This study confirms that the pathogenesis of ANCA-associated vasculitis has a genetic component, shows genetic distinctions between granulomatosis with polyangiitis and microscopic polyangiitis that are associated with ANCA specificity, and suggests that the response against the autoantigen proteinase 3 is a central pathogenic feature of proteinase 3 ANCA-associated vasculitis. These data provide preliminary support for the concept that proteinase 3 ANCA-associated vasculitis and myeloperoxidase ANCA-associated vasculitis are distinct autoimmune syndromes. (Funded by the British Heart Foundation and others.).

The kidneys are frequently targeted by pathogenic immune responses against renal autoantigens or by local manifestations of systemic autoimmunity. Recent studies in rodent models and humans have uncovered several underlying mechanisms that can be used to explain the previously enigmatic immunopathology of many kidney diseases. These mechanisms include kidney-specific damage-associated molecular patterns that cause sterile inflammation, the crosstalk between renal dendritic cells and T cells, the development of kidney-targeting autoantibodies and molecular mimicry with microbial pathogens. Conversely, kidney failure affects general immunity, causing intestinal barrier dysfunction, systemic inflammation and immunodeficiency that contribute to the morbidity and mortality of patients with kidney disease. In this Review, we summarize the recent findings regarding the interactions between the kidneys and the immune system.

Patients with the Goodpasture syndrome and severe renal failure should be considered for urgent immunosuppression therapy, including plasma exchange, to maximize the chance of renal recovery. Patients needing immediate dialysis are less likely to recover.

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Pauci-immune focal necrotizing glomerulonephritis (FNGN) is a severe inflammatory disease associated with autoantibodies to neutrophil cytoplasmic antigens (ANCA). Here we characterize autoantibodies to lysosomal membrane protein-2 (LAMP-2) and show that they are a new ANCA subtype present in almost all individuals with FNGN. Consequently, its prevalence is nearly twice that of the classical ANCAs that recognize myeloperoxidase or proteinase-3. Furthermore, antibodies to LAMP-2 cause pauci-immune FNGN when injected into rats, and a monoclonal antibody to human LAMP-2 (H4B4) induces apoptosis of human microvascular endothelium in vitro. The autoantibodies in individuals with pauci-immune FNGN commonly recognize a human LAMP-2 epitope (designated P [41][42][43][44][45][46][47][48][49] ) with 100% homology to the bacterial adhesin FimH, with which they Correspondence should be addressed to R.K. (renate.kain@meduniwien.ac.at). 7 Present addresses: Interne, Hämato-Onkologie, Krankenhaus der Elisabethinen, Fadingerstrasse 1, 4010 Linz, Austria (R.Z.) and Vela Laboratories. Entwicklung und Laboranalytik Gesellschaft mit beschränkter Haftung, Brunnerstrasse 69/3, 1230 Wien, Austria (R.J.). 8 These authors contributed equally to this work. Here we establish that autoantibodies to human LAMP-2 are highly prevalent in pauci-immune FNGN and provide evidence of their pathogenicity by showing that they activate neutrophils and kill human blood microvascular endothelium in vitro and cause pauci-immune FNGN when administered to rodents. Unexpectedly, auto-antibodies to LAMP-2 in individuals with FNGN commonly recognize an epitope with considerable homology to the bacterial adhesin FimH and cross-react with it. We therefore determined whether exposure to FimH could induce antibodies to human LAMP-2 and initiate pauci-immune FNGN through molecular mimicry. The results lead us to propose a previously undescribed molecular mechanism both for the induction and development of injury in this human disease. RESULTS Autoantibodies to human LAMP-2 are common in FNGNWe established the prevalence of autoantibodies to hLAMP-2 in sera from 84 individuals with biopsy-proven active pauci-immune FNGN, either at presentation (n = 62) or during relapse (n = 22). ANCA were detectable by standard immunofluorescence assays in 80 of them (95%), and ELISA for the canonical ANCA were positive in 70 of them (83%); myeloperoxidasespecific ANCA were found in 38 people, and proteinase-3-specific ANCA were found in 39 people, including seven with antibodies to both antigens. Using a specific ELISA, we detected antibodies to human LAMP-2 in 78 of the 84 (93%) sera (Fig. 1a), and we validated the results by western blotting and indirect immunofluorescence on the O-glycosylation deficient CHO cell line ldlD cells stably expressing human LAMP-2 on their surface ( Supplementary Fig. 1a online). Notably, the human LAMP-2 ELISA was negative in all but six of the individuals when they were in remission after immunosuppressive therapy. Assays for human LA...

