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

Malignancy-associated membranous nephropathy: focus on diagnosis and treatment

BACKGROUND

The clinicopathological features of malignancy-associated membranous nephropathy have been described previously, but information about diagnosis and treatment remains limited.

METHODS

Patients with malignancy-associated membranous nephropathy in a tertiary hospital in China between June 2012 and October 2021 were retrospectively reviewed.

RESULTS

Forty-two patients with malignancy-associated membranous nephropathy were identified. Compared to patients with idiopathic membranous nephropathy, patients with malignancy-associated membranous nephropathy were older and less frequently showed glomerular phospholipase A2 receptor staining (37.9% vs 85.0%) and IgG4 predominant deposition (66.7% vs 95.0%). At diagnosis of membranous nephropathy, the malignancy was unknown in 67% (28/42) of patients and was detected only by tumor screening. Among the 19 patients with concurrent diagnosis of cancer and biopsy-proven membranous nephropathy, 15 received anticancer treatment alone initially. Six of the 10 patients who attained cancer remission achieved remission of membranous nephropathy, while none of the 5 patients without remission of cancer did, suggesting a causal relationship between the two diseases. Some patients with persistent or relapsing membranous nephropathy following cancer remission achieved remission of membranous nephropathy after immunosuppressive therapy. Over a median follow-up of 24 months, 25% (10/40) of patients died, mainly due to neoplasia.

CONCLUSIONS

Tumor screening is important in patients with membranous nephropathy, especially in elderly patients and patients with negative phospholipase A2 receptor or non-IgG4 predominant deposition. Remission of membranous nephropathy can be observed following remission of cancer in some cases. Immunosuppressive therapy may be considered if membranous nephropathy does not remit after remission of cancer.

The value of PLA2R antigen and IgG subclass staining relative to anti-PLA2R seropositivity in the differential diagnosis of membranous nephropathy

BACKGROUND

The diagnostic performance of PLA2R and IgG subclass staining of kidney biopsies relative to anti-PLA2R seropositivity in the differentiation of primary and secondary membranous nephropathy (pMN, sMN) was examined. Besides PLA2R staining - which has a lower specificity than anti-PLA2R antibody serology - there is insufficient knowledge to decide which IgG1-4 subtype immunohistological patterns (IgG4-dominance, IgG4-dominance/IgG1-IgG4-codominance or IgG4-dominance/IgG4-codominance with any IgG subtype) could be used to distinguish between pMN and sMN.

METHODS

87 consecutive Hungarian patients (84 Caucasians, 3 Romas) with the biopsy diagnosis of MN were classified clinically as pMN (n = 63) or sMN (n = 24). The PLA2R and IgG subclass staining was part of the diagnostic protocol. Anti-PLA2R antibodies were determined by an indirect immunofluorescence test in 74 patients with disease activity.

RESULTS

For pMN, the sensitivity of anti-PLA2R seropositivity was 61.1%, and the specificity was 90.0%; and similar values for PLA2R staining were 81.0%, and 66.7%, respectively. In all stages of pMN, IgG4-dominance was the dominant subclass pattern, while the second most frequent was IgG3/IgG4-codominance. The sensitivity and specificity scores were: IgG4-dominance 52.2% and 91.7%, IgG4-dominance/IgG3-IgG4-codominance 76.2% and 87.5%, IgG4-dominance/IgG1-IgG4-codominance 64.2% and 75%, and IgG4-dominance/codominance with any IgG subclass 92.1% and 70.8%, respectively. Anti-PLA2R seropositivity, glomerular PLA2R, and IgG4-dominance/codominance significantly correlated with each other. The IgG4 subclass was rarely encountered in sMN.

