Thrombospondin type-1 domain-containing 7A in idiopathic membranous nephropathy

Anti-Phospholipase A2 Receptor (PLA2R) Antibody and Glomerular PLA2R Expression in Japanese Patients with Membranous Nephropathy

The phospholipase A2 receptor (PLA2R) is the major target antigen (Ag) in idiopathic membranous nephropathy (IMN). Recently, several types of immunoassay systems for anti-PLA2R antibody (Ab) have been developed. However, the correlation of serum anti-PLA2R Abs and glomerular expression of PLA2R Ag, and their association with clinicopathological characteristics have yet to be proven in Japanese patients. We examined serum anti-PLA2R Abs by both ELISA and cell-based indirect immunofluorescence assay (CIIFA), and glomerular PLA2R expression by immunofluorescence (IF) in 59 biopsy-proven MN patients including IMN (n = 38) and secondary MN (SMN) (n = 21). In this study, anti-PLA2R Abs were present in 50% of IMN patients, but was absent in SMN patients. The concordance rate between ELISA and CIIFA was 100%. Serum IgG levels were significantly lower in anti-PLA2R Ab-positive patients. Serum albumin levels correlated inversely with serum anti-PLA2R Ab titers. The prevalence and intensity of glomerular staining for IgG4 by IF were significantly higher in anti-PLA2R Ab-positive patients than in -negative patients. Glomerular PLA2 Ag expression evaluated by IF was positive in 52.6% of IMN patients, but was absent in SMN patients. The concordance rate between the prevalence of glomerular PLA2R Ag expression and anti-PLA2R Ab was 84.2%. The prevalence of anti-PLA2R Abs measured by ELISA/CIIFA was equivalent to previous Japanese studies evaluated using Western blotting. These analyses showed an excellent specificity for the diagnosis of IMN, and anti-PLA2R positivity was associated with some clinicopathological features, especially glomerular IgG4-dominant deposition.

Rituximab for Severe Membranous Nephropathy: A 6-Month Trial with Extended Follow-Up

Randomized trials of rituximab in primary membranous nephropathy (PMN) have not been conducted. We undertook a multicenter, randomized, controlled trial at 31 French hospitals (NCT01508468). Patients with biopsy-proven PMN and nephrotic syndrome after 6 months of nonimmunosuppressive antiproteinuric treatment (NIAT) were randomly assigned to 6-month therapy with NIAT and 375 mg/m² intravenous rituximab on days 1 and 8 (n=37) or NIAT alone (n=38). Median times to last follow-up were 17.0 (interquartile range, 12.5-24.0) months and 17.0 (interquartile range, 13.0-23.0) months in NIAT-rituximab and NIAT groups, respectively. Primary outcome was a combined end point of complete or partial remission of proteinuria at 6 months. At month 6, 13 (35.1%; 95% confidence interval [95% CI], 19.7 to 50.5) patients in the NIAT-rituximab group and eight (21.1%; 95% CI, 8.1 to 34.0) patients in the NIAT group achieved remission (P=0.21). Rates of antiphospholipase A2 receptor antibody (anti-PLA2R-Ab) depletion in NIAT-rituximab and NIAT groups were 14 of 25 (56%) and one of 23 (4.3%) patients at month 3 (P<0.001) and 13 of 26 (50%) and three of 25 (12%) patients at month 6 (P=0.004), respectively. Eight serious adverse events occurred in each group. During the observational phase, remission rates before change of assigned treatment were 24 of 37 (64.9%) and 13 of 38 (34.2%) patients in NIAT-rituximab and NIAT groups, respectively (P<0.01). Positive effect of rituximab on proteinuria remission occurred after 6 months. These data suggest that PLA2R-Ab levels are early markers of rituximab effect and that addition of rituximab to NIAT does not affect safety.

Optimizing the translational value of animal models of glomerulonephritis: insights from recent murine prototypes

Animal models are indispensable for the study of glomerulonephritis, a group of diseases that destroy kidneys but for which specific therapies do not yet exist. Novel interventions are urgently needed, but their rational design requires suitable in vivo platforms to identify and test new candidates. Animal models can recreate the complex immunologic microenvironments that foster human autoimmunity and nephritis and provide access to tissue compartments not readily examined in patients. Study of rat Heymann nephritis identified fundamental disease mechanisms that ultimately revolutionized our understanding of human membranous nephropathy. Significant species differences in expression of a major target antigen, however, and lack of spontaneous autoimmunity in animals remain roadblocks to full exploitation of preclinical models in this disease. For several glomerulonephritides, humanized models have been developed to circumvent cross-species barriers and to study the effects of human genetic risk variants. Herein we review humanized mouse prototypes that provide fresh insight into mediators of IgA nephropathy and origins of antiglomerular basement membrane nephritis and Goodpasture's disease, as well as a means to test novel therapies for ANCA vasculitis. Additional and refined model systems are needed to mirror the full spectrum of human disease in a genetically diverse population, to facilitate development of patient-specific interventions, to determine the origin of nephritogenic autoimmunity, and to define the role of environmental exposures in disease initiation and relapse.

Membranous nephropathy: Pilot study of a novel regimen combining cyclosporine and Rituximab

INTRODUCTION

There is broad consensus that high grade basal proteinuria and failure to achieve remission of proteinuria are key determinants of adverse renal prognosis in patients with primary membranous nephropathy. Based on the fact that current regimens are not ideal due to short and long-term toxicity and propensity to relapse after treatment withdrawal, we developed a treatment protocol based on a novel combination of rituximab and cyclosporine which targets both the B and T cell limbs of the immune system. Herein, we report pilot study data on proteinuria, changes in autoantibody levels and renal function that offer a potentially effective new approach to treatment of severe membranous nephropathy.

METHODS

Thirteen high-risk patients defined by sustained high-grade proteinuria (mean 10.8 g/d) received combination induction therapy with rituximab plus cyclosporine for 6 months, followed by a second cycle of rituximab and tapering of cyclosporine during an 18 month maintenance phase.

RESULTS

Mean proteinuria decreased by 65% at 3 months and by 80% at 6 months. Combined complete or partial remission was achieved in 92% of patients by 9 months; 54% achieved complete remission at 12 months. Two patients relapsed during the trial. All patients with autoantibodies to PLA₂R achieved antibody depletion. Renal function stabilized. The regimen was well tolerated.

DISCUSSION

We report these encouraging preliminary results for their potential value to other investigators needing prospectively collected data to inform the design and power calculations of future randomized clinical trials. Such trials will be needed to formally compare this novel regimen to current therapies for membranous nephropathy.

