Tubular expression of Toll-like receptor 9 in lupus and primary membranous nephropathy.

INTRODUCTION: Toll-like- receptors (TLR) control important aspects of innate and adaptive immune responses. Renal cells are among the non-immune cells that express (TLR). Therefore, their activation might be implicated in renal tubulo-interstitial injury. AIM: The study aimed to compare TLR9 expression in patients with primary membranous nephropathy (MN) to patients with lupus membranous nephropathy. METHODS: Kidney sections from 10 Lupus nephritis (LN) patients and ten patients with primary MN were analyzed by immunohistochemistry using anti-human TLR9 antibody. RESULTS: Results showed that TLR9 expression was weak and exclusively tubular in primary MN patients' biopsies. There was a significant difference between LN patients' biopsies and primary MN patients' biopsies. TLR9 expression was more diffused in LN patients' specimen than in those with primary MN. CONCLUSION: This study focuses on molecular level pathogenesis of MN. The data suggest that the receptors TLR9 may play role in tubulointerstitial injury in the pathogenesis of LN but not primary membranous nephropathy.

Predictive value of the domain specific PLA2R antibodies for clinical remission in patients with primary membranous nephropathy: A retrospective study.

BACKGROUND: M-type phospholipase A2 receptor (PLA2R) is a major auto-antigen of primary membranous nephropathy(PMN). Anti-PLA2R antibody levels are closely associated with disease severity and therapeutic effectiveness. Analysis of PLA2R antigen epitope reactivity may have a greater predictive value for remission compared with total PLA2R-antibody level. This study aims to elucidate the relationship between domain-specific antibody levels and clinical outcomes of PMN. METHODS: This retrospective analysis included 87 patients with PLA2R-associated PMN. Among them, 40 and 47 were treated with rituximab (RTX) and cyclophosphamide (CTX) regimen, respectively. The quantitative detection of -immunoglobulin G (IgG)/-IgG4 targeting PLA2R and its epitope levels in the serum of patients with PMN were obtained through time-resolved fluorescence immunoassays and served as biomarkers in evaluating the treatment effectiveness. A predictive PMN remission possibility nomogram was developed using multivariate logistic regression analysis. Discrimination in the prediction model was assessed using the area under the receiver operating characteristic curve (AUC-ROC).Bootstrap ROC was used to evaluate the performance of the prediction model. RESULTS: After a 6-month treatment period, the remission rates of proteinuria, including complete remission and partial remission in the RTX and CTX groups, were 70% and 70.21% (P = 0.983), respectively. However, there was a significant difference in immunological remission in the PLA2R-IgG4 between the RTX and CTX groups (21.43% vs. 61.90%, P = 0.019). Furthermore, we found differences in PLA2R-CysR-IgG4(P = 0.030), PLA2R-CTLD1-IgG4(P = 0.005), PLA2R-CTLD678-IgG4(P = 0.003), and epitope spreading (P = 0.023) between responders and non-responders in the CTX group. Multivariate logistic analysis showed that higher levels of urinary protein (odds ratio [OR], 0.49; 95% confidence interval [CI], 0.26-0.95; P = 0.035) and higher levels of PLA2R-CTLD1-IgG4 (OR, 0.79; 95%CI,0.62-0.99; P = 0.041) were independent risk factors for early remission. A multivariate model for estimating the possibility of early remission in patients with PMN is presented as a nomogram. The AUC-ROC of our model was 0.721 (95%CI, 0.601-0.840), in consistency with the results obtained with internal validation, for which the AUC-ROC was 0.711 (95%CI, 0.587-0.824), thus, demonstrating robustness. CONCLUSIONS: Cyclophosphamide can induce immunological remission earlier than rituximab at the span of 6 months. The PLA2R-CTLD1-IgG4 has a better predict value than total PLA2R-IgG for remission of proteinuria at the 6th month.

Clinical implications of serum anti-PLA2R levels and glomerular PLA2R deposits in primary membranous nephropathy.

