Membranous nephropathy: recent travels and new roads ahead. Kidney Int. 2010;77:765-770. [PMID: 20182413 DOI: 10.1038/ki.2010.34]

Prevalence and prognosis of malignancy in THSD7A-associated membranous nephropathy: a systematic literature review and clinical case study

BACKGROUND

This study aims to investigate the incidence and prognosis of malignancy in individuals with thrombospondin type-1 domain-containing 7A (THSD7A)-associated membranous nephropathy (MN).

METHODS

First, we performed a systematic literature review of prevalence of malignancy in THSD7A-associated MN. Then, we conducted a retrospective analysis of 454 patients diagnosed with MN through renal biopsy at our hospital between January 2016 and December 2020. We assessed the presence of serum anti-THSD7A antibodies and performed immunohistochemical staining of renal tissue for THSD7A. Subsequently, we followed patients with THSD7A-associated MN for a minimum of 3-5 years, collecting their clinical, pathological characteristics, and prognosis. Additionally, we conducted a literature review on patients with THSD7A-associated MN in conjunction with malignancy.

RESULTS

We identified a total of nine articles containing comprehensive data on THSD7A-associated MN and malignancy. Among 235 patients with THSD7A-positive MN, 36 individuals had concurrent malignancies, resulting in a malignancy prevalence of 13.3% (95% CI: 8.9-17.7%). In our center, we followed up with 15 patients diagnosed with THSD7A-associated MN and observed three cases of concomitant tumors: two cases of lung adenocarcinoma and one case of small cell lung cancer with multiple metastases. The prevalence of malignancy in our cohort was 20%. Notably, we detected positive THSD7A staining in both renal and lung cancer tissues in one patient with small cell lung cancer.

CONCLUSIONS

Patients with THSD7A-associated MN should undergo vigilant follow-up assessments, with a particular focus on actively seeking potential tumorigenic lesions to prevent misdiagnosis or oversight.

IgG4 Antibodies Induced by Repeated Vaccination May Generate Immune Tolerance to the SARS-CoV-2 Spike Protein

Less than a year after the global emergence of the coronavirus SARS-CoV-2, a novel vaccine platform based on mRNA technology was introduced to the market. Globally, around 13.38 billion COVID-19 vaccine doses of diverse platforms have been administered. To date, 72.3% of the total population has been injected at least once with a COVID-19 vaccine. As the immunity provided by these vaccines rapidly wanes, their ability to prevent hospitalization and severe disease in individuals with comorbidities has recently been questioned, and increasing evidence has shown that, as with many other vaccines, they do not produce sterilizing immunity, allowing people to suffer frequent re-infections. Additionally, recent investigations have found abnormally high levels of IgG4 in people who were administered two or more injections of the mRNA vaccines. HIV, Malaria, and Pertussis vaccines have also been reported to induce higher-than-normal IgG4 synthesis. Overall, there are three critical factors determining the class switch to IgG4 antibodies: excessive antigen concentration, repeated vaccination, and the type of vaccine used. It has been suggested that an increase in IgG4 levels could have a protecting role by preventing immune over-activation, similar to that occurring during successful allergen-specific immunotherapy by inhibiting IgE-induced effects. However, emerging evidence suggests that the reported increase in IgG4 levels detected after repeated vaccination with the mRNA vaccines may not be a protective mechanism; rather, it constitutes an immune tolerance mechanism to the spike protein that could promote unopposed SARS-CoV2 infection and replication by suppressing natural antiviral responses. Increased IgG4 synthesis due to repeated mRNA vaccination with high antigen concentrations may also cause autoimmune diseases, and promote cancer growth and autoimmune myocarditis in susceptible individuals.

Membranous nephropathy: Mechanistic insights and therapeutic perspectives

Membranous nephropathy (MN) is one of the most common causes of non-diabetic nephrotic syndrome in adults. About 80% of cases are renal limited (primary MN) and 20% are associated with other systemic diseases or exposures (secondary MN). Autoimmune reaction is the main pathogenic factor of MN, and the discovery of autoantigens including the phospholipase A₂ receptor and thrombospondin type-1 domain-containing protein 7A has led to new insights into the pathogenesis, they can induce humoral immune responses led by IgG₄ makes them suitable for the diagnosis and monitoring of MN. In addition, complement activation, genetic susceptibility genes and environmental pollution are also involved in MN immune response. In clinical practice, due to the spontaneous remission of MN, the combination of supportive therapy and pharmacological treatment is widely used. Immunosuppressive drugs are the cornerstone of MN treatment, and the dangers and benefits of this approach vary from person to person. In summary, this review provides a more comprehensive review of the immune pathogenesis, interventions and unresolved issues of MN in the hope of providing some new ideas for clinical and scientific researchers in the treatment of MN.

Clinical characteristics of membranous nephropathy with spontaneous remission: An analysis of 24 patients

PURPOSE

To investigate the prognosis of patients with spontaneous remission (SR) of phospholipase A2 receptor (PLA2R)-associated membranous nephropathy (MN).

PATIENTS AND METHODS

Patients diagnosed with MN were recruited after examining their renal biopsy in the Renal Department of China-Japan Friendship Hospital between January 2015 and September 2021. Among them, 24 patients with SR were included in this study and follow-up.

RESULTS

Twenty-four patients diagnosed with SR of PLA2R-associated MN were recruited; 11 were male, and 13 were female, with a mean age of 49.5±14.5 years (range, 30-77 years). The initial 24-hour urinary total protein and serum albumin levels were 0.29±0.14g/d and 37.5±4.4g/L, respectively, and the initial serum creatinine was 65.0±15.8μmol/L. During the follow-up of 33.9±19.1 months (range, 6-73 months), 22 (91.7%) patients maintained remission; however, one patient had impaired renal function due to acute coronary syndrome and coronary angiography findings, and one patient experienced a repeated relapse caused by respiratory tract infection, at 50 and 70 months. A systematic review of the relevant literature was conducted, and records of patients with SR of PLA2R-associated MN were retrieved from 16 case reports or case series with a total of 97 cases.

CONCLUSIONS

Most patients with SR of MN had a promising long-term prognosis, with only a few cases of relapse.

Comparative efficacy of three regimens (cyclosporine, tacrolimus, and cyclophosphamide) combined with steroids for the treatment of idiopathic membranous nephropathy

INTRODUCTION AND OBJECTIVES

To investigate the efficacy of combined immunosuppressive regimens of cyclosporine (CsA), tacrolimus (TAC), or cyclophosphamide (CTX) combined with steroids in the treatment of idiopathic membranous nephropathy (IMN).

MATERIALS AND METHODS

A total of 150 biopsy-proven IMN patients were divided into three groups: CTX, TAC, and CsA groups (50 cases each). Patients received a selected regimen for 48 weeks. The efficacy (remission rate, 24h urinary protein, and serum albumin and creatinine) and safety (adverse events) profiles of administered regimens were evaluated at 12, 24 and 48 weeks.

RESULTS

At 12 weeks, the response rates for CsA, TAC, and CTX groups were 14%, 50%, and 22%, respectively. This increased to 74%, 84%, and 82%, respectively at 48 weeks. During follow-up, 24h urinary protein significantly reduced from baseline in all regimens (P<0.05), while serum albumin increased in TAC and CTX groups after 12 weeks (P<0.05), and CsA group at 48 weeks (P<0.05). No significant changes in serum creatinine levels were noted in all three regimens (P>0.05). Safety was comparable in all groups, with lower respiratory tract infection being the most frequent adverse event.

CONCLUSIONS

The combined regimens (i.e., TAC, CsA, and CTX) are effective in the treatment of patients with IMN at 48 weeks, while TAC and CTX might be more beneficial in terms of shortened time to remission and increased complete response rate.

