Immunofluorescence analysis of cells transfected with b5R S-cDNA (A) or M-cDNA (B through D). Transfection with S-cDNA results in the expression of a product distributed uniformly throughout the cell (A), while the product of M-cDNA is compartmentalized (B and C). In (B), cells expressing low levels of b5R (probably not transfected) are visible in the background. (C and D) Show the results of a double-labeling experiment, in which cells were labeled with the mitochondrial dye Mitotracker and with anti-b5R antibodies. The same field is shown viewed under the fluorescein filter for anti-b5R antibodies (C), or under the rhodamine filter for Mitotracker. The arrows point to some of the more striking identities between the two stains. The arrowhead indicates staining of the nuclear envelope by anti-b5R antibodies in (C) and absence of staining by Mitotracker in (D). The asterisk marks the position of an untransfected cell. Scale bar in (A) corresponds to 10 μm in (A) and (B) and to 6 μm in (C) and (D).