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This study assessed the safety and efficacy of B cell- and anti-PLA2R antibody-targeted low-dose rituximab therapy in patients with idiopathic membranous nephropathy (IMN). This was a multicenter, investigator-initiated, open-label, prospective cohort study. Patients were recruited from 10 hospitals in the east coastal region of China between November 1 , 2019 and June 15 , 2023. Enrolled patients were assigned to individualized rituximab therapy (guided by peripheral B cells and anti-PLA2R antibody levels) or standard rituximab therapy (1,000 mg × 2 or 375 mg/m² × 3-4): the individualized group (n = 78) and the standard group (n = 62). Odds ratios (ORs) and 95% confidence intervals (CIs) for response were estimated using multivariate logistic regression models, adjusting for key confounders, with inverse probability of treatment weighting (IPTW) applied to balance demographic and clinical characteristics. The primary outcome was a composite of complete or partial remission of proteinuria. A total of 140 patients were included in the sta tistical analysis, which was completed on June 10 , 2024. After IPTW, baseline characteristics were well balanced between the two groups. Patients were followed every 2 months for 1 year after the first rituximab injection. At 12 months, 57 of 78 patients (73.1%) in the individualized therapy group and 40 of 62 patients (64.5%) in the standard therapy group achieved complete or partial remission [the adjusted risk difference and 95% CI were 0.1 (-0.05 to 0.26); p = 0.001 for noninferiority]. In the weighted cohort, 74.1% in the individualized group and 70.5% in the standard group achieved remission (p = 0.5). The median (interquartile range) total rituximab dose per patient at 1 year was 800 mg (600-1,100 mg), with a total cost of RMB 16,227.5 (13,148-23,536) per unit utility in the individualized group, which was markedly lower than in the standard group. Anti-PLA2R autoantibody negativity at 6 months post-treatment predicted a higher probability of remission. The frequency of adverse events differed significantly between groups (6.4% vs. 12.9%,  = 0.02). B cell- and anti-PLA2R antibody-targeted rituximab therapy may be a cost-effective and safe alternative for patients with IMN. Randomized controlled trials with larger samples are needed to confirm these findings. https://www.chictr.org.cn/showproj.html?proj=42793, identifier ChiCTR1900026382.

Background Idiopathic membranous nephropathy (IMN) remains the leading cause of adult nephrotic syndrome. Immunosuppressive therapy with cyclophosphamide (CTX) is often successful in reducing proteinuria, but its use is associated with severe side effects. Tacrolimus (TAC) is effective in achieving complete remission (CR) in patients with IMN. However, whether it is as effective as CTX in inducing and maintaining complete or partial remission in these patients is unknown. This trial aims to test TAC monotherapy for its non-inferiority to CTX in inducing long-term remission of proteinuria. Methods Patients with biopsy-proven IMN with nephrotic syndrome will be randomized into a 12-month treatment period with oral TAC of 0.05–0.1 mg/kg/day for 6 months or with CTX + glucocorticoid. The efficacy of the treatment will be assessed by the remission status (based on changes in proteinuria) and relapse rate. Discussion This study will test whether treatment with TAC monotherapy is superior to CTX with glucocorticoid in inducing long-term remission of proteinuria in patients with adult IMN. The role of serum anti-PLA2R antibodies in the early assessment of the response to therapy using different therapeutic regimens will also be clarified. Trial registration ClinicalTrials.gov ChiCTR1800016140. Registered 12 June 2017. http://www.chictr.org.cn .

Idiopathic membranous nephropathy is associated with autoantibodies against the phospholipase A2 receptor (PLA2R1) in about 70% of patients. This study identifies another antigen, thrombospondin type-1 domain-containing 7A (THSD7A), which accounts for about 10% of cases. Idiopathic membranous nephropathy is an autoimmune disease and a common cause of the nephrotic syndrome in adults. 1 In 2009, the phospholipase A2 receptor 1 (PLA2R1), a protein that is expressed in glomerular podocytes, was discovered as the major antigen involved in the pathogenesis of adult idiopathic membranous nephropathy. 2 As confirmed by a number of subsequent studies, about 70% of patients with idiopathic membranous nephropathy have circulating autoantibodies against PLA2R1. 2 – 6 The remaining patients, approximately 30% of those with idiopathic membranous nephropathy, have no obvious secondary cause of the disease, and it is thought that other endogenous glomerular antigens may be . . .