Introduction. The clinical implications of serum anti-PLA2R with glomerular PLA2R deposits in primary membranous nephropathy (PMN) is scarcely reported. Hence the study was designed to demonstrate the prevalence of serum anti-PLA2R levels and PLA2R staining in glomeruli in PMN and the clinical implications of the two parameters. Objectives. Investigate the prevalence of anti PLA2R positivity in PMN. Ascertain correlation between serum anti-PLA2R levels and glomerular staining for PLA2R with clinical and lab parameters in PMN. Patients and Methods. Fifty PMN patients during the period from October 2017 to December 2018 were included. Labs were done and eGFR was calculated as per MDRD 6. Anti-PLA2R titres were done in all patients. Titres more than 20 RU/ml were considered positive. Glomerular staining for PLA2R was graded on fresh frozen tissue by immunofluorescence technique. Results. Anti-PLA2R antibody positivity and glomerular PLA2R deposition was observed in 42% (21/50) and 86% (43/50) patients respectively. 79.3% (23/29) had positive glomerular PLA2R deposition with negative serum anti PLA2R. Positive correlation were observed between serum PLA2R antibody and serum creatinine (p = 0.0001) and urine protein-creatinine ratio levels with tissue PLA2R staining grades (p = 0.04). Negative association was found between serum albumin (p = 0.026) and tissue PLA2R staining grades. Conclusion. Serum anti-PLA2R wasn't a sensitive marker of primary membranous nephropathy in our study group emphasising the need to consider a compendium of serological markers for diagnosis of primary membranous nephropathy and to rely more on glomerular deposition of PLA2R as a better clinical indicator for PMN.

The diversity of peripheral blood T cells and myeloid-derived suppressor cells in patients with idiopathic membranous nephropathy.

OBJECTIVE: Membranous nephropathy is a leading cause of adult-onset nephrotic syndrome. Peripheral T cells and myeloid-derived suppressor cells (MDSCs) are closely associated with autoimmune diseases, while their exact roles and interaction in these processes are unclear. Here, we studied the roles of T cells, MDSCs, and their subsets in patients with idiopathic membranous nephropathy (IMN). MATERIALS AND METHODS: 35 IMN patients and 30 healthy controls were included in this retrospective study. Flow cytometry was performed to determine the phenotype of human T cells and MDSCs in peripheral blood mononuclear cells (PBMCs). Anti-PLA2R was measured by ELISA. Values ≥ 20 RU/mL were defined as positive and < 14 RU/mL as negative. RESULTS: A higher ratio of CD4/CD8 T cells with a lower proportion of Tregs, a remarkably lower proportion of G-MDSCs (but not M-MDSCs), lower frequency of PD-L2+G-MDSCs, and higher frequency of PD-L1+M-MDSCs were found in IMN patients compared to healthy controls. The ratio of CD4/CD8 T cells was higher, and the frequencies of PD-1+CD4+ T cells, CTLA-4+CD4+ T cells, PD-1+Tregs, and CTLA-4+Tregs were lower in PBMCs of PLA2R-positive IMN patients compared to PLA2R-negative IMN patients. CONCLUSION: Tregs and G-MDSCs were reduced in the circulation of the IMN patients, which may promote understanding of the crucial functions that are mediated by these cells in the pathogenesis of IMN.

Combined Serologic and Genetic Risk Score and Prognostication of Phospholipase A2 receptor-Associated Membranous Nephropathy.

