TOLL Like Receptor (TLR-5) binds to :
**Core Concept**
TLR-5 is a member of the Toll-like receptor family, which plays a crucial role in the recognition of pathogen-associated molecular patterns (PAMPs) and activation of the innate immune response. Specifically, TLR-5 is involved in the detection of bacterial flagellin, a key component of bacterial motility.
**Why the Correct Answer is Right**
TLR-5 recognizes flagellin through its extracellular domain, which contains a leucine-rich repeat (LRR) motif. Upon binding to flagellin, TLR-5 undergoes oligomerization and recruits adaptor molecules such as MyD88, leading to the activation of NF-κB and the production of pro-inflammatory cytokines. This recognition of flagellin is essential for the innate immune response to prevent the spread of bacterial infections.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because TLR-4, not TLR-5, is primarily responsible for recognizing LPS (lipopolysaccharide) from Gram-negative bacteria.
* **Option B:** This option is incorrect because TLR-2 is involved in recognizing components of Gram-positive bacteria, such as peptidoglycan and lipoteichoic acid.
* **Option C:** This option is incorrect because TLR-9 is involved in recognizing unmethylated CpG DNA motifs from bacterial and viral genomes.
**Clinical Pearl / High-Yield Fact**
TLR-5's recognition of flagellin highlights the importance of bacterial motility in disease pathogenesis, and its dysregulation has been implicated in various inflammatory and autoimmune disorders.
**Correct Answer:** C. Flagellin.