The M-type phospholipase A2 receptor (PLA2R) is the major target antigen in idiopathic membranous nephropathy with detectable autoantibodies in the serum of up to 70% of patients. In retrospective studies, the PLA2R-autoantibody titer in the serum was sometimes negative indicating their measurement alone may be inconclusive. In order to better differentiate between primary and secondary membranous nephropathy, we conducted a prospective study that included 88 patients with a histologic diagnosis of membranous nephropathy. Immunohistochemical analysis for PLA2R was faintly positive in kidneys from normal individuals and patients with various other glomerular injuries. In 61 of the 88 patients, PLA2R expression was strongly positive in glomeruli, and in 60 of these patients PLA2R autoantibodies were also detected in the serum. The 27 patients negative for serum PLA2R autoantibodies were faintly positive for PLA2R staining in glomeruli and in 15 of these patients a secondary cause was found. The remaining 12 patients have a yet undetected secondary cause of membranous nephropathy or have different glomerular antigens other than PLA2R. Thus, increased staining for PLA2R in glomeruli of renal biopsies tightly correlates with the presence of PLA2R autoantibodies in the serum and this may help discriminate between primary and secondary membranous nephropathy.

In this study of patients with membranous nephropathy, serum samples from 70% of patients with idiopathic, but not secondary, membranous nephropathy were found to have antibodies against a 185-kD glycoprotein in nonreduced glomerular extracts, identified as the M-type phospholipase A 2 receptor (PLA 2 R). PLA 2 R is present in normal podocytes and in immune deposits in patients with idiopathic membranous nephropathy, indicating that PLA 2 R is a major antigen in this disease. Phospholipase A 2 receptor (PLA 2 R) is present in normal podocytes and in immune deposits in patients with idiopathic membranous nephropathy, indicating that it is a major antigen in this disease. Idiopathic membranous nephropathy, a common cause of the nephrotic syndrome in adults, is an organ-specific autoimmune disease. Despite extensive investigation, a target antigen has been elusive. Studies of membranous nephropathy in a rat model (Heymann's nephritis) established that the subepithelial immune deposits that characterize the disease are formed in situ, as a result of capping and shedding of the target antigen, megalin, from the basal surface of podocytes when it forms a complex with circulating antimegalin antibodies. 1 – 8 Although megalin is not expressed on human podocytes, we hypothesized that a similar process, albeit with an unknown antigen, is operative in . . .

To the Editor: Membranous nephropathy is a common cause of the nephrotic syndrome in adults. Treatment is controversial and challenging because of the heterogeneity of the disease and a lack of reliable biomarkers. 1 , 2 M-type phospholipase A 2 receptor (PLA 2 R) was recently identified as a major target antigen involved in idiopathic membranous nephropathy in adults. 3 Circulating autoantibodies against PLA 2 R were found in 70 to 80% of patients with idiopathic membranous nephropathy but not in those with secondary membranous nephropathy or other renal diseases. It has been suggested that the serum level of PLA 2 R autoantibody . . .