CONCLUSION

In our series, IgG4-dominance had the highest specificity in the differentiation of MN, just as high as that for anti-PLA2R seropositivity. The specificity values of PLA2R staining and IgG4-dominance/codominance with any IgG subclass or IgG4-dominance/IgG1-IgG4 codominance were ≤ 75%. Apart from IgG4 dominance, IgG4-dominance/IgG3-IgG4-codominance also had good statistical value in differentiating pMN from sMN. As IgG subclass switching during the progression of pMN was not the feature of our cohort, pMN in Hungarian patients is presumed to be an IgG4-related disorder right from the start. Although anti-PLA2R seropositivity has become the cornerstone for diagnosing pMN, if a kidney biopsy evaluation is conducted, besides the staining of PLA2R antigen, the evaluation of IgG subclasses provides relevant information for a differential diagnosis. Even in cases with IgG4-dominance, however, malignancy should be thoroughly checked.

Membranous nephropathy: Systems biology-based novel mechanism and traditional Chinese medicine therapy

Membranous nephropathy (MN) is a renal-limited non-inflammatory autoimmune disease in the glomerulus, which is the second or third main cause of end-stage kidney diseases in patients with primary glomerulonephritis. Substantial achievements have increased our understanding of the aetiology and pathogenesis of murine and human MN. The identification of nephritogenic autoantibodies against neutral endopeptidase, phospholipase A₂ receptor (PLA₂R) and thrombospondin type-1 domain-containing 7A (THSD7A) antigens provide more specific concept-driven intervention strategies for treatments by specific B cell-targeting monoclonal antibodies to inhibit antibody production and antibody-antigen immune complex deposition. Furthermore, additional antibody specificities for antigens have been discovered, but their pathogenic effects are uncertain. Although anti-PLA₂R and anti-THSD7A antibodies as a diagnostic marker is widely used in MN patients, many questions including autoimmune response development, antigenic epitopes, and podocyte damage signalling pathways remain unresolved. This review describes the current available evidence regarding both established and novel molecular mechanisms based on systems biology approaches (gut microbiota, long non-coding RNAs, metabolite biomarkers and DNA methylation) in MN, with an emphasis on clinical findings. This review further summarizes the applications of traditional Chinese medicines such as Tripterygium wilfordii and Astragalus membranaceus for MN treatment. Lastly, this review considers how the identification of novel antibodies/antigens and unresolved questions and future challenges reveal the pathogenesis of MN.

Folic acid-induced animal model of kidney disease

The kidneys are a vital organ that is vulnerable to both acute kidney injury (AKI) and chronic kidney disease (CKD) which can be caused by numerous risk factors such as ischemia, sepsis, drug toxicity and drug overdose, exposure to heavy metals, and diabetes. In spite of the advances in our understanding of the pathogenesis of AKI and CKD as well AKI transition to CKD, there is still no available therapeutics that can be used to combat kidney disease effectively, highlighting an urgent need to further study the pathological mechanisms underlying AKI, CKD, and AKI progression to CKD. In this regard, animal models of kidney disease are indispensable. This article reviews a widely used animal model of kidney disease, which is induced by folic acid (FA). While a low dose of FA is nutritionally beneficial, a high dose of FA is very toxic to the kidneys. Following a brief description of the procedure for disease induction by FA, major mechanisms of FA-induced kidney injury are then reviewed, including oxidative stress, mitochondrial abnormalities such as impaired bioenergetics and mitophagy, ferroptosis, pyroptosis, and increased expression of fibroblast growth factor 23 (FGF23). Finally, application of this FA-induced kidney disease model as a platform for testing the efficacy of a variety of therapeutic approaches is also discussed. Given that this animal model is simple to create and is reproducible, it should remain useful for both studying the pathological mechanisms of kidney disease and identifying therapeutic targets to fight kidney disease.

