Which process initiates monocyte involvement in atherosclerosis?

• A. Platelet aggregation
• B. Vasoconstriction
• C. Adhesion to endothelium
• D. Lipid oxidation

Answer: (C)

Monocyte involvement begins when the endothelium becomes activated and expresses adhesion molecules (such as VCAM-1 and ICAM-1) in response to risk factors like hypertension, smoking, and hyperlipidemia. This upregulation allows circulating monocytes to roll, adhere firmly, and then transmigrate into the intima. There, they differentiate into macrophages and ingest oxidized LDL, turning into foam cells that drive plaque formation. Platelet aggregation and vasoconstriction can influence disease progression and plaque stability, but they don’t initiate monocyte entry. Lipid oxidation occurs inside the vessel wall after monocytes/macrophages arrive and contribute to inflammation, rather than initiating monocyte recruitment.