Which pattern recognition receptors are most associated with recognizing pathogen-associated molecular patterns, and what is a classic example?

• A. NOD-like receptors primarily recognize PAMPs; example: NOD2 recognizing lipopolysaccharide.
• B. Toll-like receptors recognize PAMPs; example: TLR4 recognizing lipopolysaccharide.
• C. RIG-I-like receptors recognize PAMPs; example: RIG-I recognizing viral RNA.
• D. C-type lectin receptors recognize self-antigens; example: DC-SIGN recognizing glycans.

Answer: (B)

Pattern recognition receptors detect conserved microbial features called pathogen-associated molecular patterns. Toll-like receptors are classic PRRs that monitor the cell surface and endosomes for PAMPs. A quintessential example is TLR4 recognizing lipopolysaccharide from Gram-negative bacteria, which activates signaling pathways that drive innate immune responses. Other options mix up receptor families and their typical ligands: NOD-like receptors sense intracellular peptidoglycan fragments but aren’t the common example for LPS; RIG-I-like receptors detect viral RNA in the cytosol; C-type lectin receptors like DC-SIGN recognize pathogen glycans rather than self-antigens. Thus, the best pairing is Toll-like receptors recognizing PAMPs, with TLR4 recognizing lipopolysaccharide.