Lung cancer patients with nephropathy as the first manifestation: Literature review and clinical study report

Background

To investigate the relationship between membranous nephropathy (MN) and lung cancer.

Methods

To report patients with lung cancer detected by follow-up after the diagnosis of MN by renal biopsy in China-Japan Friendship Hospital from January 2010 to December 2019, and to study the prognosis of lung cancer-associated MN and have a review of the literature.

Results

Lung cancer was detected in six patients followed for 1–27 months (median 8 months) after the diagnosis of MN: including four cases of lung adenocarcinoma, one case of carcinoma in situ, and one case of small cell lung cancer with multiple metastases. Five cases were in remission after surgical resection, and one case was remitted after chemotherapy. Six patients were negative for serum anti-PLA2R antibodies, and glomerular IgG subclass deposition detected by immunofluorescence was positive for IgG1 and IgG2. Glomerular PLA2R, THSD7A, and NELL-1 stainings were assessed in all six patients; one patient was positive for glomerular PLA2R staining, two patients were positive for glomerular THSD7A staining, and all patients were negative for NELL-1 staining. A literature review of the relationship between MN and lung cancer was performed: seven articles about cancer-associated MN were searched, reporting 32 cases of MN associated with lung cancer, among which 14 cases had nephropathy as the first manifestation and only five patients had remission of MN after treatment of lung cancer.

Conclusions

A few lung cancer patients have nephropathy as the first clinical manifestation, and MN can also be remitted after treatment of lung cancer.

Anti-Phospholipase A2 Receptor Antibody Expression at Different Stages of Idiopathic Membranous Nephropathy

The significance of blood anti-phospholipase A2 receptor (PLA₂R) antibodies in the diagnosis of different stages of idiopathic membranous nephropathy (IMN) was investigated. The expression and distribution of anti-PLA₂R antibodies in renal biopsy tissue of patients with different stages of IMN were examined by immunohistochemistry. In addition, blood anti-PLA₂R antibodies were determined by indirect immunofluorescence for the same patients, and the results were compared with the anti-PLA₂R antibody expression in renal biopsy tissue. The positive fluorescence intensities of IMN stages I, IV, and V were mostly ± or + (40/80). There was no significant difference in fluorescence titer between these stages (p > 0.05). These results were consistent with the immunohistochemistry results, and the kappa statistic was 0.95. The positive fluorescence intensities of IMN stages II and III were mostly ++ to ++++ (33/60). There was no significant difference in fluorescence intensities between these two stages (p > 0.05), but there was a significant difference in fluorescence intensities between stages II and III and stages I, IV, and V (p < 0.001). These results were consistent with the immunohistochemistry results, and the kappa statistic was 0.97 (p < 0.001). Therefore, blood anti-PLA₂R levels were positively correlated with anti-PLA₂R expression in renal biopsy tissue in patients with different stages of IMN. In addition, the fluorescence intensities of IMN stages II and III were significantly different from those of stages I, IV, and V. Therefore, blood anti-PLA₂R levels can be used for in vitro differential diagnosis and the monitoring of treatment, as it can distinguish stage II; and III; from stage I, IV, and V IMN.

The Association Between Serum Complement 4 and Kidney Disease Progression in Idiopathic Membranous Nephropathy: A Multicenter Retrospective Cohort Study

Introduction

Complement system plays an important role in the pathogenesis of idiopathic membranous nephropathy (IMN), however, the relationship between serum complement 4 (C4) and kidney disease progression in IMN is unclear. This study aims to investigate the association of serum C4 level with the risk of kidney disease progression among patients with IMN.

Methods

The retrospective cohort assessed 1,254 participants with biopsy-proven IMN from three centers in Xi ‘an, Shaanxi Province, China. Baseline serum C4 levels were measured at renal biopsy. The association between baseline serum C4 and the risk of renal function progression, defined as a 30% decline in renal function or end stage renal disease, was evaluated in Cox proportional hazards models.

Results

A total of 328 patients with IMN and nephrotic proteinuria were eligible, and 11.3% (37/328) of them attained the renal function progression events after a median follow-up of 51 months (37-59 months). After adjustment for other confounders, a higher value of serum C4 was independently associated with a higher risk of renal function progression event with a hazard ratio (HR) of 4.76 (95% confidence interval [95% CI], 1.77-12.79) per natural log-transformed C4. In reference to the low level of C4, the adjusted HRs were 2.72 (95% CI, 1.02-7.24) and 3.65 (95% CI, 1.39-9.60), respectively, for the median and high levels of C4 (P for trend=0.008). Additionally, the results were robust and reliable in the sensitivity and subgroup analyses.

Conclusion

Among patients with IMN and nephrotic proteinuria, serum C4 at renal biopsy is an independent predictor for kidney disease progression regardless of other confounders.

The diagnostic value of immunohistochemical staining of the interstitial vascular C4d complement in membranous nephropathy

Membranous glomerulonephritis (MGN) is the most common cause of adulthood nephrotic syndrome. Diagnosis of membranous nephritis is based on light electron immunofluorescence microscopy and clinical signs. Immune complex deposition against podocyte antigens such as phospholipase A2 receptor (PLA2R) activates the complement system. Of this, complement Component C4d (C4d) is involved in the classical and lectin pathways. This marker may be used by immunohistochemistry to diagnose MGN when other methods are not available. In this work, C4d expression was monitored by immunohistochemical analysis in the glomerular capillaries of patients with primary MGN (study group, N=33) versus patients with minimal change disease (MCD, control group, N=20) in a cross-sectional evaluation performed based on the diagnosis confirmed by light microscopy and immunofluorescence. There was no significant demographic difference between the two groups except for age (P=0.002). C4d immune-expression was positive in glomerular capillary (2+ to 4+) in most of the MGN patients, while it was negative in the MCD group. The sensitivity and specificity of C4d immunostaining were 95% and 100%, respectively. The Pearson correlation coefficient was 0.74 between C4d (immunohistochemistry) and immunoglobulins (IgG; immunofluorescence) and 0.65 between C4d (immunohistochemistry) and the C3 complement product (immunofluorescence). Immunohistochemical evaluation of C4d is, therefore, a sensitive and specific method that has a high correlation with IgG immunofluorescence.

Peroxiredoxins as Markers of Oxidative Stress in IgA Nephropathy, Membranous Nephropathy and Lupus Nephritis

IgA nephropathy (IgAN), membranous nephropathy (MN), and lupus nephritis (LN) represent important causes of chronic kidney disease. They belong to the immune-mediated glomerulonephritis (GNs), and have distinct pathogenesis, distinct clinical courses, and variable responses to treatment. Therefore, specific diagnostic procedures are necessary for more effective patient management. Recently, a role for oxidative stress has been proposed in various renal disorders. Thus, molecules related to oxidative stress, such as 2-Cys-peroxiredoxins (PRDXs), may represent plausible candidates for biomarkers in renal pathologies. The aim of this study was to assess whether there are differences between individual GNs and healthy controls in the context of PRDXs serum concentration. We enrolled 108 patients with biopsy-proven IgAN (47), MN (26), LN (35) and 30 healthy age- and sex-matched controls. The serum concentrations of PRDX 1-5 were measured with ELISA assays and correlated with demographic and clinical data. The PRDXs' concentration varied depending on the GN type. We also observed an association of PRDXs with lower estimated glomerular filtration rates, complement, hemoglobin, and body mass index. Our study indicates that individual PRDX can play roles in pathophysiology of selected GNs and that their serum concentrations may become useful as a new supplementary diagnostic markers in IgAN, MN as well as LN. The results of this study open a new avenue for prospective research on PRDXs in renal diseases.

