Pattern Recognition Receptors (PRRs, [2]) (nomenclature as agreed by NC-IUPHAR sub-committee on Pattern Recognition Receptors, [1]) participate in the innate immune response to microbial agents, the stimulation of which leads to activation of intracellular enzymes and regulation of gene transcription. PRRs express multiple leucine-rich regions to bind a range of microbially-derived ligands, termed PAMPs or pathogen-associated molecular patterns or endogenous ligands, termed DAMPS or damage-associated molecular patterns. These include peptides, carbohydrates, peptidoglycans, lipoproteins, lipopolysaccharides, and nucleic acids. PRRs include both cell-surface and intracellular proteins. PRRs may be divided into signalling-associated members, identified here, and endocytic members, the function of which appears to be to recognise particular microbial motifs for subsequent cell attachment, internalisation and destruction. Some are involved in inflammasome formation, and modulation of IL-1β cleavage and secretion, and others in the initiation of the type I interferon response.

PRRs included in the Guide To PHARMACOLOGY are:

Catalytic PRRs (see links below this overview)
Toll-like receptors (TLRs)
Nucleotide-binding oligomerization domain, leucine-rich repeat containing receptors (NLRs, also known as NOD (Nucleotide oligomerisation domain)-like receptors)
RIG-I-like receptors (RLRs)
Caspase 4 and caspase 5

Non-catalytic PRRs
Absent in melanoma (AIM)-like receptors (ALRs)
C-type lectin-like receptors (CLRs)
Other pattern recognition receptors
Advanced glycosylation end-product specific receptor (RAGE)

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* Key recommended reading is highlighted with an asterisk

Barrat FJ, Elkon KB, Fitzgerald KA. (2016) Importance of Nucleic Acid Recognition in Inflammation and Autoimmunity. Annu Rev Med, 67: 323-36. [PMID:26526766]

Barton GM, Kagan JC. (2009) A cell biological view of Toll-like receptor function: regulation through compartmentalization. Nat Rev Immunol, 9 (8): 535-42. [PMID:19556980]

* Broz P, Dixit VM. (2016) Inflammasomes: mechanism of assembly, regulation and signalling. Nat Rev Immunol, 16 (7): 407-20. [PMID:27291964]

* Bryant CE, Gay NJ, Heymans S, Sacre S, Schaefer L, Midwood KS. (2015) Advances in Toll-like receptor biology: Modes of activation by diverse stimuli. Crit Rev Biochem Mol Biol, 50 (5): 359-79. [PMID:25857820]

Bryant CE, Orr S, Ferguson B, Symmons MF, Boyle JP, Monie TP. (2015) International Union of Basic and Clinical Pharmacology. XCVI. Pattern recognition receptors in health and disease. Pharmacol Rev, 67 (2): 462-504. [PMID:25829385]

Bryant CE, Symmons M, Gay NJ. (2015) Toll-like receptor signalling through macromolecular protein complexes. Mol Immunol, 63 (2): 162-5. [PMID:25081091]

Cao X. (2016) Self-regulation and cross-regulation of pattern-recognition receptor signalling in health and disease. Nat Rev Immunol, 16 (1): 35-50. [PMID:26711677]

Celis E. (2007) Toll-like receptor ligands energize peptide vaccines through multiple paths. Cancer Res, 67 (17): 7945-7. [PMID:17804699]

Davis BK, Wen H, Ting JP. (2011) The inflammasome NLRs in immunity, inflammation, and associated diseases. Annu Rev Immunol, 29: 707-35. [PMID:21219188]

Ehlers M, Ravetch JV. (2007) Opposing effects of Toll-like receptor stimulation induce autoimmunity or tolerance. Trends Immunol, 28 (2): 74-9. [PMID:17197239]

* Feerick CL, McKernan DP. (2017) Understanding the regulation of pattern recognition receptors in inflammatory diseases - a 'Nod' in the right direction. Immunology, 150 (3): 237-247. [PMID:27706808]

Garantziotis S, Hollingsworth JW, Zaas AK, Schwartz DA. (2008) The effect of toll-like receptors and toll-like receptor genetics in human disease. Annu Rev Med, 59: 343-59. [PMID:17845139]

Guo H, Callaway JB, Ting JP. (2015) Inflammasomes: mechanism of action, role in disease, and therapeutics. Nat Med, 21 (7): 677-87. [PMID:26121197]

Heaton SM, Borg NA, Dixit VM. (2016) Ubiquitin in the activation and attenuation of innate antiviral immunity. J Exp Med, 213 (1): 1-13. [PMID:26712804]

