Crescentic glomerulonephritis: new aspects of pathogenesis

Ultrasound-Based Radiomics for the Classification of Henoch-Schönlein Purpura Nephritis in Children

Henoch-Schönlein purpura nephritis (HSPN) is one of the most common kidney diseases in children. The current diagnosis and classification of HSPN depend on pathological biopsy, which is seriously limited by its invasive and high-risk nature. The aim of the study was to explore the potential of radiomics model for evaluating the histopathological classification of HSPN based on the ultrasound (US) images. A total of 440 patients with Henoch-Schönlein purpura nephritis proved by biopsy were analyzed retrospectively. They were grouped according to two histopathological categories: those without glomerular crescent formation (ISKDC grades I-II) and those with glomerular crescent formation (ISKDC grades III-V). The patients were randomly assigned to either a training cohort (n = 308) or a validation cohort (n = 132) with a ratio of 7:3. The sonologist manually drew the regions of interest (ROI) on the ultrasound images of the right kidney including the cortex and medulla. Then, the ultrasound radiomics features were extracted using the Pyradiomics package. The dimensions of radiomics features were reduced by Spearman correlation coefficients and least absolute shrinkage and selection operator (LASSO) method. Finally, three radiomics models using k-nearest neighbor (KNN), logistic regression (LR), and support vector machine (SVM) were established, respectively. The predictive performance of such classifiers was assessed with receiver operating characteristic (ROC) curve. 105 radiomics features were extracted from derived US images of each patient and 14 features were ultimately selected for the machine learning analysis. Three machine learning models including k-nearest neighbor (KNN), logistic regression (LR), and support vector machine (SVM) were established for HSPN classification. Of the three classifiers, the SVM classifier performed the best in the validation cohort [area under the curve (AUC) =0.870 (95% CI, 0.795-0.944), sensitivity = 0.706, specificity = 0.950]. The US-based radiomics had good predictive value for HSPN classification, which can be served as a noninvasive tool to evaluate the severity of renal pathology and crescentic formation in children with HSPN.

Three Diseases Mediated by Different Immunopathologic Mechanisms-ANCA-Associated Vasculitis, Anti-Glomerular Basement Membrane Disease, and Immune Complex-Mediated Glomerulonephritis-A Common Clinical and Histopathologic Picture: Rapidly Progressive Crescentic Glomerulonephritis

Immune mechanisms play an important role in the pathogenesis of glomerulonephritis (GN), with autoimmunity being the main underlying pathogenetic process of both primary and secondary GN. We present three autoimmune diseases mediated by different autoimmune mechanisms: glomerulonephritis in vasculitis mediated by anti-neutrophil cytoplasmic antibodies (ANCAs), glomerulonephritis mediated by anti-glomerular basement membrane antibodies (anti-GBM antibodies), and immune complex-mediated glomerulonephritis. Some of these diseases represent a common clinical and histopathologic scenario, namely rapidly progressive crescentic glomerulonephritis. This is a severe illness requiring complex therapy, with the main role being played by therapy aimed at targeting immune mechanisms. In the absence of immune therapy, the crescents, the characteristic histopathologic lesions of this common presentation, progress toward fibrosis, which is accompanied by end-stage renal disease (ESRD). The fact that three diseases mediated by different immunopathologic mechanisms have a common clinical and histopathologic picture reveals the complexity of the relationship between immunopathologic mechanisms and their clinical expression. Whereas most glomerular diseases progress by a slow process of sclerosis and fibrosis, the glomerular diseases accompanied by glomerular crescent formation can progress, if untreated, in a couple of months into whole-nephron glomerulosclerosis and fibrosis. The outcome of different immune processes in a common clinical and histopathologic phenotype reveals the complexity of the relationship of the kidney with the immune system. The aim of this review is to present different immune processes that lead to a common clinical and histopathologic phenotype, such as rapidly progressive crescentic glomerulonephritis.

Development of ileocolic artery pseudoaneurysm after renal biopsy

The rate of bleeding complications related to percutaneous native renal biopsy is low, and pseudoaneurysms of the extrarenal arteries are rare. There have been a few reports of extrarenal artery injuries related to renal biopsy; however, to the best of our knowledge, there have not been any reports of injuries to the ileocolic artery or multiple injuries to extrarenal arteries. Herein, we report the case of an 87-year-old man who developed multiple vascular injuries: an arteriovenous fistula at the lower pole of the right kidney, pseudoaneurysms of the second lumbar artery, and an ileocolic artery 19 days after renal biopsy. Although identifying an ileocolic artery pseudoaneurysm was slightly delayed due to its rarity, all vascular injuries were successfully embolized with microcoils.

Immunological Interaction of HLA-DPB1 and Proteinase 3 in ANCA Vasculitis is Associated with Clinical Disease Activity

BACKGROUND

PR3-ANCA vasculitis has a genetic association with HLA-DPB1. We explored immunologic and clinical features related to the interaction of HLA-DPB1*04:01 with a strongly binding PR3 peptide epitope (PR3225-239).