Comparison of 3 anti-PLA2R inmmunoassaysfor the diagnosis of idiopathic membranous nephropathy in an european population. A pilot study

Membranous nephropathy (MN) is one of the most frequent causes of nephrotic syndrome. Renal biopsy is nowadays the gold standard for the diagnosis of MN. The presence of circulating PLA2R antibody is a very specific tool for the diagnosis of this disease, especially associated with primary or idiopathic MN (IMN), even though it can be also found in a small proportion of patients with secondary MN (SMN). This pilot study compares three different techniques for the detection of anti-PLA2R autoantibodies (immunofluorescence, ELISA immunoassay, and multiplex laser bead technology). Serum of 12 IMN and 9 SMN patients was obtained at diagnosis. Additionally, we employed serum samples of 15 healthy volunteers. From our patient cohort, we obtained a 7.75 RU/ml cut-off for the ELISA and 3104 MFI for the Luminex assays. The agreement between the three techniques improved considerably when applying the new cut-off points. As several authors have suggested, cut-offs may be calculated for each specific population instead of establishing global cut-off points. Patients with IMN showed significantly lower serum albumin levels and higher 24 h proteinuria compared to those with SMN. Analysis of ROC curves suggests that ELISA and LUMINEX assays are more useful than biochemical variables to differentiate patients with IMN and SMN. This pilot study contributes to confirming that the combination of ELISA and Luminex assays provide excellent sensitivity and specificity for the identification of IMN.

Perspectives in membranous nephropathy

The identification of the phospholipase A2 receptor 1 (PLA2R) and thrombospondin type-1 domain-containing protein 7A (THSD7A) as podocyte antigens in adult patients with membranous nephropathy (MN) has strongly impacted both experimental and clinical research on this disease. Evidence has been furnished that podocyte-directed autoantibodies can cause MN, and novel PLA2R- and THSD7A-specific animal models have been developed. Today, measurement of serum autoantibody levels and staining of kidney biopsies for the target antigens guides MN diagnosis and treatment worldwide. Additionally, anti-PLA2R antibodies have been proven to be valuable prognostic biomarkers in MN. Despite these impressive advances, a variety of questions regarding the disease pathomechanisms, clinical use of antibody measurement, and future treatments remain unanswered. In this review, we will outline recent advances made in the field of MN and discuss open questions and perspectives with a focus on novel antigen identification, mechanisms of podocyte injury, clinical use of antibody measurement to guide diagnosis and treatment, and the potential of innovative, pathogenesis-based treatment strategies.

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.

Identification of biomarkers and drug repurposing candidates based on an immune-, inflammation- and membranous glomerulonephritis-associated triplets network for membranous glomerulonephritis

Background

Membranous glomerulonephritis (MGN) is a common kidney disease. Despite many evidences support that many immune and inflammation-related genes could serve as effective biomarkers and treatment targets for MGN patients, the potential associations among MGN-, immune- and inflammation-related genes have not been sufficiently understood.

Methods

Here, a global immune-, inflammation- and MGN-associated triplets (IIMATs) network is constructed and analyzed. An integrated and computational approach is developed to identify dysregulated IIMATs for MGN patients based on expression and interaction data.

Results

45 dysregulated IIMATs are identified in MGN by above method. Dysregulated patterns of these dysregulated IIMATs are complex and various. We identify four core clusters from dysregulated IIMATs network and some of these clusters could distinguish MGN and normal samples. Specially, some anti-cancer drugs including Tamoxifen, Bosutinib, Ponatinib and Nintedanib could become candidate drugs for MGN based on drug repurposing strategy follow IIMATs. Functional analysis shows these dysregulated IIMATs are associated with some key functions and chemokine signaling pathway.

Conclusions

The present study explored the associations among immune, inflammation and MGN. Some effective candidate drugs for MGN were identified based on immune and inflammation. Overall, these comprehensive results provide novel insights into the mechanisms and treatment of MGN.

Clinicopathological features in membranous nephropathy with cancer: A retrospective single-center study and literature review

BACKGROUND

Membranous nephropathy is the most common glomerular disease related to malignancy. However, it is difficult to distinguish between true malignancy-related membranous nephropathy and idiopathic membranous nephropathy coincident with cancer. It has been reported that phospholipase A2 receptor (PLA2R) is the first autoantigen involved in idiopathic membranous nephropathy and thrombospondin type-1 domain-containing 7A (THSD7A) may have a close relationship with malignancy-related membranous nephropathy. Therefore, the aim of this study was to compare the clinicopathological characteristics between membranous nephropathy patients with cancer and idiopathic membranous nephropathy patients without cancer to better detect malignancy-related membranous nephropathy, including glomerular PLA2R and THSD7A depositions and their circulating antibodies, together with glomerular IgG4 deposition.

