Autoantibodies to myeloperoxidase (MPO) are a subset of anti‐neutrophil cytoplasmic antibody (ANCA, MPO‐ANCA) detected in the sera of some patients with primary systemic vasculitis. The titer of MPO‐ANCA does not always reflect disease activity and this inconsistency may be attributable to differences in epitopic specificity by MPO‐ANCA among various patients with vasculitis. Epitope analysis may also explain the occurrence of MPO‐ANCA in different vasculitic syndromes. We screened the sera of 148 MPO‐ANCA positive patients from six vasculitic syndromes: rapidly progressive gromerulonephritis (RPGN), microscopic polyangiitis (MPA), idiopathic crescentic glomerulonephritis (I‐CrGN), classic polyangiitis nodosa (cPAN), Churg‐Strauss syndrome (CSS), Kawasaki disease (KD); and from patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). The sera were collected by the Intractable Vasculitis Research Project Group in Japan. No serum showed epitopes La and Lb of light chain of MPO, and sera with 68.6% of patients showed a positive reaction to one or more epitopes in heavy chain of MPO. Analysis of binding level showed that RPGN, I‐CrGN and MPA sera mainly reacted to the Ha epitope at the N‐termimus of the MPO heavy chain, CSS sera reacted to Ha and the Hf epitope close to the C‐terminus of the MPO heavy chain, KD reacted mainly to Hf, while SLE and RA sera reacted to all epitopes. These results suggest that MPO‐ANCA recognizing specific regions of the N‐terminus of the MPO H‐chain confer an increased risk of vasculitis RPGN, I‐CrGN, MPA and CSS. Furthermore, the epitopic specificity of MPO‐ANCA differentiates vasculitic from non‐vasculitic syndromes associated with MPO‐ANCA positivity and differentiates in the cirtain type of vasculitis from various vasculitic syndromes. In particular, vasculitic syndromes associated with kidney involvement had similar epitopic reactivity which suggests that this pattern confers an increased risk of vasculitis.

These results strongly suggest that DSG treatment of SCG/Kj mice leads to the reduction of risk antibodies in IgG2b and normalization of B-cell clones accompanied by recovery of the cytokine and chemokine balance.

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A major target protein of antineutrophil cytoplasmic antibody with a perinuclear staining pattern (P-ANCA) has been identified as myeloperoxidase (MPO). Recombinant deletion mutants of MPO, eight fragments of the heavy-chain subunit, and two fragments of the light chain subunit were expressed in E. coli using a pQE expression vector. The recombinant hexamer histidine-tagged fragments were partially purified as the denatured proteins on a Ni2+-charged nitrirotriacetic acid column. The recombinant fragments were reacted with a rabbit polyclonal antibody to human MPO in Western blotting. In addition, the reactivities of the proteins with MPO-ANCA-positive sera of four patients with renal diseases were examined by Western blotting. The profile of the reactivity showed that different sera recognized different sets of fragments of the heavy chain, whereas no serum reacted with the fragments of the light chain. These results indicate that the sera of patients with MPO-ANCA-positive diseases showed varied reactivities with the different fragments. Furthermore, an ELISA system using a set of the fragments completely purified by Sephacryl S-200HR column chromatography was established. The panel set is useful for subclassification of MPO-ANCA-related diseases.

It has been shown that myeloperoxidase (MPO) and the MPO-specific anti-neutrophil cytoplasmic auto-antibody (MPO-ANCA) are risk factors for the development of glomerulonephritis (GN). High titers of MPO-ANCA are frequently detected (2,4,5,8) in the sera of patients with microscopic polyangiitis (MPA) or crescentic GN (CrGN). Animal models have been used for understanding the mechanisms for the development of vasculitis, as a basis for establishing new therapeutic strategies. The SCG/Kj mouse is a model of spontaneous CrGN associated with activated neutrophils (6). The MRL lpr/lpr strain, the background for the SCG/Kj mouse, is known to show high levels of MPO-ANCA in association with renal lesions, including GN and vasculitis (3). MPO-deficient model mice for coronary arteritis induced with Candida albicans-derived substances indicate that MPO is a major antigen for MPO-ANCA production (7). The importance of MPO-ANCA for the development of vasculitis has been demonstrated, using immune-deficient mice with the Rag2 knockout (19). Such a mouse model for renaldamage CrGN with MPO-ANCA production is needed, since understanding the pathogenetic roles of MPO-ANCA and neutrophils in GN and vasculitis remains important for the development of new therapies. Bovine serum albumin (BSA)-induced nephritis was reported in rat (12). Recently, CrGN has been connected with MPO-ANCA production prior to the development of renal lesion. We were interested in knowing whether the development of CrGN induced by BSA administration is related to an increase in MPO-ANCA.In the present study, we established induction model mice for CrGN with vasculitis by serial injection of BSA. The mice showed three phases of renal damage: Abstract: We established a novel model mouse for myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA)-associated glomerulonephritis with crescentic formation, which was induced by administering bovine serum albumin (BSA). Neutrophil infiltration into the renal glomeruli began at 8 weeks and crescent formation was observed from 10 weeks after the first BSA injection. Platelet and neutrophil counts significantly increased, and proteinuria was observed from 5 weeks. MPO-ANCA increased slightly at 4 and markedly at 9 weeks, and the TNF-␣ level increased at 11 weeks. Glomerular neutrophil infiltration was correlated with MPO-ANCA levels. In addition, proteinuria also significantly correlated with MPO-ANCA levels. Finally, renal crescent formation was associated with an increase of MPO-ANCA levels and neutrophil infiltration into glomeruli. The glomerular immune deposition of IgG and C3 was observed. These findings indicate that BSA induces neutrophil activation of peripheral blood followed by the elevation of MPO-ANCA, resulting in the development of crescentic glomerulonephritis in mice. Editor-Communicated Paper A Novel Mouse Model for MPO-ANCA-Associated Glomerulonephritis