RBC-loaded scFv/TM inhibits platelet activation by thrombin. (A) P-selectin expression on platelets mixed with RBCs (5% hematocrit). Resting platelets (blue line) and platelets stimulated with thrombin (black line) or AYP-PAR4 peptide (red line). (B) Same as in panel A, but RBCs were preincubated with scFv/TM. scFv/TM-loaded RBCs inhibited platelet activation by thrombin (black line) but not by AYP (red line). (C) Mice (n = 3 for each arm) were injected with PBS, sTM, or scFv/TM 1 hour before collecting blood. P-selectin expression was measured as in panel A. Injection of scFv/TM prevents platelet activation by thrombin compared with sTM (P = .0357).