TABLE 1.
Recognition of microbial components by PRRs
| Receptor | Cellular localization | Microbial component(s) | Origin(s) |
|---|---|---|---|
| TLRs | |||
| TLR1/TLR2 | Cell surface | Triacyl lipopeptides | Bacteria |
| TLR2/TLR6 | Cell surface | Diacyl lipopeptides | Mycoplasma |
| Lipoteichoic acid | Gram-positive bacteria | ||
| TLR2 | Cell surface | Lipoproteins | Various pathogens |
| Peptidoglycan | Gram-positive and -negative bacteria | ||
| Lipoarabinomannan | Mycobacteria | ||
| Porins | Neisseria | ||
| Envelope glycoproteins | Viruses (e.g., measles virus, HSV, cytomegalovirus) | ||
| GPI-mucin | Protozoa | ||
| Phospholipomannan | Candida | ||
| Zymosan | Fungi | ||
| β-Glycan | Fungi | ||
| TLR3 | Cell surface/endosomes | dsRNA | Viruses |
| TLR4 | Cell surface | LPS | Gram-negative bacteria |
| Envelope glycoproteins | Viruses (e.g., RSV) | ||
| Glycoinositolphospholipids | Protozoa | ||
| Mannan | Candida | ||
| HSP70 | Host | ||
| TLR5 | Cell surface | Flagellin | Flagellated bacteria |
| TLR7/8 | Endosome | ssRNA | RNA viruses |
| TLR9 | Endosome | CpG DNA | Viruses, bacteria, protozoa |
| RLRs | |||
| RIG-I | Cytoplasm | dsRNA (short), 5′-triphosphate RNA | Viruses (e.g., influenza A virus, HCV, RSV) |
| MDA5 | Cytoplasm | dsRNA (long) | Viruses (picorna- and noroviruses) |
| NLRs | |||
| NOD1 | Cytoplasm | Diaminopimelic acid | Gram-negative bacteria |
| NOD2 | Cytoplasm | MDP | Gram-positive and -negative bacteria |
| NALP1 | Cytoplasm | MDP | Gram-positive and -negative bacteria |
| NALP3 | Cytoplasm | ATP, uric acid crystals, RNA, DNA, MDP | Viruses, bacteria, and host |
| Miscellaneous | |||
| DAI | Cytoplasm | DNA | DNA viruses, intracellular bacteria |
| AIM2 | Cytoplasm | DNA | DNA viruses |
| PKR | Cytoplasm | dsRNA, 5′-triphosphate RNA | Viruses |