INTRODUCTION: The aim of this study was to test whether a combined risk score on the basis of genetic risk and serology can improve the prediction of kidney failure in phospholipase A2 receptor (PLA2R)-associated primary membranous nephropathy. METHODS: We performed a retrospective analysis of 519 biopsy-proven PLA2R-associated primary membranous nephropathy patients with baseline eGFR ≥25 ml/min per 1.73 m 2 . The combined risk score was calculated by combining the genetic risk score with PLA2R ELISA antibody titers. The primary end point was kidney disease progression defined as a 50% reduction in eGFR or kidney failure. Cox proportional hazard regression analysis and C-statistics were applied to compare the performance of PLA2R antibody, genetic risk score, and combined risk score, as compared with clinical factors alone, in predicting primary outcomes. RESULTS: The median age was 56 years (range, 15-82 years); the male-to-female ratio was 1:0.6, the median eGFR at biopsy was 99 ml/min per 1.73 m 2 (range: 26-167 ml/min per 1.73 m 2 ), and the median proteinuria was 5.3 g/24 hours (range: 1.5-25.8 g/24 hours). During a median follow-up of 67 (5-200) months, 66 (13%) had kidney disease progression. In Cox proportional hazard regression models, PLA2R antibody titers, genetic risk score, and combined risk score were all individually associated with kidney disease progression with and without adjustments for age, sex, proteinuria, eGFR, and tubulointerstitial lesions. The best-performing clinical model to predict kidney disease progression included age, eGFR, proteinuria, serum albumin, diabetes, and tubulointerstitial lesions (C-statistic 0.76 [0.69-0.82], adjusted R 2 0.51). Although the addition of PLA2R antibody titer improved the performance of this model (C-statistic: 0.78 [0.72-0.84], adjusted R 2 0.61), replacing PLA2R antibody with the combined risk score improved the model further (C-statistic: 0.82 [0.77-0.87], adjusted R 2 0.69, difference of C-statistics with clinical model=0.06 [0.03-0.10], P < 0.001; difference of C-statistics with clinical-serologic model=0.04 [0.01-0.06], P < 0.001). CONCLUSIONS: In patients with PLA2R-associated membranous nephropathy, the combined risk score incorporating inherited risk alleles and PLA2R antibody enhanced the prediction of kidney disease progression compared with PLA2R serology and clinical factors alone.

Anti-Phospholipase A2 Receptor 1 and Anti-Cysteine Rich Antibodies, Domain Recognition and Rituximab Efficacy in Membranous Nephropathy: A Prospective Cohort Study.

RATIONALE & OBJECTIVE: Proteinuria and anti-phospholipase A2 receptor 1 (anti-PLA2R1) antibody titers are associated with primary membranous nephropathy (MN) outcomes. We evaluated the association of antibodies against the cysteine-rich (CysR) and C-type lectin 1, 7, and 8 (CTLD1, CTLD7, and CTLD8) domains of PLA2R1 with MN outcomes. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: One-hundred-thirteen consecutive, consenting patients referred to the Nephology Unit of the Azienda-Socio-Sanitaria-Territoriale (ASST) Papa Giovanni XXIII (Bergamo, Italy) with PLA2R1-related, biopsy-proven MN whose persistent nephrotic syndrome (NS) was managed conservatively for>6 months and were monitored with serial evaluations of proteinuria, autoantibodies (by enzyme-linked immunosorbent assay), and clinical outcomes. EXPOSURE: Rituximab. OUTCOME: Complete (proteinuria<0.3g/24h) or partial (proteinuria≥0.3g/24h and<3.0g/24h with>50% reduction vs basal) NS remission. ANALYTICAL APPROACH: Univariable and multivariable Cox regression analyses. RESULTS: All patients had anti-CysR antibodies; 62 (54.9%) were multidomain recognizers. Anti-PLA2R1 and anti-CysR antibody titers were strongly correlated at baseline (P<0.001, r=0.934), 6 months (P<0.001, r=0.964), and 12 months (P<0.001, r=0.944). During a median follow-up of 37.1 (IQR, 20.3-56.9) months, 71 patients (62.8%) achieved either complete or partial remission of their NS. Lower baseline anti-PLA2R1 (HR, 0.997 [95% CI, 0.996-0.999], P=0.002) and anti-CysR [HR, 0.996 [95% CI, 0.993-0.998], P=0.001) titers were associated with a higher probability of remission, along with female sex, lower proteinuria, and lower serum creatinine levels (P<0.05 for all comparisons). Anti-CTLD antibodies were not associated with outcomes. At 6 and 12 months, compared to baseline, anti-PLA2R1 and anti-CysR antibody titers decreased more in patients progressing to partial or complete remission than in those without remission (P<0.05 for all comparisons). LIMITATIONS: Observational design. CONCLUSIONS: In PLA2R1-related MN, anti-PLA2R1 and anti-CysR antibodies similarly predict rituximab efficacy independent of PLA2R1 domain recognition. The choice between these tests should be dictated by feasibility and costs. Evaluating anti-CTLD antibodies appears unnecessary. PLAIN-LANGUAGE SUMMARY: Primary membranous nephropathy (MN), a leading cause of nephrotic syndrome (NS) in adults, is an autoimmune disease caused by autoantibodies binding to the podocyte antigen phospholipase A2 receptor 1 (PLA2R1). We assessed whether the effects of anti-CD20 cytolytic therapy with the monoclonal antibody rituximab are associated with detection rates and levels of anti-PLA2R1 antibodies and antibodies against PLA2R1 domains such as cysteine-rich (CysR), and C-type lectin 1, 7, and 8 (CTLD1, 7, and 8), in patients with PLA2R1-related MN and persistent NS. The probability of rituximab-induced complete or partial NS remission was associated with baseline anti-PLA2R1 and anti-CysR antibody titers, but not with anti-CTLD1, 7 and 8 antibodies or multidomain recognition. Integrated evaluation of anti-PLA2R1 or anti-CysR antibodies with proteinuria and kidney function may play a role in monitoring the effects of rituximab in patients with PLA2R1-related NS and MN.

