Novel ELISA for thrombospondin type 1 domain-containing 7A autoantibodies in membranous nephropathy.

Autoantibodies against phospholipase A2 receptor 1 (PLA2R1) and thrombospondin type 1 domain-containing 7A (THSD7A) are emerging as biomarkers to classify membranous nephropathy (MN) and to predict outcome or response to treatment. Anti-THSD7A autoantibodies are detected by Western blot and indirect immunofluorescence test (IIFT). Here, we developed a sensitive enzyme-linked immunosorbent assay (ELISA) optimized for quantitative detection of anti-THSD7A autoantibodies. Among 1012 biopsy-proven MN patients from 6 cohorts, 28 THSD7A-positive patients were identified by ELISA, indicating a prevalence of 2.8%. By screening additional patients, mostly referred because of PLA2R1-unrelated MN, we identified 21 more cases, establishing a cohort of 49 THSD7A-positive patients. Twenty-eight patients (57%) were male, and male patients were older than female patients (67 versus 49 years). Eight patients had a history of malignancy, but only 3 were diagnosed with malignancy within 2 years of MN diagnosis. We compared the results of ELISA, IIFT, Western blot, and biopsy staining, and found a significant correlation between ELISA and IIFT titers. Anti-THSD7A autoantibodies were predominantly IgG4 in all patients. Eight patients were double positive for THSD7A and PLA2R1. Levels of anti-THSD7A autoantibodies correlated with disease activity and with response to treatment. Patients with high titer at baseline had poor clinical outcome. In a subgroup of patients with serial titers, persistently elevated anti-THSD7A autoantibodies were observed in patients who did not respond to treatment or did not achieve remission. We conclude that the novel anti-THSD7A ELISA can be used to identify patients with THSD7A-associated MN and to monitor autoantibody titers during treatment.

Treatment pattern in patients with idiopathic membranous nephropathy-practices in Sweden at the start of the millennium.

BACKGROUND: Idiopathic membranous nephropathy (MN) is one of the leading causes of nephrotic syndrome in adults and may result in end-stage renal disease (ESRD). In this retrospective study, we describe the outcomes and treatment patterns of patients with idiopathic MN in six nephrology clinics in the western part of Sweden. METHODS: Seventy-three consecutive patients with biopsy-proven MN in the years 2000-12 were classified as idiopathic, i.e. secondary forms were excluded. The patients were followed retrospectively for a mean period of 83 months and clinical data were collected through the medical files. RESULTS: A high proportion (88%) of the patients received supportive treatment with angiotensin-converting enzyme inhibition, angiotensin receptor blockade and/or statins. At the end of follow-up, 43 patients were in complete remission, 12 in partial remission, 10 patients had developed ESRD and 8 patients had on-going proteinuria. Fifty-one per cent of the patients received immunosuppressive therapy and the choice of therapy varied between and within the clinics. There was a tendency to initiate specific treatment at an early point instead of awaiting a possible spontaneous remission (21% of the patients), and non-recommended therapy such as corticosteroids only was used in a high proportion of these cases (47%). CONCLUSIONS: Even though the treatment recommendations in idiopathic MN have not changed the last decade, the question of whom and when to treat seems to lead to uncertainty. Recent studies have presented promising results supporting the PLA2R antibody the predictive marker needed for this patient group. The diverse treatment approach presented in this study might have resulted in a worse outcome than expected. Hopefully, unnecessary exposure to immunosuppressive therapy or delayed treatment can be avoided through better support, education and treatment forums, and thus result in an improved outcome.

Glomerular IgG subclasses in idiopathic and malignancy-associated membranous nephropathy.

BACKGROUND: In idiopathic membranous nephropathy (MN), antibodies directed towards the glomerular phospholipase A2 receptor (PLA2R) have mainly been reported to be of IgG4 subclass. However, the role of the different IgG subclasses in the pathogenesis of MN, both in idiopathic MN and in secondary cases, is still unclear. In this retrospective study, we test the hypothesis that the absence of glomerular IgG4 and PLA2R in patients with MN indicates malignant disease. METHODS: The distribution pattern of glomerular IgG subclasses and PLA2R was studied in 69 patients with idiopathic MN and 16 patients with malignancy-associated MN who were followed up for a mean of 83 months. RESULTS: A significant correlation between the absence of IgG4 and PLA2R and malignancy-associated MN was found. Thus, IgG4 was positive in 45 of 69 patients (65%) with idiopathic MN but only in 5 of 16 patients (31%) with malignancy-associated MN. The other IgG subclasses did not differ statistically between the groups, IgG2-positivity being present in more than 94% of patients in both groups. Thirty-five of 63 patients (56%) with idiopathic MN and 3 of 16 (19%) patients with malignancy-associated MN had glomerular deposits of PLA2R. CONCLUSIONS: We have found that the absence of glomerular IgG4 and PLA2R is common in patients with malignancy-associated MN. In our material, IgG2 could not be used as a marker of underlying malignant disease. Finally, neither IgG1 nor IgG3 seems to be involved in the pathogenesis of MN.