Measure by its ability to induce apoptosis in HeLa cells.
The ED50 for this effect is <15 ng/mL.
Measure by its ability to induce cytotoxicity in TF-1 cells.
The ED50 for this effect is <0.1 ng/mL.
The specific activity of recombinant human IFN beta 1a is approximately >1 x107 IU/ mg.