Structure of PLA2R reveals presentation of the dominant membranous nephropathy epitope and an immunogenic patch.

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.

Association of serum mannose-binding lectin, anti-phospholipase A2 receptor antibody and renal outcomes in idiopathic membranous nephropathy and atypical membranous nephropathy: a single center retrospective cohort study.

OBJECTIVES: Idiopathic membranous nephropathy (iMN) is a major cause of nephrotic syndrome. Atypical membranous nephropathy (aMN) is a new type of nephropathy in China, characterized by a 'full-house' on immunofluorescent examination, that is IgG, IgA, IgM, C3, C1q positive, but without clinical evidence of a secondary cause. Phospholipase A2 receptor (PLA2R) was the major target antigens in iMN patients. Activation of the mannose-binding lectin (MBL) pathway plays a vital role in the development of MN. Our objective was to investigate the role of PLA2R and MBL in the pathogenesis of iMN and aMN. METHODS: We conducted a retrospective observational study using propensity score matching by age, gender, and eGFR. All clinical, laboratory data, and follow-up data of the patients were collected. Serum levels of anti-PLA2R antibodies and MBL were tested. RESULTS: Finally, 30 iMN patients and 30 aMN patients were included, and 20 healthy controls were retrospectively collected in this study. The 24 h proteinuria level was higher and serum albumin was lower in anti-PLA2R (+) patients than in anti-PLA2R (-) patients in both iMN and aMN groups. In aMN patients, MBL levels were significantly higher in anti-PLA2R (+) patients than in anti-PLA2R (-) patients (p = .045). The serum level of anti-PLA2R positively correlated with no-remission in both iMN and aMN groups. CONCLUSIONS: The complement lectin pathway has an association with the development of MN, especially in patients with positive anti-PLA2R antibodies. Serum MBL cannot differentiate between the two diseases. Serum MBL levels are not associated with clinical manifestations, nor with prognosis.

Strategies Towards Antigen-Specific Treatments for Membranous Nephropathy.

Membranous nephropathy (MN) is a rare but potentially severe autoimmune disease and a major cause of nephrotic syndrome in adults. Traditional treatments for patients with MN include steroids with alkylating agents such as cyclophosphamide or calcineurin inhibitors such as cyclosporine, which have an undesirable side effect profile. Newer therapies like rituximab, although superior to cyclosporine in maintaining disease remission, do not only affect pathogenic B or plasma cells, but also inhibit the production of protective antibodies and therefore the ability to fend off foreign organisms and to respond to vaccination. These are undesired effects of general B or plasma cell-targeted treatments. The discovery of several autoantigens in patients with MN offers the great opportunity for more specific treatment approaches. Indeed, such treatments were recently developed for other autoimmune diseases and tested in different preclinical models, and some are about to jump to clinical practice. As such treatments have enormous potential to enhance specificity, efficacy and compatibility also for MN, we will discuss two promising strategies in this perspective: The elimination of pathogenic antibodies through endogenous degradation systems and the depletion of pathogenic B cells through chimeric autoantibody receptor T cells.

