RIGI and melanoma: The membrane bound PRRs include toll-like receptors (TLRs) and C-type lectin receptors (CLRs) whereas the cytosolic PRRs include retinoic acid inducible gene I (RIG-I)-like receptors (RLRs), cytosolic DNA sensors (CDSs), NOD-like receptors (NLRs) and the newly identified cytosolic absent in melanoma (AIM)-like receptors1–4.