A best practice position statement on pregnancy in chronic kidney disease: the Italian Study Group on Kidney and Pregnancy

Pregnancy is increasingly undertaken in patients with chronic kidney disease (CKD) and, conversely, CKD is increasingly diagnosed in pregnancy: up to 3 % of pregnancies are estimated to be complicated by CKD. The heterogeneity of CKD (accounting for stage, hypertension and proteinuria) and the rarity of several kidney diseases make risk assessment difficult and therapeutic strategies are often based upon scattered experiences and small series. In this setting, the aim of this position statement of the Kidney and Pregnancy Study Group of the Italian Society of Nephrology is to review the literature, and discuss the experience in the clinical management of CKD in pregnancy. CKD is associated with an increased risk for adverse pregnancy-related outcomes since its early stage, also in the absence of hypertension and proteinuria, thus supporting the need for a multidisciplinary follow-up in all CKD patients. CKD stage, hypertension and proteinuria are interrelated, but they are also independent risk factors for adverse pregnancy-related outcomes. Among the different kidney diseases, patients with glomerulonephritis and immunologic diseases are at higher risk of developing or increasing proteinuria and hypertension, a picture often difficult to differentiate from preeclampsia. The risk is higher in active immunologic diseases, and in those cases that are detected or flare up during pregnancy. Referral to tertiary care centres for multidisciplinary follow-up and tailored approaches are warranted. The risk of maternal death is, almost exclusively, reported in systemic lupus erythematosus and vasculitis, which share with diabetic nephropathy an increased risk for perinatal death of the babies. Conversely, patients with kidney malformation, autosomal-dominant polycystic kidney disease, stone disease, and previous upper urinary tract infections are at higher risk for urinary tract infections, in turn associated with prematurity. No risk for malformations other than those related to familiar urinary tract malformations is reported in CKD patients, with the possible exception of diabetic nephropathy. Risks of worsening of the renal function are differently reported, but are higher in advanced CKD. Strict follow-up is needed, also to identify the best balance between maternal and foetal risks. The need for further multicentre studies is underlined.

[Membranous nephropathy: Diagnosis, new insights in pathophysiology, and therapeutic approach]

Membranous nephropathy (MN) accounts for about 20% of cases of nephrotic syndrome in the adult. Thickening of glomerular capillary walls results from subepithelial formation of immune deposits containing IgG and the membrane attack complex of complement, which is the major mediator of proteinuria, and antigens. Idiopathic forms of MN (IMN) represent 70 to 80% of all cases. A major breakthrough was the identification of the podocyte antigen PLA2R as the target of circulating antibodies in about 70% of IMN, which confirmed that the disease was auto-immune in nature. The optimal treatment of patients with IMN is still a matter of debate. Thirty to 40% of affected patients will undergo spontaneous remission, usually within one year from disease onset, whereas about one third will progress to end-stage kidney disease. Both the evidence that B cells play a key role in the pathogenesis of IMN and drug toxicity led to target B-cells with rituximab. Rituximab induced remission of nephrotic syndrome in 60 to 80% of the patients with long-lasting proteinuria despite blockade of the renin-angiotensin system and in patients who had previously failed other treatments. Because of the lack of randomized controlled trial (RCT) using rituximab and of high rate of spontaneous remission, a French non-blinded, parallel group RCT was performed to compare rituximab added to supportive therapy, to supportive therapy alone, in patients with persistent nephrotic syndrome.

Retrospective Study of Phospholipase A2 Receptor and IgG Subclasses in Glomerular Deposits in Chinese Patients with Membranous Nephropathy

BACKGROUND AND OBJECTIVES

The research work in the past years showed that detection of phospholipase A2 receptor (PLA2R) antigen and its dominant IgG4 autoantibody in glomerular deposits of patients with membranous nephropathy (MN) was useful for the differentiation between primary MN (PMN) and secondary MN (SMN), but so far such research data from large Chinese patient series is little. Here, we are going to report a research work in a Chinese cohort.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study enrolled 179 patients with PMN, 40 patients with membranous lupus nephritis (LN-MN), 26 patients with hepatitis B virus-associated MN (HBV-MN), 2 patients with malignancy-associated MN (M-MN) and one patient with IgG4-related MN (IgG4-MN). PLA2R and IgG subclasses in glomerular deposits of these patients were examined by immunofluorescence and/or immunohistochemical staining, and the potential value of the above examinations for differential diagnosis of PMN and SMN was evaluated.

RESULTS

Glomerular PLA2R deposition was present in 92.2% patients with PMN and 7.7% patients with HBV-MN, but none of the patients with LN-MN. Predominant/codominant IgG4 deposition was found in 93.3% patients with PMN and 11.5% patients with HBV-MN, but none of the patients with LN-MN. The two M-MN patients both had glomerular PLA2R and predominant/codominant IgG4 deposition. The one IgG4-MN patient had deeply staining IgG4 but no PLA2R in glomeruli.

CONCLUSIONS

The glomerular PLA2R and predominant/codominant IgG4 deposition is frequently observed in Chinese patients with PMN. Immunofluorescence and immunohistochemical staining of renal biopsy tissue for detection of glomerular PLA2R and IgG subclasses deposition can help to distinguish PMN from LN-MN and most of HBV-MN.

Autoantibodies against thrombospondin type 1 domain-containing 7A induce membranous nephropathy

Membranous nephropathy (MN) is the most common cause of nephrotic syndrome in adults, and one-third of patients develop end-stage renal disease (ESRD). Circulating autoantibodies against the podocyte surface antigens phospholipase A2 receptor 1 (PLA2R1) and the recently identified thrombospondin type 1 domain-containing 7A (THSD7A) are assumed to cause the disease in the majority of patients. The pathogenicity of these antibodies, however, has not been directly proven. Here, we have reported the analysis and characterization of a male patient with THSD7A-associated MN who progressed to ESRD and subsequently underwent renal transplantation. MN rapidly recurred after transplantation. Enhanced staining for THSD7A was observed in the kidney allograft, and detectable anti-THSD7A antibodies were present in the serum before and after transplantation, suggesting that these antibodies induced a recurrence of MN in the renal transplant. In contrast to PLA2R1, THSD7A was expressed on both human and murine podocytes, enabling the evaluation of whether anti-THSD7A antibodies cause MN in mice. We demonstrated that human anti-THSD7A antibodies specifically bind to murine THSD7A on podocyte foot processes, induce proteinuria, and initiate a histopathological pattern that is typical of MN. Furthermore, anti-THSD7A antibodies induced marked cytoskeletal rearrangement in primary murine glomerular epithelial cells as well as in human embryonic kidney 293 cells. Our findings support a causative role of anti-THSD7A antibodies in the development of MN.

Analysis of 4931 renal biopsy data in central China from 1994 to 2014

The purpose of this study is to investigate the changing spectrum and clinicopathologic correlation of biopsy-proven renal diseases in central China. We retrospectively analyzed data of 4931 patients who underwent renal biopsy in ten hospitals between September 1994 and December 2014. Among them, 81.55% were primary glomerular diseases (GD), and 13.02% were secondary GD. IgA nephropathy (IgAN) was the most common primary GD (43.45%), followed by focal glomerulonephritis (16.79%), mesangial proliferative glomerulonephritis (MsPGN, 14.35%), and membranous nephropathy (MN, 13.28%). IgAN was leading primary GD in patients under 60 years old, while MN was the leading one over 60 years old. The most frequent secondary GD was lupus nephritis (LN) (47.35%). The prevalence of IgAN, MN and minimal change disease was found to increase significantly (p < 0.001, p < 0.001, and p < 0.01, respectively), while that of MsPGN, membranoproliferative glomerulonephritis and LN decreased significantly (p < 0.001, p < 0.001, and p < 0.05, respectively). The main indication for renal biopsy was proteinuria and hematuria (49.03%), followed by nephrotic syndrome (NS, 20.36%). IgAN was the most common cause in patients with proteinuria and hematuria, chronic-progressive kidney injury, hematuria and acute kidney injury; and MN was the leading cause of NS. Primary GD remained the predominant renal disease in central China. IgAN and LN were the most prevalent histopathologic lesions of primary and secondary GD, respectively. The spectrum of biopsy-proven renal disease had a great change in the past two decades. Proteinuria and hematuria was the main indication for renal biopsy.