Negative anti-phospholipase A2 receptor antibody status at three months predicts remission in primary membranous nephropathy.

BACKGROUND: The value of anti-phospholipase A2 receptor antibody (anti-PLA2R ab) monitoring at 3 months after diagnosis in membranous nephropathy (MN) remains uncertain. METHODS: We retrospectively examined the outcome on 1 August 2020 of 59 adult patients (age 54 (44, 68) years, 69% male, SCr 1.0 (0.9, 1.3) mg/dL) diagnosed with MN (kidney biopsy, positive serum anti-PLA2R ab). The outcomes were: kidney survival; partial and/or complete remission. RESULTS: Most of the studied patients (97%) received immunosuppression, cyclophosphamide regimens were the most frequent (87%), followed by cyclosporine (10%). The median time to remission was 12.0 months and the cumulative remission rates were 34% at 6, 54% at 12, and 73% at 24 months. Forty (69%) patients had negative anti-PLA2R ab at 3 months, they had similar age, serum creatinine, albumin, proteinuria, and treatment with the group with positive ab at 3 months. In the Cox proportional hazard model, three months anti-PLA2R ab negativization (HR 0.4 (95%CI 0.1, 0.9)) was an independent predictor for remission, while baseline hypoalbuminemia (HR 3.0 (95%CI 1.5, 5.7)) was associated with absence of remission. Six (10%) patients died, mostly due to cardiovascular disease and infections. A total of five (9%) patients started dialysis. Mean kidney survival time was 50.3 months and there was no survival difference in relation to baseline anti-PLA2R ab titer (p .09) or 3 months negativization (p .8). CONCLUSIONS: Three months anti-PLA2R ab negativization seems to be a late predictor of remission, and lower serum albumin at diagnosis is an early marker for remission absence. Abbreviations: anti-P LA2R ab, anti-phospholipase A2 receptor antibody; eGFR, estimated glomerular filtration rate; ESKD, end stage kidney disease; MN, membranous nephropathy; NELL-1, neural epidermal growth factor-like 1 protein; RAAS: renin-angiotensin-aldosterone system; RBC: red blood cells; RRT, renal replacement therapy; T HSD7A, thrombospondin type-1 domain containing 7A.

Structural determinants of the dominant conformational epitopes of phospholipase A2 receptor in primary membranous nephropathy.

Anti-phospholipase A2 receptor autoantibody (PLA2R-Ab) plays a critical role in the pathogenesis of primary membranous nephropathy (PMN), an autoimmune kidney disease characterized by immune deposits in the glomerular subepithelial spaces and proteinuria. However, the mechanism of how PLA2R-Abs interact with the conformational epitope(s) of PLA2R has remained elusive. PLA2R is a single transmembrane helix receptor containing ten extracellular domains that begin with a CysR domain followed by a FnII and eight CTLD domains. Here, we examined the interactions of PLA2R-Ab with the full PLA2R protein, N-terminal domain truncations, and C-terminal domain deletions under either denaturing or physiological conditions. Our data demonstrate that the PLA2R-Abs against the dominant epitope (the N-terminal CysR-CTLD1 triple domain) possess weak cross-reactivities to the C-terminal domains beyond CTLD1. Moreover, both the CysR and CTLD1 domains are required to form a conformational epitope for PLA2R-Ab interaction, with FnII serving as a linker domain. Upon close examination, we also observed that patients with newly diagnosed PMN carry two populations of PLA2R-Abs in sera that react to the denatured CysR-CTLD3 (the PLA2R-Ab1) and denatured CysR-CTLD1 (the PLA2R-Ab2) domain complexes on Western blots, respectively. Furthermore, the PLA2R-Ab1 appeared at an earlier time point than PLA2R-Ab2 in patients, whereas the increased levels of PLA2R-Ab2 coincided with the worsening of proteinuria. In summary, our data support that an integrated folding of the three PLA2R N-terminal domains, CysR, FnII, and CTLD1, is a prerequisite to forming the PLA2R conformational epitope and that the dominant epitope-reactive PLA2R-Ab2 plays a critical role in PMN clinical progression.

