Altered TG by increasing or blocking phosphatidylserine exposure on RBC. (A-B) Flow cytometry of phosphatidylserine exposure of washed RBC after 30 minutes treatment with 10 μM ionomycin/CaCl₂ or with 7.5 μg/mL annexin A5/CaCl₂ (A5), analyzed after labeling with FITC–annexin A5. Shown are representative fluorescence-scatter profiles (F1 vs SSC) (A) and fractions of phosphatidylserine-exposing RBC (B). Visualization of RBC without or with ionomycin/CaCl₂ treatment (C). Arrows indicate activated, rounded RBC. (D) Effect of RBC treatment with ionomycin/CaCl₂ or annexin A5/CaCl₂ and wash, in comparison with no treatment (control) on TG in PRP samples reconstituted at 10% hematocrit at 0.1 pM tissue factor. Panels show representative curves (i), quantified lag times (ii), thrombin peak levels (iii), and ETP values (iv). (E) Effect of RBC treatment with ionomycin/CaCl₂ or annexin A5/CaCl₂ on factor Xa generation in a purified system. Indicated are representative factor Xa generation curves (i) and increased fluorescence units over 40 minutes (ii). Means ± SD (n = 3), 1-way ANOVA, ∗P < .05; ∗∗P < .01; ∗∗∗P < .001.