Primary glomerulonephritides

Most glomerulonephritides, even the more common types, are rare diseases. They are nevertheless important since they frequently affect young people, often cannot be cured, and can lead to chronic kidney disease, including end-stage renal failure, with associated morbidity and cost. For example, in young adults, IgA nephropathy is the most common cause of end-stage renal disease. In this Seminar, we summarise existing knowledge of clinical signs, pathogenesis, prognosis, and treatment of glomerulonephritides, with a particular focus on data published between 2008 and 2015, and the most common European glomerulonephritis types, namely IgA nephropathy, membranous glomerulonephritis, minimal change disease, focal segmental glomerulosclerosis, membranoproliferative glomerulonephritis, and the rare complement-associated glomerulonephritides such as dense deposit disease and C3 glomerulonephritis.

Phospholipase A2 Receptor-Related Membranous Nephropathy and Mannan-Binding Lectin Deficiency

Most patients with idiopathic membranous nephropathy (IMN) have IgG4 autoantibodies against phospholipase A2 receptor (PLA2R). C3 and C5b-9 are found in immune deposits of IMN kidney biopsy specimens, but the pathway of complement activation in IMN remains elusive. We report the case of a patient who developed IMN with intense staining for PLA2R, IgG4, C3, C5b-9, factor B, and properdin and very weak staining for C1q, C4d, and IgG1. Measurement of mannan binding lectin (MBL) antigenic level and activity revealed MBL deficiency. Genotyping revealed a heterozygous (A/C) polymorphism in codon 57 of MBL2 exon 1 associated with homozygous and heterozygous variations in the promoter region at -550 (L/L) and -221 (X/Y), respectively, suggesting that the patient harbored the LXA/LYC haplotypes linked to MBL deficiency. Genetic sequencing in 77 consecutive patients with IMN identified four patients with MBL2 promoter and coding region variations associated with MBL deficiency and the same complement pattern in immune deposits as the index patient. In contrast, patients with wild-type MBL2 had immune deposits with intense Cd4 staining. Thus, IMN can develop in patients with complete MBL deficiency, with complement activated mainly by the alternative pathway, whereas the lectin pathway is also activated in those with wild-type MBL2.

Alternative Pathway Dysregulation and the Conundrum of Complement Activation by IgG4 Immune Complexes in Membranous Nephropathy

Membranous nephropathy (MN), a major cause of nephrotic syndrome, is a non-inflammatory immune kidney disease mediated by IgG antibodies that form glomerular subepithelial immune complexes. In primary MN, autoantibodies target proteins expressed on the podocyte surface, often phospholipase A2 receptor (PLA2R1). Pathology is driven by complement activation, leading to podocyte injury and proteinuria. This article overviews the mechanisms of complement activation and regulation in MN, addressing the paradox that anti-PLA2R1 and other antibodies causing primary MN are predominantly (but not exclusively) IgG4, an IgG subclass that does not fix complement. Besides immune complexes, alterations of the glomerular basement membrane (GBM) in MN may lead to impaired regulation of the alternative pathway (AP). The AP amplifies complement activation on surfaces insufficiently protected by complement regulatory proteins. Whereas podocytes are protected by cell-bound regulators, the GBM must recruit plasma factor H, which inhibits the AP on host surfaces carrying certain polyanions, such as heparan sulfate (HS) chains. Because HS chains present in the normal GBM are lost in MN, we posit that the local complement regulation by factor H may be impaired as a result. Thus, the loss of GBM HS in MN creates a micro-environment that promotes local amplification of complement activation, which in turn may be initiated via the classical or lectin pathways by subsets of IgG in immune complexes. A detailed understanding of the mechanisms of complement activation and dysregulation in MN is important for designing more effective therapies.

THSD7A staining of membranous glomerulopathy in clinical practice reveals cases with dual autoantibody positivity

Thrombospondin type I domain-containing 7A (THSD7A) is a known antigenic target of autoantibodies leading to primary membranous glomerulopathy and was reported to account for ~10% of phospholipase A2 receptor (PLA2R)-negative membranous glomerulopathy. It has been proposed that PLA2R and THSD7A autoantibodies are mutually exclusive in membranous glomerulopathy. We validated an immunohistochemical assay to investigate for THSD7A-associated membranous glomerulopathy and utilized it in 258 consecutive native kidney biopsies, which showed membranous glomerulopathy in our laboratory, with the exception of membranous lupus nephritis. Membranous glomerulopathy stained positive for THSD7A-only in 7 (3%) cases, PLA2R-only in 141 (55%) cases, and showed dual positivity for THSD7A and PLA2R in 2 (1%) cases. Serologic testing for antibodies to PLA2R and THSD7A was performed in a subset of these patients. There was 100% correlation between positive THSD7A and/or PLA2R tissue staining and the presence of the corresponding autoantibodies in the serum including the two cases with dual positive THSD7A and PLA2R antibodies. We describe and provide a protocol for detection of THSD7A-associated membranous glomerulopathy in clinical practice. The cases with dual THSD7A and PLA2R positivity show that these autoantibodies are not mutually exclusive. They also emphasize the importance of using a panel-based approach when subtyping membranous glomerulopathy as a patient could conceptually be identified and treated based on anti-PLA2R titers, but still have anti-THSD7A antibodies driving persistent disease.

Combined Assessment of Phospholipase A2 Receptor Autoantibodies and Glomerular Deposits in Membranous Nephropathy

Serum phospholipase A2 receptor antibodies (SAbs) and glomerular phospholipase A2 receptor antigen (GAg) deposits have been observed in idiopathic membranous nephropathy (IMN). However, the clinical application of these two biomarkers, particularly GAg deposition, needs to be further evaluated. We measured SAb concentration by ELISA and GAg deposition by immunofluorescence in 572 patients with biopsy-proven IMN. Overall, 68.5% of patients (392 of 572) had detectable SAb (SAb+), and 98.7% of patients who were SAb+ (387 of 392) and 70.6% of patients who were SAb- (127 of 180) had GAg deposition (GAg+). Compared with patients who were SAb-/GAg+, patients who were SAb+/GAg+ exhibited higher levels of proteinuria (P<0.001) and a lower chance of proteinuria remission (P<0.001). In 52 patients who underwent repeat biopsies, patients who did not achieve remission had a higher SAb+ rate on the first biopsy than patients who went into remission (P=0.001). Furthermore, SAb+ levels persisted in patients who did not achieve remission but significantly decreased in patients who achieved remission by the second biopsy. Patients who did not achieve remission also had a higher GAg+ rate on the first biopsy than patients who achieved remission (P<0.01). Sustained GAg+ deposits correlated with disease relapse. In conclusion, combining the measurements of SAb levels and detection of GAg deposition may provide additional information regarding diagnoses, treatment response, and disease relapse in patients with IMN.