METHODS

Twelve membranous nephropathy patients with cancer and 257 idiopathic membranous nephropathy patients without cancer were included in this study and had been followed up for more than 1 year. The glomerular expression of PLA2R, THSD7A, and IgG4 was analyzed by immunohistochemistry. Circulating anti-PLA2R and anti-THSD7A antibodies were assessed by enzyme-linked immunosorbent assay and indirect immunofluorescence testing, respectively.

RESULTS

Membranous nephropathy patients with cancer were significantly older and had higher serum creatinine and a lower estimated glomerular filtration rate than idiopathic membranous nephropathy patients (P<0.05). The positive rates of glomerular PLA2R and IgG4 depositions and circulating anti-PLA2R antibodies in membranous nephropathy patients with cancer were significantly lower than those in idiopathic membranous nephropathy patients without cancer (P<0.01).

CONCLUSION

The absence of glomerular PLA2R deposition and negative circulating anti-PLA2R antibodies, along with negative glomerular IgG4 staining, may be useful clues to more accurately screen underlying malignancies in membranous nephropathy patients.

Antigen-Specific IgG Subclasses in Primary and Malignancy-Associated Membranous Nephropathy

Membranous nephropathy (MN) is an autoimmune disease caused by binding of circulating antibodies to podocyte antigens in the kidney. For decades and still today primary MN has been considered to have an unspecified IgG4-driven autoimmune genesis, while secondary MN has been associated with other diseases, most notably cancer, and not linked to IgG4. Immunologic mechanisms of primary and malignancy-associated MN are assumed to be different, however, this has never been systematically evaluated. The identification of Phospholipase A₂ Receptor 1 (PLA₂R1) and Thrombospondin Type-1 Domain-Containing 7A (THSD7A) as target antigens in MN allows a pathogenesis-driven differential diagnosis. Recent data showing a molecular link between increased THSD7A-expression in tumors and THSD7A-antibody positive MN suggest a similar pathogenesis of malignancy-associated and primary MN. In order to better define the underlying immunologic processes, we systematically analyzed circulating antigen-specific IgG subclasses in the serum of 76 patients with PLA₂R1-associated MN and 41 patients with THSD7A-associated MN in relationship to concurrent malignancy and disease outcome. Twenty-three patients in the study had malignancy-associated MN. We analyzed antigen-specific IgG subclasses in the serum of all patients at baseline and in 55 patients during follow-up by Western blot applying antigens derived from human kidney and lung. At baseline all 117 patients were positive for IgG4-antibodies against either PLA₂R1 or THSD7A, while IgG3, IgG1, and IgG2-antibodies were found in 87, 72, and 26% of patients, respectively. There were no differences in the IgG subclass distribution between patients with primary vs. cancer-associated MN and no association with disease outcome. Moreover, levels of antigen-specific IgG4-antibodies were not different between primary and malignancy-associated MN and levels of all IgG subclasses did not differ between these groups. Both podocytes and lung bronchioles showed expression of both PLA₂R1 and THSD7A when analyzed by immunofluorescence and Western blot. Every antigen-specific IgG subclass showed identical binding in both organs and autoantibodies bound the respective antigen only under non-reducing conditions. We conclude that antigen-specific IgG subclasses do not differentiate primary from malignancy-associated MN or predict disease prognosis. These data support the view that one common pathway may lead to primary and cancer-associated MN induced by PLA₂R1- or THSD7A-antibodies.

