Genetic ablation of Abcg1 results in a shift in macrophage phenotype from a M2 (pro-resolution) to a M1 (pro-inflammatory) phenotype (Sag et al. 2015) with increased pro-inflammatory signalling via toll like receptors (TLR), in particular TLR4 (Yvan-Charvet et al. 2008) which would promote atherosclerosis progression and inhibit atherosclerosis regression which is promoted by pro-resolution M2 like macrophages. Here, TLR4 is linked to atherosclerosis.