polyinosinic:polycytidylic acid polyinosinic:polycytidylic acid polyinosinic:polycytidylic acid (usually abbreviated poly i:c or poly(i:c)) is an immunostimulant. it is used in the form of its sodium salt to simulate viral infections. polyinosinic:polycytidylic acid, sodium saltclinical dataatc codel03ax07 (who) identifiers iupac name polymethyl dihydrogen phosphate; cas number24939-03-5 ypubchem cid32744chemspidernoneunii3r630iww5io84c90hh2l ycomptox dashboard (epa)dtxsid90947819 chemical and physical dataformula(c10h10n4nao7p)x • (c9h11n3nao7p)x ny (what is this?) (verify) poly i:c is known to interact with toll-like receptor 3 (tlr3), which is expressed at the endosomal membrane of b-cells, macrophages and dendritic cells. poly i:c is structurally similar to double-stranded rna, which is present in some viruses and is a "natural" stimulant of tlr3. thus, poly i:c can be considered a synthetic analog of double-stranded rna and is a common tool for scientific research on the immune system. chemistry poly i:c is a mismatched double-stranded rna with one strand being a polymer of inosinic acid, the other a polymer of cytidylic acid. variants optimization of physicochemical properties of poly i:c has led to generation of derivatives that have increased stability in body fluids (such as polyiclc), or reduced toxicity through reduced stability in body fluids (such as poly i:c12u).