Pre-transplant phospholipase A2 receptor autoantibody concentration is associated with clinically significant recurrence of membranous nephropathy post-kidney transplantation

Previous studies that have assessed the association of pre-transplant antiphospholipase A2 receptor autoantibody (PLA2R-Ab) concentration with a recurrence of membranous nephropathy (rMN) post-kidney transplant have yielded variable results. We tested 16 consecutive transplant patients with a history of iMN for pre-transplant PLA2R-Ab. Enzyme-linked immunosorbent assay titers (Euroimmun, NJ, USA) >14 RU/mL were considered positive. A receiver operating characteristic (ROC) analysis was performed after combining data from Quintana et al. (n = 21; Transplantation February 2015) to determine a PLA2R-Ab concentration which could predict rMN. Six of 16 (37%) patients had biopsy-proven rMN at a median of 3.2 yr post-transplant. Of these, five of six (83%) had a positive PLA2R-Ab pre-transplant with a median of 82 RU/mL (range = 31-1500). The only patient who had rMN with negative PLA2R-Ab was later diagnosed with B-cell lymphoma. One hundred percent (n = 10) of patients with no evidence of rMN (median follow-up = five yr) had negative pre-transplant PLA2R-Ab. In a combined ROC analysis (n = 37), a pre-transplant PLA2R-Ab > 29 RU/mL predicted rMN with a sensitivity of 85% and a specificity of 92%. Pre-transplant PLA2R-Ab could be a useful tool for the prediction of rMN. Patients with rMN in the absence of PLA2R-Ab should be screened for occult malignancy and/or alternate antigens.

Membranous nephropathy: A fairy tale for immunopathologists, nephrologists and patients

This article reviews the considerable progress which has been made in the recent years in the understanding of the pathophysiology of membranous nephropathy, a model of organ-specific auto-immune disease. It shows how experimental models developed more than 30 years ago have led to the identification of several human antigens including neutral endopeptidase in the neonate, phospholipase A2 receptor, and thrombospondin 1 domain 7A in the adult, and cationic bovine serum albumin in children. Thanks to a successful GWAS performed in European Caucasians, the genetics of the disease begins to be understood. These groundbreaking findings already have a major impact on patients' care owing to the development of reliable ELISA and immunofluorescence test for the detection of PLA2R antibodies and of PLA2R antigen screening in biopsies. This review will tell the story from the careful clinical observation of cases to the most recent therapeutic perspectives which have been made possible by these advances. Advances in medical science often proceed by steps which are highly interdependent. New, groundbreaking findings with important clinical implications often result from the combination of faithful experimental models and careful clinical observations. This is well illustrated by the story of membranous nephropathy which started more than 50 years ago. It is remarkable that in this disease, the experimental models predicted the pathophysiology of the human glomerulopathy. The stories that we will tell in this article are aimed at young clinical investigators who are sometimes reluctant to embark on research projects. We hope that they will convince them that bedside research performed with intellectual curiosity and a bit of chance can lead to significant progress in clinical medicine.

Biologics for the treatment of autoimmune renal diseases

Biological therapeutics (biologics) that target autoimmune responses and inflammatory injury pathways have a marked beneficial impact on the management of many chronic diseases, including rheumatoid arthritis, psoriasis, inflammatory bowel disease, and ankylosing spondylitis. Accumulating data suggest that a growing number of renal diseases result from autoimmune injury - including lupus nephritis, IgA nephropathy, anti-neutrophil cytoplasmic antibody-associated glomerulonephritis, autoimmune (formerly idiopathic) membranous nephropathy, anti-glomerular basement membrane glomerulonephritis, and C3 nephropathy - and one can speculate that biologics might also be applicable to these diseases. As many autoimmune renal diseases are relatively uncommon, with long natural histories and diverse outcomes, clinical trials that aim to validate potentially useful biologics are difficult to design and/or perform. Some excellent consortia are undertaking cohort studies and clinical trials, but more multicentre international collaborations are needed to advance the introduction of new biologics to patients with autoimmune renal disorders. This Review discusses the key molecules that direct injurious inflammation and the biologics that are available to modulate them. The opportunities and challenges for the introduction of relevant biologics into treatment protocols for autoimmune renal diseases are also discussed.

Melanocortin 1 receptor agonist protects podocytes through catalase and RhoA activation

Drugs containing adrenocorticotropic hormone have been used as therapy for patients with nephrotic syndrome. We have previously shown that adrenocorticotropic hormone and a selective agonist for the melanocortin 1 receptor (MC1R) exert beneficial actions in experimental membranous nephropathy with reduced proteinuria, reduced oxidative stress, and improved glomerular morphology and function. Our hypothesis is that MC1R activation in podocytes elicits beneficial effects by promoting stress fibers and maintaining podocyte viability. To test the hypothesis, we cultured podocytes and used highly specific agonists for MC1R. Podocytes were subjected to the nephrotic-inducing agent puromycin aminonucleoside, and downstream effects of MC1R activation on podocyte survival, antioxidant defense, and cytoskeleton dynamics were studied. To increase the response and enhance intracellular signals, podocytes were transduced to overexpress MC1R. We showed that puromycin promotes MC1R expression in podocytes and that activation of MC1R promotes an increase of catalase activity and reduces oxidative stress, which results in the dephosphorylation of p190RhoGAP and formation of stress fibers through RhoA. In addition, MC1R agonists protect against apoptosis. Together, these mechanisms protect the podocyte against puromycin. Our findings strongly support the hypothesis that selective MC1R-activating agonists protect podocytes and may therefore be useful to treat patients with nephrotic syndromes commonly considered as podocytopathies.

Genetic risk variants for membranous nephropathy: extension of and association with other chronic kidney disease aetiologies

Background

Membranous nephropathy (MN) is a common cause of nephrotic syndrome in adults. Previous genome-wide association studies (GWAS) of 300 000 genotyped variants identified MN-associated loci at HLA-DQA1 and PLA2R1.

Methods

We used a combined approach of genotype imputation, GWAS, human leucocyte antigen (HLA) imputation and extension to other aetiologies of chronic kidney disease (CKD) to investigate genetic MN risk variants more comprehensively. GWAS using 9 million high-quality imputed genotypes and classical HLA alleles were conducted for 323 MN European-ancestry cases and 345 controls. Additionally, 4960 patients with different CKD aetiologies in the German Chronic Kidney Disease (GCKD) study were genotyped for risk variants at HLA-DQA1 and PLA2R1.

Results

In GWAS, lead variants in known loci [rs9272729, HLA-DQA1, odds ratio (OR) = 7.3 per risk allele, P = 5.9 × 10^-27 and rs17830558, PLA2R1, OR = 2.2, P = 1.9 × 10^-8] were significantly associated with MN. No novel signals emerged in GWAS of X-chromosomal variants or in sex-specific analyses. Classical HLA alleles (DRB1*0301-DQA1*0501-DQB1*0201 haplotype) were associated with MN but provided little additional information beyond rs9272729. Associations were replicated in 137 GCKD patients with MN (HLA-DQA1: P = 6.4 × 10^-24; PLA2R1: P = 5.0 × 10^-4). MN risk increased steeply for patients with high-risk genotype combinations (OR > 79). While genetic variation in PLA2R1 exclusively associated with MN across 19 CKD aetiologies, the HLA-DQA1 risk allele was also associated with lupus nephritis (P = 2.8 × 10^-6), type 1 diabetic nephropathy (P = 6.9 × 10^-5) and focal segmental glomerulosclerosis (P = 5.1 × 10^-5), but not with immunoglobulin A nephropathy.

Conclusions

PLA2R1 and HLA-DQA1 are the predominant risk loci for MN detected by GWAS. While HLA-DQA1 risk variants show an association with other CKD aetiologies, PLA2R1 variants are specific to MN.

