In resolution of acute inflammation, apoptotic neutrophils are cleared by macrophages through a process called efferocytosis. Which phospholipid, normally confined to the inner membrane leaflet, appears on the outer leaflet of apoptotic cells to serve as an 'eat-me' signal?
- A Phosphatidylserine ✓
- B Phosphatidylcholine
- C Sphingomyelin
- D Phosphatidylinositol
Correct answer: A. Phosphatidylserine
Explanation
Phosphatidylserine (PS) is maintained on the cytoplasmic leaflet of the plasma membrane by flippase enzymes in viable cells. During apoptosis, scramblase activation and flippase inhibition cause PS to appear on the outer membrane leaflet, where it serves as an 'eat-me' signal recognized by macrophage receptors (e.g., TIM-4, MFG-E8/integrin bridges). This promotes anti-inflammatory efferocytosis and resolution. Phosphatidylcholine and sphingomyelin are enriched on the outer leaflet of normal cells.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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