Membranous Glomerulonephritis as an Uncommon Presentation of Secondary Syphilis: A Reminder on Therapeutic Decision-Making in Clinical Practice

Membranous glomerulonephritis is one of the common causes of nephrotic syndrome in the adult population. It is idiopathic in the majority of patients, but the secondary forms can be seen in the setting of autoimmune disease, cancer, infection, and following exposure to certain medications. However, subclinical syphilis-related membranous nephropathy remains a particularly rare clinicopathologic entity in modern times. In this article, we chronicle an interesting case of latent syphilis masquerading as membranous glomerulonephritis, which resolved with benzathine penicillin without requiring immunosuppressive treatment. We further supplement this paper with a concise review of the relevant literature that delineates the utility of appropriate antibiotic therapy in the management of luetic membranous nephropathy. Clinicians should remain cognizant of secondary syphilis while evaluating patients for possible glomerulonephritis or those presenting with proteinuria. Additionally, patients with hepatitis B, hepatitis C, and human immunodeficiency virus infections are not infrequently coinfected with Treponema pallidum. Therefore, a high index of suspicion for systemic manifestations of syphilis such as nephrotic syndrome is warranted in the setting of a coinfection. Prompt diagnosis and treatment of syphilis may result in resolution of proteinuria, without the need for standard immunosuppressive therapy commonly used in clinical practice.

Nomogram to predict the progression of patients with primary membranous nephropathy and nephrotic syndrome

Background

The outcome of patients with primary membranous nephropathy (pMN) who present with nephrotic syndrome (NS) is variable and difficult to predict. The goal of this study was to develop a nomogram to predict the risk of progression for specific individuals.

Methods

This retrospective study involved biopsy-proven patients with pMN and NS treated between January 2012 and June 2018. The primary outcome of our investigation was progression, defined as a reduction of estimated glomerular filtration rate (eGFR) that was equal to or over 20% compared with baseline at the end of follow-up or the onset of end-stage renal disease (ESRD). We used backwards stepwise logistic regression analysis to create a nomogram to predict prognosis. The model was validated internally using bootstrap resampling.

Results

A total of 111 patients were enrolled. After a median follow-up of 40.0 months (range 12–92 months), 18.9% (21/111) patients showed progression. Backwards stepwise selection using the Akaike information criterion (AIC) identified the following four variables as independent risk factors for progression, which were all used in the nomogram: age ≥ 65 years [odds ratio (OR) 7.004; 95% confidence interval (CI) 1.783–27.505; p = 0.005], Ln (sPLA2R-Ab) (OR 2.150; 95% CI 1.293–3.577; p = 0.003), Ln (proteinuria) (OR 5.939; 95% CI 1.055–33.436; p = 0.043) and Ln (Uα1m/Cr) (OR 2.808; 95% CI 1.035–7.619; p = 0.043). The discriminative ability and calibration of the nomogram revealed good predictive ability, as indicated by a C-index of 0.888 (95% CI 0.814–0.940) and a bootstrap-corrected C-index of 0.869; calibration curves were also well fitted. A receiver operating characteristic (ROC) curve for the nomogram score revealed significantly better discrimination than each of the three risk factors alone, including Ln (sPLA2R-Ab) [area under the curve (AUC) 0.769], Ln (proteinuria) (AUC 0.653) and Ln (Uα1m) (AUC 0.781) in the prediction of progression (p < 0.05). The optimal cutoff value of the nomogram score was 117.8 with a positive predictive value of 44.4% and a negative predictive value of 98.5%.

Conclusion

The nomogram successfully achieved good predictive ability of progression for patients with pMN who present with NS. It can therefore help clinicians to individualize treatment plans and improve the outcome of pMN.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11255-021-02859-x.

A cohort study of membranous nephropathy, primary or secondary

Background

Although IgG4 deposit against phospholipase A2 receptor (anti-PLA2R) is predominantly presented in the renal biopsy of patients with primary membranous nephropathy (MN), its diagnostic value of this immune complex has not been fully established.

Methods

In this cohort study, 108 biopsy-proven MN patients with proteinuria were evaluated during two years follow up and were divided into primary and secondary groups. Renal biopsy specimens were pathologically assessed for IgG4 and PLA2R depositions by immunohistochemistry (IHC). Therefore, the relationships between staining severity, MN type and total proteinuria in all patients were determined.

Results

Of 108 patients, 73.1% had primary MN and 26.9% were diagnosed as secondary form. IHC staining in patients with primary MN was positive for PLA2R in 76 (96.2%) and IgG4 in 68 (86.1%). Cases with positive PLA2R expression had a significantly higher rate among patients with mild to moderate stages (P = 0.03). No significant relationship was found between intensity of PLA2R and IgG4 deposits with proteinuria and serum creatinine. Based on our data, double positivity/negativity of PLA2R and IgG4 expression adds prominent information to the clinical data and were found to be useful and robust biomarkers for detection of primary MN patients with high sensitivity and specificity (97.1 and 96.3% respectively, PPV = 98.5% and NPV = 92.9%).

Conclusions

Simultaneously expression of PLA2R and IgG4 in renal biopsy specimens of patients with MN could possibly be used as a potential diagnostic method to distinguish primary from secondary MN and also pathological severity of the disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-021-02338-6.

Serum Antibody and Glomerular Antigen of Antiphospholipase A2 Receptor in Chinese Patients with Idiopathic Membranous Nephropathy

Background

M-type phospholipase A2 receptor (PLA2R) is the first autoantigen responsible for idiopathic membranous nephropathy (IMN). However, serum PLA2R antibody (PLA2R-Ab) can be inaccurate in distinguishing between IMN and secondary membranous nephropathy, while renal PLA2R antigen (PLA2R-Ag) emerges as an ancillary diagnostic. The present study is aimed at examining the associations between PLA2R-Ab in sera and PLA2R-Ag in kidneys in IMN patients.

Methods

A total of 93 patients with IMN were retrospectively identified. Their serum PLA2R-Ab and renal PLA2R-Ag expression levels were determined, and the clinical correlations between these parameters and clinical features were examined.

Results

The sensitivities of serum PLA2R-Ab and renal PLA2R-Ag for diagnosing IMN were 74.2% and 88.2%, respectively (P < 0.001), with poor consistency. Higher serum PLA2R-Ab levels were correlated to stronger renal PLA2R-Ag expression (P = 0.048). Patients with positive PLA2R-Ab significantly differed from those with negative levels, in terms of proteinuric levels over 24 hours (4.54 vs. 3.46 g/day, P = 0.015) and serum albumin (23.28 vs. 27.95 g/L, P = 0.038). Among patients with positive renal PLA2R-Ag, patients with positive PLA2R-Ab had significantly higher 24-hour proteinuria, when compared to patients with negative PLA2R-Ab (4.57 vs. 3.08 g/day, P = 0.005). Among those with positive PLA2R-Ab in sera, their PLA2R-Ab levels were correlated with the estimated glomerular filtration and serum creatinine.

Conclusion

Serum PLA2R-Ab exhibits a closer correlation with proteinuric severity and renal function, when compared to renal PLA2R-Ag.

Clinical correlation and prognostic significance of immunofluorescence in renal biopsies of patients having Glomerulonephritis

Objective

To correlate the immunofluorescence (IF) findings on renal biopsies of patients of glomerulonephritis (GN) with the clinical course of the disease.

Methods

This retrospective descriptive study was done at the Department of Pediatrics Medicine Unit-I, Nishtar Hospital Multan, from January 2008 to January 2019. A total of 387 cases of both gender, aged up to 16 years, diagnosed having GN on the basis of renal biopsies by light microscopy (LM) and IF findings, were included. Outcome as remission, partial remission, no remission with stable kidney disease, no remission with progressive kidney disease and end-stage kidney disease (ESKD) were computed. Chi square test was applied to see the correlation of IF findings and outcome by taking p value less than 0.05 as statistically significant.

