Fig. 3. Subcellular distribution and internalization of FcRn. FO-1 cells (a,e,i), FO-1ß2m cells (b,f,j), FO-1 cells expressing Myc-hFcRn (c,g,k) and FO-1ß2m cells expressing Myc-hFcRn (d,h,l) were fixed, permeabilized and stained with anti-myc antibodies to visualize the subcellular distribution of Myc-hFcRn (a-d). Alternatively, cells were incubated with anti-Myc antibodies at 4°C, fixed and surface-bound anti-Myc was detected with labeled secondary antibodies to visualize Myc-hFcRn present on the cell surface (e-h). In panels i-l, cells were allowed to internalize anti-Myc antibodies for 60 minutes at 37°C, washed with acid to remove non-internalized antibodies bound to the cell surface and then fixed, permeabilized and stained with labeled secondary antibodies to detect anti-Myc antibodies that had been internalized. Panels show representative data of one of two clones analyzed.