APOE and atherosclerosis: Most importantly, this distribution pattern of adventitial immune cells in Apoe-deficient rats was in agreement with a previous report on human early stage type I atherosclerosis, wherein it was reported that macrophages comprise the majority of immune cell population in the adventitia, followed by T cells, and that B cells are scarcely found49, suggesting the possibility that Apoe-deficient rats reflect the immune response of atherosclerosis at initial-to-early stage.