Correlation between B Lymphocyte Abnormality and Disease Activity in Patients with Idiopathic Membranous Nephropathy

Integrative profiling of untreated primary membranous nephropathy at the single-cell transcriptome level

Background

Primary membranous nephropathy (PMN) is an autoimmune kidney disease. Despite the identification of certain autoantigens, the etiology and pathophysiology of PMN are still largely unknown.

Methods

Five patients with biopsy-proven PMN were enrolled in this study. Their blood, kidney and urine samples were collected respectively to profile cellular, molecular and immunological alterations by using single-cell RNA sequencing (scRNA-seq). Experimental verifications were also implemented in kidney tissue.

Results

In the peripheral blood mononuclear cell (PBMC) samples, portions of B cells and plasma cells were increased in PMN patients. Cell-cell communication analysis suggests that APRIL (a proliferation-inducing ligand from B cells) might be a potential molecule that regulates the activity of plasma cells. In the kidney samples, scRNA-seq analysis showed that the infiltration of T cells, as well as the myeloid cells, appears abundant compared with healthy controls, suggesting that immune cells are actively recruited to kidney. Furthermore, we observed an enhanced interaction between inflammatory cells and podocytes, which might contribute to kidney injury. Accordingly, scRNA-seq analysis of urinary samples is partially reminiscent of the kidney cell landscape, especially T cells and myeloid cells, suggesting monitoring urinary samples is a promising method to monitor PMN development. Additionally, integrative analysis across the blood, kidney and urine identified LTB, HERP1, ANXA1, IL1RN and ICAM1 as common regulators of PMN. Finally, immune repertoire in PBMC also showed an elevated diversity of clonal type, implying the existence of autoreactive T-cell receptor/B-cell receptor.

Conclusion

Our study comprehensively profiled the transcriptomic landscapes of blood, kidney and urine in patients with PMN using scRNA-seq. We depicted the alterations including cell compositions and cell-cell communication in PMN. These results offer important clues with regard to the diagnosis and pathogenesis of PMN and potential intervention of PMN progression.

Rituximab may affect T lymphocyte subsets balance in primary membranous nephropathy

BACKGROUND

The aim of this study was to investigate the effects and significance of rituximab (RTX) on the levels of T lymphocyte subsets in patients diagnosed with primary membranous nephropathy (PMN).

METHODS

A total of 58 PMN patients and 25 healthy donors were chosen as the subjects. Among the PMN patients, 40 individuals received RTX treatment and completed at least 6 months of follow-up. All subjects underwent flow cytometry analysis to determine the peripheral blood lymphocyte subsets. The changes in anti-PLA2R antibody titers and 24-hour urinary protein levels were evaluated by ELISA and Biuret method before and after treatment.

RESULTS

(1) The PMN group exhibited a significantly greater percentage of peripheral blood CD3-CD19+ B cells than the healthy group, which is consistent with the findings of previous reports. Additionally, compared with those in the peripheral blood of healthy individuals, the numbers of CD4+ central memory T cells, CD4+ effector memory T cells, CD4+/CD8+, and CD4+CD25+ T cells in the PMN peripheral blood were markedly greater. However, the number of peripheral blood Treg cells was reduced in the PMN group. (2) After 6 months of RTX treatment, PMN patients exhibited significant decreases in anti-PLA2R antibody titers, 24-hour urinary protein levels, and peripheral blood CD3-CD19+ B cells. Importantly, RTX administration decreased CD4+CD25+ T cells and CD4+/CD8+ in the peripheral blood of PMN patients and improved Treg cell levels. (3) RTX treatment induced alterations in the CD4+ T lymphocyte subsets in PMN patients, which did not correlate with B lymphocyte counts or anti-PLA2R antibody titers.

CONCLUSIONS

RTX treatment might have a beneficial impact on cellular immunity by effectively restoring the balance of CD4+ T lymphocyte subsets in PMN patients, which is beyond its effects on B cells and antibody production.

TRIAL REGISTRATION

The research was registered at the First Affiliated Hospital of Soochow University.

REGISTRATION NUMBER

MR-32-23-016211. Registration Date: May 31, 2023.

Identification of hub genes and their correlation with immune infiltrating cells in membranous nephropathy: an integrated bioinformatics analysis

BACKGROUND

Membranous nephropathy (MN) is a chronic glomerular disease that leads to nephrotic syndrome in adults. The aim of this study was to identify novel biomarkers and immune-related mechanisms in the progression of MN through an integrated bioinformatics approach.

