Type I IFNs act in a species-specific manner.

<p>(a) Cells derived from different species were treated for 20 h with the indicated type I IFNs (5 units/well) and subsequently infected with VSV*ΔG(Luc). Expression of GFP was monitored 6 h post infection by fluorescence microscopy. Bar, 30 µm. (b) NHDF were incubated for 20 h with serial fourfold dilutions of human, porcine and murine type I IFNs. The cells were subsequently infected with VSV*ΔG(Luc) for 5 h and firefly luciferase activity was recorded in the cell lysates.