Sjoerd A.M.E.G. Timmermans

Evaluation of Anti-PLA2R1 as Measured by a Novel ELISA in Patients With Idiopathic Membranous Nephropathy A Cohort Study

OBJECTIVES Autoantibodies against the M-type phospholipase A2 receptor 1 (anti-PLA2R1) have been demonstrated to be very specific for idiopathic membranous nephropathy (MN). We studied a novel enzyme-linked immunosorbent assay (ELISA) and compared results with results obtained using an indirect immunofluorescence (IIF) and a Western blotting test (WB). METHODS One-hundred nine patients with idiopathic MN were recruited between November 1979 and March 2011. The control cohort comprised serum samples from patients with secondary MN (n = 16) and nephrotic controls (n = 17). The presence of anti-PLA2R1 in serum samples obtained at the time of renal biopsy was determined using ELISA, IIF, and WB. RESULTS With similar specificity (≥ 97%), sensitivity varied from 68% (IIF) to 72% (ELISA, WB). Remarkably, patients who were seronegative for anti-PLA2R1 more often entered spontaneous remission (P = .038), whereas seropositive patients were more frequently treated with immunosuppressive agents (P < .001). CONCLUSIONS ELISA performs excellently in differentiating idiopathic from secondary MN. Furthermore, ELISA shared high agreement with WB and IIF.

Positron emission tomography scanning in anti-neutrophil cytoplasmic antibodies-associated vasculitis

AbstractTools for evaluation of disease activity in patients with anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) include scoring clinical manifestations, determination of biochemical parameters of inflammation, and obtaining tissue biopsies. These tools, however, are sometimes inconclusive. 2-deoxy-2-[18F]-fluoro-D-glucose (FDG) positron emission tomography (PET) scans are commonly used to detect inflammatory or malignant lesions. Our objective is to explore the ability of PET scanning to assess the extent of disease activity in patients with AAV.Consecutive PET scans made between December 2006 and March 2014 in Maastricht (MUMC) and between July 2008 and June 2013 in Brussels (EUH) to assess disease activity in patients with AAV were retrospectively included. Scans were re-examined and quantitatively scored using maximum standard uptake values (SUVmax). PET findings were compared with C-reactive protein (CRP) and ANCA positivity at the time of scanning.Forty-four scans were performed in 33 patients during a period of suspected active disease. All but 2 scans showed PET-positive sites, most commonly the nasopharynx (n = 22) and the lung (n = 22). Forty-one clinically occult lesions were found, including the thyroid gland (n = 4 patients), aorta (n = 8), and bone marrow (n = 7). The amount of hotspots, but not the highest observed SUVmax value, was higher if CRP levels were elevated. Seventeen follow-up scans were made in 13 patients and showed decreased SUVmax values.FDG PET scans in AAV patients with active disease show positive findings in multiple sites of the body even when biochemical parameters are inconclusive, including sites clinically unsuspected and difficult to assess otherwise.

Anti-PLA2R Antibodies as a Prognostic Factor in PLA2R-Related Membranous Nephropathy

Background: The natural course of idiopathic membranous nephropathy (MN) varies, as it is known through favorable outcomes in most patients. However, one third of patients with idiopathic MN will slowly progress to end-stage renal disease (ESRD). To prevent disease progression, patients at high risk to develop ESRD are treated with immunosuppressive agents. Therefore, a correct selection of patients who need immunosuppressive treatment is important. Methods: Here, we evaluated the prognostic value of anti-phospholipase A2 receptor 1 antibody (anti-PLA2R) levels regarding clinical outcome in a well-defined cohort of 73 PLA2R-related MN patients with long-term follow-up. At baseline, patients were subdivided into patients with either low or high antibody levels based on ELISA testing. Results: Spontaneous remission rates were highest among patients with low anti-PLA2R levels (79%; hazard ratio 2.72 (95% CI 1.22-6.08), p = 0.02) after a median follow-up of 2.9 (95% CI 0.8-5.0, p < 0.001) years, whereas high anti-PLA2R levels were associated with persistent proteinuria (p = 0.04) and/or the need for immunosuppressive therapy (p < 0.001). Renal survival rates were 97% at 5 years, 93% at 10 years, and 89% at 15 years; however, this was not different between the anti-PLA2R groups. ESRD occurred significantly faster in patients with severe proteinuria as compared to patients with either mild (p = 0.02) or moderate proteinuria (p = 0.05). Conclusions: Low anti-PLA2R levels may predict spontaneous remissions in patients with PLA2R-related MN. Therefore, we suggest that quantification of anti-PLA2R is of value to monitor these patients.