Treatment preferences for primary membranous nephropathy: Results of a multinational survey among nephrologists in the South Asia Pacific region.

AIM: There is no clear consensus on how best to treat primary membranous nephropathy (PMN). This study aimed to ascertain prevailing views among nephrologists on their choice of immunosuppressive agents to treat this disease. METHODS: The Australasian Kidney Trials Network conducted a multinational online survey among nephrologists from the South Asia-Pacific region to identify prescribing practices to treat PMN. Survey questions focused on the types of immunosuppressive therapies used, preferred first-line and second-line therapies, indications for starting immunosuppressive therapy, the preferred mode of combining corticosteroid and cyclophosphamide, the use of serum phospholipase A2 receptor antibody testing in clinical practice, indications for anticoagulation, and interest in participating in future clinical trials in PMN. RESULTS: One hundered fifty-five nephrologists from eight countries responded to the online survey. The majority of them were senior nephrologists from Australia and India with significant experience managing patients with PMN. The combination of cyclophosphamide and corticosteroid was the preferred first-line therapy. Of those who used this combination, only 34.8% followed the Kidney Disease Improving Global Outcomes (KDIGO) 2012 guidelines by adding intravenous methylprednisolone. The combination of calcineurin inhibitor with corticosteroid was the most common second-line therapy. Most respondents considered prophylactic anticoagulation if serum albumin was less than 25 g/L. Most nephrologists were keen to participate in a clinical trial with a control arm consisting of cyclophosphamide and corticosteroids. CONCLUSION: The combination of corticosteroid with cyclophosphamide (without intravenous methylprednisolone) is the most commonly reported first-line immunosuppressive therapy for the management of PMN.

Peptide GAM immunoadsorption in anti-PLA2 R positive autoimmune membranous nephropathy. The PRISM trial.

Membranous nephropathy associated with anti-PLA2 R autoantibody is a significant cause of nephrotic syndrome worldwide. Treatment remains empiric with a significant side-effect burden despite an increase in our understanding of the disease. We studied the effect of selectively removing this pathogenic autoantibody using immunoadsorption in adult patients with biopsy proven anti-PLA2 R membranous nephropathy. This was a multicenter, single-arm prospective clinical trial carried out in the United Kingdom. Twelve patients underwent five consecutive sessions of peptide GAM immunoadsorption with 12 months follow-up. Primary outcome was anti-PLA2 R titer at week 2. Secondary outcomes were safety and tolerability of therapy, antibody profile, and change in proteinuria, renal excretory function, serum albumin, total immunoglobulin, and quality of life at weeks 12, 24, and 52. Patients were also stratified by the presence or absence of the high-risk allele (heterozygous or homozygous for HLA-DQA1*05). Median pretreatment anti-PLA2 R was 702.50 U/mL, 1045.00 U/mL at week 2 (P-value .023) and 165.00 U/mL at week 52 (P-value .017). The treatment was well tolerated and safe. Two patients required rescue immunosuppression during the follow-up period. There was a significant improvement in serum albumin with a median at baseline of 20.50 g/L rising to 25.00 g/L at week 52 (P-value <.001). There was no statistical difference over the follow-up period in proteinuria or renal function. Patients in possession of a high-risk allele saw improvement in anti-PLA2 R titers, possibly representing a cohort more likely to benefit from immunoadsorption. Immunoadsorption therapy is a safe treatment and well-tolerated treatment in anti-PLA2 R positive autoimmune membranous nephropathy.

Immune-mediated membranous nephropathy: Long term fluconazole usage caused podocyte autophagy.

