Q.54 Identify the sequence in the mechanism of local inflammatory response:
- Presence of pathogen at the site of injury
- Capillaries widen and become more permeable
- Mast cells release histamines
- Entry of anti-microbial peptides at the site of injury
- Signals released by immune cells attract neutrophils which digest the pathogen and heal the tissue
- A, B, C, D, E
- A, C, B, D, E
- B, A, C, D, E
- A, C, D, E, B
The correct answer is A, C, B, D, E (Presence of pathogen → Mast cells release histamines → Capillaries widen → Entry of anti-microbial peptides → Neutrophils attracted and digest pathogen).
This sequence outlines the classic acute inflammatory response, starting with pathogen detection and progressing through vascular changes, innate defenses, and leukocyte recruitment for pathogen clearance.
Option Analysis
A, B, C, D, E
Capillaries dilating before mast cell degranulation reverses cause-effect; histamine release from mast cells must precede vasodilation and permeability increase. Incorrect.A, C, B, D, E (Pathogen → Mast cells histamines → Capillaries widen → Anti-microbial peptides → Neutrophils digest)
Pathogen presence (A) triggers resident mast cells to release histamine (C), causing vasodilation and permeability (B). Antimicrobial peptides (D) from degranulating cells or epithelia enter, followed by neutrophil chemotaxis via cytokines (E). Correct.B, A, C, D, E
Vascular changes cannot precede pathogen detection, as inflammation initiates from tissue injury/pathogen recognition by pattern recognition receptors on local cells. Incorrect.A, C, D, E, B
Anti-microbial peptides and neutrophils arrive before full vascular changes; increased permeability (B) enables plasma leakage containing peptides and facilitates diapedesis. Incorrect.The mechanism of local inflammatory response protects tissues via coordinated innate immunity steps triggered by pathogens or injury at infection sites. This acute process manifests as redness, heat, swelling, and pain.
Trigger and Mediator Release
Pathogen presence (A) at injury activates resident mast cells and macrophages via PAMPs/PRRs, prompting histamine/chemical mediator release (C). Histamine binds H1 receptors on endothelium.
Vascular Changes and Leakage
Capillaries widen and become permeable (B), causing hyperemia (redness/heat) and exudate formation (swelling). This allows plasma proteins, antimicrobial peptides like defensins (D), and fluid to reach the site.
Cellular Clearance
Cytokines/chemokines from immune cells attract neutrophils (E), which undergo margination, diapedesis, and phagocytosis to digest pathogens, releasing NETs and enzymes for debris clearance and tissue repair.
