Innate immune responses are the ground troops that provide resistance to pathogen attack, even in the absence of the more targeted defense systems provided by circulating neutralizing antibodies and cytotoxicT lymphocytes. A few years ago researcher M. Yoneyama and colleagues identified phosphorylation of the transcription factor interferon regulatory factor 3 (IRF3) as the key downstream event triggered by virus infection to induce type I interferon. Yoneyama and colleagues report that a cytoplasmic RNA helicase is an essential component of the detection system upstream of IRF3 phosphorylation and that it uses a caspase recruitment domain protein interaction module to relay the signal.