METHODS

Patients with ANCA vasculitis with active disease and disease in remission were followed longitudinally. Peripheral blood mononuclear cells from patients and healthy controls with HLA-DPB1*04:01 were tested for HLA-DPB1*04:01 expression and interaction with a PR3 peptide identified via in silico and in vitro assays. Tetramers (HLA/peptide multimers) identified autoreactive T cells in vitro. RESULTS: The HLA-DPB1*04:01 genotype was associated with risk of relapse in PR3-ANCA (HR for relapse 2.06; 95% CI, 1.01 to 4.20) but not in myeloperoxidase (MPO)-ANCA or the combined cohort. In silico predictions of HLA and PR3 peptide interactions demonstrated strong affinity between ATRLFPDFFTRVALY (PR3225-239) and HLA-DPB1*04:01 that was confirmed by in vitro competitive binding studies. The interaction was tested in ex vivo flow cytometry studies of labeled peptide and HLA-DPB1*04:01-expressing cells. We demonstrated PR3225-239 specific autoreactive T cells using synthetic HLA multimers (tetramers). Patients in long-term remission off therapy had autoantigenic peptide and HLA interaction comparable to that of healthy volunteers.

CONCLUSIONS

The risk allele HLA-DPB1*04:01 has been associated with PR3-ANCA, but its immunopathologic role was unclear. These studies demonstrate that HLA-DPB1*04:01 and PR3225-239 initiate an immune response. Autoreactive T cells specifically recognized PR3225-239 presented by HLA-DPB1*04:01. Although larger studies should validate these findings, the pathobiology may explain the observed increased risk of relapse in our cohort. Moreover, lack of HLA and autoantigen interaction observed during long-term remission signals immunologic nonresponsiveness.

Etiological Spectrum and Clinical Features in 215 Patients of Crescentic Glomerulonephritis: Is it Different in India?

INTRODUCTION

Crescentic glomerulonephritis (CrGN) characterized by the presence of crescents in most (≥50%) glomeruli on renal histology clinically presents as rapidly progressive renal failure. It can occur due to diverse etiologies with varying course and renal outcomes. We studied the prognostic significance of its classification as pauci-immune, anti-GBM, and immune-complex mediated CrGN.

MATERIALS AND METHODS

Renal biopsies diagnosed as CrGN over 9 years were included. Clinical, biochemical, serological, and histological features of various classes of CrGN were correlated with renal outcome.

RESULTS

215 biopsies were diagnosed as CrGN during this period. A majority (63%) were immune-complex mediated while 32% were pauci-immune, followed by anti-GBM disease (5%). 85.5% of pauci-immune CrGN were ANCA associated. The levels of proteinuria and serum creatinine were significantly higher in anti-GBM CrGN as compared to the other two classes. The various histological features including Bowman's capsule rupture, peri-glomerular granulomatous reaction, fibrinoid necrosis, and vasculitis were more common in anti-GBM disease and pauci-immune CrGN. The median renal survival was 6.3, 5.3, 2.1 months in immune-complex mediated, pauci-immune, and anti-GBM CrGN, respectively.

CONCLUSION

Immune-complex mediated is the commonest etiology of CrGN in India. Anti-GBM disease has the worst prognosis followed by pauci-immune and immune-complex mediated CrGN. Raised serum creatinine levels (>5mg%) and the degree of glomerulosclerosis at diagnosis were predictors of poor renal survival. High index of suspicion and prompt diagnosis can improve the outcome in these patients.

Rapidly progressive glomerulonephritis and acute kidney injury associated with cocaine use - Case report

A wide spectrum of renal complications can occur with acute and chronic use of cocaine. Most cases are related to rhabdomyolysis, but other mechanisms are malignant hypertension, renal ischemia, and rapidly progressive glomerulonephritis (RPGN) associated-ANCA vasculitis. In recent years, the use of cocaine adulterated with levamisole has been associated with ANCA vasculitis and pauci-immune RPGN. RPGN is clinically manifested as a nephritic syndrome with a rapid and progressive decline in renal function, and its histopathological finding is the presence of crescents in more than 50% of the glomeruli. We report a case of a 38-year-old man chronic user of cocaine, alcohol, and cigarettes who had red urine, oliguria, swollen legs and eyelids, as well as the uremic symptoms anorexia, emesis, and mental confusion. He was admitted with acute kidney injury and performed six hemodialysis sessions during the first 16 days of hospitalization and then was transferred to a tertiary hospital for diagnostic investigation. Tests of ANF (antinuclear factor), ANCA, anti-DNA, serology for hepatitis B, C, and HIV virus were negative. A renal percutaneous biopsy revealed crescentic glomerulonephritis with mild tubular atrophy. The patient underwent pulse therapy with methylprednisolone (for 3 days) and cyclophosphamide. Then he maintained daily prednisone and monthly intravenous cyclophosphamide and evolved with progressive improvement of renal function.

