IKKε and TBK1 are serine/threonine kinases and are highly homologous to other IkB kinases (IKK-α and IKK-β). The two kinases play an integral role in the innate immune system. Double-stranded RNA viruses are recognized by Toll-like receptors 3 and 4 and RNA helicases RIG-1 and MDA-5, and lead to the activation of the TRIF-TBK1/IKKε-IRF3 signaling cascade, resulting in type I interferon. response.