It is also believed that Ly6C+ monocytes play a role in chronic inflammation, such as the formation of the atherosclerotic plaque, because Ccr2-deficient mice on low density lipoprotein receptor- or apolipoprotein E-deficient backgrounds and a high-fat diet have decreased atherosclerosis (Boring et al., 1998; Dawson et al., 1999). This evidence concerns the gene CCR2 and atherosclerosis.