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Low Serum Complement C3 Levels at Diagnosis of Renal ANCA-Associated Vasculitis Is Associated with Poor Prognosis.

ABSTRACT: Recent studies have demonstrated the key role of the complement alternative pathway (cAP) in the pathophysiology of experimental ANCA-associated vasculitis (AAV). However, in human AAV the role of cAP has not been extensively explored. In the present work, we analysed circulating serum C3 levels measured at AAV onset and their relation to outcomes.We conducted a retrospective observational cohort study including 45 consecutive patients with AAV diagnosed between 2000 and 2014 with serum C3 measurement at diagnosis, before immunosuppressive treatment initiation. Two groups were defined according to the median serum C3 level value: the low C3 group (C3<120 mg/dL) and the high C3 level group (C3?120 mg/dL). Patient and renal survivals, association between C3 level and renal pathology were analysed.Serum complement C3 concentration remained in the normal range [78-184 mg/dL]. Compared with the high C3 level, the patients in the low C3 level group had lower complement C4 concentrations (P = 0.008) and lower eGFR (P = 0.002) at diagnosis. The low C3 level group had poorer patient and death-censored renal survivals, compared with the high C3 level group (P = 0.047 and P = 0.001, respectively). We observed a significant negative correlation between C3 levels and the percentage of glomeruli affected by cellular crescent (P = 0.017, r = -0.407). According to the Berden et al renal histologic classification, patients in the crescentic/mixed category had low C3 levels more frequently (P<0.01). Interestingly, we observed that when patients with the crescentic/mixed histologic form were analysed according to C3 level, long term renal survival was significantly greater in the high C3 level group than in the low C3 level group (100% vs 40.7% at 6 years, p = 0.046). No relationship between serum C4 and renal outcome was observed.A Low C3 serum level in AAV patients at diagnosis is associated with worse long-term patient and renal survival.

SUBMITTER: Augusto JF

PROVIDER: S-EPMC4938207 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Low Serum Complement C3 Levels at Diagnosis of Renal ANCA-Associated Vasculitis Is Associated with Poor Prognosis.

Augusto Jean-François JF Langs Virginie V Demiselle Julien J Lavigne Christian C Brilland Benoit B Duveau Agnès A Poli Caroline C Chevailler Alain A Croue Anne A Tollis Frederic F Sayegh Johnny J Subra Jean-François JF

PloS one 20160708 7

<h4>Background</h4>Recent studies have demonstrated the key role of the complement alternative pathway (cAP) in the pathophysiology of experimental ANCA-associated vasculitis (AAV). However, in human AAV the role of cAP has not been extensively explored. In the present work, we analysed circulating serum C3 levels measured at AAV onset and their relation to outcomes.<h4>Methods</h4>We conducted a retrospective observational cohort study including 45 consecutive patients with AAV diagnosed betwee ...[more]

PMID: 27391243

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Project description:IntroductionAntineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a potentially life-threatening systemic small-vessel vasculitis that is characterized by pauci-immune glomerulonephritis, depicting in turn a major denominator of AAV mortality. It is well established that AAV patients feature an increased risk of developing thrombotic events, and platelets are activated in AAV patients being triggered by the alternative complement pathway. Platelets guard vessels integrity and initiate thrombus formation in response to endothelial damage, further constituting a triangular interconnection with the activation of neutrophils and the complement system. We here aimed to systematically assess the relevance of platelet counts and systemic complement system activation regarding distinct histopathological lesions in ANCA-associated renal vasculitis.MethodsA cohort of 53 biopsy-proven cases of ANCA-associated renal vasculitis were retrospectively enrolled in a single-center observational study. Univariate and multivariate regression analysis was performed to identify parameters associated with platelet counts in ANCA-associated renal vasculitis compared to disease controls. Finally, the relevance of platelets for disease course and recovery was assessed by survival analysis.ResultsLower platelet counts correlated with markers of kidney injury including eGFR loss (p=0.0004) and lower complement C3 levels (p=0.0037). Multivariate and subgroup analysis revealed that this association was only present in the subgroup with MPO-ANCA seropositivity (eGFR loss: p=0.0009, lower C3: p=0.0032). While lower platelet counts correlated with kidney injury in the PR3-ANCA subgroup (eGFR loss: p=0.0272), we did not observe an independent association with complement C3 levels (p=0.4497). Independent of any glomerular lesion, lower platelet counts correlated with interstitial fibrosis (p=0.0313), tubular atrophy (p=0.0073), and tubulitis in areas of interstitial fibrosis and tubular atrophy (p=0.0033). Finally, we observed significant differences with increased requirement of kidney replacement therapy (KRT) or death in the subgroup below median platelet counts (HR: 4.1, 95% CI: 1.6-10, p=0.0047), associated with a lower probability of discharge and prolonged hospitalization in this subgroup (HR: 0.5, 95% CI: 0.3-0.9, p=0.0113).ConclusionBased on our observation that an association between platelets and complement system activation is only observed in the MPO-ANCA subgroup, this could implicate that platelets and complement C3 link innate immunity to tubulointerstitial injury in the presence of MPO-ANCA autoantibodies.

Project description:Antineutrophil cytoplasm antibody (ANCA)-associated vasculitides are small-vessel vasculitides that include granulomatosis with polyangiitis (formerly Wegener's granulomatosis), microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome). Renal-limited ANCA-associated vasculitides can be considered the fourth entity. Despite their rarity and still unknown cause(s), research pertaining to ANCA-associated vasculitides has been very active over the past decades. The pathogenic role of antimyeloperoxidase ANCA (MPO-ANCA) has been supported using several animal models, but that of antiproteinase 3 ANCA (PR3-ANCA) has not been as strongly demonstrated. Moreover, some MPO-ANCA subsets, which are directed against a few specific MPO epitopes, have recently been found to be better associated with disease activity, but a different method than the one presently used in routine detection is required to detect them. B cells possibly play a major role in the pathogenesis because they produce ANCAs, as well as neutrophil abnormalities and imbalances in different T-cell subtypes [T helper (Th)1, Th2, Th17, regulatory cluster of differentiation (CD)4+ CD25+ forkhead box P3 (FoxP3)+ T cells] and/or cytokine-chemokine networks. The alternative complement pathway is also involved, and its blockade has been shown to prevent renal disease in an MPO-ANCA murine model. Other recent studies suggested strongest genetic associations by ANCA type rather than by clinical diagnosis. The induction treatment for severe granulomatosis with polyangiitis and microscopic polyangiitis is relatively well codified but does not (yet) really differ by precise diagnosis or ANCA type. It comprises glucocorticoids combined with another immunosuppressant, cyclophosphamide or rituximab. The choice between the two immunosuppressants must consider the comorbidities, past exposure to cyclophosphamide for relapsers, plans for pregnancy, and also the cost of rituximab. Once remission is achieved, maintenance strategy following cyclophosphamide-based induction relies on less toxic agents such as azathioprine or methotrexate. The optimal maintenance strategy following rituximab-based induction therapy remains to be determined. Preliminary results on rituximab for maintenance therapy appear promising. Efforts are still under way to determine the optimal duration of maintenance therapy, ideally tailored according to the characteristics of each patient and the previous treatment received.

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Low Serum Complement C3 Levels at Diagnosis of Renal ANCA-Associated Vasculitis Is Associated with Poor Prognosis.

Publications

Low Serum Complement C3 Levels at Diagnosis of Renal ANCA-Associated Vasculitis Is Associated with Poor Prognosis.

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