C5 and atherosclerosis: In contrast, the WD group, with advanced fibrous plaque formation in the aortic root, had the highest C5 and macrophage infiltration in plaque, indicating that a WD triggered the activation of the complement system, increased complement factor C5 expression, and boosted macrophage counts in the endothelium site in the aortic root, thereby promoting the development of atherosclerosis.