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The renal mononuclear phagocytic system, conventionally composed of macrophages (Mø) and dendritic cells (DCs), plays a central role in health and disease of the kidney. Overlapping definitions of renal DCs and Mø, stemming from historically separate research tracks and the lack of experimental tools to specifically study the roles of these cells in vivo, have generated confusion and controversy, however, regarding their immunologic function in the kidney. This brief review provides an appraisal of the current state of knowledge of the renal mononuclear phagocytic system interpreted from the perspective of immunologic function. Physical characteristics, ontogeny, and known functions of the main subsets of renal mononuclear phagocytes as they relate to homeostasis, surveillance against injury and infection, and immune-mediated inflammatory injury and repair within the kidney are described. Gaps and inconsistencies in current knowledge are used to create a roadmap of key questions to be answered in future research.

Abstract. Lipoxins (LX) are eicosanoids with antiinflammatory activity in glomerulonephritis (GN) and inflammatory diseases, hypersensitivity, and ischemia reperfusion injury. It has been demonstrated that LXA 4 stimulates non-phlogistic phagocytosis of apoptotic polymorphonuclear neutrophils (PMN) by monocyte-derived macrophages (M) in vitro, suggesting a role for LX as endogenous pro-resolution lipid mediators. It is here reported that LXA 4 , LXB 4 , the aspirin-triggered LX (ATL) epimer, 15-epi-LXB 4 , and a stable synthetic analogue 15(R/S)-methyl-LXA 4 stimulate phagocytosis of exogenously administered excess apoptotic PMN by macrophages (M) in vivo in a classic model of acute inflammation, namely thioglycollate-induced peritonitis. Significant enhancement of phagocytosis in vivo was observed with 15-min exposure to LX and with intraperitoneal doses of LXA 4 , LXB 4 , 15(R/S)-methyl-LXA 4 , and 15-epi-LXB 4 of 2.5 to 10 g/kg. Non-phlogistic LX-stimulated phagocytosis by M was sensitive to inhibition of PKC and PI 3-kinase and associated with increased production of transforming growth factor-␤ 1 (TGF-␤ 1 ). LX-stimulated phagocytosis was not inhibited by phosphatidylserine receptor (PSR) antisera and was abolished by prior exposure of M to ␤1,3-glucan, suggesting a novel M-PMN recognition mechanism. Interestingly, the recently described peptide agonists of the LXA 4 receptor (MYFINITL and LESI-FRSLLFRVM) stimulated phagocytosis through a process associated with increased TGF-␤ 1 release. These data provide the first demonstration that LXA 4 , LXB 4 , ATL, and LX stable analogues rapidly promote M phagocytosis of PMN in vivo and support a role for LX as rapidly acting, proresolution signals in inflammation. Engagement of the LXR by LX generated during cell-cell interactions in inflammation and by endogenous LXR peptide agonists released from distressed cells may be an important stimulus for clearance of apoptotic cells and may be amenable to pharmacologic mimicry for therapeutic gain.Rapid, efficient and tightly regulated recruitment and clearance of polymorphonuclear neutrophil (PMN) at sites of inflammation are essential components of effective host defense. Evidence from in vitro models and from histopathology suggests that tissue damage mediated by PMN is limited by apoptosis and subsequent phagocytosis of the apoptotic PMN by macrophages (M) and "nonprofessional" phagocytes (1). A direct role for PMN in tissue injury in inflammation and ischemia reperfusion injury of the kidney and other organs is well established (2). Impaired clearance of apoptotic cells by M has been implicated in the pathogenesis of chronic inflammatory conditions, including glomerulonehritis (GN) and systemic lupus erythematosus (SLE) (3). The endogenous signals that promote clearance of apoptotic PMN from an inflammatory focus are still being defined. By dissecting out the mediator systems that regulate this process, it may be possible to design new pro-resolution strategies for inflammatory diseases.Lipoxins (LX), an acronym for...