Figure 1

Francisella , but not Salmonella requires TfR1 for proliferation inside macrophages. A. RAW264.7 macrophages were transfected with siRNA (coupled to Alexa Fluor 555, red fluorescence) specific for TfR1 or as control with random siRNA (no red fluorescence). After 48 h cells were fixed and processed for immunofluorescence with a mouse anti-TfR1 antibody followed by an Alexa488 conjugated goat-anti-mouse IgG (green fluorescence). Overlay of both fluorescence channels is shown. B. Proteins were solubilized from transfected and infected cells as above, separated on a 9% SDS-PAGE, transferred to Westran membranes, and immunoblotted with antiserum to TfR1. Visualization was by chemiluminescence C. RAW264.7 macrophages were transfected with TfR1-siRNA or with random siRNA (control). 48 h cells after transfection cells were infected with Francisella for 2 h or 24 h. The number of intracellular bacteria was obtained by plating a lysate of the host cells on chocolate agar plates for colony-forming units (cfus). Means of triplicate experiments +/- 1 standard error of mean are shown. D. RAW264.7 cells were treated as in C and then infected with Salmonella for 2 h or 24 h. The number of intracellular bacteria was determined as in C. Means of triplicate experiments +/- 1 standard error of mean are shown.