PLA2R-IgG4 antibody as a predictive biomarker of treatment effectiveness and prognostic evaluation in patients with idiopathic membranous nephropathy: a retrospective study.

Background: The Kidney Disease Improving Global Outcomes (KDIGO) 2021 guidelines recommend Rituximab (RTX) as the first-line therapy and phospholipase A2 receptor (PLA2R) antibody as a biomarker for remission and prognosis in patients with idiopathic membranous nephropathy (IMN). Methods: This study was a retrospective analysis of 70 patients with IMN treated with either rituximab (RTX) or cyclophosphamide (CTX) and steroid. Quantitative detection of PLA2R-IgG and PLA2R-IgG4 antibodies at sixth month after treatment, determined using time-resolved fluoroimmunoassay (TRFIA), were used for treatment effectiveness analysis and prognostic evaluation in patients with IMN. Results: After 12 months of therapy, the remission rate of proteinuria, including complete remission (CR) and partial remission (PR) in the RTX group and the CTX group, were 74% versus 67.5% (P = 0.114), respectively. Both PLA2R-IgG and PLA2R-IgG4 levels were decreased in patients with remission of proteinuria after 6 months of therapy. Receiver operating characteristic curve (ROC) curve analysis exhibited that the AUC of PLA2R-IgG4 and the PLA2R-IgG as laboratory criteria for proteinuria remission were 0.970 versus 0.886 (P = 0.0516), respectively, after 6 months of treatment. The cut-off value of PLA2R-IgG4 was 7.67 RU/mL and the sensitivity and specificity of remission rate at 6th month were 90.9% and 100%, respectively. Furthermore, the AUC of the PLA2R-IgG4 and PLA2R-IgG to predict the outcome after 12 months of treatment were 0.922 versus 0.897 (P = 0.3270), respectively. With the cut-off value of PLA2R-IgG4 being 22.985 RU/mL, the sensitivity and specificity of remission rate at 12th month were 100% and 87.1%, respectively. Logistic regression analysis revealed that the PLA2R-IgG4 level (P = 0.023), the rate of decrease of PLA2R-IgG4 level (P = 0.034), and eGFR level (P = 0.012) were significantly associated with remission. Conclusions: We found that the patients in the RTX group and CTX group achieved effective remission of proteinuria after 12 months of treatment. PLA2R-IgG4 may be a more effective biomarker for treatment effectiveness analysis and prognostic assessment, compared with anti-PLA2R-IgG for PLA2R associated IMN.

Primary membranous glomerulonephritis with negative serum PLA2R in haemophilia A successfully managed with rituximab - case report and review of the literature.

BACKGROUND: Hepatitis C virus (HCV) and human immunodeficiency virus (HIV) cause a wide range of glomerular pathologies. In people with haemophilia, transfusion-associated infections with these viruses are common and definitive pathological diagnosis in this population is complicated by the difficulty of safely obtaining a renal biopsy. Membranous nephropathy (MN) is a common cause of adult onset nephrotic syndrome occurring in both primary and secondary forms. Primary MN is associated with podocyte autoantibodies, predominantly against phospholipase A2 receptor (PLA2R). Secondary disease is often associated with viral infection; however, infrequently with HIV or HCV. Distinguishing these entities from each other and other viral glomerular disease is vital as treatment strategies are disparate. CASE PRESENTATION: We present the case of a 48-year-old man with moderate haemophilia A and well-controlled transfusion-associated HCV and HIV coinfection who presented with sudden onset nephrotic range proteinuria. Renal biopsy demonstrated grade two membranous nephropathy with associated negative serum PLA2R testing. Light and electron microscopic appearances were indeterminant of a primary or secondary cause. Given his extremely stable co-morbidities, treatment with rituximab and subsequent angiotensin receptor blockade was initiated for suspected primary MN and the patient had sustained resolution in proteinuria over the following 18 months. Subsequent testing demonstrated PLA2R positive glomerular immunohistochemistry despite multiple negative serum results. CONCLUSIONS: Pursuing histological diagnosis is important in complex cases of MN as the treatment strategies between primary and secondary vary significantly. Serum PLA2R testing alone may be insufficient in the presence of multiple potential causes of secondary MN.

