Platelet activation by soluble TGFBIp. (A) Washed platelets were incubated with soluble TGFBIp (1 μg/mL) for 15 minutes. Phosphatidylserine and P-selectin exposure and binding affinity of fibrinogen were detected by annexin V–FITC, anti–P-selectin-FITC antibody, and fibrinogen-FITC, respectively, by the use of FACS analysis. (B) Washed platelets were incubated with the soluble FAS1 domain (Do1, Do2, Do3, Do4, Do4-RGD, and Do1-4; each 1 μg/mL), fibrinogen (Fg; 5 mg/mL, as negative control), and thrombin (1 U/mL, as positive control) for 15 minutes, and PS exposure (annexin V–FITC) was analyzed by FACS. Washed platelets were allowed to adhere on noncoated slides for 15 minutes, and platelet adhesion (C) and platelet spreading (D) were assessed (pixels/cells) in the presence of soluble each indicated protein (1 μg/mL). Platelet adhesion was detected by the acid phosphatase assay, and spreading was detected by the use of the MetaMorph program. All results are shown as the means ± SD of 3 different experiments and ANOVA. *P < .05 compared with BSA.