Negative dominance assay for IFNAR1 variants. (A–C) IFNAR1-deficient HEK293T cells cotransfected with luciferase reporter plasmids plus EV (up to 15 ng) and various amounts of plasmids encoding WT and/or variant IFNAR1 (0.5, 1.5, 4.5, and 5 ng). The amount of plasmid used for transfection (ng) is indicated in the figure. Cells were stimulated with IFN-α2 (A, 1,000 U/ml), IFN-ω (B, 1 ng/ml), or IFN-β (C, 100 U/ml) for 24 h, and luciferase activity was measured. Graphs depict the mean ± SEM of two independent experiments.