Polyinosinic-polycytidylic acid (Poly(I:C)) is a synthetic double-stranded RNA (dsRNA) analog and an agonist of TLR3 as well as retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated protein 5 (MDA5). It can induce innate immune responses in mammals and serve as a vaccine adjuvant to enhance both innate and adaptive immunity, while modulating the tumor microenvironment and directly inducing apoptosis in cancer cells. Poly(I:C) is commonly used to establish acute respiratory distress syndrome (ARDS) animal models for studying immune responses and disease mechanisms.