Flow Cytometry Approach to Differentiate Resident Versus Infiltrated Macrophages in Atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arteries characterized by the formation of atherosclerotic plaques within the arterial walls. Chronic inflammation is important in all phases of plaque development, vulnerability, and regression. A disproportionate presence of inflammatory macrophages contributes to plaque progression while increased anti-inflammatory macrophages help in regression. Resident macrophages maintain the intima and clear the dead endothelial cells whose dysfunction is an underlying pathogenesis for atherosclerosis. Thus, it is important to characterize the macrophage population and the subtypes in the blood of a person with atherosclerosis to have an idea of the disease’s progression and stage. This will help plan the appropriate treatment by targeting macrophage polarization to attenuate plaque progression and vulnerability. Flow cytometry rapidly analyzes single cells from a pool of mixed cell population suspended in a solution using lasers in a short time with accuracy and specificity. Thus, flow cytometry is a useful tool in effectively and efficiently analyzing the patient’s sample. This chapter discusses various macrophage subtypes present in atherosclerosis in mice and humans, followed by how flow cytometry can be applied to differentiate between different subtypes via immunophenotyping of macrophages in atherosclerosis.