Based on their stable and intense ACE expression and, thus, enhanced permissiveness to productive SARS-CoV infection, compared to that of parental Calu-3 cells (Figure 1), we chose the cloned 2B4 cells for studying the temporal expression of airway epithelial genes related to the innate antiviral defense against SARS-CoV infection by using microarray-based functional genomics. This evidence concerns the gene ACE and severe acute respiratory syndrome.