METHODS

The microarray data were downloaded from the Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) between MN and normal samples were identified and analyzed by the Gene Ontology analysis, the Kyoto Encyclopedia of Genes and Genomes analysis and the Gene Set Enrichment Analysis (GSEA) enrichment. Hub The hub genes were screened and identified by the weighted gene co-expression network analysis (WGCNA) and the least absolute shrinkage and selection operator (LASSO) algorithm. The receiver operating characteristic (ROC) curves evaluated the diagnostic value of hub genes. The single-sample GSEA analyzed the infiltration degree of several immune cells and their correlation with the hub genes.

RESULTS

We identified a total of 574 DEGs. The enrichment analysis showed that metabolic and immune-related functions and pathways were significantly enriched. Four co-expression modules were obtained using WGCNA. The candidate signature genes were intersected with DEGs and then subjected to the LASSO analysis, obtaining a total of 6 hub genes. The ROC curves indicated that the hub genes were associated with a high diagnostic value. The CD4+ T cells, CD8+ T cells and B cells significantly infiltrated in MN samples and correlated with the hub genes.

CONCLUSIONS

We identified six hub genes (ZYX, CD151, N4BP2L2-IT2, TAPBP, FRAS1 and SCARNA9) as novel biomarkers for MN, providing potential targets for the diagnosis and treatment.

Membranous nephropathy: Clearer pathology and mechanisms identify potential strategies for treatment

Primary membranous nephropathy (PMN) is one of the common causes of adult-onset nephrotic syndrome and is characterized by autoantibodies against podocyte antigens causing in situ immune complex deposition. Much of our understanding of the disease mechanisms underpinning this kidney-limited autoimmune disease originally came from studies of Heymann nephritis, a rat model of PMN, where autoantibodies against megalin produced a similar disease phenotype though megalin is not implicated in human disease. In PMN, the major target antigen was identified to be M-type phospholipase A2 receptor 1 (PLA2R) in 2009. Further utilization of mass spectrometry on immunoprecipitated glomerular extracts and laser micro dissected glomeruli has allowed the rapid discovery of other antigens (thrombospondin type-1 domain-containing protein 7A, neural epidermal growth factor-like 1 protein, semaphorin 3B, protocadherin 7, high temperature requirement A serine peptidase 1, netrin G1) targeted by autoantibodies in PMN. Despite these major advances in our understanding of the pathophysiology of PMN, treatments remain non-specific, often ineffective, or toxic. In this review, we summarize our current understanding of the immune mechanisms driving PMN from animal models and clinical studies, and the implications on the development of future targeted therapeutic strategies.

Novel Biomarkers in Membranous Nephropathy

Membranous nephropathy (MN) is the main cause of adult nephrotic syndrome (NS). The pathogenesis of MN is complex and involves subepithelial immune complex deposition. Approximately one-third of patients with MN develop end-stage renal disease (ESRD). Timely diagnosis and reasonable intervention are the keys to improving prognosis. In recent years, with the development of high-throughput technologies, such as mass spectrometry (MS), microarray, and sequencing technologies, the discovery of biomarkers for MN has become an important area of research. In this review, we summarize the significant progress in biomarker identification. For example, a variety of podocyte target antigens and their autoantibodies have been reported. Phospholipase A2 receptor (PLA2R) is the most well-established target antigen in MN. PLA2R and its autoantibodies have clinical significance, with both diagnostic and therapeutic value for MN. In addition, a variety of new biomarkers, including proteins, metabolites, noncoding RNAs (ncRNAs), and immune cells, have recently been found. These MN-related biomarkers have great significance in the diagnosis, progression, prognosis, and treatment response of MN.

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.

