological dysfunction. The heterogeneity and rarity of this condition is a major obstacle to conducting properly designed, double blinded, placebo-controlled studies. There is no Class I evidence for any form of treatment in these situations, and management guidelines represent expert opinion, based primarily on trials investigating therapies affecting systemic conditions with a CNS vasculitic component. Cyclophosphamide is still the main immunosuppressive drug used during active disease in combination with high dose steroids. Rituximab may be an equally efficacious, less toxic alternative, but its use is still limited due to its cost.

Late recovery of renal function by rituximab in a patient with Wegener's granulomatosis

BACKGROUND

Rituximab has proven effective in the treatment of complicated granulomatosis with polyangiitis (Wegener's, GPA). Two controlled trials in adults demonstrated beneficial effects of rituximab compared to cyclophosphamide in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis to induce remission and to treat relapses. Pediatric experience with rituximab in GPA is limited; the impact on renal function is unknown.

CASE-DIAGNOSIS/TREATMENT

We report a female adolescent with GPA and necrotizing glomerulonephritis that lead to end-stage renal disease (ESRD). After 22 months of peritoneal dialysis, she still experienced relapses and major treatment-associated adverse effects. After a single dose of rituximab, she rapidly achieved clinical remission and, unexpectedly, steadily recovered glomerular filtration rate, plateauing at 25 ml/min/1.73 m(2). Peritoneal dialysis could be discontinued for 16 months.

CONCLUSIONS

This case documents a potent beneficial effect of rituximab on renal manifestation of GPA even in long-established ESRD.

Improved outcome in anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis: a 30-year follow-up study

BACKGROUND

Anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis has a poor prognosis. In the current study, we assessed whether prognosis in these patients improved over the last three decades.

METHODS

In a large inception cohort, all consecutive patients with ANCA-associated glomerulonephritis were included between January 1979 and December 2009. Inclusion criteria were the presence of ANCA and the availability of a kidney biopsy. To assess renal and patient survival, patients were divided in three groups through time: 1979-89, 1990-2000 and 2001-09.

RESULTS

A total of 181 patients were included. One-, 5- and 10-year survival was 77, 66 and 49%, respectively. Survival within the time groups was significantly different, yielding a hazard ratio for death of 2.9 for 1990-2000 and 3.9 for 1979-89 compared with 2001-09 (P < 0.001). Serum creatinine and active lesions as found in the kidney biopsy significantly decreased through the three decades.

CONCLUSIONS

Both patient and renal survival in patients with ANCA-associated renal vasculitis have improved over the last three decades. We postulate that both earlier diagnosis and better therapeutic management of patients are responsible for this effect.

Th17 expansion in granulomatosis with polyangiitis (Wegener's): the role of disease activity, immune regulation and therapy

INTRODUCTION

In autoimmune diseases, IL-17 producing T-cells (Th17), a pro-inflammatory subset of T-cells, are pathophysiologically involved. There is little knowledge on the role of Th17 cells in granulomatosis with polyangiitis (GPA). In the present study, we investigated Th17 cells, Tregs and subsets of circulating Th17 cells in GPA and related results to disease activity.

METHODS

42 GPA patients in remission, 18 with active disease and 14 healthy controls (HC) were enrolled. Th17 cells, their subsets and regulatory T-cells were determined by intracellular fluorescence activated cell sorter (FACS). Data are given as mean percentage ±SD of total T-helper-cells.

RESULTS

Th17 cells are expanded in active and quiescent GPA as compared to HC (1.7±1.4% vs. 0.7 ±0.3%, P = 0.006 and 1.9 ±1.5% vs. 0.7 ±0.3%, P<0.0001). Th17 expansion is stable over time and does not decline when remission is achieved. However, a negative association of Th17 cells and steroid dosage is observed (r=-0.46, P = 0.002). The Th17 expansion was not balanced by Tregs as indicated by skewed Th17/Treg ratios in active and quiescent GPA. Th17 subsets co-producing IFNγ or IL-10 are significantly increased in GPA. GPA patients in remission not receiving maintenance therapy have significantly more IL-10/IL-17A double positive T-cells than HC (0.0501 ±0.031% vs. 0.0282 ±0.016%, P = 0.007).

