Cultured retinal pigment epithelial cells immunofluorescently labeled for transferrin receptor (TfnR) (green) and nucleus (blue). The cells were fixed in 2% PFA and 0.5% Triton X-100 for 2 minutes followed by post-fixation 4% PFA. TfnR was detected with H68.4 primary antibody and secondary FITC antibody. The nucleus was detected with DAPI staining. Images were collected on an Olympus IX-71 epifluorescence microscope using a 100X 1.4 NA objective with 4.500ms exposure for TnfR and 50ms exposure for DAPI (67nm/pixel).