Assessing in Atherosclerotic Lesions .

Whereas most atherosclerotic lesions are relatively benign, some plaques with large necrotic cores and thin fibrous caps are vulnerable to rupture, which results in many cardiovascular events and sudden death. Defects in the clearance of apoptotic cells, termed “efferocytosis,” is the leading cause of necrotic core expansion. This chapter describes a method that identifies macrophage-associated terminal deoxynucleotidyl transferase (TUNEL)-positive events (i.e., efferocytosis events) and TUNEL events free from association with macrophages (i.e., uncleared apoptotic events) in atherosclerotic lesions. This assay has been critical to the understanding of how clinically dangerous atherosclerotic plaques form and will remain a crucial assay that reveals new insights into how macrophages carry out efferocytosis and how this process becomes defective as atherosclerosis advances.