Results

Focal segmental glomerulosclerosis (FSGS) was found to be the commonest histopathology finding noted in 158 (40.8%) followed by mesangioproliferative GN 74 (19.1%) and membranous nephropathy 42 (10.9%). Complete remission was observed in 145 (37.5%) cases whereas ESKD was seen in 26 (6.7%). Distinct pattern of IF findings were shown when distribution of IF findings were seen with respect to all study variables (p value < 0.001). For outcome, 134 (51.3%) IF negative cases had complete remission while 93 (35.6%) negative IF findings also had partial remission. ESKD was seen among 14 (25.9%) IgM positive and three (33.3%) IgA positive cases.

Conclusion

Immunofluorescence proved an important diagnostic tool in reaching the exact diagnosis in various types of GN. Distinct correlation between IF findings and clinical course of various types of GN was observed. IF negative cases had better outcome and was not having progressive course of disease so prognosis remained better than IF positive cases in this study.

Lung cancer with nephrotic syndrome as a paraneoplastic syndrome: A case report

Paraneoplastic syndromes are immune disorders associated with clinical signs and symptoms caused by substances produced by malignant diseases and are not directly associated with a primary or metastatic tumour. The symptoms are the effects of hormones, immune cross-reactivity or cytokines. Paraneoplastic nephrotic syndrome (PNS) is often associated with membranous nephropathy (MN) in elderly patients with solid tumours, and there is continued debate regarding whether corticosteroids or immunosuppressants should be combined with cancer therapy for the syndrome. The present report describes a male patient with lung cancer associated with secondary MN who achieved remission under radiotherapy, with no use of corticosteroids or immunosuppressants. This case is rare. Therefore, when treating PNS related to lung cancer, more attention should be paid to the treatment of the cancer.

[Update membranous nephropathy]

Membranous nephropathy is an autoimmune disease caused in most cases by binding of circulating antibodies to antigens on podocytes. PLA₂R1 and THSD7A have been identified as target antigens in 70-80 % and 2-3 % of patients, respectively. The detection of PLA₂R1- and THSD7A-antibodies in the blood and staining of renal biopsies for the respective antigens allow the correct diagnosis of PLA₂R1- and THSD7A-associated membranous nephropathy, respectively, in practically 100 % of cases. Measurement of PLA₂R1- and THSD7A-antibodies is helpful in order to further individualize the decision whether to perform a renal biopsy in patients with suspected membranous nephropathy. PLA₂R1-antibody level is a strong predictor for remission of proteinuria, loss of renal function and relapse of disease. Moreover, treatment decisions in patients with PLA₂R1-associated MN are increasingly based on the PLA₂R1-antibody levels. Rituximab was shown to be non-inferior to ciclosporine A to induce remission of proteinuria after 12 months. After 24 months rituximab was superior to ciclosporine A for the same endpoint. Development of novel treatment strategies, focusing on disease pathogenesis, remains highly relevant for these patients.

sPLA2-IB Level Correlates with Hyperlipidemia and the Prognosis of Idiopathic Membranous Nephropathy

Recent studies suggested that serum secretory phospholipase A2 group IB (sPLA2-IB) was increased in idiopathic membranous nephropathy (IMN). However, the interference of high lipemia on the sPLA2-IB levels was not taken into account in these studies. The present study aimed to investigate the correlation between sPLA2-IB and lipemia, and the clinical merit of sPLA2-IB in the prediction of prognosis of IMN patients. A total of 64 IMN patients, 39 immunoglobulin A nephropathy (IgAN) patients and 64 healthy controls were included in the study. The levels of serum sPLA2-IB, lipemia and proteinuria were measured. Fifty IMN patients were followed up for 6 months. Pathologic stages were made for all IgAN and IMN patients. The results showed that the levels of serum sPLA2-IB, cholesterol and low-density lipoprotein cholesterol (LDL-C) were significantly higher, and the levels of albumin and high-density lipoprotein cholesterol (HDL-C) were significantly lower in IMN patients than in healthy controls and IgAN patients. Serum sPLA2-IB levels were also found to be higher in IgAN patients than in heathy controls, but the association of serum sPLA2-IB levels with proteinuria, cholesterol and albumin was only shown in IMN patients. Antibody against M-type receptor for secretory phospholipase A2 (PLA2R1) was positive in 81.3% IMN patients. Glomerular sPLA2-IB deposition, podocyte fused processes, and density deposition on thickened basement membrane were seen in IMN patients, but not in IgAN patients. IMN patients with lower sPLA2-IB and proteinuria levels were found to have better outcome after the 6-month follow-up. In IMN patients, sPLA2-IB levels were significantly increased in both serum and renal tissue. In conclusion, serum sPLA2-IB was closely correlated with proteinuria, albumin and cholesterol, and IMN patients with lower sPLA2-IB levels were more likely to achieve a better outcome.

Phospholipase A2 Receptor Autoantibodies as a Novel Serological Biomarker for Autoimmune Thyroid Disease Associated Nephropathy

Aims: To develop a highly sensitive immunoassay for PLA2R autoantibodies and study the relationship between PLA2R autoantibodies and autoimmune thyroid disease-associated nephropathy.

Methods: We applied a highly sensitive time-resolved fluoroimmunoassay to quantitatively detect the concentration of phospholipase A2 receptor (PLA2R) antibodies in the serum of patients with Graves' disease, Hashimoto's thyroiditis (HT), nephrotic patients with idiopathic membranous nephropathy (IMN), and normal controls. We immunohistochemically analyzed the existing PLA2R target antigen in the thyroid tissue of patients with Graves' disease and HT, as well as the nephridial tissue of nephrotic patients with IMN.

Results: PLA2R antibody concentrations in the serum of normal controls, patients with nodular goiter, Graves' disease, and HT, as well as patients with IMN were 1.13 ± 0.43, 1.07 ± 0.22, 2.12 ± 2.11, 8.07 ± 4.74, and 15.91 ± 19.50 mg/L, respectively. PLA2R antibody concentration in the serum and the area under the receiver operating characteristic curve in patients with HT and IMN were increased significantly. Immunohistochemistry revealed obvious staining of PLA2R in tissues from patients with HT, with a positive rate of 66.67%.

Conclusions: PLA2R is a potential pathogenic target antigen for HT, and the production of PLA2R antibodies may cause autoimmune thyroid disease-associated nephropathy.

Diagnostic efficacy of serum anti-phospholipase A2 receptor antibodies for idiopathic membranous nephropathy in patients with diabetic kidney disease

AIM

Serum anti-phospholipase A2 receptor (anti-PLA2R) antibodies are highly accurate in diagnosing idiopathic membranous nephropathy (IMN) in populations with kidney disease. However, the diagnostic value of anti-PLA2R antibodies for IMN in diabetic kidney disease (DKD) is unclear. The objective of this study is to determine the diagnostic efficacy and the optimal cut-off value of this marker in populations with DKD.

METHODS

This study included 227 patients with type 2 diabetes who were admitted to the Department of Nephrology of the Chinese People's Liberation Army General Hospital from May 2016 to January 2018 and underwent pathological diagnosis by renal biopsy. Anti-PLA2R antibodies were detected by enzyme-linked immunosorbent assay in this population. According to the pathological results, the participants were divided into an IMN group and non-membranous nephropathy (non-MN) group. The clinical characteristics were analyzed, the diagnostic ability of anti-PLA2R antibodies was evaluated, and the receiver operating characteristic (ROC) curve was constructed to obtain the optimal cut-off value.

