HBEpCs were grown on chamber slides (Chamber slide, Lab-TekII; Thermo Fisher Scientific, Rochester, NY) and infected with H1N1 or H3N2 for 2–6 h. Confocal staining of the cells was done as described earlier (25 (link)). Cells were treated with rabbit anti-human FADD or DR3 antibody (Cell Signaling) and anti-mouse TRADD (Millipore, Billerica, MA) followed by a secondary Alexa-488 conjugated anti-rabbit antibody and Alexa-546 conjugated anti-mouse antibody (Invitrogen).