Diagnostic performance of glomerular PLA2R and THSD7A antibodies in biopsy confirmed primary membranous nephropathy in South Africans.

BACKGROUND: Serum and tissue-based tests using phospholipase A2 receptor 1 (PLA2R) and thrombospondin type-1 domain containing 7A (THSD7A) are established immune biomarkers for the diagnosis of primary membranous nephropathy (PMN). This study assessed the diagnostic performance of these biomarkers in the diagnosis of PMN in South Africans. METHODS: This was a cross-sectional analysis from a single centre in Cape Town, South Africa. Relevant biodata was collected from all patients. Histology, including slides for PLA2R and THSD7A were processed and assessed by typical microscopic and immunohistochemical features. Biopsy tissues of patients with membranous lupus nephritis (LN-V) and diabetic nephropathy (DN) were used as controls. The diagnostic accuracy for diagnosis of PMN using positive PLA2R and THSD7A were evaluated. RESULTS: Of the 88 patients included, 41 had PMN with a mean age of 44.5 ± 17.5 years and 61.0% were female. Histologically, PLA2R and THSD7A were only positive in the PMN group (51.2% and 4.9%, respectively) but negative in both control groups. The sensitivity of PLA2R and THSD7A for identifying PMN was 51.2% and 4.9%, respectively. The sensitivity of both tests together was 53.7% while the specificity and positive predictive values (PPV) for any of the tests (alone or in combination) was 100%. There was no difference in the sensitivity and specificity when using PLA2R alone compared to combining the two tests (p=0.32). CONCLUSION: Glomerular staining of PLA2R and THSD7A could have potential diagnostic values in South Africans. This has implications on how immunotherapies can be initiated and used in these settings.

Effect of Glomerular Mannose-Binding Lectin Deposition on the Prognosis of Idiopathic Membranous Nephropathy.

OBJECTIVE: Co-deposition of mannose-binding lectin (MBL) and IgG4 anti-phospholipase A2 receptor (anti-PLA2R) autoantibodies under subepithelial cells has been observed in patients with idiopathic membranous nephropathy (iMN), but the relationships of MBL deposition to iMN severity and progression remain unclear. METHODS: Patients diagnosed with iMN who underwent renal puncture were enrolled and followed up for a median of 17 months (interquartile range [IQR], 9-25 months). Serum anti-PLA2R and anti-thrombospondin type-1 domain-containing 7A antibodies and MBL were detected by ELISA. Glomerular MBL and anti-PLA2R antibodies were detected by immunofluorescence. Proteinuria remission, including complete remission (CR), was defined as a clinical event. Clinicopathological characteristics and kidney outcomes were compared between patients with and without MBL deposition. RESULTS: In 67 prevalent patients with biopsy-proven iMN, serum anti-PLA2R antibodies and anti-THSD7A antibodies were present in 37 (55.3%) and 1 (1.4%) patient with iMN. The positivity of glomerular MBL deposition and tissue anti-PLA2R antibody was 53 (79.1%) and 49 (73.1%), respectively. No significant difference was found between the MBL-positive and negative groups in the albumin level (26.5 ± 6.6 and 28.6 ± 6.1 g/L), eGFR (104.8 ± 17.4 and 114.6 ± 16.1 mL/min/1.73 m2), 24-h proteinuria (5.35 and 4.25 g/day), or serum MBL level corrected by serum Cr 4.92 (IQR, 0.86, 8.90) and 2.28 (IQR, 0.4, 5.62). In a Cox proportional hazards regression model adjusted for sex, age, systolic blood pressure, eGFR, immunosuppressive agent use, 24-h proteinuria, and anti-PLA2R antibody concentration, glomerular MBL deposition was independently associated with ICR of proteinuria (HR, 6.31; 95% CI, 1.1-36.1; p = 0.039). CONCLUSIONS: The MBL pathway of complement activation is commonly initiated in patients with iMN, and patients with MBL deposition reach ICR faster than patients without MBL deposition.

