Toll-like receptor 4 (TLR-4) recognises which bacterial component as its primary ligand?

• A Peptidoglycan of Gram-positive cell wall
• B Flagellin of flagellated bacteria
• C Lipopolysaccharide (LPS/endotoxin) of Gram-negative bacteria ✓
• D Unmethylated CpG DNA

Explanation

TLR-4 (in complex with MD-2 and CD14) is the primary pattern recognition receptor for lipopolysaccharide (LPS/endotoxin) from Gram-negative bacterial outer membranes. LPS binding activates NFκB pathway, inducing pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) responsible for septic shock. TLR-2 recognises peptidoglycan and lipoteichoic acid (Gram-positive). TLR-5 recognises flagellin. TLR-9 recognises unmethylated CpG DNA (bacterial/viral DNA). Understanding TLR biology is important for NEET PG immunology.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.