Definition of a new cut-off for the anti-phospholipase A2 receptor (PLA2R) autoantibody immunoassay in patients affected by idiopathic membranous nephropathy

Autoantibodies against phospholipase A2 receptor (PLA2R) are a sensitive and specific marker for idiopathic membranous nephropathy (IMN). The aim of our study was to redefine the cut-off value for the measurement of anti-PLA2R autoantibody levels by an automated enzyme immunoassay, in a large single-center cohort of Italian IMN patients at the time of diagnosis. Sixty-seven consecutive incident patients, with biopsy-proven IMN, were recruited. All patients were naïve to preceding immunosuppressive therapeutic regimens. The patient population had a mean age of 57 years and included 48 males and 19 females. Also, 200 patients with other renal diseases and 36 healthy subjects were studied as controls. The anti-PLA2R autoantibody levels were measured using the commercial enzyme-linked immunosorbent assay kit at the time of renal biopsy. At a cut-off value of 2.7 RU/ml (significantly lower than the manufacturer's recommended value of 14 RU/ml), calculated by receiver operating characteristic curves, the sensitivity and specificity of anti-PLA2R autoantibodies in the diagnosis of IMN was 88.1 and 96% respectively. The adapted cut-off value of 2.7 UI/ml increased sensitivity without affecting the specificity and it should be the recommended value for this method. Additionally our study confirmed the correlation, at baseline, between anti-PLA2R autoantibody levels and other biomarkers of disease activity.

Routine immunohistochemical staining in membranous nephropathy: in situ detection of phospholipase A2 receptor and thrombospondin type 1 containing 7A domain

BACKGROUND

Membranous nephropathy (MN) can be idiopathic (iMN) or manifest as a result of systemic underlying conditions as a secondary epiphenomenon. For the prognostic and predictive consequences of this discrimination, the routine use of reliable markers is crucial. This large MN series aimed to evaluate the routine and standardized immunohistochemical (IHC) employment of a panel of 3 biomarkers-phospholipase A2 receptor (PLA2R), thrombospondin type-1 domain-containing 7A (THSD7A), and immunoglobulin (Ig)G4-in the differential diagnosis of MN forms, contributing to the validation of the technique and the correct interpretation of reproducible patterns of reactivity.

METHODS

We classified 95 patients with a biopsy proven diagnosis of MN as primary (n = 72) or secondary (n = 23) cases based on clinical data. After performing an IHC assay directed against PLA2R, THSD7A and IgG4 antigens, samples were interpreted by three different nephropathologists to assess the positivity/negativity of the staining according to new interpretation criteria.

RESULTS

Useful interpretation criteria were introduced to exclude false positive patterns of reactivity and to identify only true granular membranous or mesangial deposits in MN. The IHC directed against PLA2R resulted positive in 51 iMN cases and negative in 21, while 4/23 secondary forms were considered positive. Based on these data the technique showed a sensitivity of 71% and specificity of 83%. On the other hand, the IHC analysis for IgG4 resulted positive in 44 cases of iMN and negative in 28 cases, while only 4/23 secondary forms were positive (same cases positive to PLA2R). Finally, THSD7A was found to be positive only in 1 case, which was negative to PLA2R and IgG4. The combination of the results allowed a classification of the series into two major groups: "double-positive" (PLA2R+/IgG4+/THSD7A-) and "triple-negative" (PLA2R-/IgG4-/THSD7A-) cases.

CONCLUSIONS

Based on these data, the diagnostic performance of the three biomarkers used in a "tandem fashion" can reach 79% sensitivity and 83% specificity, significantly reducing the risk of a false-positive or false-negative result and improving the routine characterization of this frequent glomerulonephritis.

Diagnostic specificity of autoantibodies to M-type phospholipase A2 receptor (PLA2R) in differentiating idiopathic membranous nephropathy (IMN) from secondary forms and other glomerular diseases

