Fig. 3.

The effect of interferon treatment with or without IFNAR1 knockdown on cell survival and EC₅₀s. (A) Antiproliferative dose-response curve of WISH cells after 48 h of siRNA transfection. Five concentrations (0.25 nM to 5 nM) of siRNA against IFNAR1 were applied, followed by a 72-h treatment with YNS-α8tail. Two parameters were analyzed: EC₅₀ and the amplitude, which is the difference in cell densities between no treatment and the highest interferon concentration for each siRNA. Note that even at the highest interferon concentration, 40% of the cells survive. (B) Cell death following treatment with interferon. WISH cells were incubated with either 30 or 300 pM of IFN-α2, YNS, or IFN-β for 72, 96, or 120 h (x axis). Cells were labeled with annexin V-FITC and PI (propidium iodide) and analyzed by FACS. The percentage of dead cells (y axis) was determined according to the levels of phosphatidylserine in the outer leaflet of the plasma membrane, an apoptotic marker detected by annexin V, and the levels of cell permeability (PI). (C) Tighter interferon-receptor binding compensates for reduced receptor numbers. Five concentrations (0.25 nM to 5 nM) of siRNA against IFNAR1 were applied for 48 h, followed by interferon treatment. The EC₅₀s were determined from the dose-response curves (see panel A) for antiviral (AV) and antiproliferative (AP) activities. Error bars represent the standard deviations of results from three independent experiments.