Assessment of atherosclerosis in brachiocephalic arteries of apoE−/−/CD55−/− and apoE−/− control mice after 12 weeks of high-fat feeding. Histologic appearance of representative sections of brachiocephalic arteries from a single experiment that compared apoE−/−/CD55−/− mice (A, D, G, J, and M) with apoE−/− control mice (B, E, H, K, and N); both groups had been fed a high-fat diet for 12 weeks. Sections were stained with Miller's/Elastic Van Gieson (A and B; n = 13 and 12, respectively); immunostained for α-smooth muscle actin (smooth muscle cells; D and E; n = 7 and 7, respectively); F/480 (macrophages; G and H; n = 8 and 6, respectively); C3 fragments (J and K; n = 7 and 6, respectively), or MAC deposition (M and N; n = 7 and 7, respectively). Scale bars: 200 μm (A, B, D, E, G, H, J, K, M, and N). C, F, I, L, and O: Composite data from each group compiled from digital analyses of individual sections as described in Materials and Methods. C: Average plaque size for the two groups as determined from five individual sections taken from each mouse. F, I, L, and O: Mean percentage of plaque area staining for smooth muscle cells, macrophages, C3b/iC3b/C3c, and MAC, respectively. Mean values ± SEM are represented. *P < 0.0001, **P < 0.05.