Flow cytometric analyses of PS⁺ and CD36⁺ erythrocytes from a representative patient with SCD.

For the analysis of PS⁺ RBCs, dot plots of anti-CD235a–PE fluorescence and annexin V–FITC fluorescence from an RBC preparation stained in the presence of EDTA and calcium are presented in panels A and B, respectively. PS⁻ (quadrant Q1) and PS⁺(quadrant Q2) dot plot regions were set using the erythrocyte sample stained in the presence of EDTA (A). Corresponding histogram profiles of annexin V–FITC fluorescence are presented in panels C and D, respectively. PS⁻ (gate M1) and PS⁺ (gate M2) histogram regions were set using the RBC sample stained in the presence of EDTA (C). Values obtained for PS⁺ RBCs from both dot plot and histogram analyses were identical. For the analysis of CD36⁺ erythrocytes, dot plots of anti-CD235a–PE fluorescence and either FITC fluorescence from an isotype-matched negative control antibody or anti-CD36–FITC fluorescence from an RBC preparation are presented in panels E and F, respectively. Corresponding histogram profiles of FITC fluorescence from RBCs stained with the negative control antibody and anti-CD36 are presented in panels G and H, respectively. Events in quadrant Q1 (F) and gate M1 (H) represent CD36⁻ RBCs, and those in quadrant Q2 (F) and gate M2 (H) are from the CD36⁺ erythrocytes. Analyses procedures similar to those described for PS⁺ RBCs were also used to assess data related to CD36 presented in panels E through H.