Cultured 16HBE14o-airway epithelial cells and mucociliarydifferentiated primary human bronchial epithelial cells, simultaneously exposed to the proinflammatory cytokine TNF and infected with RV39, had a synergistic increase in IL-8 production and an additive increase in the transactivation of transcription factors required for maximal CXCL-8 production, NF-kB, and activator protein-1 (34) .