Remissions in Patients with Idiopathic Membranous Nephropathy Treated with Rituximab in Senegal

Objectives: This study aimed to evaluate the efficacy of Rituximab in the management of idiopathic membranous nephropathy (IMN) based on the following criteria: (I) Biological remission at three months (M3) and six months (M6); (II) change in mean proteinuria (24PU), mean serum albumin, and mean serum creatinine at M3 and M6; (III) and side effects. Methods: This retrospective descriptive and analytical study included patients with histologically confirmed IMN with positive plasma anti-PLA2R antibodies who received at least one dose of Rituximab after six months of follow-up without spontaneous remission. Patients with unexplainable records were not included. Results: A total of five patients (P1, P2, P3, P4, and P5), including four males and one female were analyzed. The mean age was 44.20 ± 23.14 years. All patients had IMN type 2. At inclusion, the mean albuminemia, mean creatinine, and mean 24hPU levels were 15.56 ± 5.27 g/L, 17.3 ± 7.6 mg/L, and 6.54 ± 1.13 g/24h, respectively. The median anti-PLA2R antibody titer was 100 IU with extremes of 10 and 800 IU. Partial remission was noted in three patients at M3 (P2, P4, and P5), and it was maintained until M6 in P2. No complete remission was observed. A significant decrease in mean 24hPU at M3 was noted (P < 0.001). Generalized pruritus associated with seizures was noticed in P4 after the first dose of Rituximab. Conclusions: Partial remission was noted in three patients at M3, and one patient maintained this remission at M6. Rituximab significantly reduced 24hPU at M3 after administration. Rituximab administration was well tolerated by the patients.

Increased levels of circulating class-switched memory B cells and plasmablasts are associated with serum immunoglobulin G in primary focal segmental glomerulosclerosis patients

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) is a kidney-specific autoimmune disease, but its pathogenesis is not fully known. The present study detected the frequencies of circulating memory B cells and plasmablasts and other clinical parameters in FSGS.

METHODS

We monitored 16 primary FSGS patients and 23 healthy controls (HC). Flow cytometry was used to analyze circulating memory B cell and plasmablastspercentages. Serum IgG levels were detected using a cytometric bead array (CBA).

RESULTS

The proportions of CD27 + IgD- class-switched memory B cells (P = 0.0002), CD27 + IgD-IgG + class-switched memory B cells (P < 0.0001), CD27hiCD38hi plasmablasts (P < 0.0001) and CD138 + plasma cells (P < 0.0001) were markedlyelevated in FSGS patients, and the frequency of CD38 + IgG + plasmablasts (P < 0.0001) and serum IgG levels (P < 0.0001) were lower compared to HC. In the FSGS patients, the frequency of CD27 + IgD-IgG + class-switched memory B cells negatively correlated with CD38 + IgG + plasmablasts (P = 0.0183, R = -0.3375), serum IgG levels (P = 0.0061, R = -0.4263) and estimated glomerular filtration rate (eGFR) (P = 0.0074, R = -0.4114) but positively correlated with 24-h urinary protein levels (P = 0.0077, R = 0.4085). The proportion of CD38 + IgG + plasmablasts positively correlated with serum IgG levels (P = 0.0151, R = 0.3538).

CONCLUSIONS

We speculate that alterations in the frequencies of CD27 + IgD-IgG + class-switched memory B cells and plasmablasts may be responsible for the etiopathogenesis of FSGS.

Helper T Cells in Idiopathic Membranous Nephropathy

Idiopathic membranous nephropathy (IMN) is an autoimmune disease in which the immune system produces an antibody response to its own antigens due to impaired immune tolerance. Although antibodies are derived from plasma cells differentiated by B cells, the T-B cells also contribute a lot to the immune system. In particular, the subsets of helper T (Th) cells, including the dominant subsets such as Th2, Th17, and follicular helper T (Tfh) cells and the inferior subsets such as regulatory T (Treg) cells, shape the immune imbalance of IMN and promote the incidence and development of autoimmune responses. After reviewing the physiological knowledge of various subpopulations of Th cells and combining the existing studies on Th cells in IMN, the role model of Th cells in IMN was explained in this review. Finally, the existing clinical treatment regimens for IMN were reviewed, and the importance of the therapy for Th cells was highlighted.