Autoantibody against phospholipase A2 receptor (anti-PLA2R) is a sensitive and specific biomarker of idiopathic membranous nephropathy (iMN), being found in approximately 70% of iMN patients and only occasionally in other glomerular diseases. However, whereas its diagnostic specificity vs. normal controls and other glomerulonephritides (GN) has been firmly established, its specificity vs. membranous nephropathy associated with various diseases (sMN) has given inconsistent results. The aim of our study was to evaluate the prevalence of anti-PLA2R antibodies in iMN in comparison with various control groups, including sMN. A total of 252 consecutive iMN patients, 184 pathological and 43 healthy controls were tested for anti-PLA2R antibody using indirect immunofluorescence (PLA2R IIFT, Euroimmun). Anti-PLA2R autoantibodies were detectable in 178/252 iMN patients, 1/80 primary GN, 0/72 secondary GN, 9/32 sMN and 0/43 healthy controls, with a diagnostic sensitivity of 70.6%. The diagnostic specificity of anti-PLA2R antibody vs. normal and pathological controls was 100 and 94.6% respectively. However, when the diagnostic specificity was calculated only vs. secondary forms of MN, it decreased considerably to 71.9%. Interestingly enough, 9 out of 10 anti-PLA2R positive patients in the disease control groups had membranous nephropathy associated with various diseases (7 cancer, 1 Crohn's disease, 1 scleroderma). In conclusion, anti-PLA2R positivity in a patient with MN, should not be considered sufficient to abstain from seeking a secondary cause, especially in patients with risk factors for neoplasia. The causal relationship between tumors and anti-PLA2R-induced MN remains to be established, as well as the possible mechanisms through which malignancies provoke autoimmunity.

Treatment of primary membranous nephropathy: where are we now?

In the last 10 years, basic science and clinical research have made important contributions to the understanding and management of primary membranous nephropathy (MN). The identification of antibodies directed against the M-type phospholipase A₂ receptor (PLA2R) and thrombospondin type-1 domain-containing 7A protein have added a new perspective on diagnosis, monitoring the immunological activity, predicting prognosis and guiding therapy in patients with primary MN. Mounting evidence suggests that quantification and follow-up of antiPLA2R Abs levels can help in assessing prognosis and evaluate the response to treatment. The kidney disease improving global outcomes guidelines published in 2012 have not been updated. New data on the use of rituximab suggest it should be considered as a potential initial therapy in the treatment of patients with primary MN.

Malignancy in Membranous Nephropathy: Evaluation of Incidence

Background

Membranous nephropathy (MN) can be associated with malignancy. However, the relative risk for malignancy remains unclear. It has been reported that higher numbers of inflammatory cells seen in the glomeruli at biopsy correlate with the occurrence of malignancy in patients with MN and might be used to direct screening.

Methods

We examined the occurrence of malignancy in 201 MN patients in Auckland, New Zealand. We also examined the pathology of renal biopsies from 17 MN patients with malignancies and compared the number of inflammatory cells per glomerulus with matched control patients with MN but no malignancy.

Results

40 malignancies were identified in 37 patients, 28 of which occurred after the MN diagnosis. The standardized incidence ratio (SIR) was 2.1 (95% CI, 1.3–2.85) which was similar between patients ≥ 60 years and those <60 years. The median number of inflammatory cells per glomerulus did not differ between MN patients with and without malignancy at 1.86 (IQR, 1.17–2.7) and 2.07 (IQR, 1.17–3.65), respectively (p value 0.56).

Conclusions

The relative risk of malignancy in MN patients was similar across different age groups. The number of inflammatory cells per glomerulus did not differentiate between MN patients with and without malignancies.

Pain in autoimmune disorders

Most autoimmune diseases are associated with pathological pain development. Autoimmune diseases with pathological pain include complex regional pain syndrome, rheumatoid arthritis, and Guillian-Barré syndrome to name a few. The present Review explores research linking the immune system to the development of pathological pain in autoimmune diseases. Pathological pain has been linked to T-cell activation and the release of cytokines from activated microglia in the dorsal horn of the spinal cord. New research on the role of autoantibodies in autoimmunity has generated insights into potential mechanisms of pain associated with autoimmune disease. Autoantibodies may act through various mechanisms in autoimmune disorders. These include the alteration of neuronal excitability via specific antigens such as the voltage-gated potassium channel complexes or by mediating bone destruction in rheumatoid arthritis. Although more research must be done to understand better the role of autoantibodies in autoimmune disease related pain, this may be a promising area of research for new analgesic therapeutic targets. © 2016 Wiley Periodicals, Inc.