Effect of IL-28A on the antiviral activity of IFNα. Varying doses of IL-28A and IFNα2b, either alone or in combination, were added to the GSB1 cells and incubated for 48 hours. Total RNA was isolated for real-time PCR analysis. The vertical axis represents the fold of viral RNA reduction by IL-28A or IFN. The data represents the results of normalization with the internal control GADPH.