Polyuridylic acid (Poly(U)), a homopolymer of uridine, is used as a single-stranded RNA model compound often in comparison with other ssRNA model oligonucleotides such as Poly(I) and Poly(C) to study processes that are dependent upon ssRNA regulation such as Toll-like receptor regulation. Poly(U) is used as an effective agonist for TLR7.