Secreted IFNβ is responsible for the action of dsRNA in the induction of MHC class I and related genes. Hu-H7 cells were transfected with dsRNA and treated with neutralizing concentrations of anti-hIFNβ and anti-hTNFα antibodies (1000 U/ml and 20 μg/ml, respectively) [43,44], and Northern blot analysis performed (a). Concentrations of secreted hIFNβ in culture supernatant fluids were measured by ELISA at the indicated time points following transfection with RNase-free dsRNA (○), ssRNA (□) or mock transfection with RNase-free water (▵). Hu-H7 cells were transfected with various concentrations of dsRNA. Northern blot analysis performed and showed similar results. Lanes 2–5: 5 μg, 1·0 μg, 0·1 μg and 0·01 μg of poly IC-poly IC was transfected, respectively, into Hu-H7 cells grown in a 10 cm dish to 60% confluency (c).