RESULTS

There were 45 patients in the IMN group, accounting for 19.8% of the study sample. The patients in this group were older at the time of renal biopsy than the non-MN group and presented a shorter duration of diabetes, better glycemic control, lower blood pressure and uric acid, and better renal function; in addition, their clinical symptoms indicated nephrotic syndrome. The optimal cut-off value for anti-PLA2R antibodies for the diagnosis of IMN in DKD was 2.71 Ru/ml, sensitivity was 0.800, specificity was 0.951, positive predictive value was 0.800, negative predictive value was 0.951, accuracy was 0.921, and the Yoden index was 0.750. The area under the ROC curve was 0.87 (95% CI, 0.788-0.952) (p < 0.001).

CONCLUSIONS

Patients in the IMN group were older, had better renal function and general condition, and the clinical symptoms indicated nephrotic syndrome. Anti-PLA2R antibodies had a good diagnostic performance for IMN in the population with DKD, and the optimal cut-off value was 2.71.

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.

A comparison of clinical features between idiopathic membranous nephropathy patients with and without serum antibody against phospholipase A2 receptor

Patients with idiopathic membranous nephropathy (IMN) can be categorized into phospholipase A2 receptor (PLA2R)-associated and non-PLA2R-associated cases, according to serum PLA2R antibody status. The present study aimed to determine whether clinical features differed between these.A total of 89 patients with IMN were retrospectively recruited for the present study. Serum PLA2R-Ab levels were determined by time-resolved fluoroimmunoassay. Furthermore, the relationship between serum PLA2R antibody levels and their responses to immunosuppressants among patients with a complete follow-up period, which was defined as at least 1 year, was analyzed.Among these enrollees, 71 (80.0%) patients were positive for serum PLA2R antibody. Furthermore, patients with PLA2R-associated IMN had significantly higher age (with vs without, 54.31 ± 14.03 vs 46.67 ± 13.30 years old; P = .04), proteinuria (4.32 ± 1.84 vs 3.29 ± 1.90 g/d, P = .039), and serum albumin (25.33 ± 9.60 vs 31.38 ± 9.52 g/L, P = .019), but had lower serum immunoglobulin G (6.83 ± 2.89 vs 8.72 ± 2.95 g/L, P = .016) and erythrocyte sedimentation rate (47.31 ± 32.11 vs 26.33 ± 27.94, P = .013), when compared to IMN patients without PLA2R. Furthermore, IMN patients without PLA2R exhibited a better response to immunosuppressants, when compared to patients with PLA2R-associated IMN (without vs with, 66.7% vs 62.5% at 6 months and 100% vs 87.5% at 12 months), but the difference was not statistically significant.Patients with PLA2R-associated IMN had higher disease severity than IMN patients without PLA2R. Furthermore, PLA2R negative patients had a better response to immunosuppressive therapies than PLA2R-positive patients, but the difference was not statistically significant.

Primary Membranous Glomerulonephritis: The Role of Serum and Urine Biomarkers in Patient Management

The detection of phospholipase A2 receptor (PLA2R) and thrombospondin domain containing 7A THSD7A among primary membranous glomerulonephritis (MGN) patients transformed the diagnosis, treatment monitoring, and prognosis. Anti-PLA2R can be detected in 70-90% of primary MGN patients while anti-THSD7A in 2-3% of anti-PLA2R negative primary MGN patients depending on the technique used. Serum and urine samples are less invasive and non-invasive, respectively, and thus can detect the presence of anti-PLA2R and anti-THSD7A with higher sensitivity and specificity, which is significant in patient monitoring and prognosis. It is better than exposing patients to a frequent biopsy, which is an invasive procedure. Different techniques of detection of PLA2R and THSD7A in patients' urine and sera were reviewed to provide newer and alternative techniques. We proposed the use of biomarkers (PLA2R and THSD7A) in the diagnosis, treatment decision, and follow-up of patients with primary MGN. In addition, other prognostic renal biomarkers like retinol binding protein (RBP) and beta-2 microglobulin were reviewed to detect the progression of renal damage for early intervention.

Comprehensive expression profiles and bioinformatics analysis reveal special circular RNA expression and potential predictability in the peripheral blood of humans with idiopathic membranous nephropathy

The etiology of idiopathic membranous nephropathy (IMN) is considered to be closely associated with immunoregulation and genetic factors. Circular RNAs (circRNAs) have been found to regulate gene expression in various organisms, and to play an important role in multiple physiological and pathological processes, which may be involved in the pathogenesis of IMN. The purpose of the present study was to investigate the potential relationship between circRNAs in peripheral blood and disease. The diagnoses of IMN were confirmed using electron microscopy and immunofluorescence. Total RNA was isolated and microarray analysis was used to detect the expression levels of circRNAs in the peripheral blood of patients with IMN and in normal subjects. Selected genes from the microarray were selected and verified by reverse transcription‑quantitative (RT‑q)PCR. Bioinformatics tools were applied for further functional evaluation, and the potential disease predictability of circRNAs was determined using receiver‑operating characteristic (ROC) curves. The results showed that a total of 955 differentially expressed circRNAs were found in blood samples, 645 of which were upregulated and 310 which were downregulated. In total, five candidate circRNAs were validated using RT‑qPCR analysis. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses identified numerous types of target genes and their corresponding microRNAs (miRNAs). The miRNAs identified were involved in biological processes and enriched in multiple important pathways, including the mitogen‑activated protein kinase, transforming growth factor‑β and Ras signaling pathways. The levels of circ_101319 were significantly higher (P<0.001) and exhibited promising diagnostic value in patients with IMN (area under ROC =0.89). The co‑expression network constructed for circ_101319 indicated that it may be associated with membranous nephropathy‑related pathways by mediating miRNAs. In conclusion, the present study revealed the expression and functional profile of differentially expressed circRNAs in the peripheral blood of patients with IMN, and provided new perspectives to predict and elucidate the development of IMN.

Expression of THSD7A in neoplasm tissues and its relationship with proteinuria

Background

Thrombospondin type 1 domain containing 7A (THSD7A) was recently identified target autoantigen in membranous nephropathy (MN). However, patients with positive THSD7A expression were prone to have malignancies. THSD7A was found to be expressed in a variety of malignant tumors. In this study, we investigated the histologic expression of THSD7A in colorectal or breast cancers, as well as the relationship between THSD7A expression and proteinuria in the patients with cancers.

Method

A total of 101 patients were enrolled in the study, 81 of them had colorectal cancer and 20 had breast cancer. THSD7A expression was detected by immunohistochemical staining in tumor tissues. The clinical and laboratory parameters of these patients before their tumor resection were collected.

Results

Positive expression rates of THSD7A in the two types of tumor tissues were very high, 97.5% in colorectal cancer, and 100% in breast cancer. THSD7A expression was also detected in lymph nodes of two patients with lymph node metastasis. Total 11 patients (10.9%) had proteinuria before surgery. Among the 4 patients who had proteinuria and were followed up, the proteinuria of 3 patients disappeared after surgery.

Conclusions

The positive rate of THSD7A expression was very high in human colorectal cancer or breast cancer. It might be an important link between malignant tumors and kidney diseases.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1489-5) contains supplementary material, which is available to authorized users.

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

Background

Complement activation plays a substantial role in the pathogenesis of primary membranous nephropathy (pMN). C5b-9, C3c, MBL, and factor B have been documented in the subepithelial immune deposits. However, the changing of complement activation products in circulation and urine is not clear.

Methods

We measured the circulating and urinary levels of C1q, MBL, C4d, Bb, properdin, C3a, C5a, and sC5b-9, in 134 patients with biopsy-proven pMN, by enzyme-linked immunosorbent assay. All the plasma values were corrected by eGFR and all the urinary values were corrected by urinary creatinine and urinary protein excretion. Anti-PLA2R antibodies were measured in all patients.

