Infection of human bronchial epithelial cells with human influenza viruses. (A) The influenza M-gene mRNA profiles were assayed after infection. The concentrations of M-gene mRNA were normalized to those of β-actin mRNA in the corresponding sample. Means of duplicate assays are shown. (B) Virus yields (log10TCID50/ml) were determined in aliquots of supernatant collected from influenza-infected bronchial epithelial cells at various times. Data are the means and the standard errors of two independent experiments.