Published customer image: . Mouse anti Influenza A Matrix Protein antibody, clone GA2B used for the evaluation of influenza matrix protein expression in infected cell lysates by western blotting. Image caption: . Tyrosine kinase activity is required for efficient uptake of IAV. (A, B, C) A549 cells were treated with genistein (50 uM, [+]) or (D, E) a mixture of several RTK inhibitors (each 10 uM, [+] see experimental procedures) or the solvent control (DMSO,[−]) respectively for 60 min at 37°C or over night prior to infection. (A) Upon genistein treatment, cells were either mock infected or infected with influenza virus A/FPV/Bratislava/79 (H7N7) (FPV; MOI = 100) for further 30 min. Virus particles were visualized in immunofluorescence (IF) microscopy, via a hemagglutinin (HA)-specific rabbit antiserum and an Alexa 594-conjugated chicken anti-rabbit IgG. The nuclei were stained with DAPI. The white arrowheads point to virus particles lining at the cell border. (B, D) After infection with influenza virus A/Puerto-Rico/8/34 (H1N1) PR8 (MOI = 8) for further 30 min, an acidic wash (PBS, pH 1.3, 4°C) was performed before cell-lysis. Internalized virus particles were visualized with a M1 monoclonal antibody in Western-blot (WB) analysis. Equal protein load was verified by ERK2 detection. The relative amount of M1 was quantified (B and D lower panels). Relative M1 densities are expressed as mean ±SD of three independent experiments. (C, E) Cells were infected with FPV or PR8 (MOI = 4) for 8 h; upon the virus-attachment period an acidic wash (PBS-HCl, pH 5.5) was included. Progeny virus titers were determined by standard plaque assays. Data represent mean values of at least three independent experiments ±SD. Statistical significance was assessed by student s t-test (*) p PLoS Pathog 6(9): e1001099 .