TREM2 and atherosclerosis: To this extent, multiple independent studies have described a huge heterogeneity in macrophages present in the atherosclerotic plaques and identified various markers to distinguish resident macrophages (5, 7, 9, 59–64), TREM2 (35, 63–67), Interferon inducible macrophages (5, 62, 66), Inflammatory macrophages (63, 65–67), and smooth muscle-derived macrophages (68, 69), all of which may have the ability to transform into foamy macrophages in mouse models of atherosclerosis (Figure 1).