In the pathogenesis of atherosclerosis, oxidized LDL (oxLDL) plays a central role. Which specific receptor on macrophages binds oxLDL and is primarily responsible for foam cell formation?

• A LDL receptor (LDLR), which is upregulated by cholesterol depletion
• B VLDL receptor on macrophages mediating triglyceride-rich lipoprotein uptake
• C Scavenger receptors (SR-A and CD36), which are not downregulated despite intracellular cholesterol accumulation ✓
• D Toll-like receptor 4 (TLR4), which endocytoses oxLDL via MyD88 signaling

Explanation

Macrophage scavenger receptors, particularly SR-A (MARCO, SR-AI/II) and CD36, mediate uptake of oxLDL and modified lipoproteins. Crucially, unlike the native LDL receptor, scavenger receptors are NOT downregulated by intracellular cholesterol accumulation — so macrophages continue internalizing lipid even when already engorged, ultimately transforming into foam cells. This unregulated uptake is central to atherogenesis. The LDLR is downregulated when intracellular cholesterol is high.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.