Role of CD8+ T cells in crescentic glomerulonephritis

Crescentic glomerulonephritis (cGN) comprises three main types according to the pathogenesis and immunofluorescence patterns: anti-glomerular basement membrane antibody cGN, vasculitis-associated cGN and post-infectious immune complex cGN. In this brief review of the immune-pathogenesis of cGN, the focus is mainly on the role of CD8+ T cells in the progression of cGN. Under control conditions, Bowman's capsule (BC) provides a protected immunological niche by preventing access of cytotoxic CD8+ T cells to Bowman's space and thereby podocytes. Even in experimental nephrotoxic nephritis, leukocytes accumulate around the glomeruli, but remain outside of BC, as long as the latter remains intact. However, when and where breaches in BC occur, the inflammatory cells can gain access to and destroy podocytes, thus converting cGN into rapidly progressive glomerulonephritis (RPGN). These conclusions also apply to human cGN, where biopsies show that loss of BC integrity is associated with RPGN and progression to end-stage kidney disease. We propose a two-hit hypothesis for the role of cytotoxic CD8+ T cells in the progression of cGN. The initial insult occurs in response to the immune complex formation or deposition, resulting in local capillary and podocyte injury (first hit). The injured podocytes release neo-epitopes, eventually causing T-cell activation and migration to the glomerulus. Upon generation of breaches in BC, macrophages and CD8+ T cells can now gain access to the glomerular space and destroy neo-epitope expressing podocytes (second hit), resulting in RPGN. While further investigation will be required to test this hypothesis, future therapeutic trials should consider targeting of CD8+ T cells in the therapy of progressive cGN.

Prognostic factors in glomerular diseases with crescents

INTRODUCTION

More than 50% of glomerular crescent formation is required for a diagnosis of crescentic glomerulonephritis in a kidney biopsy. Although treatment protocols have been established for diffuse crescentic glomerulonephritis, there is no standard treatment for patients with fewer crescents in renal biopsies. In this study the importance of crescent percentage and clinical features on renal survival independent of underlying disease was investigated.

METHODS

This retrospective observational study was conducted between 2013 and 2017. Forty-nine patients with crescent formation in their kidney biopsies were evaluated. We compared clinicopathological features and renal survival. We evaluated the factors affecting the course of end stage renal disease (ESRD).

RESULTS

A total of 49 patients (57% male and median age 49 years) were enrolled in this study. 39% of patients developed ESRD at follow-up. Logistic regression analysis showed that the requirement for renal replacement treatment on admission (p < 0.001), serum creatinine level above 2.7 mg/dL (p < 0.001), the presence of more than 50% glomerulosclerosis (p = 0.04) and more than 34% crescent formation (p = 0.002) were significantly associated with ESRD. Kaplan-Meier survival analysis revealed that patients with less than 34% crescent in kidney biopsy and a serum creatinine level less than 2.7 mg/dL had increased kidney survival (log-rank test p: 0.01 and p: 0.002).

CONCLUSION

Patients with crescent formation in kidney biopsy more than 34% should be evaluated for more aggressive treatment modalities regardless of the underlying disease, especially if the serum creatinine level is above 2.7 mg/dL.

Urinary podocyte and TGF-β1 mRNA as markers for disease activity and progression in anti-glomerular basement membrane nephritis

Background

Podocyte depletion causes glomerulosclerosis, with persistent podocyte loss being a major factor driving disease progression. Urinary podocyte mRNA is potentially useful for monitoring disease progression in both animal models and in humans. To determine whether the same principles apply to crescentic glomerular injury, a rat model of anti-glomerular basement membrane (anti-GBM) nephritis was studied in parallel with a patient with anti-GBM nephritis.

Methods

Podocyte loss was measured by Wilms' Tumor 1-positive podocyte nuclear counting and density, glomerular epithelial protein 1 or synaptopodin-positive podocyte tuft area and urinary podocyte mRNA excretion rate. Glomerulosclerosis was evaluated by Azan staining and urinary transforming growth factor (TGF)-β1 mRNA excretion rate.

Results

In the rat model, sequential kidney biopsies revealed that after a threshold of 30% podocyte loss, the degree of glomerulosclerosis was linearly associated with the degree of podocyte depletion, compatible with podocyte depletion driving the sclerotic process. Urinary podocyte mRNA correlated with the rate of glomerular podocyte loss. In treatment studies, steroids prevented glomerulosclerosis in the anti-GBM model in contrast to angiotensin II inhibition, which lacked a protective effect, and urinary podocyte and TGF-β1 mRNA markers more accurately reflected both the amount of podocyte depletion and the degree of glomerulosclerosis compared with proteinuria under both scenarios. In a patient successfully treated for anti-GBM nephritis, urinary podocyte and TGB-β1 mRNA reflected treatment efficacy.

Conclusion

These results emphasize the role of podocyte depletion in anti-GBM nephritis and suggest that urinary podocyte and TGF-β1 mRNA could serve as markers of disease progression and treatment efficacy.

