Irradiated Apoe−/− mice receiving Apoe−/− bone marrow had large, and Apoe−/−/IL-R1−/− mice receiving Apoe−/−/IL-R1−/− marrow relatively little, atherosclerosis in their aortic sinus following 8 weeks on a WHC diet, as expected and analogous to Apoe−/− and Apoe−/−/IL-R1−/− non-chimeric animals. This evidence concerns the gene APOE and atherosclerosis.