Chemokine mRNA expression induced by RSV and TNFα. 2 × 107 A549 cells were either infected by RSV (MOI = 1) or stimulated with 100 ng/ml TNF-α. Total RNA was isolated at 1,2, 4, 8, and 24 h and assessed for chemokine expression by RNase protection. Chemokine expression was quantified by densitometry as described in the Methods. The graphs show the time course of chemokine mRNA after normalizing to GAPDH (lowest band in the gel). Shown is representative of 3 independent experiments.