Positive antineutrophil cytoplasmic antibody serology in patients with lupus nephritis is associated with distinct histopathologic features on renal biopsy

Class IV-S lupus nephritis is often associated with more necrosis and fewer subendothelial immune deposits compared to class IV-G lupus nephritis, suggestive of necrotising glomerular inflammation found in antineutrophil cytoplasmic antibody (ANCA)–associated vasculitis. ANCAs are present in a significant proportion of patients with lupus nephritis. Here we determine whether ANCAs are associated with distinct clinical and histopathologic features of lupus nephritis. Thirty-two ANCA-positive biopsies were compared to 222 ANCA-negative biopsies from patients with lupus nephritis. The majority (82%) of ANCA-positive patients had antimyeloperoxidase antibodies. Class IV-S lupus nephritis and glomerular necrosis were significantly more common (36% vs. 16% and 35% vs. 15%, respectively) and isolated Class V lupus nephritis significantly less common (10% vs. 29%) in the ANCA-positive group. ANCA-positive patients had significantly higher dsDNA titers (335u/ml vs. 52u/ml), significantly lower serum C4 concentrations (0.125g/L vs. 0.15g/L) and significantly higher serum creatinine (130μmol/L vs. 84μmol/L) at the time of biopsy. Hence ANCAs appear to influence the histological pattern of lupus nephritis and are associated with worse baseline renal function and more active lupus serology. There was no significant difference in outcome between groups when matched for severity of disease and treatment using propensity scoring. Thus, further studies are needed to examine whether ANCAs in patients with lupus nephritis have a pathogenic role and whether they are associated with worse renal outcomes or are simply a marker of more severe disease.

Clinicopathological characteristics of typical and atypical anti-glomerular basement membrane nephritis

Anti-glomerular basement membrane (GBM) antibody disease is a rare pathological condition that mainly involves renal and/or pulmonary parenchyma. It is characterized by the presence of circulating anti-GBM antibodies accompanied by a linear deposition of immunoglobulins (Ig) detected through immunofluorescence (IF) technique and typical signs and symptoms of organ dysfunction, such as rapidly progressive glomerulonephritis (RPGN) and pulmonary hemorrhage (PH). However, recently atypical forms of anti-GBM disease have been described and the presence of overlapping diseases contributed to make its diagnosis challenging. In this review will be discussed the entire spectrum of renal anti-GBM related conditions, focusing the attention on the differences in terms of pathogenesis, diagnosis and therapy of these disparate entities.

The Small Tellurium Compound AS101 Ameliorates Rat Crescentic Glomerulonephritis: Association with Inhibition of Macrophage Caspase-1 Activity via Very Late Antigen-4 Inactivation

Crescentic glomerulonephritis (CGN) is the most aggressive form of GN and, if untreated, patients can progress to end-stage renal failure within weeks of presentation. The α4β1 integrin very late antigen-4 (VLA-4) is an adhesion molecule of fundamental importance to the recruitment of leukocytes in inflammation. We addressed the role of VLA-4 in mediating progressive renal injury in a rat model of CGN using a small tellurium compound. AS101 [ammonium trichloro(dioxoethylene-o,o')tellurate]. This compound has been previously shown to uniquely inhibit VLA-4 activity by redox inactivation of adjacent thiols in the exofacial domain of VLA-4. The study shows that administration of AS101 either before or after glomerular basement membrane anti-serum injection ameliorates crescent formation or preserves renal function. This was associated with profound inhibition of critical inflammatory mediators, accompanied by decreased glomerular infiltration of macrophages. Mechanistic studies demonstrated vla-4 inactivation on glomerular macrophages both in vitro and in vivo as well as inhibition of caspase-1 activity. Importantly, this cysteine protease activity modification was dependent on VLA-4 inactivation and was associated with the anti-inflammatory activity of AS101. We propose that inactivation of macrophage VLA-4 by AS101 in vivo results in a decrease of inflammatory cytokines and chemokines produced in the glomeruli of diseased rats, resulting in decreased further macrophage recruitment and decreased extracellular matrix expansion. Thus, AS101, which is currently in clinical trials for other indications, might be beneficial for treatment of CGN.

Pulmonary Vasculitis: Spectrum of Imaging Appearances

Pulmonary vasculitis is a relatively uncommon disorder, usually manifesting as part of systemic vasculitis. Imaging, specifically computed tomography, is often performed in the initial diagnostic workup. Although the findings in vasculitis can be nonspecific, they can provide important clues in the diagnosis, and guide the clinical team toward the right diagnosis. Radiologists must have knowledge of common and uncommon imaging findings in various vasculitides. Also, radiologists should be able to integrate the clinical presentation and laboratory test findings together with imaging features, so as to provide a meaningful differential diagnosis.

Pauci-immune glomerulonephritis in a captive chimpanzee (Pan troglodytes), and a review of spontaneous cases in animals

BACKGROUND

Crescentic glomeruli are the hallmark finding in rapidly progressive glomerulonephritis (RPGN) and are characterized by disruption and proliferation of the glomerular capsule and an influx of cells into Bowman's space. Pauci-immune-type RPGN is identified by a lack of immunoglobulins and immune complexes in the glomerular basement membrane.