Role of Serum and Urine Biomarkers (PLA2R and THSD7A) in Diagnosis, Monitoring and Prognostication of Primary Membranous Glomerulonephritis.

Differentiating primary and secondary membranous glomerulonephritis (MGN) using biomarkers for MGN is essential in patients' diagnosis, treatment and follow-up. Although biopsy has been the primary tool in making the diagnosis, not all patients can withstand it due to its invasive nature, and it cannot be used to monitor treatment. Hence, there is the need for less invasive or even non-invasive biomarkers for effective diagnosis, treatment monitoring and prognostication. This study aimed at providing an alternative way of differentiating primary and secondary MGN using enzyme-linked immunosorbent assay (ELISA) technique for serum and urine biomarkers (M-type phospholipase A2 receptor (PLA2R) and thrombospondin type-1 domain-containing 7A (THSD7A)) for prompt diagnosis, treatment and prognosis. A total of 125 subjects, including 81 primary and 44 secondary MGN subjects, were diagnosed from January 2012 to October 2019 at Hospital Serdang and Hospital Kuala Lumpur from which 69 subjects consisting of 45 primary and 24 secondary MGN subjects participated in the study. Of these, 13 primary MGN subjects were positive for both serum and urine anti-PLA2R antibodies (Ab) whereas only one secondary MGN subject associated with hepatitis B virus was positive for both serum and urine anti-PLA2R Ab. At the same time, anti-THSD7A Ab was found positive in four primary MGN subjects and two secondary MGN subjects with malignancy.

Neural epidermal growth factor-like 1 protein (NELL-1) associated membranous nephropathy.

Membranous nephropathy is characterized by deposition of immune complexes along the glomerular basement membrane. PLA2R and THSD7A are target antigens in 70% and 1-5% of primary membranous nephropathy cases, respectively. In the remaining cases, the target antigen is unknown. Here, laser microdissection of glomeruli followed by mass spectrometry was used to identify novel antigen(s) in PLA2R-negative membranous nephropathy. An initial pilot mass spectrometry study in 35 cases of PLA2R-negative membranous nephropathy showed high spectral counts for neural tissue encoding protein with EGF-like repeats, NELL-1, in six cases. Mass spectrometry failed to detect NELL-1 in 23 PLA2R-associated membranous nephropathy and 88 controls. NELL-1 was localized by immunohistochemistry, which showed bright granular glomerular basement membrane staining for NELL-1 in all six cases. Next, an additional 23 NELL-1 positive cases of membranous nephropathy were identified by immunohistochemistry in a discovery cohort of 91 PLA2R-negative membranous nephropathy cases, 14 were confirmed by mass spectrometry. Thus, 29 of 126 PLA2R-negative cases were positive for NELL-1. PLA2R-associated membranous nephropathy and controls stained negative for NELL-1. We then identified five NELL-1 positive cases of membranous nephropathy out of 84 PLA2R and THSD7A-negative cases in two validation cohorts from France and Belgium. By confocal microscopy, both IgG and NELL-1 co-localized to the glomerular basement membrane. Western blot analysis showed reactivity to NELL-1 in five available sera, but no reactivity in control sera. Clinical and biopsy findings of NELL-1 positive membranous nephropathy showed features of primary membranous nephropathy. Thus, a subset of membranous nephropathy is associated with accumulation and co-localization of NELL-1 and IgG along the glomerular basement membrane, and with anti-NELL-1 antibodies in the serum. Hence, NELL-1 defines a distinct type of primary membranous nephropathy.

Complement activation products in the circulation and urine of primary membranous nephropathy.