Results

The plasma complement activation products were elevated both in the patients with and without anti-PLA2R antibodies. C3a levels were remarkably increased in the circulation and urine, much higher than the elevated levels of C5a. C5b-9 was in normal range in plasma, but significantly higher in urine. The urinary C5a had a positive correlation with anti-PLA2R antibody levels and urinary protein. The plasma level of C4d was elevated, but C1q and MBL were comparable to healthy controls. Positive correlations were observed between plasma C4d/MBL and urinary protein, only in the patients with positive anti-PLA2R antibodies but not in those without. The plasma level of Bb was elevated and had positive correlation with urinary protein only in the patients without anti-PLA2R antibodies.

Conclusion

Complement activation products were remarkable increased in pMN and may serve as sensitive biomarkers of disease activity. The complement may be activated through lectin pathway with the existence of anti-PLA2R antibodies, while through alternative pathway in the absence of antibody.

Phospholipase A2 Receptor Antibody IgG4 Subclass Improves Sensitivity and Specificity in the Diagnosis of Idiopathic Membranous Nephropathy

AIMS

The aim of this study was to develop a new method for detecting anti-phospholipase A2 receptor-IgG4 to improve the sensitivity and specificity in the diagnosis of idiopathic membranous nephropathy (IMN).

METHODS

A highly sensitive quantitative assay was developed for the detection of serum anti-phospholipase A2 receptor-IgG4 with europium chelation by time-resolved fluoroimmunoassay (TRFIA), and a mouse anti-human IgG4 tracer was prepared using europium chelation for detection. The specificity and sensitivity of anti-phospholipase A2 receptor-IgG4 in the diagnosis of IMN were further assessed in patients with different kidney diseases.

RESULTS

The detection limit of anti-PLA2R-IgG4 was 0.69 ng/mL. The measurement range of anti-PLA2R-IgG4 TRFIA was 0.69-2,500 ng/mL. Mean serum anti-PLA2R-IgG4 was 21.27 ± 15.15 ng/mL in 45 healthy volunteers, 31.08 ± 18.17 ng/mL in 29 IgA nephropathy patients, 49.10 ± 34.32 ng/mL in 8 lupus nephropathy patients, and 10,324.11 ± 17,030.40 ng/mL in 30 IMN patients. The anti-PLA2R-IgG4 cutoff concentration was >161.2 ng/mL with the sensitivity of 90.0% and specificity of 100% in the diagnosis of IMN. However, the cutoff for other kidney diseases was lower than 161.2 ng/mL.

CONCLUSION

The serum anti-phospholipase A2 receptor IgG4 detected with the method developed in this study has higher sensitivity and higher specificity than total IgG in the diagnosis of IMN.

Thrombospondin Type 1 Domain-Containing 7A Localizes to the Slit Diaphragm and Stabilizes Membrane Dynamics of Fully Differentiated Podocytes

BACKGROUND

About 3%-5% of adults with membranous nephropathy have autoantibodies directed against thrombospondin type 1 domain-containing 7A (THSD7A), a podocyte-expressed transmembrane protein. However, the temporal and spatial expression of THSD7A and its biologic function for podocytes are unknown, information that is needed to understand the effects of THSD7A autoantibodies in this disease.

METHODS

Using a variety of microscopic techniques, we analyzed THSD7A localization in postnatal, adult, and autoantibody-injected mice as well as in human podocytes. We also analyzed THSD7A function in human podocytes using confocal microscopy; Western blotting; and adhesion and migration assays.

RESULTS

We found that THSD7A expression begins on glomerular vascularization with slit diaphragm formation in development. THSD7A localizes to the basal aspect of foot processes, closely following the meanders of the slit diaphragm in human and mice. Autoantibodies binding to THSD7A localize to the slit diaphragm. In human podocytes, THSD7A expression is accentuated at filopodia and thin arborized protrusions, an expression pattern associated with decreased membrane activity of cytoskeletal regulators. We also found that, phenotypically, THSD7A expression in human podocytes is associated not only with increases in cell size, enhanced adhesion, and reduced detachment from collagen type IV-coated plates but also, with decreased ability to migrate.

CONCLUSIONS

Our findings suggest that THSD7A functions as a foot process protein involved in the stabilization of the slit diaphragm of mature podocytes and that autoantibodies to THSD7A, on the basis of their localization, might structurally and functionally alter the slit diaphragm's permeability to protein.

Clinicopathological characteristics of thrombospondin type 1 domain-containing 7A-associated membranous nephropathy

Thrombospondin type 1 domain-containing 7A (THSD7A) is a recently identified target antigen of idiopathic membranous nephropathy (iMN). The clinicopathological characteristics of THSD7A-associated MN are poorly characterised due to low prevalence among MN patients. Among 469 consecutive cases of pathologically confirmed MN diagnosed at four centres in Japan, 14 cases were confirmed positive for THSD7A by immunohistochemistry (3.0%). The prevalence of THSD7A-associated MN tended to be higher in northern Japan. Most cases demonstrated nephrotic-range proteinuria (12/14 cases, 86%). In two patients, cancer was detected at the time of renal biopsy (small-cell carcinoma of the lung and prostatic adenocarcinoma with neuroendocrine differentiation). Both tumours were negative for THSD7A. Four patients had concurrent or previous incidence of allergic diseases, including one patient with Kimura’s disease. Pathological analysis of kidney biopsy tissue revealed slight mesangial cell proliferation in three cases and spike formation in one case. Immunofluorescence studies demonstrated that IgG subclass was mainly IgG4-dominant/codominant (12/13, 92% cases), while the case with prostatic cancer had an IgG2-dominant distribution. The immunostaining profile for components of the lectin complement pathways was not significant in three cases including two patients with malignancy. One case was dual positive for THSD7A and PLA2R. Of 10 cases with known clinical follow-up data, 6 demonstrated reduced serum creatinine and 8 presented reduced proteinuria. In summary, although the major IgG phenotype was usually IgG4-dominant/codominant, clinical background was otherwise heterogeneous. Further investigation of regional differences in THSD7A-associated MN prevalence may reveal genetic and environmental risk factor and associated pathogenic mechanisms.

Primary membranous nephropathy: comprehensive review and historical perspective

Membranous nephropathy (MN) is the most common cause of nephrotic syndrome in non-diabetic Caucasian adults over 40 years of age. It has an estimated incidence of 8–10 cases per 1 million. Fifty per cent of patients diagnosed with primary MN continue to have nephrotic syndrome and 30% of patients may progress to end-stage renal disease over 10 years. Although it was recognised as a distinct clinic-pathological entity in 1940s by immunofluorescence and electron microscopy, the pathogenesis and treatment have become more apparent only in the last decade. Discovery of M-type phospholipase A2 receptor (PLA2R) antibodies and thrombospondin type 1 domain-containing 7A antibodies has given new perspectives in understanding the pathogenesis of the disease process. Anti-PLA2R antibody is the first serologic marker that has promising evidence to be used as a tool to prognosticate the course of the disease. More importantly, therapeutic agents such as rituximab and adrenocorticotropic hormone analogues are the newer therapeutic options that should be considered in the therapy of primary MN.

