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, which includes 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 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-like receptors (NLRs, also known as NOD-like receptors)
RIG-I-like receptors (RLRs)

Non-catalytic pattern recognition receptors
Absent in melanoma (AIM)-like receptors (ALRs)
C-type lectin-like receptors (CLRs), and
Other pattern recognition receptors.

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* Key recommended reading is highlighted with an asterisk

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]

* 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]

Buchanan MM, Hutchinson M, Watkins LR, Yin H. (2010) Toll-like receptor 4 in CNS pathologies. J. Neurochem., 114 (1): 13-27. [PMID:20402965]

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

Chao W. (2009) Toll-like receptor signaling: a critical modulator of cell survival and ischemic injury in the heart. Am. J. Physiol. Heart Circ. Physiol., 296 (1): H1-12. [PMID:19011041]

Chiron D, Jego G, Pellat-Deuceunynck C. (2010) Toll-like receptors: expression and involvement in multiple myeloma. Leuk. Res., 34 (12): 1545-50. [PMID:20594595]

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

Downes CE, Crack PJ. (2010) Neural injury following stroke: are Toll-like receptors the link between the immune system and the CNS?. Br. J. Pharmacol., 160 (8): 1872-88. [PMID:20649586]

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

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]

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

Hirsch I, Caux C, Hasan U, Bendriss-Vermare N, Olive D. (2010) Impaired Toll-like receptor 7 and 9 signaling: from chronic viral infections to cancer. Trends Immunol., 31 (10): 391-7. [PMID:20832362]

Hori M, Nishida K. (2008) Toll-like receptor signaling: defensive or offensive for the heart?. Circ. Res., 102 (2): 137-9. [PMID:18239139]

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]

Lecat A, Piette J, Legrand-Poels S. (2010) The protein Nod2: an innate receptor more complex than previously assumed. Biochem. Pharmacol., 80 (12): 2021-31. [PMID:20643110]

Li H, Sun B. (2007) Toll-like receptor 4 in atherosclerosis. J. Cell. Mol. Med., 11 (1): 88-95. [PMID:17367503]

Marsh BJ, Williams-Karnesky RL, Stenzel-Poore MP. (2009) Toll-like receptor signaling in endogenous neuroprotection and stroke. Neuroscience, 158 (3): 1007-20. [PMID:18809468]

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]

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]

Sanjuan MA, Milasta S, Green DR. (2009) Toll-like receptor signaling in the lysosomal pathways. Immunol. Rev., 227 (1): 203-20. [PMID:19120486]

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]

* 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]

Trinchieri G, Sher A. (2007) Cooperation of Toll-like receptor signals in innate immune defence. Nat. Rev. Immunol., 7 (3): 179-90. [PMID:17318230]

Wenzel J, Tormo D, Tüting T. (2008) Toll-like receptor-agonists in the treatment of skin cancer: history, current developments and future prospects. Handb Exp Pharmacol,  (183): 201-20. [PMID:18071661]

Werling D, Jann OC, Offord V, Glass EJ, Coffey TJ. (2009) Variation matters: TLR structure and species-specific pathogen recognition. Trends Immunol., 30 (3): 124-30. [PMID:19211304]

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 Tom Monie The Department of Veterinary Medicine The University of Cambridge Madingley Road Cambridge, UK, CB3 0ES