BACKGROUND: Complement activation plays a substantial role in the pathogenesis of primary membranous nephropathy (pMN). C5b-9, C3c, MBL, and factor B have been documented in the subepithelial immune deposits. However, the changing of complement activation products in circulation and urine is not clear. METHODS: We measured the circulating and urinary levels of C1q, MBL, C4d, Bb, properdin, C3a, C5a, and sC5b-9, in 134 patients with biopsy-proven pMN, by enzyme-linked immunosorbent assay. All the plasma values were corrected by eGFR and all the urinary values were corrected by urinary creatinine and urinary protein excretion. Anti-PLA2R antibodies were measured in all patients. RESULTS: The plasma complement activation products were elevated both in the patients with and without anti-PLA2R antibodies. C3a levels were remarkably increased in the circulation and urine, much higher than the elevated levels of C5a. C5b-9 was in normal range in plasma, but significantly higher in urine. The urinary C5a had a positive correlation with anti-PLA2R antibody levels and urinary protein. The plasma level of C4d was elevated, but C1q and MBL were comparable to healthy controls. Positive correlations were observed between plasma C4d/MBL and urinary protein, only in the patients with positive anti-PLA2R antibodies but not in those without. The plasma level of Bb was elevated and had positive correlation with urinary protein only in the patients without anti-PLA2R antibodies. CONCLUSION: Complement activation products were remarkable increased in pMN and may serve as sensitive biomarkers of disease activity. The complement may be activated through lectin pathway with the existence of anti-PLA2R antibodies, while through alternative pathway in the absence of antibody.

Co-occurrence of PLA2R-positive membranous nephropathy without crescents, and PR3-positive eosinophilic granulomatosis with polyangiitis
.

Primary membranous nephropathy (PMN) is a common cause of adult nephrotic syndrome, most commonly associated with autoantibodies against M-type phospholipase A2 receptor (PLA2R). Eosinophilic granulomatosis with polyangiitis (EGPA), previously known as Churg-Strauss syndrome, is a rare disorder characterized by asthma, eosinophilia, and multiorgan vasculitis. Here, we report the case of an adult who presented with typical nephrotic syndrome. Renal biopsy revealed PLA2R-positive PMN without crescents. He had a history of asthma, eczema, and eosinophilia, and testing revealed positive serological proteinase 3 (PR3) and antineutrophil cytoplasmic antibody (ANCA). Further skin and bone marrow biopsy revealed histologic eosinophilic infiltration, and a diagnosis of EGPA was made. The renal biopsy revealed a few eosinophils in glomerular capillary lumen and tubulointerstitial. Treatment with a glucocorticoid and cyclophosphamide was initiated. At 32 months after completing therapy, the patient was in complete clinical remission, and the PR3-ANCA result was negative.

Membranous nephropathy and thrombotic microangiopathy secondary to metastatic prostate cancer after Iodine-125 prostate brachytherapy: A case report
.

BACKGROUND: Prostate cancer is the second most common solid tumor leading to membranous nephropathy (MN). Thrombotic microangiopathy (TMA) has been reported to be related to prostate cancer. Nonetheless, the association between prostate cancer and MN and TMA has not been well established. CASE REPORT: A 73-year-old man presented with nephritic syndrome 40 days after implantation of iodine-125 seed for stage II T2N0M0 prostatic carcinoma. The prostatic-specific antigen (PSA) was normalized, and the tumor disappeared after the initial brachytherapy. The circulating autoantibody to phospholipase A2 receptor (PLA2R) and thrombospondin type 1 domain containing 7A (THSD7A) was undetectable. Kidney biopsy revealed MN and TMA in glomerulus. Staining of PLA2R, THSD7A, prostate-specific membrane antigen, and prostate acid phosphatase in glomeruli were all negative. The diagnosis of MN and TMA was made, and a combination of steroid therapy and tacrolimus was prescribed. Two weeks after immunosuppressive treatment with prednisone 30 mg/d and tacrolimus 2 mg/d, the patient achieved partial remission in terms of proteinuria. CONCLUSION: This case study was the first report of MN with TMA as manifestations in patients with prostate cancer after I-125 seeds implantation. We hypothesize that prostate cancer may cause MN and TMA, and the mechanism behind this relationship merits further study.
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Compared staining of the phospholipase A2 receptor in the glomeruli of Chinese adults and children with idiopathic membranous nephropathy.

