Polyinosinic acid (Poly(I)) is a homopolymer of inosine that may be used with polycytidylic acid (poly(C)) to form the double-stranded homopolymer (Poly(I) Poly(C)). TLR3 recognizes double-stranded RNA and is a major effector of the immune response against viral pathogens. (Poly(I) Poly(C)) is a used as a model RNA to study cell signaling at the level of TLR3. Poly(IC) is a TRIF-dependent toll-like receptor-3 (TLR3) ligand.