Figure 1.

The classic putative mechanism for AAA formation. Extrinsic antigens such as protein from microorganisms cause autoimmunity which can cross-react the medial layer of the aortic wall. This induces and amplifies the autoimmune reaction through inflammatory cell infiltration, cytokine and chemokine production in the three layers of the vascular wall, oxidative stress, and so on. All of these responses further damage the vascular wall via induction of SMC apoptosis and ECM degradation due to TIMP/MMP disorder. VSMCs: vascular smooth muscle cells; ECM: extracellular matrix; TIMP: tissue inhibitors of metalloproteinases; MMP: matrix metalloproteinase; MCP-1: monocyte chemoattractant protein-1.