BACKGROUND: The identification of the M-type phospholipase A2 receptor (PLA2R) is a breakthrough recognized as a major target for adults with idiopathic membranous nephropathy (IMN). However, the role PLA2R played in pediatric patients with IMN, particularly in Chinese, has yet to be determined. METHODS: This retrospective study included 187 adult patients and 38 pediatric patients aged 17 years or younger with biopsy proved IMN. The pediatric cohort consisted of 27 children aged from 1 to 12 years and 11 children aged from 13 to 17. Glomerular expression of PLA2R was analyzed in stored, formalin-fixed, paraffin-embedded kidney biopsy sections. RESULTS: PLA2R staining in glomerular deposits was observed in 82.7% and 42.1% of adult and pediatric patients with IMN, respectively. The PLA2R-positive staining patients with IMN presented with more severe clinical features than PLA2R-negative staining patients in both adult and pediatric cohorts. When compared to the young children patients with IMN, the adolescents exhibited a higher positive rate of PLA2R staining (81.8% versus 25.9%), similar to the adult patients. CONCLUSION: The clinical features and prevalence of PLA2R positive staining in adolescent patients with IMN were similar to adult patients, suggesting that they probably have a close etiology and pathogenesis. However, most of the young children patients with IMN were PLA2R negative staining, suggesting a different underlying etiology.

The neurotoxic secreted phospholipase A2 from the Vipera a. ammodytes venom targets cytochrome c oxidase in neuronal mitochondria.

The ß-neurotoxic secreted phospholipases A2 (sPLA2s) block neuro-muscular transmission by poisoning nerve terminals. Damage inflicted by such sPLA2s (ß-ntx) on neuronal mitochondria is characteristic, very similar to that induced by structurally homologous endogenous group IIA sPLA2 when its activity is elevated, as, for example, in the early phase of Alzheimer's disease. Using ammodytoxin (Atx), the ß-ntx from the venom of the nose-horned viper (Vipera a. ammodytes), the sPLA2 receptor R25 has been detected in neuronal mitochondria. This receptor has been purified from porcine cerebral cortex mitochondria by a new Atx-affinity-based chromatographic procedure. Mass spectrometry analysis revealed R25 to be the subunit II of cytochrome c oxidase (CCOX), an essential constituent of the respiratory chain complex. CCOX was confirmed as being the first intracellular membrane receptor for sPLA2 by alternative Atx-affinity-labellings of purified CCOX, supported also by the encounter of Atx and CCOX in PC12 cells. This discovery suggests the explanation of the mechanism by which ß-ntx hinders production of ATP in poisoned nerve endings. It also provides a new insight into the potential function and dysfunction of endogenous GIIA sPLA2 in mitochondria.

Correlation and discrepancy of phospholipase A2 receptor staining in membranous nephropathy in paraffin-embedded kidney biopsies.

Distinguishing primary from secondary forms of membranous nephropathy (MN) in paraffin-embedded kidney biopsies is challenging. Previous studies have measured the accuracy, sensitivity, and specificity of phospholipase A2 receptor (PLA2R) on MN. However, due to the absence of a gold standard method for diagnosis, further studies are necessary. Here, we measure the correlation and discrepancy of PLA2R on MN in paraffin-embedded kidney biopsies by correlating PLA2R findings with immunofluorescence (IF), light microscopy (LM), and electron microscopy (EM) results. A total of 116 kidney biopsies were investigated including 87 MN and 29 nonmembranous kidney diseases. PLA2R was examined by indirect IF assay. A total of 79 MN cases were subjected to PLA2R staining and histopathological analyses. The remaining eight cases were excluded due to the lack of the glomeruli in the sections. The correlation and discrepancy between PLA2R and IF findings were seen in 65.45% and 34.55%, respectively. PLA2R and EM findings showed a 65.52% correlation and 34.48% discrepancy. LM features and PLA2R findings showed a correlation of 58.44% and discrepancy of 41.56%. Overall correlation between histopathology and PLA2R was seen in 65.82% and 34.18% showed discordant cases. All 29 non-membranous MN cases were negative for PLA2R. Staining for PLA2R could be a useful adjunctive tool in the stratification of cases of MN. The findings of this study strongly recommend the use of PLA2R IF staining method as a routine test for all MN cases.

