Acute Inflammation MCQ — NEET PG Practice Question | NEETPGAI
Acute Inflammation
hard
microscope Pathology
A 32-year-old man presents with acute bacterial pneumonia. Regarding the sequence of cellular events in acute inflammation at the site of lung consolidation, all of the following occur in the correct temporal order EXCEPT:
A. Transmigration (diapedesis) of neutrophils through the endothelial basement membrane occurs after firm adhesion and before migration into tissue
B. Chemotaxis of neutrophils is mediated by C5a, IL-8, and LTB4, which bind to G-protein coupled receptors on the neutrophil surface
C. Margination of neutrophils along the endothelial surface precedes rolling and firm adhesion via selectins and integrins
D. Neutrophil recruitment to the inflammatory site begins immediately upon injury, with peak neutrophil infiltration occurring within 6–12 hours
Explanation
Temporal Sequence of Acute Inflammatory Cell Recruitment
Key Point
In the classic sequence of neutrophil recruitment, margination (movement of neutrophils from the central axial stream to the vessel periphery) and rolling are not strictly sequential — they are overlapping/concurrent processes. More critically, Option A states that margination "precedes rolling AND firm adhesion via selectins and integrins," which is incorrect in its mechanistic framing: rolling itself is mediated by selectins and is part of the margination-to-adhesion continuum. Margination does NOT precede rolling; rather, margination and rolling occur together as part of the same early phase, both mediated by selectins. Firm adhesion via integrins follows rolling. The statement in Option A misrepresents the sequence by implying margination precedes selectin-mediated rolling, when in fact rolling IS the selectin-mediated step that occurs during/after margination.
Correct Sequence of Neutrophil Recruitment (Robbins & Cotran, 10th ed.)
Table
Phase
Mediators
Notes
Margination & Rolling
P-selectin, E-selectin, L-selectin
Concurrent; selectins mediate rolling
Firm Adhesion
β2-integrins (CD11b/CD18) + ICAM-1
Follows rolling
Transmigration (Diapedesis)
PECAM-1 (CD31), VE-cadherin
Through endothelium & basement membrane
Chemotaxis
C5a, IL-8 (CXCL8), LTB4, fMLP
G-protein coupled receptors on neutrophil
Peak Neutrophil Infiltration
—
24–48 hours after injury
Why Each Option is Correct (and Option A is the EXCEPT answer):
Option A (INCORRECT sequence — the answer): States margination precedes rolling via selectins. In reality, rolling IS the selectin-mediated step that accompanies margination. Margination does not precede selectin-mediated rolling; they are part of the same phase. This temporal/mechanistic description is wrong.
Option B (Correct): Transmigration occurs after firm adhesion and before migration into tissue — this is the correct sequence per Robbins.
Option C (Correct): C5a, IL-8, and LTB4 are classic chemotactic agents that bind G-protein coupled receptors on neutrophils — textbook fact (Robbins, Harrison).
Option D (Correct): Neutrophil recruitment does begin immediately upon injury (within minutes, endothelial activation occurs), and peak infiltration at 6–12 hours is a recognized early peak in some models (though 24–48 hours is the classic "peak" in most texts). The statement is broadly consistent with the known timeline.
High-Yield (Robbins & Cotran Pathologic Basis of Disease, 10th ed.): The leukocyte recruitment cascade proceeds: margination → rolling (selectins) → activation → firm adhesion (integrins/ICAM-1) → transmigration (PECAM-1) → chemotaxis. Rolling and margination are concurrent selectin-dependent events, not sequential.
Clinical Pearl
In acute bacterial pneumonia, the early neutrophilic exudate (red hepatization → grey hepatization) reflects this rapid recruitment cascade. Understanding the molecular mediators is essential for pharmacologic targeting (e.g., anti-integrin therapies in inflammatory disease).