Characterization of autoantibodies in primary membranous nephropathy and their clinical significance

Introduction: Membranous nephropathy (MN) is the most common cause of a nephrotic syndrome in Caucasian adults. The identification of target antigens in MN in the last decade has had a major impact on the clinical approach to these patients. Areas covered: Since the discoveries in animal models in the 1980s that circulating autoantibodies induce disease upon in situ binding to glomerular podocytes, many attempts have been undertaken to define the human antigens responsible for disease induction. Only in 2009 was Phospholipase A₂ Receptor 1 described as the major antigen responsible for MN onset in about 70% of patients. Subsequently, in 2014, Thrombospondin Type-1 Domain-Containing 7A was identified as a second antigen, accounting for 2-3% of patients with MN. The knowledge of the role of these antibodies in MN has improved the diagnosis and management of patients and helped to better define the need for immunosuppressive treatment. Expert commentary: These discoveries over the last 10 years in the discipline of nephrology have clearly shown the improvements a better understanding of disease pathogenesis can bring for patient care.

An update on clinical significance of use of THSD7A in diagnosing idiopathic membranous nephropathy: a systematic review and meta-analysis of THSD7A in IMN

BACKGROUND

THSD7A is a new target antigen of idiopathic membranous nephropathy (IMN). Moreover, malignancies are also found in patients with THSD7A-positive membranous nephropathy. We aimed to systematically evaluate the prevalence of THSD7A in IMN patients and malignancies in THSD7A-positive patients.

METHODS

We searched English and Chinese database to 31 December 2017 with the term 'THSD7A' or 'thrombospondin type 1 domain-containing 7A'. Meta-analysis was used to explore the positive rate of THSD7A in the IMN patients. Subgroup analysis was performed according to the race, sample size, and detecting method of THSD7A.

RESULTS

Ten studies involving 4121 participants were eventually included. The prevalence of THSD7A was 3% (95% CI, 3%-4%) in all patients and 10% (95% CI, 6%-15%) in PLA2R-negative patients. 77 patients had positive circulating antibodies, and the prevalence of THSD7A was also low at 3% (95% CI, 2%-4%). Overall, 72 patients had positive THSD7A staining on renal biopsy, and the prevalence was 3% (95% CI 2%-4%). Subgroup analysis showed significant differences in the prevalence of THSD7A based on the study sample sizes, however, no significant differences were seen in different ethnic groups. Furthermore, among THSD7A-positive patients, 3/10 studies reported malignancies with the incidence varied from 6% to 25%.

CONCLUSIONS

The prevalence of THSD7A is more common in the PLA2R-negative patients than the IMN patients. Screening for malignancies in THSD7A-positive MN patients is recommended.

Identification of a two-SNP PLA2R1 Haplotype and HLA-DRB1 Alleles as Primary Risk Associations in Idiopathic Membranous Nephropathy

The associations of single nucleotide polymorphisms (SNPs) in PLA2R1 and HLA-DQA1, as well as HLA-DRB1*15:01-DQB1*06:02 haplotype with idiopathic membranous nephropathy (IMN) is well known. However, the primary associations of these loci still need to be determined. We used Japanese-specific SNP genotyping array and imputation using 2,048 sequenced Japanese samples to fine-map PLA2R1 region in 98 patients and 413 controls. The most significant SNPs were replicated in a separate sample set of 130 patients and 288 controls. A two-SNP haplotype of intronic and missense SNPs showed the strongest association. The intronic SNP is strongly associated with PLA2R1 expression in the Genotype-Tissue Expression (GTEx) database, and the missense SNP is predicted to alter peptide binding with HLA-DRB1*15:01 by the Immune Epitope Database (IEDB). In HLA region, we performed relative predispositional effect (RPE) tests and identified additional risk alleles in both HLA-DRB1 and HLA-DQB1. We collapsed the risk alleles in each of HLA-DRB1 and HLA-DQB1 into single risk alleles. Reciprocal conditioning of these collapsed risk alleles showed more residual significance for HLA-DRB1 collapsed risk than HLA-DQB1 collapsed risk. These results indicate that changes in the expression levels of structurally different PLA2R protein confer risk for IMN in the presence of risk HLA-DRB1 alleles.

A Refractory Case of Secondary Membranous Nephropathy Concurrent with IgG4-related Tubulointerstitial Nephritis

A 58-year-old man with type 1 autoimmune pancreatitis was referred to nephrologists for severe proteinuria. Laboratory data revealed a high serum IgG4 level, hypoalbuminemia, and massive proteinuria, which were compatible with nephrotic syndrome. The renal pathological findings confirmed the diagnosis of secondary membranous nephropathy concurrent with IgG4-related tubulointerstitial nephritis. Despite the improvement of interstitial markers, the proteinuria was refractory to prednisolone, requiring cyclosporine to achieve complete remission. Membranous nephropathy is a rare manifestation of IgG4-related kidney disease. This case shows that the therapeutic response to prednisolone significantly differs between glomerular lesions and interstitial lesions of IgG4-related kidney disease.

A case report of remission of refractory membranous nephropathy progressing to stage 4 chronic kidney disease using low-dose rituximab: A long-term follow-up

RATIONALE

As suggested by the 2012 KDIGO guidelines, persistent elevation of serum creatinine > 3.5 mg/dl (> 309 μmol/l) (or an estimated glomerular filtration rate < 30 ml/min per 1.73 m is one of contradictions for the use of immunosuppressive therapy in membranous nephropathy.

PATIENT CONCERNS

A 45-year-old man with membranous nephropathy negative for serum anti-phospholipase-A2-receptor antibody, showed no response to corticosteroids and cyclophosphamide. He progressed to chronic kidney disease stage 4 (CKD4) under tacrolimus and relapsed after withdrawal.

DIAGNOSES

The patient received repeated renal biopsy, comfirming the diagnosis of membranous nephropathy with progressive glomerular and tubulointerstitial scarring.

INTERVENTIONS

He was treated with successfully four times with lose-dose (180 mg/m every 2-3 months) rituximab (RTX) depending on his B cell counts, aiming to remain at 0-5 cells/μl.

OUTCOMES

The patient was followed-up for almost 6 years. He achieved a partial remission at 11 months and a complete remission of the nephritic range of proteinuria at 34 months following infusion of RTX. RTX was well tolerated and the patient's renal function improved. He had no edema and his dosage of corticosteroids could be discontinued.

LESSONS

This case strongly suggested that rituximab has promising therapeutic significance, even in patients progressing to CKD4.

Idiopathic membranous nephropathy in children treated with rituximab: report of two cases

BACKGROUND

Idiopathic membranous nephropathy is an uncommon cause of nephrotic syndrome in children and can present treatment challenges. The current treatment options of steroids and cyclophosphamide, cyclosporine, or mycophenolate require prolonged treatment durations and the associated side effects may result in nonadherence in children, especially in adolescents.

CASE-DIAGNOSIS

We report two adolescent patients with idiopathic membranous nephropathy with nephrotic range proteinuria and elevated anti-phospholipase A2 receptor levels who did not achieve remission with steroids and were later treated with rituximab. Both patients received two doses of rituximab and responded with remission. In addition, anti-PLA2R antibody levels normalized and/or significantly improved.

CONCLUSIONS

Rituximab seems to be a safe and effective treatment option in children with idiopathic membranous nephropathy due to anti-PLA2R. Further studies are needed to evaluate this effectiveness.

Diagnostic Test Accuracy of Serum Anti-PLA2R Autoantibodies and Glomerular PLA2R Antigen for Diagnosing Idiopathic Membranous Nephropathy: An Updated Meta-Analysis

Background

M-type phospholipase A2 receptor (PLA2R) is known as a major antigen on podocytes, which is involved with the pathogenesis of idiopathic membranous nephropathy (iMN). Many studies have shown that serum anti-PLA2R autoantibodies (sPLA2R) are prevalent in patients with iMN but are rarely detected in secondary membranous nephropathy (SMN) or other glomerulonephritis. The anti-PLA2R is considered as a promising serum biomarker in iMN but reports about its diagnostic value are variable and inconsistent.

