The role of complement activation in atherosclerosis.

Atherosclerosis is a chronic inflammatory disease in which dyslipidemia, inflammation, and the immune system play an important pathogenetic role. A role in atherogenesis was demonstrated for monocyte/macrophages, complement system, and T-lymphocytes. Complement activation and C5b-9 deposition occurs both in human and experimental atherosclerosis. Complement C6 deficiency has a protective effect on diet-induced atherosclerosis, indicating that C5b-9 assembly is required for the progression of atherosclerotic lesions. The maturation of atherosclerotic lesions beyond the foam cell stage was shown to be strongly dependent on an intact complement system. C5b-9 may be responsible for cell lysis, and sublytic assembly of C5b-9 induces smooth muscle cell (SMC) and endothelial cell (EC) activation and proliferation. All these data suggest that activation of the complement system plays an important role in atherogenesis.