CCL1 knockdown exacerbated atherosclerosis in fat-fed ApoE-KO mice, and high-fat-fed ApoE/CCL1-DKO (double knockout) mice demonstrated a reduced percentage of Tregs in the aorta and spleen compared to ApoE-KO control mice, and significantly reduced IL-10 in the splenocytes and plasma, while the proliferative activity of CD4+ T cells isolated from the spleen and lymph nodes was not affected. Here, CD4 is linked to atherosclerosis.