In leukocyte rolling, P-selectin appears on the endothelial surface within minutes of histamine or thrombin exposure. Where is P-selectin stored before such stimulation?

• A Weibel-Palade bodies of endothelial cells ✓
• B Specific granules of neutrophils
• C The endothelial Golgi awaiting new synthesis
• D Platelet dense granules

Explanation

P-selectin is preformed and stored in Weibel-Palade bodies of endothelial cells and in alpha granules of platelets; histamine or thrombin triggers rapid redistribution to the luminal surface, allowing rolling within minutes. In contrast, E-selectin is absent from resting endothelium and must be newly synthesized over 1 to 2 hours after TNF and IL-1 induction, which is why option C describes E-selectin kinetics. Neutrophil specific granules carry their own adhesion molecules, and dense granules store ADP and serotonin.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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