CONCLUSIONS

We provide evidence for a persistent, unbalanced expansion of Th17 cells and Th17 subsets which seems to be independent of disease activity. Maintenance therapy reduces -but does not normalize- Th17 expansion.

Proteinase 3, the autoantigen in granulomatosis with polyangiitis, associates with calreticulin on apoptotic neutrophils, impairs macrophage phagocytosis, and promotes inflammation

Proteinase 3 (PR3) is the target of anti-neutrophil cytoplasm Abs in granulomatosis with polyangiitis, a form of systemic vasculitis. Upon neutrophil apoptosis, PR3 is coexternalized with phosphatidylserine and impaired macrophage phagocytosis. Calreticulin (CRT), a protein involved in apoptotic cell recognition, was found to be a new PR3 partner coexpressed with PR3 on the neutrophil plasma membrane during apoptosis, but not after degranulation. The association between PR3 and CRT was demonstrated in neutrophils by confocal microscopy and coimmunoprecipitation. Evidence for a direct interaction between PR3 and the globular domain of CRT, but not with its P domain, was provided by surface plasmon resonance spectroscopy. Phagocytosis of apoptotic neutrophils from healthy donors was decreased after blocking lipoprotein receptor-related protein (LRP), a CRT receptor on macrophages. In contrast, neutrophils from patients with granulomatosis with polyangiitis expressing high membrane PR3 levels showed a lower rate of phagocytosis than those from healthy controls not affected by anti-LRP, suggesting that the LRP-CRT pathway was disturbed by PR3-CRT association. Moreover, phagocytosis of apoptotic PR3-expressing cells potentiated proinflammatory cytokine in vitro by human monocyte-derived macrophages and in vivo by resident murine peritoneal macrophages, and diverted the anti-inflammatory response triggered by the phagocytosis of apoptotic cells after LPS challenge in thioglycolate-elicited murine macrophages. Therefore, membrane PR3 expressed on apoptotic neutrophils might amplify inflammation and promote autoimmunity by affecting the anti-inflammatory "reprogramming" of macrophages.

Plasma leakage through glomerular basement membrane ruptures triggers the proliferation of parietal epithelial cells and crescent formation in non-inflammatory glomerular injury

Glomerular crescents are most common in rapidly progressive glomerulonephritis but also occur in non-inflammatory chronic glomerulopathies; thus, factors other than inflammation should trigger crescent formation, eg vascular damage and plasma leakage. Here we report that Alport nephropathy in Col4A3-deficient Sv129 mice is complicated by diffuse and global crescent formation in which proliferating parietal epithelial cells are the predominant cell type. Laminin staining and transmission and acellular scanning electron microscopy of acellular glomeruli documented disruptions and progressive disintegration of the glomerular basement membrane in Col4A3-deficient mice. FITC-dextran perfusion further revealed vascular leakage from glomerular capillaries into Bowman's space, further documented by fibrin deposits in the segmental crescents. Its pathogenic role was validated by showing that the fibrinolytic activity of recombinant urokinase partially prevented crescent formation. In addition, in vitro studies confirmed an additional mitogenic potential of serum on murine and human parietal epithelial cells. Furthermore, loss of parietal cell polarity and unpolarized secretion of extracellular matrix components were evident within fibrocellular crescents. Among 665 human Alport nephropathy biopsies, crescent formation was noted in 0.4%. We conclude that glomerular vascular injury and GBM breaks cause plasma leakage which triggers a wound healing programme involving the proliferation of parietal cells and their loss of polarity. This process can trigger cellular and fibrocellular crescent formation even in the absence of cellular inflammation and rupture of the Bowman's capsule.

Aberrant expression of the negative costimulator PD-1 on T cells in granulomatosis with polyangiitis

OBJECTIVE

Persistent T-cell activation is frequently observed in granulomatosis with polyangiitis (GPA, formerly known as Wegener's granulomatosis). T-cell activation is usually balanced by negative costimulatory molecules. The negative costimulator programmed death receptor-1 (PD-1) and its relevance to T-cell immunity have not been studied so far in GPA. Thus it is the aim of the study to characterize the role of PD-1 in GPA.

METHODS

Thirty-two patients suffering from GPA and 19 age-matched healthy controls (HCs) were enrolled. T-lymphocyte subsets from peripheral blood were analysed by flow cytometry for the expression of PD-1. The frequency of memory T cells and T cells producing pro-inflammatory cytokines was determined. Renal biopsies from GPA patients were stained for CD3 and PD-1.

