Objectives Anti-neutrophil cytoplasmic antibody (ANCA) vasculitis is a complex disease, with much debate about the utility of systems for classification and diagnosis. We compared three currently used classification systems in predicting disease prognosis. Methods Three classification systems were applied to 502 patients with biopsy proven ANCA vasculitis: the Chapel Hill Consensus Conference (CHCC) definition with categories for granulomatosis with polyangiitis (GPA, Wegener’s granulomatosis), microscopic polyangiitis (MPA) and the Kidney Limited Disease (KLD); European Medicines Agency (EMA) system with categories for GPA and MPA, and classification based on ANCA specificity (PR3 versus MPO). Outcomes included treatment resistance, relapse, end stage kidney disease (ESKD) and death. Proportional hazards models were compared between systems using an information-theoretic approach to rank models by predictive fit. Hazard Ratios (HR) with 95% confidence intervals (CI) and p-values are reported. Results ANCA specificity was predictive of relapse, with PR3-ANCA patients almost twice as likely as those with MPO-ANCA to relapse (HR=1.89, 95% CI=1.33–2.69, p=0.0004), and ANCA specificity had the best predictive model fit (Model Rank=1) compared to CHCC and EMA. CHCC and EMA systems did not predict relapse. By ANCA specificity, categories of GPA, MPA and KLD did not distinguish differences in probability of relapse-free survival. None of the systems predicted treatment resistance, ESKD or death. Conclusion ANCA specificity independently predicts relapse among patients with ANCA vasculitis with renal disease. Classification and diagnostic systems that incorporate ANCA specificity, such as PR3-ANCA-MPA and MPO-ANCA-MPA, provide a more useful tool for predicting relapse than the clinic pathologic category alone.

Anti-neutrophil cytoplasmic antibody-associated (ANCA-associated) small vessel necrotizing vasculitis is caused by immune-mediated inflammation of the vessel wall and is diagnosed in some cases by the presence of myeloperoxidase-specific antibodies (MPO-ANCA). This multicenter study sought to determine whether differences in ANCA epitope specificity explain why, in some cases, conventional serologic assays do not correlate with disease activity, why naturally occurring anti-MPO autoantibodies can exist in disease-free individuals, and why ANCA are undetected in patients with ANCA-negative disease. Autoantibodies from human and murine samples were epitope mapped using a highly sensitive epitope excision/mass spectrometry approach. Data indicated that MPO autoantibodies from healthy individuals had epitope specificities different from those present in ANCA disease. Importantly, this methodology led to the discovery of MPO-ANCA in ANCAnegative disease that reacted against a sole linear sequence. Autoantibodies against this epitope had pathogenic properties, as demonstrated by their capacity to activate neutrophils in vitro and to induce nephritis in mice. The confounder for serological detection of these autoantibodies was the presence of a fragment of ceruloplasmin in serum, which was eliminated in purified IgG, allowing detection. These findings implicate immunodominant epitopes in the pathology of ANCA-associated vasculitis and suggest that autoantibody diversity may be common to other autoimmune diseases.

SummaryBackground and objectives The aims of this study were to determine the frequency of venous thromboembolic events in a large cohort of patients with idiopathic membranous nephropathy and to identify predisposing risk factors.Design, setting, participants, & measurements We studied patients with biopsy-proven membranous nephropathy from the Glomerular Disease Collaborative Network (n=412) and the Toronto Glomerulonephritis Registry (n=486) inception cohorts. The cohorts were pooled after establishing similar baseline characteristics (total n=898). Clinically apparent and radiologically confirmed venous thromboembolic events were identified. Potential risk factors were evaluated using multivariable logistic regression models.Results Sixty-five (7.2%) subjects had at least one venous thromboembolic event, and this rate did not differ significantly between registries. Most venous thromboembolic events occurred within 2 years of first clinical assessment (median time to VTE = 3.8 months). After adjusting for age, sex, proteinuria, and immunosuppressive therapy, hypoalbuminemia at diagnosis was the only independent predictor of a venous thromboembolic event. Each 1.0 g/dl reduction in serum albumin was associated with a 2.13-fold increased risk of VTE. An albumin level ,2.8 g/dl was the threshold below which risk for a venous thromboembolic event was greatest.Conclusions We conclude that clinically apparent venous thromboembolic events occur in about 7% of patients with membranous nephropathy. Hypoalbuminemia, particularly ,2.8 g/dl, is the most significant independent predictor of venous thrombotic risk.

Objective The development of pathogenic anti-neutrophil cytoplasmic autoantibodies (ANCAs) can result in systemic small vessel vasculitis. However, the breakdown in immune tolerance that results in the induction and persistence of ANCAs is not well-understood. We hypothesized that abnormal T cell regulation is central to disease pathogenesis and demonstrate here two separate abnormalities in T cell regulation in ANCA-associated vasculitis patients. Methods Peripheral blood samples were obtained from patients with ANCA-associated vasculitis (n=63) and healthy controls (n=19) for flow cytometric analysis of CD4+ T cell populations. Functional T cell studies were performed with FACS sorted CD4+ T cell populations stimulated with anti-CD3/28. Results First, we show that the Treg frequency in the peripheral blood of active disease patients is increased, but Tregs from patients with ANCA-associated vasculitis have decreased suppressive function. Tregs from active disease patients disproportionately utilize a FOXP3 isoform lacking exon 2, which may alter Treg function. Second, we identify a CD4+ T cell population with increased frequency that is resistant to Treg suppression, produces pro-inflammatory cytokines, and is antigen-experienced. Conclusion ANCA-associated vasculitis is associated with disruption of the suppressive Treg network and increased frequency of a distinct pro-inflammatory effector T cell subset which comprises the majority of peripheral CD4+ T cells.

Lysosomal membrane protein 2 (LAMP-2) is a target of antineutrophil cytoplasmic autoantibodies (ANCA) in addition to the more commonly known targets proteinase 3 and myeloperoxidase. The prevalence of anti-LAMP-2 antibodies and their relationship to disease in ANCA glomerulonephritis are not well described. We measured anti-LAMP-2 reactivity in 680 sera samples (two academic centers) from patients with ANCA glomerulonephritis (n=329); those with ANCA-negative glomerulonephritis (n=104); those with fimbriated, gram-negative Escherichia coli urinary tract infection (n=104); disease controls (n=19); and healthy volunteers (n=124). With levels in healthy controls used to define a reference range, anti-LAMP-2 reactivity was present in 21% of ANCA sera from two of the centers; reactivity was present in 16% of the control group with urinary tract infection. Western blotting and immunofluorescence microscopy did not verify positivity. Titers of anti-myeloperoxidase and anti-proteinase 3 antibodies were 1500-fold and 10,000-fold higher than anti-LAMP-2 titers, respectively. There was no correlation between anti-LAMP-2 antibodies and disease activity. Furthermore, Wistar Kyoto rats injected with anti-LAMP-2 antibodies did not develop glomerulonephritis. In conclusion, antibodies that react with LAMP-2 may exist at very low titers in a minority of patients with ANCA disease. These data do not support a mechanistic relationship between anti-LAMP-2 antibodies and ANCA glomerulonephritis.