Liver gene expression was studied, by large-scale real-time RT-PCR, in patients with untreated chronic hepatitis C and mild fibrosis compared with histologically normal controls.25 The most significant changes in gene expression mainly affected the transcriptional network regulated by IFNs, including both IFNα/β-inducible genes (STAT1, STAT2, ISGF3G/IRF9, IFI27, G1P3, G1P2, OAS2 and MX1) and IFNγ-inducible genes (CXCL9, CXCL10 and CXCL11). The gene discussed is IRF9; the disease is chronic hepatitis C virus infection.