Endothelial progenitor cells are differentially impaired in ANCA-associated vasculitis compared to healthy controls

BackgroundEndothelial progenitor cells (EPC) are of major importance in vascular repair under healthy circumstances. Vascular injury in need of repair occurs frequently in ANCA-associated vasculitis (AAV). A specialized T cell subset enhancing EPC function and differentiation has recently been described. These angiogenic T cells (Tang) may have an important impact on the vascular repair process. Therefore, the aim of our study was to investigate EPC and Tang in AAV.MethodsFifty-three patients suffering from AAV and 29 healthy controls (HC) were enrolled in our study. Forty-four patients were in remission, nine patients were in active state of disease. Patients were either untreated or were under monotherapy with low-dose steroids (max. 5 mg/day) at the time of sampling. Circulating EPC and Tang were determined by flow cytometry (FACS). The functional capacity of EPC was assessed by established cell culture methods.ResultsCirculating EPC were significantly decreased in AAV as compared to HC. The capacity of EPC to differentiate and proliferate was differentially impaired in patients as compared to HC. The outgrowth of endothelial colony-forming cells (ECFC) was severely decreased in patients whereas colony-forming units-endothelial cell (CFU-EC) outgrowth was unaffected. ECFC and CFU-EC differentiation was strictly T cell-dependent. Patients with a relapsing disease course had an impaired ECFC outgrowth and expansion of Tang as compared to patients with a stable, nonrelapsing disease.ConclusionsThe differentiation process of EPC is impaired in AAV. This may favor insufficient vascular repair promoting a relapsing disease course. Finally, these factors may explain a higher cardiovascular morbidity as has been previously documented in AAV.

Seasonal Influence on the Risk of Relapse at a Rise of Antineutrophil Cytoplasmic Antibodies in Vasculitis Patients with Renal Involvement

Objective. The objective of this study was to identify risk factors for a relapse at the time of an increase in antineutrophil cytoplasmic antibodies (ANCA) in patients with renal ANCA-associated vasculitis (AAV). Methods. All patients between January 2000 and November 2011 with renal AAV having an ANCA rise during remission were included. Differences in time to relapse since the ANCA rise were assessed using a Cox regression model. The level of 25-hydroxy Vitamin D (25(OH)D) was assessed at the ANCA rise and at a subsequent relapse or time-matched during remission. Results. Sixty patients had an ANCA rise, of whom 36 patients relapsed. Three risk factors were associated with a relapse at the time of the ANCA increase: previous disease activity not treated with cyclophosphamide or rituximab (HR 3.48, 95% CI 1.60–7.59), an ANCA rise during the fall season (HR 4.37, 95% CI 1.60–11.90), and an extended ANCA rise (HR 3.57, 95% CI 1.50–8.48). Levels of 25(OH)D significantly decreased during followup in relapsing patients, but not in patients who remained in remission (difference −6.3 ± 14.4, p = 0.017 vs 2.7 ± 16.3, p = 0.430). Conclusion. ANCA rises occurring during the fall season are more frequently followed by a relapse than ANCA rises occurring during other seasons. Although it is tempting to speculate that decreasing Vitamin D levels following the ANCA rise can be held responsible for the subsequent relapse, this remains to be determined.

Granulomatous interstitial nephritis and Crohn's disease

Granulomatous interstitial nephritis has been observed in <1% of native renal biopsies. Here, we describe two patients with granulomatous interstitial nephritis in relation to Crohns disease. Circulating helper and cytotoxic T cells were highly activated, and both cell types predominated in the interstitial infiltrate, indicating a cellular autoimmune response. After immunosuppressive treatment, renal function either improved or stabilized in both patients. In conclusion, granulomatous interstitial nephritis is a genuine extraintestinal manifestation of Crohns disease, the treatment of which should include immunosuppressive agents.

Recent advances in the understanding of immune-mediated nephrotic syndrome: diagnostic and prognostic implications.

Glomerular diseases with severe defects in glomerular permeability give rise to heavy proteinuria and can present as nephrotic syndrome. There are many different causes of the nephrotic syndrome and a renal biopsy is nearly always needed to elucidate the underlying disease. During the last decade, substantial advances have occurred in the understanding of the pathophysiological mechanisms involved in immune-mediated glomerular diseases. Here, we review the diagnostic and prognostic implications of recent progress on the understanding of membranous nephropathy, minimal change disease, focal segmental glomerulosclerosis, amyloidosis, IgA nephropathy and membranoproliferative glomerulonephritis.

C5b9 Formation on Endothelial Cells Reflects Complement Defects among Patients with Renal Thrombotic Microangiopathy and Severe Hypertension

Background Severe hypertension can induce thrombotic microangiopathy (TMA) in the renal vasculature, the occurrence of which has been linked to mechanical stress to the endothelium. Complement defects may be the culprit of disease in patients who present with severe renal disease and often progress to ESRD, despite BP control.Methods We studied a well defined cohort of 17 patients with hypertension-associated TMA to define the prevalence of complement defects by a specific ex vivo serum-based microvascular endothelial cell assay.Results Compared with normal human serum and samples from patients with hypertensive arterionephrosclerosis, 14 of 16 (87.5%) serum samples collected at presentation from 16 patients with hypertension-associated TMA induced abnormal C5b9 formation on microvascular endothelial cells. We detected rare variants in complement genes in eight of 17 (47%) patients. ESRD occurred in 14 of 17 (82%) patients, and recurrent TMA after transplant occurred in seven of 11 (64%) donor kidneys. Eculizumab improved the renal function in three patients and prevented TMA recurrence in an allograft recipient.Conclusions These observations point to complement defects as the key causative factor of ESRD and recurrent TMA after transplant in patients presenting with severe hypertension. Complement defects can be identified by measurements of complement activation on microvascular endothelial cells, which should substantially influence treatment and prognosis.