Membranous nephropathy is a major cause of nephrotic syndrome of non-diabetic origin in adults. It is the second or third leading cause of end-stage renal disease in patients with primary glomerulonephritis, and is the leading glomerulopathy that recurs after kidney transplantation (occurring in about 40% of patients). Treatment with costly and potentially toxic drugs remains controversial and challenging, partly because of insufficient insight into the pathogenesis of the disease and absence of sensitive biomarkers of disease activity. The disease is caused by the formation of immune deposits on the outer aspect of the glomerular basement membrane, which contain podocyte or planted antigens and circulating antibodies specific to those antigens, resulting in complement activation. In 2002, podocyte neutral endopeptidase was identified as an antigenic target of circulating antibodies in alloimmune neonatal nephropathy, and in 2009, podocyte phospholipase A2 receptor (PLA2R) was reported as an antigenic target in autoimmune adult membranous nephropathy. These major breakthroughs were translated to clinical practice very quickly. Measurement of anti-PLA2R antibodies in serum and detection of PLA2R antigen in glomerular deposits can now be done routinely. Anti-PLA2R antibodies have high specificity (close to 100%), sensitivity (70–80%), and predictive value. PLA2R detection in immune deposits allows for retrospective diagnosis of PLA2R-related membranous nephropathy in archival kidney biopsies. These tests already have a major effect on diagnosis and monitoring of treatment, including after transplantation.

As recently as 2002, most cases of primary membranous nephropathy (MN), a relatively common cause of nephrotic syndrome in adults, were considered idiopathic. We now recognize that MN is an organ-specific autoimmune disease in which circulating autoantibodies bind to an intrinsic antigen on glomerular podocytes and form deposits of immune complexes in situ in the glomerular capillary walls. Here we define the clinical and pathological features of MN and describe the experimental models that enabled the discovery of the major target antigen, the M-type phospholipase A2 receptor 1 (PLA2R). We review the pathophysiology of experimental MN and compare and contrast it with the human disease. We discuss the diagnostic value of serological testing for anti-PLA2R and tissue staining for the redistributed antigen, and their utility for differentiating between primary and secondary MN, and between recurrent MN after kidney transplant and de novo MN. We end with consideration of how knowledge of the antigen might direct future therapeutic strategies.

Membranous nephropathy is an autoimmune kidney disease caused by autoantibodies targeting antigens present on glomerular podocytes, instigating a cascade leading to glomerular injury. The most prevalent circulating autoantibodies in membranous nephropathy are against phospholipase A2 receptor (PLA2R), a cell surface receptor. The dominant epitope in PLA2R is located within the cysteine-rich domain, yet high-resolution structure-based mapping is lacking. In this study, we define the key nonredundant amino acids in the dominant epitope of PLA2R involved in autoantibody binding. We further describe two essential regions within the dominant epitope and spacer requirements for a synthetic peptide of the epitope for drug discovery. In addition, using cryo-electron microscopy, we have determined the high-resolution structure of PLA2R to 3.4 Å resolution, which shows that the dominant epitope and key residues within the cysteine-rich domain are accessible at the cell surface. In addition, the structure of PLA2R not only suggests a different orientation of domains but also implicates a unique immunogenic signature in PLA2R responsible for inducing autoantibody formation and recognition.

Antibodies to the phospholipase A2 receptor 1 (PLA2R1) have been reported in 70% of cases of idiopathic membranous nephropathy (IMN). The genetic susceptibility of IMN has been accounted for by HLA DQA1 and PLA2R1 genes. Here we retrospectively quantified PLA2R antibodies by ELISA, and genotyped DQ alleles and PLA2R1 single-nucleotide polymorphisms for association with clinical criteria for disease activity at the time of first sample and with outcome over a median total follow-up of 90 months. In 90 prevalent patients with biopsy-proven IMN, anti-PLA2R antibodies were present in 75% of patients with IMN with active disease and were significantly higher than in patients in partial or complete remission at the time of antibody measurement. There was a differential IgG subclass response (4>2>3>1) at an early stage, i.e., within 6 months of biopsy. Levels of PLA2R antibodies were significantly linked to DQA1*05:01 and DQB1*02:01. Survival analysis of patients with IMN showed that PLA2R antibodies are significantly linked with outcome. Thus, high levels of PLA2R antibodies are linked with active disease and a higher risk of declining renal function during follow-up. Future therapeutic trials in IMN should monitor anti-PLA2R, as patients with a high antibody burden may benefit from earlier therapeutic intervention.