Briefly, 293T cells were co-transfected with Mx expression plasmids and a plasmid expressing GFP in a ratio of 3∶1, and 48 h later infected with A/PR/8/34 at a multiplicity that achieved approximately 60% infection, as determined by FACS analysis using anti-influenza RNP-specific antibody, and phycoerythrin (PE)-conjugated secondary antibody. Here, MX1 is linked to infection.