Hennessy EJ, Parker AE, O'Neill LA. (2010) Targeting Toll-like receptors: emerging therapeutics?. Nat Rev Drug Discov, 9 (4): 293-307. [PMID:20380038]

Kanzler H, Barrat FJ, Hessel EM, Coffman RL. (2007) Therapeutic targeting of innate immunity with Toll-like receptor agonists and antagonists. Nat Med, 13 (5): 552-9. [PMID:17479101]

Könner AC, Brüning JC. (2011) Toll-like receptors: linking inflammation to metabolism. Trends Endocrinol Metab, 22 (1): 16-23. [PMID:20888253]

Marshak-Rothstein A, Rifkin IR. (2007) Immunologically active autoantigens: the role of toll-like receptors in the development of chronic inflammatory disease. Annu Rev Immunol, 25: 419-41. [PMID:17378763]

Monie TP, Bryant CE, Gay NJ. (2009) Activating immunity: lessons from the TLRs and NLRs. Trends Biochem Sci, 34 (11): 553-61. [PMID:19818630]

O'Neill LA, Bowie AG. (2007) The family of five: TIR-domain-containing adaptors in Toll-like receptor signalling. Nat Rev Immunol, 7 (5): 353-64. [PMID:17457343]

O'Neill LA, Sheedy FJ, McCoy CE. (2011) MicroRNAs: the fine-tuners of Toll-like receptor signalling. Nat Rev Immunol, 11 (3): 163-75. [PMID:21331081]

Patel MN, Carroll RG, Galván-Peña S, Mills EL, Olden R, Triantafilou M, Wolf AI, Bryant CE, Triantafilou K, Masters SL. (2017) Inflammasome Priming in Sterile Inflammatory Disease. Trends Mol Med, 23 (2): 165-180. [PMID:28109721]

Patin EC, Thompson A, Orr SJ. (2019) Pattern recognition receptors in fungal immunity. Semin Cell Dev Biol, 89: 24-33. [PMID:29522806]

* Rathinam VA, Fitzgerald KA. (2016) Inflammasome Complexes: Emerging Mechanisms and Effector Functions. Cell, 165 (4): 792-800. [PMID:27153493]

Sabroe I, Parker LC, Dower SK, Whyte MK. (2008) The role of TLR activation in inflammation. J Pathol, 214 (2): 126-35. [PMID:18161748]

Saitoh S, Miyake K. (2009) Regulatory molecules required for nucleotide-sensing Toll-like receptors. Immunol Rev, 227 (1): 32-43. [PMID:19120473]

Schroder K, Tschopp J. (2010) The inflammasomes. Cell, 140 (6): 821-32. [PMID:20303873]

Shaw PJ, Lamkanfi M, Kanneganti TD. (2010) NOD-like receptor (NLR) signaling beyond the inflammasome. Eur J Immunol, 40 (3): 624-7. [PMID:20201016]

Takeuchi O, Akira S. (2010) Pattern recognition receptors and inflammation. Cell, 140 (6): 805-20. [PMID:20303872]

Tan X, Sun L, Chen J, Chen ZJ. (2018) Detection of Microbial Infections Through Innate Immune Sensing of Nucleic Acids. Annu Rev Microbiol, 72: 447-478. [PMID:30200854]

Ting JP, Lovering RC, Alnemri ES, Bertin J, Boss JM, Davis BK, Flavell RA, Girardin SE, Godzik A, Harton JA et al.. (2008) The NLR gene family: a standard nomenclature. Immunity, 28 (3): 285-7. [PMID:18341998]

* Unterholzner L. (2013) The interferon response to intracellular DNA: why so many receptors?. Immunobiology, 218 (11): 1312-21. [PMID:23962476]

* Yin Q, Fu TM, Li J, Wu H. (2015) Structural biology of innate immunity. Annu Rev Immunol, 33: 393-416. [PMID:25622194]

1. Bryant CE, Orr S, Ferguson B, Symmons MF, Boyle JP, Monie TP. (2015) International Union of Basic and Clinical Pharmacology. XCVI. Pattern recognition receptors in health and disease. Pharmacol Rev, 67 (2): 462-504. [PMID:25829385]

2. Takeuchi O, Akira S. (2010) Pattern recognition receptors and inflammation. Cell, 140 (6): 805-20. [PMID:20303872]

Clare Bryant Professor of Innate Immunity The Department of Veterinary Medicine The University of Cambridge Madingley Road Cambridge, UK, CB3 0ES UK Tom P. Monie Assistant Director (Academic) and Academic Director for STEM (Biological) Institute of Continuing Education University of Cambridge Madingley Hall Madingley Cambridge CB3 0ES UK