MACS using antitransferrin receptor (TfR) antibody in normal and OHSt cells (patient A-II-1). In these plots, the x-axis always denotes side scatter, whereas the y-axis denotes either the emission of the FITC-labeled swine anti–rabbit IgG (detecting the antistomatin antibody; A-B, E-F) or thiazole orange (C-D). OHSt cells that bound to the anti-TfR beads (A, C) show positive antistomatin antibody immunoreactivity (A) and enhanced thiazole orange staining (C), whereas unbound OHSt cells show less antistomatin antibody immunoreactivity (B) and less thiazole orange staining (D). Control experiments shown in panels E-F show the level of FITC emission from normal cells in the presence (E) and absence (F) of the primary antistomatin antibody. These control experiments define the horizontal demarcating boundary between “stomatin-positive” and “stomatin-negative” cells seen in panels A-B.