The Potential Role of Regulatory B Cells in Idiopathic Membranous Nephropathy

Regulatory B cells (Breg) are widely regarded as immunomodulatory cells which play an immunosuppressive role. Breg inhibits pathological autoimmune response by secreting interleukin-10 (IL-10), transforming growth factor-β (TGF-β), and adenosine and through other ways to prevent T cells and other immune cells from expanding. Recent studies have shown that different inflammatory environments induce different types of Breg cells, and these different Breg cells have different functions. For example, Br1 cells can secrete IgG4 to block autoantigens. Idiopathic membranous nephropathy (IMN) is an autoimmune disease in which the humoral immune response is dominant and the cellular immune response is impaired. However, only a handful of studies have been done on the role of Bregs in this regard. In this review, we provide a brief overview of the types and functions of Breg found in human body, as well as the abnormal pathological and immunological phenomena in IMN, and propose the hypothesis that Breg is activated in IMN patients and the proportion of Br1 can be increased. Our review aims at highlighting the correlation between Breg and IMN and proposes potential mechanisms, which can provide a new direction for the discovery of the pathogenesis of IMN, thus providing a new strategy for the prevention and early treatment of IMN.

Advances in Pathogenesis of Idiopathic Membranous Nephropathy

BACKGROUND

Membranous nephropathy (MN), a major cause of nephrotic syndrome, has attracted people's attention in recent years for its growing prevalence. It is the second or third leading cause of ESRD in patients with primary glomerulonephritis and is the leading glomerulopathy that recurs after kidney transplantation.

SUMMARY

MN can be classified as idiopathic membranous nephropathy (IMN) and secondary MN. The discovery of the M-type phospholipase A2 receptor (PLA2R) and thrombospondin type-1 domain-containing 7A (THSD7A) provides the new diagnostic methods and treatment strategies for IMN on the molecular level. The study on single nucleotide polymorphism of IMN genes, such as the single M-type phospholipase A2 receptor 1 (PLA2R1) gene and human leukocyte antigen (HLA) gene, explains the pathogenesis of the disease from the perspective of genetics and conforms to the trend of the era of precision medicine.

KEY MESSAGES

This review focuses on advances in the pathogenesis of IMN, including molecular and genetic pathogenesis, as well as discussing the diagnostic and treatment guiding value brought by these new discoveries.

Myeloid-Derived Suppressor Cells Promote the Progression of Primary Membranous Nephropathy by Enhancing Th17 Response

Several studies have confirmed that the myeloid-derived suppressor cells (MDSCs) are closely associated with autoimmune diseases, but their exact role in these processes remains largely unclear. Here, we investigated the role MDSCs in patients with primary membranous nephropathy (PMN). Compared to healthy controls (HCs), PMN patients showed significantly increased number of HLA-DR^-CD11b⁺CD33⁺ MDSCs in the peripheral blood, including both CD14⁺CD66b^- monocytic and CD14^-CD66b⁺ granulocytic MDSCs. The frequency of MDSCs was positively correlated with the level of serum anti-phospholipase A2 receptor (anti-PLA2R), 24-h urine protein quantification, and disease activity in PMN patients. Consistently, enhanced T helper 2 (Th2) and T helper 17 (Th17) immune responses were positively associated with plasma anti-PLA2R levels, 24-h urine protein quantification, and the disease activity in PMN patients. Moreover, compared to HCs, MDSCs from PMN patients exhibited significantly elevated arginase-1 (ARG-1) production and increased potential to promote Th17 differentiation in vitro in an ARG-1-dependent manner. This study directly demonstrates a pathogenic role for MDSCs in human PMN and provides a molecular mechanism for the pathogenesis of PMN. Our data show that MDSCs may promote PMN disease progression mainly by enhancing Th17 response. Therefore, MDSCs may be an important diagnostic, therapeutic, and prognostic marker for PMN diseases.

A Comprehensive Phenotypic and Functional Immune Analysis Unravels Circulating Anti-Phospholipase A2 Receptor Antibody Secreting Cells in Membranous Nephropathy Patients

Introduction

Primary membranous nephropathy (MN) is characterized by the presence of antipodocyte antibodies, but studies describing phenotypic and functional abnormalities in circulating lymphocytes are limited.

Methods

We analyzed 68 different B- and T-cell subsets using flow cytometry in 30 MN patients (before initiating immunosuppression) compared with 31 patients with non–immune-mediated chronic kidney disease (CKD) and 12 healthy individuals. We also measured 19 serum cytokines in MN patients and in healthy controls. Lastly, we quantified the ex vivo production of phospholipase A2 receptor (PLA2R)-specific IgG by plasmablasts (measuring antibodies in culture supernatants and by the newly developed FluoroSpot assay [AutoImmun Diagnostika, Strasberg, Germany]) and assessed the circulating antibody repertoire by phage immunoprecipitation sequencing (PhIP-Seq).

