Atherosclerotic plaque formation in aortas of HCII^+/+ and HCII^−/− mice in the apoE-null background. Lesion areas are expressed as percentages of the total intimal surface area of the aortic arch, the thoracic aorta, and the abdominal aorta. No lesions were observed in HCII^+/+ or HCII^−/− mice in the wild-type apoE background. Mean lesion areas are indicated. Error bars equal 1 SD.