Granulomatosis with Polyangiitis (Wegener Granulomatosis): A Proteinase-3 Driven Disease?

Granulomatosis with polyangiitis (GPA, Wegener granulomatosis) is a systemic autoimmune vasculitis that affects small arteries, arterioles, and capillaries, most notably in the kidneys and lungs. In this disease, proteinase-3 (PR3), produced by neutrophils, is targeted by antineutrophil cytoplasmic antibodies (ANCA). Recent work by our group has shown how PR3 impairs the resolution of inflammation and deregulates the immune system. Normally, the clearance of activated neutrophils triggers an anti-inflammatory, pro-resolution process. In patients with GPA, however, macrophages phagocytose apoptotic neutrophils then release massive amounts of pro-inflammatory mediators, notably interleukin-1, thereby generating a pro-inflammatory microenvironment conducive to autoimmunity. This deregulation of immune processes is accompanied with activation of plasmacytoid dendritic cells and with polarization of T-helper-2 (Th2), Th9, and Th17 cells. These recent data highlight the dual role of PR3, both auto-antigenic and auto-inflammatory, thus potentially opening up new therapeutic avenues.