RIG-I-like receptors (retinoic acid-inducible gene-I-like receptors, RLRs) are a type of intracellular pattern recognition receptor involved in the recognition of viruses by the innate immune system.[1][2] RIG-I (retinoic-acid inducible gene or DDX58) is the best characterized receptor within the RIG-I like receptor (RLR) family. Together with MDA5 (melanoma differentiation-associated 5) and LGP2 (laboratory of genetics and physiology 2), this family of cytoplasmic pattern recognition receptors (PRRs) are sentinels for intracellular viral RNA that is a product of viral infection. The RLR receptors provide frontline defence against viral infections in most tissues.
The other two families of PRRs, the NOD-like receptors (NLRs) and the RIG-like helicases (RLHs) are soluble receptors present in the cytosol and act as sensors to detect a variety of viral and bacterial products.