During the cellular phase of acute inflammation, the sequential steps of neutrophil emigration from blood vessels occur in which order?

• A Firm adhesion → Rolling → Chemotaxis → Diapedesis
• B Chemotaxis → Rolling → Firm adhesion → Diapedesis
• C Rolling → Firm adhesion → Chemotaxis → Diapedesis
• D Rolling → Firm adhesion → Diapedesis → Chemotaxis ✓

Explanation

The sequence of neutrophil emigration is: (1) Rolling — mediated by selectins (P-, E-selectin on endothelium binding PSGL-1 on neutrophils); (2) Firm adhesion — mediated by integrins (LFA-1/Mac-1 on neutrophils binding ICAM-1 on endothelium, upregulated by IL-1/TNF); (3) Transmigration/Diapedesis — through endothelial junctions via PECAM-1 (CD31); (4) Chemotaxis — directional movement along the gradient of chemokines (IL-8, C5a, LTB4, fMLF) toward the site of injury. Chemotaxis occurs after the neutrophil has left the vessel.

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

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