METHODS

Complete necropsy and histology were performed on the affected chimpanzee. Electron microscopy was performed on kidney sections. A search of the literature was performed to identify spontaneous RPGN in animals.

RESULTS

We report a case of crescentic glomerulonephritis of the pauci-immune-type in a hepatitis C virus-infected 28-year-old male chimpanzee (Pan troglodytes) who was humanely euthanized for a cardiac-related decline in health.

CONCLUSION

To our knowledge, this is the first report describing pauci-immune crescentic glomerulonephritis in a non-human primate.

The role of monocytes in ANCA-associated vasculitides

The anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitides (AAV) are a heterogeneous group of diseases causing inflammation in small blood vessels and linked by the presence of circulating ANCA specific for proteinase 3 (PR3) or myeloperoxidase (MPO). These antigens are present both in the cytoplasmic granules and on the surface of neutrophils, and the effect of ANCA on neutrophil biology has been extensively studied. In contrast, less attention has been paid to the role of monocytes in AAV. These cells contain PR3 and MPO in lysosomes and can also express them at the cell surface. Monocytes respond to ANCA by producing pro-inflammatory and chemotactic cytokines, reactive-oxygen-species and by up-regulating CD14. Moreover, soluble and cell surface markers of monocyte activation are raised in AAV patients, suggesting an activated phenotype that may persist even during disease remission. The presence of monocyte-derived macrophages and giant cells within damaged renal and vascular tissue in AAV also attests to their role in pathogenesis. In particular, their presence in the tertiary lymphoid organ-like granulomas of AAV patients may generate an environment predisposed to maintaining autoimmunity. Here we discuss the evidence for a pathogenic role of monocytes in AAV, their role in granuloma formation and tissue damage, and their potential to both direct and maintain autoimmunity. ANCA-activation of monocytes may therefore provide an explanation for the relapsing-remitting course of disease and its links with infections. Monocytes may thus represent a promising target for the treatment of this group of life-threatening diseases.

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.

Crescentic glomerulonephritis: data from the Spanish Glomerulonephritis Registry

BACKGROUND

Crescentic glomerulonephritis (CGN) is a histological finding that implies rapid deterioration of renal function and can be related to different diseases, such as type 1 or anti-glomerular basement membrane antibody (Goodpasture) disease, type 2 or immune complex CGN and type 3 or pauci-immune disease.

AIM

The present study describes CGN and its characteristics based on the data from the Spanish Glomerulonephritis Registry.

METHODS

An analysis was made of all native renal biopsies obtained from patients during 1994-2013 and classified as CGN. A patient epidemiological and clinical data questionnaire was completed by the 120 centres involved.

RESULTS

A total of 21,774 biopsies was performed, of which 2089 (8.1%) corresponded to CGN (211 type 1, 177 type 2 and 1701 type 3). Renal function was poorer in type 1 compared with types 2 and 3, and proteinuria was higher in type 2 compared to types 1 and 3. Patients diagnosed with CGN type 3 were older than those with types 1 and 2, but less hypertensive than the type 2 patients. No differences in the urine test findings were found between types 1 and 2. Microhaematuria was the most frequent feature in general, as well as in type 3 compared with types 1 and 2. The main indication for biopsy was acute renal injury. Age was the only difference between type 1 patients with and without alveolar haemorrhage (53 [33-67] vs 64 [46-73], P = 0.008).

CONCLUSION

Although classified as the same entity, the different types of CGN have different features that must be taken into account.

CXCR3+ Regulatory T Cells Control TH1 Responses in Crescentic GN

Chemokines and chemokine receptors are implicated in regulatory T cell (Treg) trafficking to sites of inflammation and suppression of excessive immune responses in inflammatory and autoimmune diseases; however, the specific requirements for Treg migration into the inflamed organs and the positioning of these cells within the tissue are incompletely understood. Here, we report that Tregs expressing the TH1-associated chemokine receptor CXCR3 are enriched in the kidneys of patients with ANCA-associated crescentic GN and colocalize with CXCR3(+) effector T cells. To investigate the functional role of CXCR3(+) Tregs, we generated mice that lack CXCR3 in Tregs specifically (Foxp3(eGFP-Cre) × Cxcr3(fl/fl)) and induced experimental crescentic GN. Treg-specific deletion of CXCR3 resulted in reduced Treg recruitment to the kidney and an overwhelming TH1 immune response, with an aggravated course of the nephritis that was reversible on anti-IFNγ treatment. Together, these findings show that a subset of Tregs expresses CXCR3 and thereby, acquires trafficking properties of pathogenic CXCR3(+) TH1 cells, allowing Treg localization and control of excessive TH1 responses at sites of inflammation.

