The complement system's role in the pathogenesis of ANCA-associated vasculitis

Anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) is a group of rare autoimmune diseases that is characterised by very few, if any, immune complex depositions on the kidney biopsies. It consists of 3 diseases: Microscopic polyangitis (MPA), Granulomatosis with Polyangitis (GPA), and Eosinophilic Granulomatosis with Polyangitis (EGPA). The complement system's role has been neglected for many decades because of the absence of complement depositions in the biopsies. Although, experimental and clinical observations have shown that the complement system is crucial for the pathogenesis of ANCA-associated vasculitis (AAV), and the development of new drugs has put emphasis on the complement inhibition.