Circulating antibodies to α-enolase and phospholipase A2 receptor and composition of glomerular deposits in Japanese patients with primary or secondary membranous nephropathy

Background

Phospholipase A₂ receptor (PLA₂R) is recognized as a target antigen in primary membranous nephropathy (MN); Anti-α-enolase antibody in primary and secondary MN has been proposed, however, little is known about the potential contribution of α-enolase to the pathogenesis of MN.

Methods

We evaluated circulating antibodies to α-enolase by a dot blotting system and PLA₂R by indirect immunofluorescence, and glomerular deposition of these proteins in 25 patients with primary MN, 20 patients with secondary MN, 44 patients with collagen disease or severe infection, 60 patients with nephritis (each ten patients of IgA nephropathy, focal segmental gloemrulosclerosis, minimal change nephrotic syndrome, membranoproliferative glomeurlonephritis, diabetic glomerulosclerosis, and tubulointerstitial nephritis) as disease control, and 20 healthy subjects.

Results

In primary MN, 18 of 25 sera (72 %) showed anti-α-enolase antibody (IgG1 and IgG4, 11 pts; IgG4 alone, six pts; IgG1 alone, one pt). In secondary MN, 15 of 20 sera (75 %) contained anti-α-enolase antibody (IgG1 and IgG3, 13 pts; IgG3 alone, two pts). No circulating anti-α-enolase antibody was found in 44 collagen diseases or septic patients, 60 nephritis without MN, and 20 healthy subjects. Twelve of 25 sera (48 %) from patients with primary MN were positive for anti-PLA₂R antibody, whereas all patients with secondary MN were negative. Eight of the 12 PLA₂R-positive patients (67 %) with primary MN also had anti α-enolase antibody. Although PLA₂R antigen was present in a subepithelial pattern in 10 of 19 (52 %) patients with primary MN, α-enolase was never detected in glomerular deposits in 19 and ten patients with primary and secondary MN, respectively.

Conclusions

Circulating anti-α-enolase antibodies are highly present in both primary and secondary MN (about 70 %, respectively), while anti-PLA₂R antibodies are specific for primary MN (48 %) with a prevalence apparently lower in the Japanese population than in Chinese and Caucasian populations. The absence of α-enolase from subepithelial immune deposits suggests that anti-α-enolase antibodies do not contribute directly to immune-deposit formation, although they may have other pathogenic effects.

Electronic supplementary material

The online version of this article (doi:10.1007/s10157-016-1235-2) contains supplementary material, which is available to authorized users.

Anti-Phospholipase A2 Receptor Autoantibody: A New Biomarker for Primary Membranous Nephropathy

Primary membranous nephropathy (also known as idiopathic membranous nephropathy, IMN) is an organ specific autoimmune kidney disease characterized by the development of immune complex deposits in the sub-epithelial spaces, podocyte effacement and glomerular capillary wall thickening in the later stages. Clinical studies have demonstrated that over 70% of patients with IMN possess circulating autoimmune antibodies specifically targeting the phospholipase A₂ receptor (PLA₂R) on the surface of podocytes. The autoantibodies only bind to the extracellular portion of PLA₂R under the non-reducing condition, indicating that the epitope in PLA₂R is conformational requiring specific disulfide bonds to maintain its structure. We recently have successfully located the dominant epitope in PLA₂R to the extreme N-terminus of the receptor. This finding has opened a new direction for understanding the pathogenesis of anti-PLA₂R autoantibody induced IMN and offered a strong basis for developing sensitive clinical assays for IMN diagnosis and prognosis, and potentially, new therapeutic approaches for IMN treatment.

Membranous glomerulonephritis: histological and serological features to differentiate cancer-related and non-related forms

Membranous nephropathy is a frequent cause of nephrotic syndrome in adults. In most patients, it appears as a primary renal disease but in about 20 % of cases membranous nephropathy is associated with systemic conditions such as systemic lupus erythematosus, infections or cancer, or with drug exposure. Reliable differentiation between primary and secondary membranous nephropathy has important implications for the patient, because of different therapeutic approaches between the different forms. The recent in vivo definition of glomerular targets of autoimmunity in idiopathic membranous nephropathy represented a real breakthrough and nowadays more than one podocyte antigen is considered in some way implicated in the pathogenesis of human membranous nephropathy. Specific antibodies against all these components have been detected in serum of patients and could become biomarkers of membranous nephropathy and/or of disease activity. In this brief review, we discuss the usefulness of newly described autoantibodies in the differential diagnosis of secondary membranous nephropathy. Histological clues for recognizing the two pathological entities are also analysed with regard to the available scientific evidence on this issue. Our evaluation shows that more research is needed to identify the best approach to reach a correct diagnosis of primary or secondary membranous nephropathy.

Membranous Nephropathy with an Enhanced Granular Expression of Thrombospondin Type-1 Domain-containing 7A in a Pregnant Woman

A 30-year-old woman with proteinuria first noted at 26 weeks of gestation was admitted to undergo further evaluation. A renal biopsy revealed membranous nephropathy (MN). There was no evidence of any secondary MN. Prednisolone was initiated 6 months after delivery. Four months later, her urine protein became negative. Enhanced granular staining for thrombospondin type-1 domain-containing 7A (THSD7A) in the glomeruli was retrospectively detected in a biopsy specimen. A literature review revealed that 60% of cases of THSD7A-related MN occurred in women of childbearing age. Therefore, THSD7A-related MN should be considered in female patients presenting with idiopathic MN in childbearing age.

Recurrent Membranous Nephropathy After Kidney Transplantation: Treatment and Long-Term Implications

BACKGROUND

Membranous nephropathy (MN) can recur in kidney allografts leading to graft dysfunction and failure. The aims of these analyses were to assess MN recurrence, clinical and histologic progression, and response to anti-CD20 therapy.

METHODS

Included were 63 kidney allograft recipients with biopsy proven primary MN followed up for 77.0 (39-113) months (median, interquartile range). Disease recurrence was diagnosed by biopsy (protocol or clinical), and follow-up was monitored by laboratory parameters and protocol biopsies.

RESULTS

Thirty of 63 patients (48%) had histologic recurrence often during the first year. In 53% of the cases, recurrence was diagnosed by protocol biopsy. Recurrence risk was higher in patients with higher proteinuria pretransplant [hazard ratio = 1.869 (95% confidence interval, 1.164-3.001) per gram, P = 0.010] and those with anti-phospholipase A2 receptor antibodies [hazard ratio = 3.761 (1.635-8.652), P = 0.002]. Thirteen patients with recurrence had no clinical progression, and in 2, MN resolved histologically. Seventeen of 63 patients (27%) had progressive proteinuria and were treated with anti-CD20 antibodies, resulting in complete response in 9 (53%), partial response in 5 (29%), and no response in 3 (18%). Posttreatment biopsies were obtained in 15 patients and showed histologic resolution in 6 (40%). Disease recurrence did not correlate with graft survival. However, 5 of 11 (45.4%) graft losses were due to recurrent MN. Death-censored graft survival in MN did not differ from that of 273 control recipients with autosomal dominant polycystic kidney disease.

CONCLUSIONS

Membranous nephropathy recurs in 48% of cases threatening the allograft. Treatment of early but progressive recurrence with anti-CD20 antibodies is quite effective achieving clinical remission and histologic resolution of MN.

