Arrest of flow platelets incubated with or without the 4N1K peptide in solution on TNF-α–treated endothelial cells. EA endothelial cells were grown onto permanox Lab-Tek 1 chamber slides and stimulated with 25 ng/mL rhTNF-α for 18 hours. After platelet labeling in PRP with calceine, platelets were incubated for 15 minutes at 37°C with or without 100 μM 4N1K or 4NGG peptides in solution. In some experiments, platelets were first incubated for 10 minutes at 37°C with 40 μg/mL anti-CD47 mAb B6H12 before stimulation with the 4N1K peptide. Whole blood was then reconstituted and perfused through the chamber at 37°C and at a shear rate of 100 seconds^–1 for 3 minutes. Platelet adhesion, expressed as percentage of surface covered with platelets, is the average ± SEM of 10 random fields per coverslip. **P < .01; ***P < .001. This experiment is representative of 3 experiments performed using blood from different donors.