What are the immune mechanisms that can cause vasculitis?
Cell-mediated, immune complex-mediated, and antineutrophil cytoplasmic antibody (ANCA)-associated mechanisms are involved depending on the vasculitis. Examples of cell-mediated vasculitis include giant cell arteritis (GCA), Takayasu arteritis, and primary central nervous system (CNS) vasculitis. Examples of immune complex-mediated vasculitis include polyarteritis nodosa (PAN), Henoch–Schönlein purpura, cryoglobulinemic vasculitis, and cutaneous leukocytoclastic angiitis. The ANCA-associated vasculitides, which may involve both cellular and humoral mechanisms, include granulomatosis with polyangiitis (GPA; Wegener granulomatosis), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA; Churg–Strauss syndrome). The immune mechanisms of the other types of vasculitis are less certain.