The primary consequences of membranous nephropathy (MN) are the development of nephrotic syndrome including hypogammaglobulinemia, the increased infectious risk, the loss of protein-bound vitamin D, and, above all, an elevated thromboembolic incidence of up to 50% in severe proteinuria patients. Membrane nephropathy may be either idiopathic or primary, not recognized (70%-80%) or secondary (20%-30%) to pathological sicknesses such as hepatitis B, systemic lupus erythematosus, malignancies, and side-effects of medicines. The immunological responses in MN involve multiple components: immunoglobulin G (IgG), long-escaped antigens, and the membrane attachment complex, formed by the supplement to form C5b-9. In general, IgG4 is the most significant IgG subclass deposited in idiopathic membranous nephropathic disease but fluctuating IgG1 levels also are linked with immunological deposits. In contrast, IgG1, IgG2, and IgG3 deposition are greater than IgG4 deposition in secondary nephropathy. Fluconazole is a synthetic antifungal triazole that is often used. It is well tolerated in general and has never been identified as a cause of nephropathies. We report on the development of MN caused by fluconazole therapy that could potentiate podocyte autophagy.

How Times Have Changed! A Cornucopia of Antigens for Membranous Nephropathy.

The identification of the major target antigen phospholipase A2 receptor (PLA2R) in the majority of primary (idiopathic) cases of membranous nephropathy (MN) has been followed by the rapid identification of numerous minor antigens that appear to define phenotypically distinct forms of disease. This article serves to review all the known antigens that have been shown to localize to subepithelial deposits in MN, as well as the distinctive characteristics associated with each subtype of MN. We will also shed light on the novel proteomic approaches that have allowed identification of the most recent antigens. The paradigm of an antigen normally expressed on the podocyte cell surface leading to in-situ immune complex formation, complement activation, and subsequent podocyte injury will be discussed and challenged in light of the current repertoire of multiple MN antigens. Since disease phenotypes associated with each individual target antigens can often blur the distinction between primary and secondary disease, we encourage the use of antigen-based classification of membranous nephropathy.

B Cells in Primary Membranous Nephropathy: Escape from Immune Tolerance and Implications for Patient Management.

Membranous nephropathy (MN) is an important cause of nephrotic syndrome and chronic kidney disease (CKD) in adults. The pathogenic significance of B cells in MN is increasingly recognized, especially following the discovery of various autoantibodies that target specific podocytic antigens and the promising treatment responses seen with B cell depleting therapies. The presence of autoreactive B cells and autoantibodies that bind to antigens on podocyte surfaces are characteristic features of MN, and are the result of breaches in central and peripheral tolerance of B lymphocytes. These perturbations in B cell tolerance include altered B lymphocyte subsets, dysregulation of genes that govern immunoglobulin production, aberrant somatic hypermutation and co-stimulatory signalling, abnormal expression of B cell-related cytokines, and increased B cell infiltrates and organized tertiary lymphoid structures within the kidneys. An understanding of the role of B cell tolerance and homeostasis may have important implications for patient management in MN, as conventional immunosuppressive treatments and novel B cell-targeted therapies show distinct effects on proliferation, differentiation and reconstitution in different B cell subsets. Circulating B lymphocytes and related cytokines may serve as potential biomarkers for treatment selection, monitoring of therapeutic response and prediction of disease relapse. These recent advances in the understanding of B cell tolerance in MN have provided greater insight into its immunopathogenesis and potential novel strategies for disease monitoring and treatment.

Rituximab Immunomonitoring Predicts Remission in Membranous Nephropathy.

