Complement in vasculitis associated with anti-neutrophil cytoplasm antibodies with renal involvement: pathogenic, prognostic and therapeutic implications.

Antineutrophil cytoplasmic antibody-associated vasculitides are primary vasculitides that affect small vessels in various organs, including the kidney. Renal involvement is characterized by the presence of glomerulonephritis with crescents and necrosis in light microscopy and a pauci-immune pattern in immunofluorescence. The participation of complement in the pathogenesis of these entities has been valued in recent years, initially in animal models and later in studies in humans, by demonstrating the presence of fragments of the alternative complement pathway, in plasma and urine, together with complement deposits in glomeruli and small vessels of patients affected by antineutrophil cytoplasmic antibody vasculitis. The presence of complement in these entities confers a worse general and renal prognosis.