Correct option is B
The correct answer is (b)
- TLR5 recognizes Flagellin (A-iii). Flagellin is the major protein of bacterial flagella, and TLR5 specifically binds to it to initiate immune responses.
- TLR9 recognizes Unmethylated CpG DNA (D-ii), which is commonly found in bacterial DNA but not in the host’s DNA, signaling the presence of infection.
- TLR7 recognizes ssRNA (F-v), which is a ligand typical of viral RNA that is recognized by TLR7 to trigger immune activation.
Incorrect option
Option (a): A-iii, B-v, C-i
- A-iii (TLR5 - Flagellin): Correct, TLR5 recognizes bacterial flagellin.
- B-v (TLR3 - ssRNA): Incorrect, TLR3 actually binds dsRNA (double-stranded RNA), not ssRNA. ssRNA is recognized by TLR7 and TLR8.
- C-i (TLR12 - Profilin): Correct, in mice TLR12 is known to recognize Profilin-like proteins
Overall, this option is incorrect mainly because of the wrong pairing of TLR3 with ssRNA.
Option (c): C-i, D-ii, F-iv
- C-i (TLR12 - Profilin): Correct, in mice TLR12 is known to recognize Profilin-like proteins.
Overall, this option is incorrect mainly because of the wrong pairing of TLR3 with ssRNA.
- D-ii (TLR9 - Unmethylated CpG DNA): Correct, TLR9 recognizes unmethylated CpG motifs in microbial DNA.
- F-iv (TLR7 -dsRNA): Incorrect pairing in the table because option F corresponds to TLR7, actually, TLR7 binds ssRNA (v).
This option is partly incorrect due to confusion or mismatch in the ligand assignments in the question table, specifically for TLR7.
Option (d): B-iv, E-vi, F-i
- B-iv (TLR3 - dsRNA): Correct, TLR3 binds double-stranded RNA.
- E-vi (TLR4 - LPS): Correct, TLR4 is the main receptor for LPS from Gram-negative bacteria.
- F-i (TLR7 - Profilin): Incorrect, TLR7 binds ssRNA (single-stranded RNA), not Profilin. Profilin is not a known ligand for any TLR in humans.
This option fails because of the incorrect pairing of TLR7 with Profilin.
