Colocalization of TfR and TfR2 in K562 cells.

K562 cells were fixed and labeled with mouse anti-TfR2 monoclonal antibody (9F8 1C11) and sheep anti-TfR serum, followed by Alexa 594 antimouse (red) and Alexa 488 antisheep (green). Merged sections of nonpermeabilized cells are shown in panels A to C. Yellow indicates overlapping fluorescence. Sections are 2.0 μm apart. Panels H and I, respectively, show the separate TfR (green) and TfR2 (red) channels of panel B. Merged sections of permeabilized cells (D-G) also indicate colocalization in perinuclear compartments. Sections in panels D to G are 1.5 μm apart; panels J and K are separate TfR (green) and TfR2 (red) channels of image in panel E. Images were captured with a × 60 oil immersion lens as described in “Materials and methods.”