A new rescue regimen with plasma exchange and rituximab in high-risk membranous glomerulonephritis

BACKGROUND

Even though current treatment guidelines for idiopathic membranous glomerulonephritis (iMGN) exist, many questions regarding an optimal therapy remain unanswered. Complete remission cannot be achieved in all patients; relapses occur, in some cases frequently, and side effects from the immunosuppressive therapy are common. Therapeutic options in high-risk patients not responding to standard immunosuppressive therapies are limited. Recent research reveals that the human M-type phospholipase A2 receptor (PLA2 R) is a causative factor in iMGN that parallels clinical disease activity. However, in some patients, this correlation is not evident and additional undetermined factors seem to play a role.

DESIGN

We evaluated a new rescue protocol including plasma exchanges (PE) against albumin, intravenous immunoglobulins (IVIGs) and rituximab for 10 patients with a biopsy-proven diagnosis of iMGN who were therapy-resistant to all conventional regimens and had a urinary protein to creatinine ratio of more than 10 000 mg/g Crea. We compared this protocol with standard immunosuppressive protocols including monthly alternating prednisolone plus cyclophosphamide (18 patients), cyclosporine plus prednisolone (23 patients) and rituximab alone (eight patients) in a retrospective design.

RESULTS

Our rescue regimen with PE, IVIGs and rituximab achieved partial remission in 90% of patients who had been otherwise refractory to therapy. The mean time to partial remission was 2·1 months. Furthermore, two anti-PLA2 R-antibody negative patients were also treated with this rescue regimen, achieving partial remission after 1 and 4 months.

CONCLUSION

A combination of PE, IVIGs and rituximab is a treatment option to consider for high-risk patients with iMGN who are refractory to conventional therapy.

Immunology of membranous nephropathy: from animal models to humans

Membranous nephropathy (MN), the leading cause of nephrotic syndrome in adults, is characterized by the deposition of subepithelial immune deposits that consist mainly of immunoglobulin (Ig)G and complement. Most of the cases are primary or idiopathic (iMN), while only approximately 25% of the cases are secondary to some known disease such as systemic lupus erythematosus, hepatitis B, drugs and malignancies. Most of our knowledge on the pathogenesis of iMN has relied upon old experimental models (i.e. Heymann nephritis) that have shown that immune deposits are formed in situ by the reaction of autoantibodies against the respective podocyte antigen. Recent findings indicate that podocyte proteins also act as an autoantigen in human iMN. The M-type phospholipase A2 receptor (PLA2R) has been identified as the main target antigen, as it can be found in approximately 70% of iMN patients but only rarely in other glomerulonephritides. Podocytes damage in the experimental model of Heymann nephritis is complement-mediated. In humans, the presence of complement within the subepithelial deposits is well established, but IgG4, which does not activate complement by classical or alternative pathways, represents the predominant subclass of IgG anti-PLA2R. Some evidence suggests that IgG4 anti-PLA2R autoantibodies can bind mannan-binding lectin (MBL) and activate the lectin complement pathway. A genetic background for iMN has been demonstrated by genome-wide association studies that have shown highly significant associations of the PLA2R1 and the human leucocyte antigen (HLA)-DQA1 loci with iMN. In addition to their diagnostic value, anti-PLA2R antibodies may be useful to monitor disease activity and predict response to treatment.

Increased expression of lysosome membrane protein 2 in glomeruli of patients with idiopathic membranous nephropathy

Urinary microvesicles constitute a rich source of membrane-bound and intracellular proteins that may provide important clues of pathophysiological mechanisms in renal disease. In the current study, we analyzed and compared the proteome of urinary microvesicles from patients with idiopathic membranous nephropathy (iMN), idiopathic focal segmental glomerulosclerosis (iFSGS), and normal controls using an approach that combined both proteomics and pathology analysis. Lysosome membrane protein-2 (LIMP-2) was increased greater than twofold in urinary microvesicles obtained from patients with iMN compared to microvesicles of patients with iFSGS and normal controls. Immunofluorescence analysis of renal biopsies confirmed our proteomics findings that LIMP-2 was upregulated in glomeruli from patients with iMN but not in glomeruli of diseased patients (iFSGS, minimal change nephropathy, IgA nephropathy, membranoproliferative glomerulonephritis) and normal controls. Confocal laser microscopy showed co-localization of LIMP-2 with IgG along the glomerular basement membrane. Serum antibodies against LIMP-2 could not be detected. In conclusion, our data show the value of urinary microvesicles in biomarker discovery and provide evidence for de novo expression of LIMP-2 in glomeruli of patients with iMN.

Antiphospholipase A2 Receptor Autoantibodies: A Step Forward in the Management of Primary Membranous Nephropathy

Since the identification of PLA2R (M-type phospholipase A2 receptor) as the first human antigenic target in primary membranous nephropathy (MN), perpetual progress has been made in understanding the pathogenesis of this disease. Accumulating clinical data support a pathogenic role for the anti-PLA2R antibodies (PLA2R ABs), but confirmation in an animal model is still lacking. However, PLA2R ABs were related to disease activity and outcome, as well as to response therapy. Accordingly, PLA2R ABs assay seems to be promising tool not only to diagnose MN but also to predict the course of the disease and could open the way to personalize therapy. Nevertheless, validation of a universal assay with high precision and definition of cut-off levels, followed by larger studies with a prolonged follow-up period, are needed to confirm these prospects.

A European multicentre and open-label controlled randomized trial to evaluate the efficacy of Sequential treatment with TAcrolimus-Rituximab versus steroids plus cyclophosphamide in patients with primary MEmbranous Nephropathy: the STARMEN study

BACKGROUND

Patients with primary membranous nephropathy (MN) and persistent nephrotic syndrome have a high risk of progression to end-stage renal disease. The Ponticelli protocol (steroids with alkylating agents) is the most effective immunosuppressive therapy for this condition, but it has severe adverse effects. Tacrolimus and rituximab have demonstrated efficacy for remission of nephrotic syndrome in MN with a safer profile. However, the published evidence is largely based on small or short-term observational studies, historical cohorts, comparisons with conservative therapy or clinical trials without appropriate control groups, and there is no head-to-head comparison with the Ponticelli protocol.

METHODS

The STARMEN randomized clinical trial will compare the efficacy of sequential tacrolimus-rituximab therapy with a modified Ponticelli protocol (steroids plus cyclophosphamide). The trial will also evaluate the role of antibodies against the M-type phospholipase A2 receptor (anti-PLA2R) and other antibodies as markers of response to treatment and long-term prognosis.

RESULTS

The trial has already started with 23 patients having been enrolled as of 1 April 2015, an estimated 21.7% of the estimated sample.

Enigma (partially) resolved: phospholipase A2 receptor is the cause of "idiopathic" membranous glomerulonephritis

Membranous glomerulonephritis (MGN) is a very significant kidney disease. It is one of the frequent causes of heavy protein excretion in urine. MGN is thought to be an immune-mediated disease caused by glomerular deposition of antigen-antibody complexes. The pathogenic antigen, however, has been an enigma until recently. It was discovered in 2009 that phospholipase A2 receptor (PLA2R), a normal transmembrane protein in podocyte plasma membrane, is the antigen causing MGN. Within 5 yr of its discovery, this seminal finding has leaded to novel insights into the treatment of this disease including diagnosis, therapy, and prediction of outcome. This finding also paves the way for fundamental studies on how and why autoimmunity against PLA2R develops. The discovery of PLA2A as the cause of "idiopathic" MGN after a half century of speculation, followed by further fundamental insights with such an expedient and successful application in patient care, embodies the elegance of science at its junction with society. This perspective traces the story of this remarkable discovery.