Primary membranous nephropathy (pMN) is an autoimmune kidney disease and a common cause of nephrotic syndrome in adults. Rituximab is becoming a first line therapy for patients with persistent nephrotic syndrome with proven safety and efficacy, achieving remission in 60%-80% of cases. For the remaining 20%-40% of patients there is an urgent need to identify early biomarkers of resistance to rituximab to adapt therapeutic management. In nephrotic patients, rituximab is found in the blood more transiently than in other autoimmune diseases without proteinuria, due to rituximab wasting in the urine. However, rituximab immunomonitoring is not routinely performed. We evaluated the predictive value of serum rituximab levels in patients with pMN three months after rituximab injection (month-3) on clinical remission rates six months (month-6) and 12 months (month-12) after injection and investigated predictive factors for serum rituximab levels at month-3. Sixty-eight patients treated with rituximab between July 2015 and January 2020 from two French nephrology centers were included. We identified residual rituximab levels at month-3 as a novel early predictor of remission at month-6 (p <0.0001) and month-12 (p = 0.001). Reduced likelihood of remission in patients with undetectable rituximab at month-3 was associated with lower serum albumin and higher anti-PLA2R1 titers at baseline and with lower serum albumin, higher proteinuria, higher CD19+ counts and higher anti-PLA2R1 titers during follow-up. In multivariate analysis, high baseline proteinuria and undetectable rituximab levels at month-3 were independent risk factors for treatment failure at month-6 and high baseline weight and undetectable rituximab levels at month-3 were independent risk factors for treatment failure at month-12. We identified serum albumin at baseline as a predictive factor for serum rituximab levels at month-3. Patients with serum albumin below 22.5 g/L at baseline had an 8.66-fold higher risk of having undetectable rituximab levels at month-3. Therefore, rituximab immunomonitoring in pMN patients treated with rituximab would allow the detection of patients at risk of treatment failure as early as month-3. Studies are needed to assess whether patients with low residual rituximab levels at month-3 may benefit from an early additional course of rituximab.

Characteristics of Anti-Contactin1 Antibody-Associated Autoimmune Nodopathies With Concomitant Membranous Nephropathy.

Background: The concurrence of anti-contactin 1 (CNTN1) antibody-associated chronic inflammatory demyelinating polyneuropathy (CIDP) and membranous nephropathy (MN) has previously been reported in the literature. CIDP with autoantibodies against paranodal proteins are defined as autoimmune nodopathies (AN) in the latest research. In view of the unclear relationship between CIDP and MN, we performed a case study and literature review to investigate the clinical characteristics of anti-CNTN antibody-associated AN with MN. Methods: We detected antibodies against NF155, NF186, CNTN1, CNTN2, CASPR1 and PLA2R in blood samples of a patient with clinically manifested MN and concomitant peripheral neuropathy via double immunofluorescence staining and conducted a quantitative measurement of anti-PLA2R IgG antibodies via enzyme-linked immunosorbent assay (ELISA). Case reports of anti-CNTN1 antibody-associated AN, anti-CNTN1 antibody-associated AN with MN, and CIDP with MN were retrieved through a literature search for a comparative analysis of clinical characteristics. The cases were grouped according to the chronological order of CIDP and MN onset for the comparison of clinical characteristics. Results: A 57-year-old man with anti-PLA2R positive MN was admitted to the hospital due to limb numbness, weakness, and proprioceptive sensory disorder. He was diagnosed with anti-CNTN1 antibody-associated AN and recovered well after immunotherapy. Our literature search returned 22 cases of CIDP with MN that occurred before, after, or concurrently with CIDP. Good responses were achieved with early single-agent or combination immunotherapy, but eight out of the 22 patients with CIDP and concomitant MN ultimately developed different motor sequelae. Five patients had anti-CNTN1 antibody-associated AN with MN. Among these patients, males accounted for the majority of cases (male:female=4:1), the mean age at onset was late (60.2 ± 15.7 years, range 43-78 years), and 40% had acute to subacute onset. Clinical manifestations included sensory-motor neuropathy, sensory ataxia caused by proprioceptive impairment, and elevated cerebrospinal fluid protein levels. Conclusion: The age at onset of CIDP with MN was earlier than that of anti-CNTN1 antibody-associated AN. MN may occur before, after or concurrently with CIDP. The early detection and isotyping of anti-CNTN1 and anti-PLA2R antibodies and the monitoring of isotype switching may be essential for suspected CIDP patients.