[Vasculitis: New nomenclature of the Chapel Hill consensus conference 2012]

Within the last years, many advances have been made in the understanding of the etiopathology of vasculitis as well as of different disease courses. The revised 2012 Chapel Hill consensus conference (CHCC) nomenclature reflects current knowledge on the etiopathology in addition to the descriptive principles of vessel size and types of inflammation. The anti-neutrophil cytoplasmic antibody (ANCA)-associated forms of vasculitis have been separated as a group, as opposed to immune complex small vessel vasculitis. When consensus was achieved eponyms have been replaced by systematic names, such as granulomatosis with polyangiitis (Wegener's granulomatosis) or eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome). Moreover, clinically important but less well-known types of vasculitis have now been included in the CHCC nomenclature. This article presents the changes and summarizes the results of important new articles on the clinical picture and morphology of vasculitis.

CD14 expression is increased on monocytes in patients with anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis and correlates with the expression of ANCA autoantigens

Monocyte subsets with differing functional properties have been defined by their expression of CD14 and CD16. We investigated these subsets in anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) and determined their surface expression of ANCA autoantigens. Flow cytometry was performed on blood from 14 patients with active AAV, 46 patients with AAV in remission and 21 controls. The proportion of classical (CD14(high) CD16(neg/low)), intermediate (CD14(high) CD16(high)) and non-classical (CD14(low) CD16(high)) monocytes and surface expression levels of CD14 and CD16 were determined, as well as surface expression of proteinase 3 (PR3) and myeloperoxidase (MPO) on monocyte subsets. There was no change in the proportion of monocytes in each subset in patients with AAV compared with healthy controls. The expression of CD14 on monocytes from patients with active AAV was increased, compared with patients in remission and healthy controls (P < 0.01). Patients with PR3-ANCA disease in remission also had increased monocyte expression of CD14 compared with controls (P < 0.01); however, levels in patients with MPO-ANCA disease in remission were lower than active MPO-ANCA patients, and not significantly different from controls. There was a correlation between CD14 and both PR3 and MPO expression on classical monocytes in AAV patients (r = 0.79, P < 0.0001 and r = 0.42, P < 0.005, respectively). In conclusion, there was an increase in monocyte CD14 expression in active AAV and PR3-ANCA disease in remission. The correlation of CD14 expression with ANCA autoantigen expression in AAV may reflect cell activation, and warrants further investigation into the potential for increased CD14 expression to trigger disease induction or relapse.

Autoimmunity to the alpha 3 chain of type IV collagen in glomerulonephritis is triggered by 'autoantigen complementarity'

'Autoantigen complementarity' is a theory proposing that the initiator of an autoimmune response is not necessarily the autoantigen or its molecular mimic, but may instead be a peptide that is 'antisense/complementary' to the autoantigen. We investigated whether such complementary proteins play a role in the immunopathogenesis of autoimmune glomerulonephritis. Experimental autoimmune glomerulonephritis, a model of anti-glomerular basement membrane (GBM) disease, can be induced in Wistar Kyoto (WKY) rats by immunization with the α3 chain of type IV collagen. In this study, WKY rats were immunized with a complementary α3 peptide (c-α3-Gly) comprised of amino acids that 'complement' the well characterized epitope on α3(IV)NC1, pCol(24-38). Within 8 weeks post-immunization, these animals developed cresentic glomerulonephritis, similar to pCol(24-38)-immunized rats, while animals immunized with scrambled peptide were normal. Anti-idiotypic antibodies to epitopes from c-α3-Gly-immunized animals were shown to be specific for α3 protein, binding in a region containing sense pCol(24-38) sequence. Interestingly, anti-complementary α3 antibodies were identified in sera from patients with anti-GBM disease, suggesting a role for 'autoantigen complementarity' in immunopathogenesis of the human disease. This work supports the idea that autoimmune glomerulonephritis can be initiated through an immune response against a peptide that is anti-sense or complementary to the autoantigen. The implications of this discovery may be far reaching, and other autoimmune diseases could be due to responses to these once unsuspected 'complementary' antigens.

Necrotizing and crescentic glomerulonephritis presenting with preserved renal function in patients with underlying multisystem autoimmune disease: a retrospective case series

Objective. Necrotizing and crescentic GN usually presents with rapidly declining renal function, often in association with multisystem autoimmune disease, with a poor outcome if left untreated. We aimed to describe the features of patients who have presented with these histopathological findings but minimal disturbance of renal function.

Methods. We conducted a retrospective review (1995–2011) of all adult patients with native renal biopsy–proven necrotizing or crescentic GN and normal serum creatinine (<120 μmol/l) at our centre.

Results. Thirty-eight patients were identified. The median creatinine at presentation was 84 μmol/l and the median proportion of glomeruli affected by necrosis or crescents was 32%. Clinicopathological diagnoses were ANCA-associated GN (74%), LN (18%), anti-GBM disease (5%) and HScP (3%). Only 18% of cases had pre-existing diagnoses of underlying multisystem autoimmune disease, although the majority (89%) had extra-renal manifestations accompanying the renal diagnosis. All patients received immunosuppression and most had good long-term renal outcomes (median duration of follow-up 50 months), although two progressed to end-stage renal disease within 3 years. We estimate that renal biopsy had an important influence on treatment decisions in 82% of cases.

