IRF1 and infection: Moreover, as one promoter regulator of the IFN-α/β genes and MHC-I antigens in chicken fibroblast cell line C32 [24, 25], IRF-1 was up-regulated to 12- and 7-fold changes in the infection group on days 1 and 3, respectively, while the fold change of the IRF-1 gene expression in CEFs was 23-fold in a previous study on day 3 following infection with IBDV [26].