Prevalence of Enhanced Granular Expression of Thrombospondin Type-1 Domain-Containing 7A in the Glomeruli of Japanese Patients with Idiopathic Membranous Nephropathy

Membranous nephropathy (MN) is a leading cause of nephrotic syndrome in adults. Autoantibodies against M-type phospholipase A2 receptor (PLA2R) and thrombospondin type-1 domain-containing 7A (THSD7A), which mainly belong to the IgG4 subclass, were reported as associated antibodies for the development of MN. Although PLA2R is a major target antigen for idiopathic MN, the prevalence of MN patients seropositive for PLA2R in Japan is lower than that in other countries. In this study, we conducted immunohistochemical analysis of the presence of THSD7A and PLA2R in renal specimens of MN patients to estimate the prevalence of THSD7A/PLA2R-related idiopathic MN in Japan. Enhanced granular expression of THSD7A and PLA2R was detected in 9.1% and 52.7%, respectively, of the patients with idiopathic MN. Although none of patients with secondary MN displayed enhanced granular expression of THSD7A, 5.4% of them had enhanced granular expression of PLA2R. In conclusion, the prevalence of enhanced granular expression of THSD7A in the glomeruli of Japanese patients with idiopathic MN was higher than the prevalence of MN patients seropositive for THSD7A in USA and Europe.

Onset of Graves' disease during long-term immunosuppressive therapy in a patient with membranous nephropathy

A 67-year-old man was referred to our department for thyrotoxicosis with intermittent palpitation and 4-kg weight loss during the previous month. At the first visit, the patient was treated with cyclosporine A (CyA) for membranous nephropathy during the last 3 years and 8 months. Laboratory studies revealed that the serum TSH level was <0.005 μU/ml, and free thyroxine (fT₄) and triiodothyronine (fT₃) levels were elevated at 2.76 ng/dl and 5.96 pg/ml respectively. Anti-TSH receptor antibody (TRAb) level was increased at 26.4%. A clinical diagnosis of Graves' hyperthyroidism was given, and then thyrostatic treatment with thiamazole (MMI) at a dose of 10 mg daily was initiated after CyA withdrawal. After the initiation of MMI therapy, serum fT₄ and fT₃ attained the normal level within 1.5 months, with relief of symptoms followed by a remarkable decrease in urinary protein excretion from 2.0–5.2 g/day to ≤0.03 g/day. The patient maintained euthyroid with a low titre of TRAb for the succeeding 2 years and then MMI was finally stopped. Neither a relapse of hyperthyroidism nor a flare-up of nephrotic syndrome was observed for 3 years after MMI discontinuation. CyA has conflicting effects on immunologic self-tolerance by modulation of self-reactive T cells and natural CD4⁺CD25⁺Foxp3⁺ regulatory T cell (Treg) functions, and possibly becomes a triggering factor in the development of autoimmune disorders. This case may be interesting when considering the effect of each T cell subset on the development of Graves' disease.

Management of Membranous Nephropathy in Asia

BACKGROUND

Membranous nephropathy (MN) is the most common cause of nephrotic syndrome (NS) in adults, accounting for about 20.0% of all NS cases. With an increasing prevalence, especially in the elderly, it has received great attention in Asia.

SUMMARY

Recently, the prevalence of idiopathic MN (IMN) has significantly increased among the elderly people in Asia and other places in the world. Although the exact mechanism of IMN remains unveiled, the identification of new antigens such as PLA2R and THSD7A has greatly enhanced our understanding of its pathogenesis. However, consensus has not yet been reached for the treatment of IMN in Asia. For example, there are many choices of immunosuppressive agents, including corticosteroid monotherapy, corticosteroids combined with cytotoxic agents [such as alkylating agents, calcineurin inhibitors or mycophenolate mofetil (MMF)] or traditional Chinese medicine (triptolide, Shenqi and other Chinese herbal soups). Patients with IMN in Asia often have a favorable prognosis, and progression to end-stage renal disease is relatively uncommon compared to other populations.

KEY MESSAGES

The prevalence of MN has significantly increased in the last years. The treatment strategies for IMN have not reached consensus in Asia. Traditional Chinese medicine is generally preferred by the Chinese, and compelling results have been reported recently.

FACTS FROM EAST AND WEST

(1) The prevalence of IMN is increasing worldwide, particularly in elderly patients, and has been reported in 20.0-36.8% of adult-onset NS cases. The presence of anti-PLA2R antibodies in serum or PLA2R on renal biopsy is the most predictive feature for the diagnosis of IMN and is used in both the East and West; however, appropriate screening to rule out secondary causes should still be performed. (2) Several observational (nonrandomized) Asian studies indicate a good response to corticosteroids alone in IMN patients, although no randomized controlled trials have been done in Asian membranous patients at high risk of progression. Corticosteroid monotherapy has failed in randomized controlled trial studies in Western countries and is therefore not recommended. (3) Cyclophosphamide is the most commonly prescribed alkylating agent in Europe and China. Also, chlorambucil is still used in some Western countries, particularly in Europe. In North America, calcineurin inhibitors are the more common first-line treatment. (4) Cyclosporine is predominantly used as monotherapy in North America, although KDIGO (Kidney Disease: Improving Global Outcomes) and Japanese guidelines still recommend a combination with low-dose corticosteroids. Clinical studies both in Asia and Europe showed no or little effects of monotherapy with MMF compared to standard therapies. (5) There are encouraging data from nonrandomized Western studies for the use of rituximab and a few small studies using adrenocorticotropic hormone. Clinical trials are ongoing in North America to confirm these observations. These drugs are rarely used in Asia. (6) A Chinese study reported that 36% of IMN patients suffered from venous thromboembolism versus 7.3% in a North American study. Prophylactic anticoagulation therapy is usually added to IMN patients with a low risk of bleeding in both Eastern and Western countries. (7) The Chinese traditional medicine herb triptolide, which might have podocyte-protective properties, is used in China to treat IMN. An open-label, multicenter, randomized controlled trial showed that Shenqi, a mixture of 13 herbs, was superior to corticosteroids plus cyclophosphamide therapy to restore epidermal growth factor receptor in IMN patients, although proteinuria improvement was equal in the two groups. Importantly, Shenqi treatment induced no severe adverse events while standard therapy did.