Conclusion. Necrotizing and crescentic GN may present in patients with no or only minor disturbance of renal function. This often occurs in patients with underlying systemic autoimmune disease; early referral for biopsy may affect management and improve long-term outcomes in these cases.

[Vasculitis. New nomenclature of the Chapel Hill consensus conference 2012]

In recent years, many advances have been made in our understanding of vasculitis etiopathology as well as of different disease courses. The revised Chapel Hill Consensus Conference (CHCC) 2012 nomenclature reflects current knowledge about etiopathology, in addition to the descriptive principles of vessel size and type of inflammation. Anti-neutrophil cyptoplasmic antibody (ANCA)-associated vasculitides have been classified as a separate group, as opposed to immune complex small vessel vasculitis. In cases where consensus was achieved, eponyms have been replaced by systematic names, such as granulomatosis with polyangiitis (Wegener's) or eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome). Moreover, clinically important but less well-known types of vasculitis have now been included in the CHCC nomenclature. This article presents the changes, focussing on those types that are relevant to the histopathologist, and summarizes the results of important new articles on morphology and clinical picture of vasculitis.

Multiple cranial neuropathies in cerebral venous sinus thrombosis

Clinical presentation of cerebral venous sinus thrombosis (CVST) is varied and often mimics many neurological disorders, making it a diagnostic challenge, and cranial nerve palsy in CVST is rare and its pathophysiology remains unclear. We report a case of a 19-year-old male with a history of whiplash injury, admitted with extensive CVST, developed right facial nerve palsy with extension of thrombus into the ipsilateral transverse sinus, sigmoid sinus and internal jugular vein. Later, he developed left facial nerve palsy with partial left occulomotor weakness. We suggest that either reversible compromised oxygen or glucose consumption within the intrinsic vascular system of the nerve, resulting in cranial nerve abnormalities. CVST should be considered in cases of trivial trauma, even in the absence of hyper-coagulable states, and it can have atypical presentation like multiple cranial neuropathies.

Childhood Cogan syndrome with aortitis and anti-neutrophil cytoplasmic antibody-associated glomerulonephritis

Cogan syndrome is a systemic disease manifesting interstitial keratitis, sensorineural hearing loss, tinnitus, and rotatory vertigo. Renal complications of this syndrome are very rare. We encountered an adolescent with Cogan syndrome complicated by aortitis and anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis. At the age of 14, the patient showed proteinuria in a screening urinalysis at school and was found to lack a right radial pulse. Magnetic resonance angiography disclosed right subclavian artery stenosis. Examination of a renal biopsy specimen showed ANCA-positive crescentic glomerulonephritis. Steroid and immunosuppressant treatment improved renal function and histopathology, but repeated recurrences followed. At 18, the patient developed rotatory vertigo, a sense of ear fullness, and sensorineural hearing loss. The patient was diagnosed with Cogan syndrome. We know of no previous description of ANCA-positive crescentic glomerulonephritis in children with Cogan syndrome. Accordingly, evaluation of aortitis in childhood should include not only otolaryngologic and ophthalmologic examinations, but also periodic urine examination and renal function tests.

Current and future prospects in the management of granulomatosis with polyangiitis (Wegener's granulomatosis)

Granulomatosis with polyangiitis (GPA, formerly Wegener's granulomatosis) is a multisystem autoimmune condition associated with anti-neutrophil cytoplasm antibodies. Management of GPA can be complex, owing to the sometimes fulminant and multisystem nature of the presentation, the age demographics of the affected population, and a significant incidence of disease relapse. In this paper, we discuss how some of the challenges in the management of GPA have been and continue to be addressed including: reducing the toxicity of induction therapy; developing biomarkers to determine who can safely stop maintenance immunosuppression; improving the efficacy of maintenance therapy for relapsing patients; managing localized disease; and management of disease and treatment-associated comorbidity. Consideration is also given to emerging therapeutics in the treatment of GPA.

Vasculitis 2013. What are the changes introduced in the 2012 Chapel Hill Consensus Conference?

Vasculitis is a heterogeneous group of rare disorders in which inflammation of blood vessels is the common feature. Due to the increasing number of diseases as well as overlaps and gaps in the definition and nomenclature, the classification criteria were constantly changing in the past decades. The classifications were based essentially on the size of affected blood vessels and pathologic characteristics of inflamed vessel walls. The standard procedures and validated diagnostic criteria are missing from the diagnostics of vasculitis, thus in clinical practice the classification criteria are applicable. The 2012 Chapel Hill Consensus Conference brought a change in the definition, nomenclature and classification of previously uncategorized diseases. The definitions of subgroups accurately determine the diagnosis of the specific disease, and they are suitable for establishing homogeneous disease groups. By better understanding of the etiopathogenetic factors, further diseases and subgroups may be defined in the near future. Orv. Hetil., 2013, 154, 1571–1578.

