PRRs

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 pathogen-associated molecular patterns (PAMPs), which are associated with microbial pathogens or cellular stress, as well as damage-associated molecular patterns (DAMPs), which are associated with cell components released during cell damage. They are also called pathogen recognition receptors or primitive pattern recognition receptors because they evolved before other parts of the immune system, particularly before adaptive immunity.