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Autoreactivity to myeloperoxidase (MPO) causes anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), with rapidly progressive glomerulonephritis. Here, we show that a Staphylococcus aureus peptide, homologous to an immunodominant MPO T-cell epitope (MPO 409–428 ), can induce anti-MPO autoimmunity. The peptide (6PGD 391–410 ) is part of a plasmid-encoded 6-phosphogluconate dehydrogenase found in some S. aureus strains. It induces anti-MPO T-cell autoimmunity and MPO-ANCA in mice, whereas related sequences do not. Mice immunized with 6PGD 391–410 , or with S. aureus containing a plasmid expressing 6PGD 391–410 , develop glomerulonephritis when MPO is deposited in glomeruli. The peptide induces anti-MPO autoreactivity in the context of three MHC class II allomorphs. Furthermore, we show that 6PGD 391–410 is immunogenic in humans, as healthy human and AAV patient sera contain anti-6PGD and anti-6PGD 391–410 antibodies. Therefore, our results support the idea that bacterial plasmids might have a function in autoimmune disease.

Objectives Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is an autoimmune disease characterised by small blood vessel inflammation, commonly affecting the kidneys and respiratory tract. It is unclear why the incidence of this condition increases with age. Previous studies in a passive antibody transfer system in aged mice have implicated innate effectors. To test the hypothesis that autoimmunity to myeloperoxidase, an autoantigen responsible for ANCA-associated vasculitis, increases with age, anti-myeloperoxidase autoimmunity was studied in murine models of active autoimmunity and disease induced by cellular immunity. Methods Young (8 weeks) and aged (either 15 or 22 month) mice were immunised with whole proteins or peptides from ovalbumin, as a model foreign antigen, or myeloperoxidase protein or peptides. Mice were subjected to a model of active anti-myeloperoxidase glomerulonephritis. Cellular and humoral immune responses and tissue inflammation were assessed. Results While cellular immunity to ovalbumin was diminished in aged mice, cellular autoimmunity to myeloperoxidase and its immunodominant CD4+ and CD8+ T cell epitopes was increased after immunization with either MPO peptides or whole MPO protein, assessed by peptide and antigen specific production of the pro-inflammatory cytokines interferon-γ and interleukin-17A. MPO-ANCA titres were not increased in aged mice compared with young mice. In experimental anti-MPO glomerulonephritis, cell mediated injury was increased, likely due to CD4+ and CD8+ T cells, innate immunity and the increased vulnerability of aged kidneys. Conclusion Heightened cellular immunity to MPO develops with ageing in mice and may contribute to the increased incidence and severity of ANCA-associated vasculitis in older people.

ABSTRACT:Thrombotic microangiopathy (TMA) is a well-recognised complication following transplantation, often due to an underlying genetic predisposition, medications or rejection. The use of eculizumab in these settings has been previously described, but its role still remains to be clarified. A 45-year-old man, with a history of type 1 diabetes mellitus and subsequent end-stage kidney failure, presented for a simultaneous pancreas-kidney transplant. Immunologically, he was well matched with the donor, and he received standard induction immunosuppression including tacrolimus. His early transplant course was complicated by Haemophilus parainfluenzae paronychia and a Pseudomonas aeruginosa catheter-associated urinary tract infection. Within 1 week, he developed thrombotic microangiopathy with significant renal dysfunction and eventual dialysis dependence, without evidence of transplant rejection on biopsy. He was also noted to have antiphospholipid antibodies in moderate titres. The TMA did not resolve despite cessation of tacrolimus, and he was subsequently commenced on eculizumab. The patient achieved a partial remission from TMA, with ongoing biochemical evidence of haemolysis, although now with stable graft function, despite significant damage. His transplanted pancreas remained seemingly unaffected by TMA, and continues to function well. This case describes an unusual presentation of TMA post-transplantation and is the only described case of eculizumab use following pancreas-kidney transplant. It remains unclear in this case what the likely precipitant for TMA was, although it seems to be, at least in part, controlled by ongoing use of eculizumab, presumably by terminal complement inhibition.Development of thrombotic microangiopathy (TMA) after kidney transplantation is a well-recognized complication, which can significantly affect the function of the graft. Dysregulation of the alternative complement pathway is thought to be intrinsically involved, culminating in production of the membrane attack complex (MAC, C5-9). Eculizumab, a high-affinity humanized anti-C5 monoclonal antibody, prevents generation of the MAC, thereby attenuating complement-mediated injury in diseases such a paroxysmal nocturnal haemoglobinuria and atypical haemolytic uraemic syndrome (aHUS). As yet, its utility in management of TMA post-solid organ transplantation due to various causes is unknown.Here, we present a case of a 45-year-old man who developed TMA of unclear aetiology after simultaneous pancreas and kidney transplantation, which has been managed with eculizumab. CASE REPORTA 45-year-old man presented for a simultaneous pancreaskidney transplant. He had developed type 1 diabetes mellitus at 24 years of age, with end stage kidney disease presumed secondary to diabetic nephropathy. He undertook peritoneal dialysis for 2 years prior to transplantation. His other past history included diabetic retinopathy, hypertension and hypercholesterolaemia.Immunologically, the patient was well matched to the donor, being blood group matched a...

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Purpose of reviewVasculitis describes a wide spectrum of rare, inflammatory, multisystem disorders. These heterogenous diseases all have inflammation of blood vessels as a central feature. However, they differ in terms of their genetic and environmental risk factors, disease pathogenesis, clinical presentations and treatment strategies. Many animal models of vasculitis exist, each resembling a different human clinical phenotype. This review provides an overview of recently published findings from experimental animal models of vasculitis. Recent findingsSeveral new animal models have been described during the review period. New insights gleaned from existing animal models regarding cause, disease effector mechanisms and novel treatments identified in established animal models are discussed. SummaryAnimal models continue to be an important tool for understanding disease pathogenesis, especially in rare and complex diseases such as vasculitis. They also provide an invaluable platform for development and preclinical testing of new treatments.