Experimental crescentic glomerulonephritis: a new bicongenic rat model

Crescentic glomerulonephritis (CRGN) is a major cause of human kidney failure, but the underlying mechanisms are not fully understood. Wistar Kyoto (WKY) rats are uniquely susceptible to CRGN following injection of nephrotoxic serum, whereas Lewis (LEW) rats are resistant. Our previous genetic studies of nephrotoxic nephritis (NTN), a form of CRGN induced by nephrotoxic serum, identified Fcgr3 and Jund as WKY genes underlying the two strongest quantitative trait loci for NTN phenotypes: Crgn1 and Crgn2, respectively. We also showed that introgression of WKY Crgn1 or Crgn2 individually into a LEW background did not lead to the formation of glomerular crescents. We have now generated a bicongenic strain, LEW.WCrgn1,2, in which WKY Crgn1 and Crgn2 are both introgressed into the LEW genetic background. These rats show development of NTN phenotypes, including glomerular crescents. Furthermore, we characterised macrophage function and glomerular cytokine profiles in this new strain. Additionally, we show that LEW.WCrgn1,2 rats are resistant to the development of glomerular crescents that is usually induced following immunisation with recombinant rat α3(IV)NC1, the specific Goodpasture autoantigen located in the glomerular basement membrane against which the immune response is directed in experimental autoimmune glomerulonephritis. Our results show that the new bicongenic strain responds differently to two distinct experimental triggers of CRGN. This is the first time that CRGN has been induced on a normally resistant rat genetic background and identifies the LEW.WCrgn1,2 strain as a new, potentially valuable model of macrophage-dependent glomerulonephritis.

Immature renal dendritic cells recruit regulatory CXCR6(+) invariant natural killer T cells to attenuate crescentic GN

Immature renal dendritic cells (DCs) are protective early in murine crescentic GN, but the mechanisms underlying this protection are unknown. Here, depletion of DCs reduced the recruitment of invariant natural killer T (iNKT) cells, which attenuate GN, into the kidney in the early stage of experimental crescentic GN. More than 90% of renal iNKT cells expressed the chemokine receptor CXCR6, and renal DCs produced high amounts of the cognate ligand CXCL16 early after induction of nephritis, suggesting that renal DC-derived CXCL16 might attract protective CXCR6(+) iNKT cells. Consistent with this finding, CXCR6-deficient mice exhibited less iNKT cell recruitment and developed nephritis that was more severe, similar to the aggravated nephritis observed in mice depleted of immature DCs. Finally, adoptive transfer of CXCR6-competent NKT cells ameliorated nephritis. Taken together, these results suggest an immunoprotective mechanism involving immature DCs, CXCL16, CXCR6, and regulatory iNKT cells, which might stimulate the development of new therapeutic strategies for GN.

IL-17A production by renal γδ T cells promotes kidney injury in crescentic GN

The Th17 immune response appears to contribute to the pathogenesis of human and experimental crescentic GN, but the cell types that produce IL-17A in the kidney, the mechanisms involved in its induction, and the IL-17A-mediated effector functions that promote renal tissue injury are incompletely understood. Here, using a murine model of crescentic GN, we found that CD4(+) T cells, γδ T cells, and a population of CD3(+)CD4(-)CD8(-)γδT cell receptor(-)NK1.1(-) T cells all produce IL-17A in the kidney. A time course analysis identified γδ T cells as a major source of IL-17A in the early phase of disease, before the first CD4(+) Th17 cells arrived. The production of IL-17A by renal γδ T cells depended on IL-23p19 signaling and retinoic acid-related orphan receptor-γt but not on IL-1β or IL-6. In addition, depletion of dendritic cells, which produce IL-23 in the kidney, reduced IL-17A production by renal γδ T cells. Furthermore, the lack of IL-17A production in γδ T cells, as well as the absence of all γδ T cells, reduced neutrophil recruitment into the kidney and ameliorated renal injury. Taken together, these data suggest that γδ T cells produce IL-17A in the kidney, induced by IL-23, promoting neutrophil recruitment, and contributing to the immunopathogenesis of crescentic GN.

Anti-glomerular basement membrane antibody disease: a rare autoimmune disorder affecting the kidney and the lung

Anti-glomerular basement membrane antibody disease is a rare, but well characterized cause of glomerulonephritis. By definition serum anti-GBM antibody and/or a linear binding of IgG detected by direct immunofluorescence (IF) in a histological specimen of the kidney or the lung have to be detected. These antibodies can lead to acute rapid progressive glomerulonephritis(RPGN) and/or pulmonary hemorrhage (PH) because of collagen similarities in the basement membrane. Principally anti-GBM antibody disease can be divided into two groups: anti-GBM antibody disease without PH was regarded as renal-limited anti-GBM antibody disease and that with PH was defined as Goodpasture's syndrome (GPS). The important determinant for the response of therapy and long term diagnosis on anti-GBM disease is early diagnosis to prevent endstage renal disease. Therefore, standard treatment is a combined therapy of plasmapherisis, prednisolone and cyclophosphamide. The aim of this review is an overview of the pathogenesis, clinical presentation, diagnosis and treatment of anti-GBM disease.