RESULTS

PD-1 expression was increased on T-helper cells (Th cells) from GPA patients as compared with HCs. In addition, parameters of persistent T-cell activation and production of pro-inflammatory cytokines were positively associated with numbers of PD-1(+) Th cells in patients but not in HCs. Latent infection with CMV seemed to enhance PD-1 expression on CD4(+) and CD4(+)CD25(-) T cells. Interestingly, expression of PD-1 on CD4(+)CD25(+)T cells was inversely correlated with relapse rate. Importantly, lesional T cells were mostly lacking PD-1.

CONCLUSIONS

The expression of the negative costimulator PD-1 is altered in GPA and might counterbalance persistent T-cell activation.

Complement-dependent cytotoxicity in neuromyelitis optica requires aquaporin-4 protein assembly in orthogonal arrays

Neuromyelitis optica (NMO) is an inflammatory demyelinating disease of the central nervous system in which binding of pathogenic autoantibodies (NMO-IgG) to astrocyte aquaporin-4 (AQP4) causes complement-dependent cytotoxicity (CDC) and inflammation. We previously reported a wide range of binding affinities of NMO-IgGs to AQP4 in separate tetramers versus intramembrane aggregates (orthogonal arrays of particles, OAPs). We report here a second, independent mechanism by which CDC is affected by AQP4 assembly. Utilizing lactate dehydrogenase release and live/dead cell cytotoxicity assays, we found in different cell lines, and with different monoclonal and patient-derived NMO-IgGs, that CDC was greatly (>100-fold) reduced in cells expressing M1- versus M23-AQP4. Studies using a M23-AQP4 mutant containing an OAP-disrupting mutation, and in cells expressing AQP4 in different M1/M23 ratios, indicated that NMO-IgG-dependent CDC requires AQP4 OAP assembly. In contrast, antibody-dependent cell-mediated cytotoxicity produced by natural killer cells did not depend on AQP4 OAP assembly. Measurements of C1q binding and complement attack complex (C9neo) supported the conclusion that the greatly enhanced CDC by OAPs is due to efficient, multivalent binding of C1q to clustered NMO-IgG on OAPs. We conclude that AQP4 assembly in OAPs is required for CDC in NMO, establishing a new mechanism of OAP-dependent NMO pathogenesis. Disruption of AQP4 OAPs may greatly reduce NMO-IgG dependent CDC and NMO pathology.

Mizoribine for crescentic glomerulonephritis with sarcoidosis: effectiveness not only for urinalysis abnormalities but also for hilar lymph node enlargement

Sarcoidosis is a multisystem disease related to helper T cell responses. We recently experienced the case of a 57-year-old woman with sarcoidosis complicated by crescentic glomerulonephritis with low levels of myeloperoxidase-antineutrophil cytoplasmic antibody. We herein describe the details of her clinical course and discuss the effectiveness of mizoribine, which has an immunosuppressive effect equivalent to that of mycophenolate mofetil, not only for urinalysis abnormalities but also for hilar lymph node enlargement.

Basic and translational concepts of immune-mediated glomerular diseases

Genetically modified immune responses to infections and self-antigens initiate most forms of GN by generating pathogen- and danger-associated molecular patterns that stimulate Toll-like receptors and complement. These innate immune responses activate circulating monocytes and resident glomerular cells to release inflammatory mediators and initiate adaptive, antigen-specific immune responses that collectively damage glomerular structures. CD4 T cells are needed for B cell-driven antibody production that leads to immune complex formation in glomeruli, complement activation, and injury induced by both circulating inflammatory and resident glomerular effector cells. Th17 cells can also induce glomerular injury directly. In this review, information derived from studies in vitro, well characterized experimental models, and humans summarize and update likely pathogenic mechanisms involved in human diseases presenting as nephritis (postinfectious GN, IgA nephropathy, antiglomerular basement membrane and antineutrophil cytoplasmic antibody-mediated crescentic GN, lupus nephritis, type I membranoproliferative GN), and nephrotic syndrome (minimal change/FSGS, membranous nephropathy, and C3 glomerulopathies). Advances in understanding the immunopathogenesis of each of these entities offer many opportunities for future therapeutic interventions.