Results

After adjusting for multiple testing, plasma cells and regulatory B cells (B_REG) were significantly higher (P < 0.05) in MN patients compared with both control groups. The percentages of circulating plasma cells correlated with serum anti-PLA2R antibody levels (P = 0.042) and were associated with disease activity. Ex vivo–expanded PLA2R-specific IgG-producing plasmablasts generated from circulating PLA2R-specific memory B cells (mBCs) correlated with serum anti-PLA2R IgG antibodies (P < 0.001) in MN patients. Tumor necrosis factor-α (TNF-α) was the only significantly increased cytokine in MN patients (P < 0.05), whereas there was no significant difference across study groups in the autoantibody and antiviral antibody repertoire.

Conclusion

This extensive phenotypic and functional immune characterization shows that autoreactive plasma cells are present in the circulation of MN patients, providing a new therapeutic target and a candidate biomarker of disease activity.

Regulatory B Cells Are Reduced and Correlate With Disease Activity in Primary Membranous Nephropathy

Introduction

Primary membranous nephropathy (PMN) is an autoimmune disease. Both T-regulatory cells (TREGs) and B-regulatory cells (BREGs) are decreased in patients with autoimmune disease. We evaluated the TREG and BREG population in patients of PMN treated with cyclical cyclophosphamide and steroid therapy (cCYC/GC).

Methods

Twenty-four patients with PMN resistant to a restrictive strategy and treated with cCYC/GC therapy and 10 healthy controls were enrolled. The proteinuria, serum creatinine, and serum albumin were tested at monthly intervals and blood samples were collected before starting cCYC/GC and at 6 and 8 (2 months wash out) months of therapy. The peripheral blood mononuclear cells (PBMCs) after staining with fluorochrome-conjugated antibodies were then subjected to flow cytometric analysis for detection of TREGs (CD3+CD4+CD25hiCD127loFoxP3+) and BREGs (CD19+CD5+CD1dhiIL10+). TREGs and BREGs are presented as the percentage of T and B cells, respectively. Cases with remission at month 18 were classified as responders, and those without any remission as nonresponders.

Results

Patients with PMN had a lower percentage of TREGs (P = 0.07) and BREGs compared with healthy controls (P = 0.0007). As compared with baseline, there was a significant increase in both BREGs (P = 0.001) and TREGs (P = 0.02) with the treatment (8 months). Patients who responded to therapy by 18 months had an increase in TREG (P = 0.05) and BREG (P = 0.0001) at month 8 compared with baseline.

Conclusion

As compared with healthy controls, patients with PMN displayed a lower percentage of BREGs. Both TREGs and BREGs significantly improved with disease-specific therapy. BREGs had an association with clinical activity.

The Landscape and Prognosis Potential of the T-Cell Repertoire in Membranous Nephropathy

Membranous nephropathy (MN), a common pathological type of adult nephrotic syndrome, is an antibody-mediated kidney disease. It is widely accepted now that MN is an immune-related disease that involves the whole immune system. In this study, we analyzed the T-cell receptor beta chain (TCRβ) repertoire of the circulating T lymphocytes of MN patients and healthy controls using high-throughput sequencing. We compared multiple aspects of the TCRβ repertoire, including diversity and the Vβ and Jβ genes between MN patients and healthy controls, and we found that the diversities within the VJ cassette combination in the peripheral blood of MN patients were lower than in the healthy controls. We also found the TCRβ repertoire similarity between pre- and post-therapy could reflect the clinical outcome, and two Vβ genes in pre-therapy had the potential to predict the therapeutic effect. These findings indicated the potential of the TCRβ repertoire as non-invasive biomarkers for the prognosis prediction of MN. The characteristics of circulating T-lymphocyte repertoires shed light on MN detection, treatment, and surveillance.

