Antimyeloperoxidase-associated proliferative glomerulonephritis: an animal model.

Abstract

SummaryTo develop an animal model for antimyeloperoxidase (MPO)-associated necrotizing crescentic glomerulonephritis (NCGN), we immunized Brown Norway rats with MPO and localized a neutrophil lysosomal enzyme extract, primarily consisting of MPO and elastinolytic enzymes, plus H202, the substrate of MPO, to the glomerular basement membrane (GBM). Upon immunization rats developed antibodies and positive skin tests to MPO. After unilateral perfusion of the left kidney with the lysosomal enzyme extract and H202, MPO and immunoglobulin (Ig)G localized transiently along the GMB. At the time of maximal inflammation, at 4 and 10 d after perfusion, MPO, IgG, and C3 could not be detected anymore. MPO-immunized rats perfused with the lysosomal enzyme extract and H202, in contrast to control-immunized and/or control-perfused rats, developed a proliferative GN characterized by intra-and extracapillary cell proliferation, ruptured Bowman's capsule, periglomerular granulomatous inflammation, and formation of giant cells. Monocytes, polymorphonuclear leukocytes (PMN), and to a far lesser extent T cells were found in the glomeruli. Interstitial infiltrates consisted of monocytes, PMN, and T cells. Granulomatous vasculitis of small vessels was found at 10 d after perfusion. The proliferative NCGN in this rat model closely resembles human anti-MPO-associated pauci-immune NCGN, and enables the study of the pathophysiology of anti-MPO-associated NCGN. N 'ecrotizing crescentic glomerulonephritis (NCGN), 1 a clinically rapidly progressive form of glomerular disease, can be associated with multisystem disorders (infectious or noninfectious), or may occur in patients without a definite diagnosis of systemic illness (1). NCGN can be classified into three immunopathogenic categories: (a) anti-glomerular basement membrane (GBM) antibody mediated; (b) immune complex mediated; and (c) antineutrophil cytoplasmic antibody (ANCA) associated (2). ANCA in patients with ANCAassociated NCGN are either directed to proteinase 3 (Pr3) (3-5) or myeloperoxidase (MPO) (2, 6, 7), both myeloid lysosomal enzymes. NCGN associated with anti-MPO antibodies is characterized by segmental fibrinoid necrosis of the GBM, marked infiltration of neutrophils and mononuclear cells, and paucity of IgG deposits (8-12). NCGN can be accompanied by granuloma formation (13,14). The pathogen-1 Abbreviations used in this paper: ANCA, antineutrophil cytoplasmic antibody; GBM, glomerular basement membrane; MPO, myeloperoxidase; NCGN, necrotizing crescentic glomerulonephritis; Pr3, proteinase 3. esis of ANCA-associated NCGN has not been elucidated so far. The close association between pauci-immune NCGN and anti-MPO antibodies (6, 7) suggests a pathogenetic role for an anti-MPO-directed immune response. In vitro studies showed that anti-MPO antibodies can activate PMN to cause a respiratory burst and to mediate degranulation (15). We hypothesized that NCGN may develop after focal release of lysosomal enzymes and production of H202 by activated neutrophils in the presence of an an...

T Cells in Crescentic Glomerulonephritis

“…The capacity for MPO autoimmunity to induce crescentic GN has been established in experimental models. Rats that are immunized with MPO develop crescentic GN after infusion of a crude preparation of this antigen into their kidneys (73). Splenocytes or antibodies from MPO-deficient mice that are immunized with murine MPO induce a necrotizing and crescentic GN after passive transfer to immunodeficient mice (74).…”

Toll‐like receptor 2 induces Th17 myeloperoxidase autoimmunity while Toll‐like receptor 9 drives Th1 autoimmunity in murine vasculitis

“…Furthermore, while antineutrophil cytoplasmic antibody (ANCA) characterizes (and defines) the disease, the vasculitis involving the glomerular capillary bed has little or no antibody deposited, but rather demonstrates infiltration of delayed-type hypersensitivity (DTH) effector cells and fibrin. This finding is most likely a consequence of autoreactive CD4ϩ effector cells recognizing MPO, which is present in glomeruli in both human and experimental AAV (8)(9)(10). Further support for the notion of the involvement of CD4ϩ cells and cellular immunity is provided by studies that demonstrate that stimulated peripheral blood lymphocytes from patients with MPO ANCA produce interferon-␥ (IFN␥) (11).…”

Elastase, but not proteinase 3 (PR3), induces proteinuria associated with loss of glomerular basement membrane heparan sulphate after in vivo renal perfusion in rats

“…Perfusion of the left kidney was performed according to the methods of Hoyer et al with minor modifications, as described [22] Briefly, rats were anaesthetized with halothane, O 2 , and NO 2 . The aorta and vena cava were then exposed and the tributaries ligated.…”