Flow cytometry on fixed and permeabilized, OHSt and normal, red cells. In all plots, the y-axis denotes the emission of the R-PE label conjugated to the secondary antibody in the stomatin detection system, whereas the x-axis denotes thiazole orange fluorescence emission. Both are expressed in arbitrary units. The panels show data from separate experiments on peripheral blood of patient A-II-1 (top row) and patient B-II-1 (lower row). In each experiment, we analyzed a patient (A-B) and a healthy control (C-D) in the presence of the antistomatin antibody and thiazole orange, and then the healthy control in the presence of thiazole only (E-F). The horizontal and vertical demarcation boundaries were set by the control experiments on normal blood shown in panels E-F, in which normal blood, containing about 1% reticulocytes, was subjected to the same analysis in the absence of the antistomatin antibody, defining the threshold fluorescence of the antibody detection method. In the normal samples (C-D), essentially all erythrocytes were stomatin-positive and thiazole-negative, and were present in the upper left box, labeled W. In patients A-II-1 and B-II-1 (panels A and B, respectively), the stomatin expression was always less than that of healthy controls, but nevertheless positive in a minority of the cells (regions W + X), quantitated at 23.6% in patient A-II-1 and 16% in patient B-II-1. In each OHSt case, about 20% to 25% of the stomatin-positive cells were also thiazole-positive (region X, panels A-B), whereas only about 5% of the stomatin-negative cells were thiazole-positive (region Z, panels A-B). Thus stomatin-positive cells tended also to be thiazole-positive.