Produced by immune-activated cells or virus-infected cells in response to tviral genomes, interferons exert their antiviral activity by binding to uninfected neighboring cells and inducing them to produce enzymes that degrade mRNA. This not only prevents translation of viral mRNA into viral protein it also eventually kills the host cell, the factory producing the viruses. Interferons also enhance body defenses against viruses by enhancing the activities of CTLs, macrophages, NK cells, and antibody-producing cells.