PRTN3 and granulomatosis with polyangiitis: PR3, which is one of the major targets of autoantibodies in patients with granulomatosis with polyangiitis (GPA), binds to the plasma membrane of apoptotic cells, prevents the clearance of apoptotic cells by macrophages, interferes with common anti-inflammatory reprogramming of macrophages and initiates the synthesis of proinflammatory cytokines in macrophages, and blocks pDC-mediated induction of T regulatory cells.