Pattern recognition receptor

Pattern recognition receptors (PRRs) are a primitive part of the immune system. They are proteins expressed by cells of the innate immune system to identify two classes of molecules: pathogen-associated molecular patterns (PAMPs), which are associated with microbial pathogens, and damage-associated molecular patterns (DAMPs), which are associated with cell components that are released during cell damage or death. They are also called primitive pattern recognition receptors because they evolved before other parts of the immune system, particularly before adaptive immunity.

The microbe-specific molecules that are recognized by a given PRR are called pathogen-associated molecular patterns (PAMPs) and include bacterial carbohydrates (such as lipopolysaccharide or LPS, mannose), nucleic acids (such as bacterial or viral DNA or RNA), bacterial peptides (flagellin, microtubule elongation factors), peptidoglycans and lipoteichoic acids (from Gram-positive bacteria), N-formylmethionine, lipoproteins and fungal glucans and chitin.

Endogenous stress signals are called damage-associated molecular patterns (DAMPs) and include uric acid and extracellular ATP, among many other compounds.

PRRs are classified according to their ligand specificity, function, localization and/or evolutionary relationships. On the basis of function, PRRs may be divided into endocytic PRRs and signaling PRRs.

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