Objective

To evaluate the diagnostic test accuracy (DTA) of anti-PLA2R and glomerular PLA2R antigen (gPLA2R) for diagnosing iMN.

Method

MEDLINE, EMBASE, WEB OF SCIENCE, and COCHRANE LIBRARY were searched from 2009 January to February 2018. Heterogeneity was evaluated by Q test and I². Source of heterogeneity was explored by subgroup analysis and meta-regression. Meta-analysis was executed and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement.

Results

Totally, 35 studies were retrieved under the pre-set study eligibility criteria. Twenty-eight studies were included to evaluate the DTA of anti-PLA2R for differentiating iMN from non-iMN. They indicated a pooled sensitivity of 65% (63–67%), specificity of 97% (97–98%), positive likelihood ratio of 15.65 (9.95–24.62), and negative likelihood ratio of 0.37 (0.32–0.42) with a diagnostic OR (sDOR) of 50.41 (31.56 to 80.52) and AUC of 0.9393. No threshold effect was detected. The heterogeneity analysis for sDOR showed that I² = 50.3% and Cochran-Q = 54.29, df = 27 (p = 0.0014). Heterogeneity was significant. Meta-regression revealed that sample size might be the potential source of heterogeneity. Subgroup analysis demonstrated that method type and ratio of patients with nephrotic-range proteinuria at baseline might be the source of heterogeneity. Sixteen studies reported the diagnostic value of glomerular PLA2R antigen for differentiating iMN from non-iMN. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, sDOR, and AUC were 79% (76–81%), 90% (88–92%), 8.17 (5.60–11.93), 0.25 (0.19–0.33), 39.37 (22.18–60.13), and 0.9278. Heterogeneity analysis showed that Cochran-Q = 35.36; df = 15 (p = 0.002), and I² for sDOR was 57.6%.

Conclusion

sPLA2R and gPLA2R demonstrated a good diagnostic accuracy in differentiating iMN and non-iMN.

Kidney disease models: tools to identify mechanisms and potential therapeutic targets

Acute kidney injury (AKI) and chronic kidney disease (CKD) are worldwide public health problems affecting millions of people and have rapidly increased in prevalence in recent years. Due to the multiple causes of renal failure, many animal models have been developed to advance our understanding of human nephropathy. Among these experimental models, rodents have been extensively used to enable mechanistic understanding of kidney disease induction and progression, as well as to identify potential targets for therapy. In this review, we discuss AKI models induced by surgical operation and drugs or toxins, as well as a variety of CKD models (mainly genetically modified mouse models). Results from recent and ongoing clinical trials and conceptual advances derived from animal models are also explored.

Antiphospholipase 2 receptor antibody levels to predict complete spontaneous remission in primary membranous nephropathy

Background

M-type phospholipase A2 receptor (APLA2R) is considered the major antigen involved in the pathogenesis of adult primary membranous nephropathy (MN), which is the leading cause of non-diabetic nephrotic syndrome. Antibodies to this antigen have been proved to be an excellent biomarker of disease activity in primary MN. In fact, preliminary data suggest that the higher the antibody level the more proteinuria, and that a decrease in antibody level precedes the remission of proteinuria, but more solid evidence is needed.

Methods

The present work aims to characterize the predictive value of the level of antibodies against PLA2R as a biomarker of disease course and treatment response in a well-defined cohort of 62 patients from University Hospitals Clinic of Barcelona and Josep Trueta in Girona. The primary outcome was the appearance of a spontaneous complete remission (CR), defined as induction of a CR without the use of immunosuppressive agents.

Results

In common with other reports, this work confirms that spontaneous CR is more frequent in patients with low titre of APLA2R at diagnosis, but strikingly, in this cohort we found that spontaneous CR was achieved in patients with APLA2R levels <40 UI/mL. Furthermore, spontaneous CR were less frequently observed in patients with proteinuria >8 g/day.

Conclusions

In conclusion, these findings point out the important role of APLA2R as a tool to predict the disease course and establish personalized therapeutic options at the moment of diagnosis of primary MN. Specifically, patients with low titre of APLA2R (<40 UI/mL) and proteinuria <4/day could obtain benefit of a longer period of follow-up with conservative treatment after diagnosis.

Primary Membranous Nephropathy

Membranous nephropathy (MN) is a unique glomerular lesion that is the most common cause of idiopathic nephrotic syndrome in nondiabetic white adults. About 80% of cases are renal limited (primary MN, PMN) and 20% are associated with other systemic diseases or exposures (secondary MN). This review focuses only on PMN. Most cases of PMN have circulating IgG4 autoantibody to the podocyte membrane antigen PLA2R (70%), biopsy evidence PLA2R staining indicating recent immunologic disease activity despite negative serum antibody levels (15%), or serum anti-THSD7A (3%-5%). The remaining 10% without demonstrable anti-PLA2R/THSd7A antibody or antigen likely have PMN probably secondary to a different, still unidentified, anti-podocyte antibody. Considerable clinical and experimental data now suggests these antibodies are pathogenic. Clinically, 80% of patients with PMN present with nephrotic syndrome and 20% with non-nephrotic proteinuria. Untreated, about one third undergo spontaneous remission, especially those with absent or low anti-PLA2R levels, one-third progress to ESRD over 10 years, and the remainder develop nonprogressive CKD. Proteinuria can persist for months after circulating anti-PLA2R/THSD7A antibody is no longer detectable (immunologic remission). All patients with PMN should be treated with supportive care from the time of diagnosis to minimize protein excretion. Patients with elevated anti-PLA2R/THSD7A levels and proteinuria >3.5 g/d at diagnosis, and those who fail to reduce proteinuria to <3.5 g after 6 months of supportive care or have complications of nephrotic syndrome, should be considered for immunosuppressive therapy. Accepted regimens include steroids/cyclophosphamide, calcineurin inhibitors, and B cell depletion. With proper management, only 10% or less will develop ESRD over the subsequent 10 years.

Anti-pituitary antibodies against corticotrophs in IgG4-related hypophysitis

PURPOSE

IgG4-related disease is a systemic inflammatory disease characterized by infiltration of IgG4-positive plasma cells into multiple organs, including the pituitary gland. Autoimmunity is thought to be involved in the pathogenesis of IgG4-related disease. The diagnosis of IgG4-related hypophysitis (IgG4-RH) is difficult because its clinical features, such as pituitary swelling and hypopituitarism, are similar to those of other pituitary diseases, including lymphocytic hypophysitis and sellar/suprasellar tumors. The presence and significance of anti-pituitary antibodies (APA) in IgG4-RH is unclear.

METHODS

In this case-control study, we used single indirect immunofluorescence on human pituitary substrates to assess the prevalence of serum APA in 17 patients with IgG4-RH, 8 control patients with other pituitary diseases (lymphocytic infundibulo-neurohypophysitis, 3; craniopharyngioma, 2; germinoma, 3), and 9 healthy subjects. We further analyzed the endocrine cells targeted by the antibodies using double indirect immunofluorescence.

RESULTS

APA were found in 5 of 17 patients with IgG4-RH (29%), and in none of the pituitary controls or healthy subjects. The endocrine cells targeted by the antibodies in the 5 IgG4-RH cases were exclusively corticotrophs. Antibodies were of the IgG1 subclass, rather than IgG4, in all 5 cases, suggesting that IgG4 is not directly involved in the pathogenesis. Finally, antibodies recognized pro-opiomelanocortin in 2 of the cases.

CONCLUSIONS

Our study suggests that autoimmunity is involved in the pathogenesis of IgG4-RH and that corticotrophs are the main antigenic target, highlighting a possible new diagnostic marker for this condition.