The anti-neutrophil cytoplasmic antibody (ANCA)associated vasculitides (AAVs) are diseases characterized by inflammation of blood vessels, endothelial injury and tissue damage. The three types of small-vessel vasculitis, namely granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and eosinophilic GPA (EGPA; previously known as Churg-Strauss syndrome), feature a loss of tolerance to neutrophil primary granule proteins, most often leukocyte proteinase 3 (PR3; also known as myeloblastin) or myeloperoxidase (MPO) (Table 1). The vessels involved in AAV are typically capillaries, arterioles and venules but small arteries and veins may also be affected. Autoimmunity is documented clinically by serum ANCAs to PR3 (PR3-ANCA) or MPO (MPO-ANCA), which are generally associated with the main syndromic AAV presentations (box 1). AAVs collectively represent one of several types of autoimmune vasculitis (Fig. 1). GPA and MPA can involve small blood vessels in any organ or tissue but commonly affect the upper and lower respiratory tract and the kidneys (box 2). Patients with AAV typically present with severe organ-threatening or life-threatening disease, although less severe presentations also occur. GPA is predominantly associated with PR3-ANCA and its clinical features typically include sinonasal disease, lower respiratory tract involvement with pulmonary haemorrhage and granulomatous inflammation, and glomerulonephritis. MPA is usually associated with MPO-ANCA and clinical features include more severe renal disease and some of the manifestations of GPA but without granulomatous inflammation. EGPA is characterized by asthma, eosinophilia and, in many (but not all) cases, vasculitis. EGPA is less common than GPA or MPA and, in some cases, is associated with ANCAs, mainly MPO-ANCA (Table 1). Although categorized as a form of AAV, EGPA has less overlap with the other AAVs than that between GPA and MPA with regard to its genetic, pathogenetic, and clinical features and its management and is typically considered a separate entity. Improvements in treatment and prognosis for patients with AAV have resulted from the translation of both preclinical and clinical research findings. Here, we provide an updated overview of the clinical and

BACKGROUND In Goodpasture’s disease, circulating autoantibodies bind to the noncollagenous-1 (NC1) domain of type IV collagen in the glomerular basement membrane (GBM). The specificity and molecular architecture of epitopes of tissue-bound autoantibodies are unknown. Alport’s post-transplantation nephritis, which is mediated by alloantibodies against the GBM, occurs after kidney transplantation in some patients with Alport’s syndrome. We compared the conformations of the antibody epitopes in Goodpasture’s disease and Alport’s post-transplantation nephritis with the intention of finding clues to the pathogenesis of anti-GBM glomerulonephritis. METHODS We used an enzyme-linked immunosorbent assay to determine the specificity of circulating autoantibodies and kidney-bound antibodies to NC1 domains. Circulating antibodies were analyzed in 57 patients with Goodpasture’s disease, and kidney-bound antibodies were analyzed in 14 patients with Goodpasture’s disease and 2 patients with Alport’s post-transplantation nephritis. The molecular architecture of key epitope regions was deduced with the use of chimeric molecules and a three-dimensional model of the α345NC1 hexamer. RESULTS In patients with Goodpasture’s disease, both autoantibodies to the α3NC1 monomer and antibodies to the α5NC1 monomer (and fewer to the α4NC1 monomer) were bound in the kidneys and lungs, indicating roles for the α3NC1 and α5NC1 monomers as autoantigens. High antibody titers at diagnosis of anti-GBM disease were associated with ultimate loss of renal function. The antibodies bound to distinct epitopes encompassing region EA in the α5NC1 monomer and regions EA and EB in the α3NC1 monomer, but they did not bind to the native cross-linked α345NC1 hexamer. In contrast, in patients with Alport’s post-transplantation nephritis, alloantibodies bound to the EA region of the α5NC1 subunit in the intact hexamer, and binding decreased on dissociation. CONCLUSIONS The development of Goodpasture’s disease may be considered an autoimmune “conformeropathy” that involves perturbation of the quaternary structure of the α345NC1 hexamer, inducing a pathogenic conformational change in the α3NC1 and α5NC1 subunits, which in turn elicits an autoimmune response. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases.)

In contrast with many capillary beds, the glomerulus readily supports leukocyte recruitment. However, little is known regarding the actions of leukocytes following their recruitment to glomeruli. We used multiphoton confocal microscopy to examine leukocyte behavior in the glomerular microvasculature. In normal glomeruli, neutrophils and monocytes were retained in capillaries for several minutes, remaining static or migrating intravascularly. Induction of glomerular inflammation resulted in an increase in the duration of retention of static and migratory leukocytes. In response to immune complex deposition, both static and migratory neutrophils generated oxidants in inflamed glomeruli via a Mac-1-dependent mechanism. Our results describe a new paradigm for glomerular inflammation, suggesting that the major effect of acute inflammation is to increase the duration of leukocyte retention in the glomerulus. Moreover, these findings describe a previously unknown form of multicellular intravascular patrolling that involves both monocytes and neutrophils, which may underlie the susceptibility of the glomerulus to inflammation.