Table 2.
The PRRs, subcellular localization, and recognized ligands
| Receptor | Subcellular localization | Ligand | Origin of ligand |
| TLR2 | Cell surface | Lipoteichoic acid | G (+) bacteria |
| Lipoprotein/ lipopeptides | Various pathogens | ||
| Hemoagglutinin protein | Viruses (Measles Virus) | ||
| Glycosyl-phosphatidylinositols | Parasites (Toxoplasma gondii) | ||
| TLR2/1 | Cell surface | Triacyl lipopeptides | Bacteria and mycobacteria |
| TLR2/6 | Cell surface | Diacyl lipopeptides | Mycobacteria |
| Zymosan | Fungi | ||
| TLR3 | Cellular compartment | dsRNA | Viruses |
| TLR4 | Cell surface | Lipopolysaccharide | G (−) bacteria |
| Envelope proteins | Viruses (Respiratory Syncytial Virus) | ||
| Glycosyl-phosphatidylinositols | Parasites (Toxoplasma gondii) | ||
| TLR5 | Cell surface | Flagellin | Bacteria |
| TLR7/8 | Cellular compartment | ssRNA | Viruses |
| TLR9 | Cellular compartment/cell surface | CpG-containing DNA | Bacteria and viruses |
| TLR11 | Cell surface | Uropathogenic bacteria component | Bacteria (uropathogenic Escherichia coli) |
| Profilin | Parasites | ||
| NOD1 | Cell cytoplasm | Meso-diaminopimelic acid | PGN of G (−) and some G (+) bacteria |
| NOD2 | Cell cytoplasm | Muramyl dipeptide | PGN of G (+) and G (−) bacteria |
| RIG-I | Cell cytoplasm | 5′-triphosphate-bearing RNAs | Viruses |
G (+), Gram-positive; G (−), Gram-negative; dsRNA, double-stranded RNA; ssRNA, single-stranded RNA; PGN, peptidoglycan; Meso-DAP, γ-D-glutamyl-meso-diaminopimelic acid; MDP, muramyl dipeptide NOD1, nucleotide oligomerization domain-like receptor 1; NOD2 nucleotide oligomerization domain-like receptor 2.