Expression changes of the interferon(IFN) genes and interferon-stimulated genes(ISGs):it is believed that production of type I IFN is the key response to many viral infections,leading to the transcription of various ISGs, some of which encode direct antiviral effectors. It is not known whether H9N2 viruses or viral particles affect the transcriptional expression of IFNs. In this study,IFN gene expression induced by H9N2 viruses and viral particles showed no significant change in transcriptional activity at 24 h postinfection.