Plasmacytoid Dendritic Cell Activation and IFN-α Production Are Prominent Features of Murine Autoimmune Pancreatitis and Human IgG4-Related Autoimmune Pancreatitis

The abnormal immune response accompanying IgG4-related autoimmune pancreatitis (AIP) is presently unclear. In this study, we examined the role of plasmacytoid dendritic cell (pDC) activation and IFN-α production in this disease as well as in a murine model of AIP (MRL/Mp mice treated with polyinosinic-polycytidylic acid). We found that the development of AIP in treated MRL/Mp mice occurred in parallel with pancreatic accumulation of pDCs producing IFN-α, and with pDC depletion and IFN-α-blocking studies, we showed that such accumulation was necessary for AIP induction. In addition, we found that the pancreas of treated MRL/Mp mice contained neutrophil extracellular traps (NETs) shown previously to stimulate pDCs to produce IFN-α. Consistent with these findings, we found that patients with IgG4-related AIP also exhibited pancreatic tissue localization of IFN-α-expressing pDCs and had significantly higher serum IFN-α levels than healthy controls. In addition, the inflamed pancreas of these patients but not controls also contained NETs that were shown to be capable of pDC activation. More importantly, patient pDCs cultured in the presence of NETs produced greatly increased levels of IFN-α and induced control B cells to produce IgG4 (but not IgG1) as compared with control pDCs. These data suggest that pDC activation and production of IFN-α is a major cause of murine AIP; in addition, the increased pDC production of IFN-α and its relation to IgG4 production observed in IgG4-related AIP suggest that this mechanism also plays a role in the human disease.

Nephrotic syndrome: what's new, what's hot?

While the incidence of nephrotic syndrome (NS) is decreasing in Korea, the morbidity of difficult-to-treat NS is significant. Efforts to minimize treatment toxicity showed that prolonged treatment after an initial treatment for 2-3 months with glucocorticosteroids was not effective in reducing frequent relapses. For steroid-dependent NS, rituximab, a monoclonal antibody against the CD20 antigen on B cells, was proven to be as effective, and short-term daily low-dose steroids during upper respiratory infections reduced relapses. Steroid resistance or congenital NS are indications for genetic study and renal biopsy, since the list of genes involved in NS is lengthening.

Clinical features, course and prognosis of idiopathic membranous nephropathy depending on the presence of antibodies against M-type phospholipase A2 receptor

In membranous nephropathy, the presence of antibodies against M-type phospholipase A2 receptor is considered highly specific for idiopathic forms. However, no specific association to a particular clinical profile has been found for such antibodies.

OBJECTIVE

To assess potential differences in initial clinical profile, course and prognosis of idiopathic membranous nephropathy depending on the presence of anti-PLA2R antibodies.

METHODS

Eighty-five patients with idiopathic membranous nephropathy were included (55 anti-PLA2R-positive and 30 anti-PLA2R-negative). Clinical, biochemical and pathological variables were recorded at the time of diagnosis. Frequency of spontaneous remission, incidence of response to first-line therapy, frequency and number of recurrences, survival of renal function free from renal replacement therapy, survival of renal function free from chronic renal insufficiency and frequency of occurrence of malignant, infectious or autoimmune diseases during follow-up were recorded.

RESULTS

At the time of diagnosis, anti-PLA2R-negative patients were significantly older and had a higher frequency of spontaneous remission. No differences were noted in the response to first-line treatment, frequency and number of recurrences, survival of renal function free from renal replacement therapy, or survival of renal function free from chronic renal insufficiency.

CONCLUSIONS

Anti-PLA2R-negative patients with idiopathic membranous nephropathy were older and experienced spontaneous remission more often than anti-PLA2R-positive patients. No differences in terms of treatment response, recurrences, and final prognosis were observed between both groups of patients.

Spontaneous remission of proteinuria is a frequent event in phospholipase A2 receptor antibody-negative patients with membranous nephropathy

BACKGROUND

Phospholipase A2 receptor antibodies (PLA2R-Ab) and thrombospondin type-1 domain-containing 7A antibodies (THSD7A-Ab) are present in 70-80% of patients with membranous nephropathy (MN). Little, however, is known about the pathogenesis of MN and the clinical outcome in PLA2R-Ab- and THSD7A-Ab-negative patients.

METHODS

In this prospective multicentre observational study, the clinical outcome of 37 patients with biopsy-proven MN who were negative for PLA2R-Ab and THSD7A-Ab in the serum was analysed.

RESULTS

A total of 198 patients were screened for inclusion in the study. Of these, 157 patients were positive for PLA2R-Ab and 4 patients for THSD7A-Ab. The remaining 37 patients were negative for both antibodies were and included in this study. Six patients died during the follow-up, five because of malignant diseases and one of an infection. One patient went into end-stage renal disease, and two patients were lost to follow-up. The remaining 28 patients were followed for at least 24 months (35.6 ± 8.9 months). Seventeen patients received immunosuppressive (IS) therapy, and 11 received supportive care only. At the end of the follow-up, 14 of the 17 patients treated with immunosuppressants and 10 of 11 patients on supportive therapy had a remission of proteinuria. The time to reach remission of proteinuria and serum creatinine levels at the end of the follow-up were not different between both groups. A univariate Cox regression analysis indicated that the use of immunosuppression did not alter the chance to reach a remission of proteinuria.

CONCLUSIONS

A high number of PLA2R-Ab- and THSD7A-Ab-negative patients with MN have a good prognosis and might not need IS therapy.

Changing the concepts of immune-mediated glomerular diseases through proteomics

Standard classification of glomerular diseases is based on histopathologic abnormalities. The recent application of proteomic technologies has resulted in paradigm changes in the understanding and classification of idiopathic membranous nephropathy and membranoproliferative glomerulonephritis. Those examples provide evidence that proteomics will lead to advances in understanding of the molecular basis of other glomerular diseases, such as lupus nephritis. Proof of principle experiments show that proteomics can be applied to patient renal biopsy specimens. This viewpoint summarizes the advances in immune-mediated glomerular diseases that have relied on proteomics, and potential future applications are discussed.

The expanding field of IgG4-mediated neurological autoimmune disorders

At least 13 different disease entities affecting the central nervous system, peripheral nervous system and connective tissue of the skin or kidneys are associated with immunoglobulin G4 (IgG4) immune reactivity. IgG4 has always been considered a benign, non-inflammatory subclass of IgG, in contrast to the well-known complement-activating pro-inflammatory IgG1 subclass. A comprehensive review of these IgG4 autoimmune disorders reveals striking similarities in epitope binding and human leukocyte antigen (HLA) associations. Mechanical interference of extracellular ligand-receptor interactions by the associated IgG4 antibodies seems to be the common/converging disease mechanism in these disorders.

The Influence and Role of Microbial Factors in Autoimmune Kidney Diseases: A Systematic Review

A better understanding of the pathophysiology of autoimmune disorders is desired to allow tailored interventions. Despite increased scientific interest a direct pathogenic factor in autoimmune renal disease has been described only in a minority like membranous nephropathy or ANCA-associated vasculitis. Nonetheless the initial step leading to the formation of these antibodies is still obscure. In this review we will focus on the possible role of microbial factors in this context. Staphylococcus aureus may be a direct pathogenetic factor in granulomatosis with polyangiitis (GPA). Chronic bacterial colonization or chronic infections of the upper respiratory tract have been proposed as trigger of IgA vasculitis and IgA nephropathy. Interventions to remove major lymphoid organs, such as tonsillectomy, have shown conflicting results but may be an option in IgA vasculitis. Interestingly no clear clinical benefit despite similar local colonization with bacterial strains has been detected in patients with IgA nephropathy. In systemic lupus erythematosus injection of bacterial lipopolysaccharide induced progressive lupus nephritis in mouse models. The aim of this review is to discuss and summarize the knowledge of microbial antigens in autoimmune renal disease. Novel methods may provide insight into the involvement of microbial antigens in the onset, progression, and prognosis of autoimmune kidney disorders.