Cell Immunity in Inflammatory Vasculitis

The vasculitides are a highly heterogeneous group of disorders characterized by the presence of inflammatory leukocytes in the vessel walls and reactive inflammation. Giant cell arteritis (GCA) and Takayasu’s arteritis (TA) are the two primary large-vessel vasculitides. Two distinct cellular pathways have been identified in GCA: Th17 polarization and IL-17 secretion and generation of Th1 cells which secrete IFN-γ. These two pathways may play different roles in the pathogenesis of vasculitides. The antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) are small vessel vasculitis associated with antibodies directly to myeloperoxidase (MPO-ANCA) such as eosinophilic granulomatosis with polyangiitis (EGPA) and microscopic polyangiitis (MPA) or with antibodies directly to proteinase 3 (PR3-ANCA) such as granulomatosis with polyangiitis (GPA). Both in vitro and in vivo experimental data have shown that MPO-ANCA can induce necrotizing smallvessel vasculitis; however the presence of granulomatous lesions suggests the involvement of cell-mediated immune responses. Behçet syndrome (BS) is a chronic relapsing vasculitis of arteries and veins with unclear etiology. Exogenous and endogenous antigens, innate immune cells such as dendritic, NK, neutrophils and adaptive-immune cells are involved.