Importantly, the plasma membrane is not disrupted and NETs are released via vesicular transport while remaining viable, and typically contain oxidized mtDNA10,35,36. These pivotal features of lytic and nonlytic NET formation corresponded to the properties of NET formation respectively observed on AAV and SLEinduced NETs6. (within minutes), nonlytic NET formation coinciding with clustering of neutrophils in patients with SLE. AAVinduced NET formation was triggered impartial of IgG ANCAs, whereas SLE immune complexes (ICx) induced NET formation through Fc receptor signaling. AAVinduced NET formation was dependent on reactive oxygen species and peptidyl arginine deaminases, and AAVinduced NETs were enriched for citrullinated histones (imply SEM 23 2%). In contrast, SLEinduced NETs experienced immunogenic properties, including binding with high mobility group box chromosomal protein 1 (mean SEM 30 3%) and enrichment for oxidized mitochondrial DNA, and were involved in ICx formation. == Conclusion == The morphologic features, kinetics, induction pathways, and composition of excessive NET formation are all intrinsically unique in AAV compared to SLE. Recognizing the diversity of NET formation between AAV and SLE provides a better understanding of the pathophysiologic role of NETs in these different autoimmune diseases. == Introduction == Antineutrophil cytoplasmic antibody (ANCA)associated vasculitis (S)-(-)-Bay-K-8644 (AAV). and systemic lupus erythematosus (SLE) are both lifethreatening systemic Rabbit polyclonal to DYKDDDDK Tag autoimmune diseases. These patients are distinguished by their clinical phenotypes, histopathology, and autoantibody profiles. Patients with AAV display ANCAs against myeloperoxidase (MPO) or proteinase 3 (PR3), whereas patients with SLE develop diverse autoantibodies against nuclear autoantigens (ANAs)1,2. Typically, renal involvement in AAV manifests as a pauciimmune, crescentic glomerulonephritis (GN), while in SLE, a full house proliferative GN is seen. A growing body of evidence indicates that neutrophil extracellular traps (NETs) may have an important role in the pathogenesis of both AAV and SLE3,4,5,6,7,8,9,10,11,12,13. NETs are immunogenic5and harmful13,14extracellular DNA structures released by neutrophils that contain a pool of autoantigens relevant for both AAV and SLE15,16. NETderived DNA complexed with dangerassociated molecular patterns, such as LL374,5or high mobility group box chromosomal protein 1 (HMGB1)4, converts the NET DNA to potent immunogenic structures4. Indeed, NETs (S)-(-)-Bay-K-8644 were demonstrated to activate plasmacytoid dendritic cells4and autoreactive B cells in vitro17, which resulted in the production of interferon (IFN) and autoantibodies, respectively. Furthermore, NETs also have direct cytotoxic effects on (glomerular) endothelial cells18, mediated by histones13,18and MPO14, which, in a murine model, was found to lead to severe, crescentic GN19. In addition, murine plasmacytoid dendritic cells loaded with NETderived DNA led to the production of both ANAs and ANCAs11. Taken together, these findings provide ample evidence to indicate that NETs have the capability of inducing autoimmunity related to both AAV and SLE. In clinical studies, we as well as others have demonstrated that excessive NET formation or impaired NET degradation is present both in patients with active AAV3,7,20,21and in patients with severe SLE4,5,8,12,17,22,23, and this is usually correlated with the severity of disease activity. Thus, preclinical and clinical studies have exhibited an important role for NETs in the pathogenesis of both AAV and SLE. However, as both diseases are divergent clinical and histologic entities, we hypothesized that excessive NET formation should have a different pathophysiologic role in each disease. The present study resolved this hypothesis (S)-(-)-Bay-K-8644 by characterizing the quantitative, qualitative, and immunologic properties of NET formation in a direct comparison of AAV and SLE patients. == Patients and Methods == == Study populace == Serum samples were collected from 80 patients with ANCApositive AAV who met the classification criteria for vasculitis according to the Chapel Hill Consensus Conference definitions24, and 59 patients with ANApositive SLE who met the American College of Rheumatology 1997 updated classification criteria for SLE25. (S)-(-)-Bay-K-8644 The patients were followed up at the Lupus, Vasculitis, and Complementmediated Systemic Autoimmune Diseases outpatient clinic (LuVaCs) at Leiden University or college Medical Center (LUMC). All patients consented to participate in the LUMC biobank. Clinical data were extracted from your patients electronic records at the time of the collection of the serum sample. The control group consisted of 29 healthy subjects who consented to participate in the LUMC healthy donor biobank. Both biobanking studies were approved by the local ethics committee at LUMC. The characteristics of the patients and healthy controls are summarized in Supplementary Table1, and an extended methods section is usually provided inSupplementary Patients and (S)-(-)-Bay-K-8644 Methods(available on theArthritis & Rheumatologyweb.