Expression of phospholipase A2 receptor and IgG4 in patients with membranous nephropathy.

OBJECTIVES: The aims of this study were to detect the expression of M phospholipase A2 receptor (PLA2R) in the kidney tissue of patients with idiopathic membranous nephropathy (IMN), secondary membranous nephropathy (SMN), and the nonmembranous nephropathy (non-MN), to evaluate the value of PLA2R in the kidney tissue and serum anti-PLA2R antibody in the diagnosis of membranous nephropathy (MN), and to explore the relationship between PLA2R of the kidney tissue or serum anti-PLA2R antibody and clinical features of MN. METHODS: The kidney tissue was collected by kidney biopsy. Immunofluorescence assay was used to detect the level of PLA2R and IgG4 antigen in kidney tissue. Furthermore, the level of the PLA2R was detected using the enzyme-linked immunosorbent assay (ELISA). The positive and negative rates of PLA2R and IgG4 in different diseases and the sensitivity and specificity, were calculated using the statistical method. The specificity and coincidence rate of PLA2R or anti-PLA2R used in the differential diagnosis of IMN and SMN were evaluated. RESULTS: The expression intensities of anti-PLA2R antibody and IgG4 were significantly higher in patients with IMN than in patients with SMN but are not non-MN. There was no significant difference in anti-PLA2R antibody and IgG4 in patients with SMN and non-MN. The coincidence rate of serum anti-PLA2R antibody and PLA2R in kidney tissue was 100%. CONCLUSION: The expression of PLA2R and IgG4 antibody had great significance in the pathological diagnosis of MN. The detection of the serum anti-PLA2R antibody had great diagnostic value in diagnosing MN.

Anti-neutrophil cytoplasmic antibody-associated glomerulonephritis with detection of myeloperoxidase and phospholipase A2 receptor in membranous nephropathy-lesions: report of two patients with microscopic polyangiitis.

BACKGROUND: Podocyte phospholipase A2 receptor (PLA2R) is a major target antigen in idiopathic adult membranous nephropathy (MN). Histological PLA2R staining in the renal tissue has proven to be useful for the detection of idiopathic MN. However, glomerular PLA2R deposits have also been recently observed in several patients with secondary MN, such as hepatitis B virus-associated, hepatitis C virus-associated, and neoplasm-associated MN. Certain inflammatory environments have been suggested to lead to abnormal expression of PLA2R epitopes, with the resulting production of PLA2R autoantibodies. CASE PRESENTATION: We report two patients diagnosed with anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis with MN-lesions, in whom ANCA titers for myeloperoxidase (MPO) were persistently positive. The first patient was a 52-years-old man who presented with interstitial pneumonitis. Microscopic hematuria and proteinuria were found when the interstitial pneumonitis became more severe. Renal biopsy findings yielded a diagnosis of ANCA-associated glomerulonephritis (mixed class) with MN-lesions. The second patient was a 63-years-old woman who had been treated for relapsing polychondritis. Her renal tissue showed evidence of focal ANCA-associated glomerulonephritis with MN-lesions. Interestingly, both MPO and PLA2R were detected in the glomerular subepithelial deposits of both patients. Immunoglobulin G (IgG) 1 and IgG2 were positive in the glomeruli of patient 2, and all subclasses of IgGs were positive in patient 1. CONCLUSION: The present cases suggest that ANCA-associated glomerulonephritis could expose PLA2R, leading to the development of MN-lesions.