Immune-Monitoring Disease Activity in Primary Membranous Nephropathy

Primary membranous nephropathy (MN) is a glomerular disease mediated by autoreactive antibodies, being the main cause of nephrotic syndrome among adult patients. While the pathogenesis of MN is still controversial, the detection of autoantibodies against two specific glomerular antigens, phospholipase A2 receptor (PLA₂R) and thrombospondin type 1 domain containing 7A (THSD7A), together with the beneficial effect of therapies targeting B cells, have highlighted the main role of autoreactive B cells driving this renal disease. In fact, the detection of PLA₂R-specific IgG4 antibodies has resulted in a paradigm shift regarding the diagnosis as well as a better prediction of the progression and recurrence of primary MN. Nevertheless, some patients do not show remission of the nephrotic syndrome or do rapidly recur after immunosuppression withdrawal, regardless the absence of detectable anti-PLA₂R antibodies, thus highlighting the need of other immune biomarkers for MN risk-stratification. Notably, the exclusive evaluation of circulating antibodies may significantly underestimate the magnitude of the global humoral memory immune response since it may exclude the role of antigen-specific memory B cells. Therefore, the assessment of PLA₂R-specific B-cell immune responses using novel technologies in a functional manner may provide novel insight on the pathogenic mechanisms of B cells triggering MN as well as refine current immune-risk stratification solely based on circulating autoantibodies.

Calcineurin B1 subunit in human peripheral blood mononuclear cells and its role in idiopathic membranous nephropathy

The immune responses involved in the pathogenesis of idiopathic membranous nephropathy (IMN) have not been fully understood. Calcineurin, a key signaling enzyme in T-cell activation, may be implicated in IMN. The present study aimed to investigate the role of calcineurin B1 subunit (CnB1) in IMN and the potential mechanism.A total of 59 biopsy-proven IMN patients and 28 healthy controls were recruited. The CnB1 expression in human peripheral blood mononuclear cells (PBMCs) was assessed by Western blotting. Knockdown and overexpression of CnB1 in Jurkat T cell line were achieved by small interference RNA (siRNA) transfection and lentiviral transduction, respectively.It was found that PBMCs CnB1 expression was significantly increased in IMN patients (P = .002), but unrelated to the severity and prognosis of IMN. Knockdown of CnB1 in Jurkat cells inhibited the nuclear factor of activated T cells (NFAT)-regulated gene expression required for T-cell activation.Our study suggested the potential role of CnB1 in the occurrence of IMN. The mechanism maybe involved the effect of CnB1 on the T-cell activation mediated by calcineurin-NFAT signaling.

Regulatory T cells in renal disease

The kidney is vulnerable to injury, both acute and chronic from a variety of immune and metabolic insults, all of which at least to some degree involve inflammation. Regulatory T cells modulate systemic autoimmune and allogenic responses in glomerulonephritis and transplantation. Intrarenal regulatory T cells (Tregs), including those recruited to the kidney, have suppressive effects on both adaptive and innate immune cells, and probably also intrinsic kidney cells. Evidence from autoimmune glomerulonephritis implicates antigen-specific Tregs in HLA-mediated dominant protection, while in several human renal diseases Tregs are abnormal in number or phenotype. Experimentally, Tregs can protect the kidney from injury in a variety of renal diseases. Mechanisms of Treg recruitment to the kidney include via the chemokine receptors CCR6 and CXCR3 and potentially, at least in innate injury TLR9. The effects of Tregs may be context dependent, with evidence for roles for immunoregulatory roles both for endogenous Tbet-expressing Tregs and STAT-3-expressing Tregs in experimental glomerulonephritis. Most experimental work and some of the ongoing human trials in renal transplantation have focussed on unfractionated thymically derived Tregs (tTregs). However, induced Tregs (iTregs), type 1 regulatory T (Tr1) cells and in particular antigen-specific Tregs also have therapeutic potential not only in renal transplantation, but also in other kidney diseases.

A comprehensive narrative review of diagnostic biomarkers in human primary membranous nephropathy

Membranous nephropathy (MN) is relatively major cause of nephrotic syndrome in adults which is recognized as an organ-specific autoimmune disease. The etiology of most cases is idiopathic, whereas the secondary MN is caused by systemic autoimmune diseases, infections, medications and malignancies. The idiopathic disease is developed by the formation of sub-epithelial immune complex deposits most likely due to binding the circulating auto-antibodies to intrinsic antigen on podocytes. The major auto antibody is the anti-phospholipase A2 receptor (anti-PLA2R), however, it is not enough sensitive. Several attempts for diagnostic biomarker identification by modern analytical technologies have been devoted recently. This article reviews the biomarker candidates for primary type of MN that are detected by different approaches on human subjects.

Pathophysiological advances in membranous nephropathy: time for a shift in patient's care

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.