Molekulare pathogenese primär systemischer vaskulitiden

The molecular pathogenesis of primary systemic vasculitides is characterized by substantial differences in the underlying pathophysiological mechanisms. Activation of dendritic cells in the adventitia seems to be an early event in giant cell arteritis. Subsequently, CD4⁺ Th1-type cells are recruited via the vasa vasorum. Cytokine release of CD4⁺ Th1-type cells contributes to macrophage activation and giant cell formation. The cellular infiltrate in the arterial wall in Takayasu arteritis consists of perforin producing, oligoclonal γδ T-cells, CD8⁺ T-cells, NK-cells, CD4⁺ T-cells, and macrophages. Whether infectious agents activate dendritic cells and stimulate T-cell activation and recruitment, remains to be discussed. Slowing-down of P-selectin mediated rolling by immune-complexes and C1 q complement induces enhanced extravasation of neutrophils and other leukocytes in immune-complex vasculitides. This process facilitates Fc-gamma mediated recognition of deposited immune-complexes and subsequent neutrophil activation, degranulation, and endothelial damage. The interaction of anti-neutrophil cytoplasmic autoantibodies (ANCA) with neutrophils and subsequent endothelial damage are important steps in the initiation of ANCA-associated vasculitides. Recent studies indicate that both the expansion of CD28 Th1-type cells and the possible formation of ectopic lymphatic structures in granulomatous lesions, might be correlated with the sustained autoimmune reaction to "Wegener's autoantigen" proteinase 3 in Wegener's granulomatosis.