Translational Aspects of Primary Membranous Nephropathy.

Membranous nephropathy (MN) in an autoimmune disease caused by binding of circulating antibodies to podocytic antigens. The search for the responsible target antigens has extended for more than 50 years and led to the identification of the major pathomechanisms leading to MN. The combination of clinical and morphologic observations, experimental work, and technical advancements has enabled us deep insights in the pathophysiology of this disease, simultaneously improving treatment of patients. MN represents a perfect example of how patient care may profit from the convergence of scientific and clinical achievements and the benefits of translational approaches in medicine.

Response to immunosuppressive therapy in PLA2R- associated and non-PLA2R- associated idiopathic membranous nephropathy: a retrospective, multicenter cohort study.

BACKGROUND: According to renal M type phospholipase A2 receptor (PLA2R) immunohistochemistry, idiopathic membranous nephropathy (IMN) could be categorized into PLA2R-associated and non-PLA2R-associated IMN. We conducted a retrospective, multicenter cohort study with 91 patients to compare the effect of immunosuppressive therapy between PLA2R-associated and non-PLA2R-associated IMN patients. METHODS: A total of 91 biopsy-proven IMN patients from Huashan hospital and People's Hospital of Wuxi in past 5 years were collected into this study. IMN with positive PLA2R immunohistochemistry in kidney biopsies were designated as PLA2R-associated IMN. Seventy-eight of the 91 IMN patients was PLA2R-associated IMN and 13 were non-PLA2R-associated IMN. Forty-five patients were treated with prednisone plus cyclophosphamide (CTX), and 46 with prednisone plus calcineurin inhibitors (CNIs). The follow-up duration was 15 months. RESULTS: The total remission rate (76.9% versus 44.9%, p = 0.032) and complete remission rate (30.8% versus 2.6%, p = 0.003) were both significantly higher in the non-PLA2R-associated group than in the PLA2R-associated group at the 3rd month visit point, and at the 6th month time point, the complete remission rate was still significantly higher in the non-PLA2R-associated group (46.2% versus 11.5%,p = 0.007). But similar remission rates were found after the 9th month. Relapses were observed in 8 patients in PLA2R-associated group and none in non-PLA2R-associated group, although there was no significant difference between these two groups. CONCLUSION: Compared with the PLA2R-associated IMN, the non-PLA2R-associated IMN responded quicker to the immunosuppressive therapy.

PLA2R-positive (primary) membranous nephropathy in a child with IPEX syndrome.

BACKGROUND: Immunodysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare primary immunodeficiency syndrome characterized by the development of multiple autoimmune disorders in affected individuals. Different forms of renal injury have been reported in IPEX syndrome, and membranous nephropathy (MN) is among the most common glomerulopathies found. However, the exact pathogenesis of MN in this setting has not been elucidated, and it is not clear whether it is part of the clinical spectrum of the disease or secondary to medications, infections or other concomitant insults. DIAGNOSIS/TREATMENT: We describe a child diagnosed with IPEX syndrome shortly after birth who presented with nephrotic syndrome at the age of 11 weeks. Renal biopsy revealed a MN with enhanced immunohistochemical staining for phospholipase A2 receptor (PLA2R). CONCLUSION: This is the first report of a PLA2R-positive MN in a patient with IPEX syndrome. We suggest that, in this context, MN results from an autoimmune process against podocytic antigens, namely PLA2R.

Detection and clinical significance of glomerular M-type phospholipase A2 receptor in patients with idiopathic membranous nephropathy.

