Effect of CIS family members and JAB on the antiviral effect of IFNs. Parental NIH3T3 cells and transformants were infected with VSV for 3 days after incubation with the indicated amount of IFN-β (A) or IFN-γ (B) for 24 hours. The viable cells were measured by MTT assay. The optical density (OD) value at 420 nm that represents viable cell number is shown.