BACKGROUND: Glomerular M-type phospholipase A2 receptor (PLA2 R) is important for diagnosing idiopathic membranous nephropathy (IMN). The relation between glomerular PLA2 R expression and response to treatment remains to be explored. AIMS: We conducted the study to explore the positive rate and clinical significance of glomerular M-type PLA2 R in IMN patients. METHODS: A total of 122 IMN patients receiving neither glucocorticoid nor immunosuppressant therapy prior to renal biopsies was included and followed for more than 1 year. The control group comprised 30 patients with secondary membranous nephropathy and 100 patients with non-membranous forms of nephropathy. PLA2 R level and IgG subclasses in glomeruli were detected. The primary end-point was the reduction of proteinuria to less than 50% of baseline value. RESULTS: A total of 82.0% of patients with IMN had positive glomerular PLA2 R deposits, compared with 16.7% in the secondary membranous nephropathy group (P < 0.001). Additionally, PLA2 R-positive expression combined with IgG4 ≥ 2+ was found in 94.3% IMN patients, compared with 40.0% in secondary membranous nephropathy patients (P < 0.01). Among IMN patients, the remission rate of proteinuria after either glucocorticoid or glucocorticoid combined immunosuppressant therapy for at least 6 months was 83.9% in the PLA2 R-positive group compared with 54.5% in the negative group (P < 0.05). CONCLUSION: The positive rate of glomerular PLA2 R was more prevalent in IMN patients. Both PLA2 R and IgG4 glomerular deposits may help in discriminating between idiopathic and secondary membranous nephropathy. IMN patients with positive PLA2 R expression probably have a more beneficial response to glucocorticoid and/or immunosuppressant therapy.

Serum Anti-PLA2R Antibody Predicts Treatment Outcome in Idiopathic Membranous Nephropathy.

BACKGROUND: M-type phospholipase A2 receptor (PLA2R) has been identified as the major target antigen in idiopathic membranous nephropathy (IMN). However, the role of glomerular PLA2R (gPLA2R) and the associations of serum anti-PLA2R antibody (sPLA2R-Ab) titre with diagnosis, treatment and prognosis in IMN need to be further investigated. METHODS: We screened 148 consecutive patients with biopsy-proven membranous nephropathy (MN; 113 with IMN and 35 with secondary MN (SMN)) who were followed up for ≤20 months. Serum and urine samples were simultaneously collected at different time points. The levels of sPLA2R-Ab were detected using immunofluorescence and enzyme-linked immunosorbent assay. gPLA2R was assessed by immunofluorescence. RESULTS: Most patients with IMN displayed both gPLA2R and sPLA2R-Ab positive (85.8 and 82.3%, respectively). In contrast, very few patients with SMN showed either gPLA2R or sPLA2R-Ab positive. The sPLA2R-Ab titre, not gPLA2R, was significantly correlated with proteinuria. Surprisingly, changes in sPLA2R-Ab titre occurred earlier and faster than proteinuria in patients who were followed up for ≤20 months during the whole period of observation. Survival analysis of IMN patients indicated a significant association between sPLA2R-Ab titre and outcome, whereas, no significant difference was observed between the gPLA2R intensity and outcome. CONCLUSIONS: These data indicate that sPLA2R-Ab might be a better biomarker for IMN diagnosis and treatment outcome. In addition, monitoring sPLA2R-Ab titre may assist in determining when to initiate the administration of immunosuppressive agents and in evaluating treatment efficacy.

Expression of phospholipase A2 receptor in primary cultured podocytes derived from dog kidneys.

Phospholipase A2 receptor (PLA2R) expressed in human podocytes has been highlighted as a causative autoantigen of human idiopathic membranous nephropathy. However, its expression was found to be minimal or absent in murine and rat podocytes. In this study, immunofluorescence revealed the expression of PLA2R in the glomerular podocytes in the kidney tissue sections of dogs. We then attempted to culture canine podocytes and investigate the expression of PLA2R in these cells. Glomeruli were isolated from dog kidneys and cultured to obtain podocytes using nylon mesh-based isolation method as followed for isolating rat podocytes. The cultured cells expressed PLA2R mRNA and protein in addition to other podocyte markers (synaptopodin, podocin and nephrin). These results indicate that the canine podocytes express PLA2R.