Fibrin-rich clots recruit circulating platelets in a GPVI-dependent manner. (A-B) In a first step, platelet-rich thrombi were formed in the capillary chambers by perfusing recalcified human whole blood containing Alexa Fluor 647–conjugated fibrinogen over an immobilized mixture of TF and collagen. In a second step, hirudinated blood containing platelets labeled with an Alexa Fluor 488–conjugated antibody (RAM.1) was perfused through the chambers for 5 minutes at 1500 s−1, in the presence of a control Fab or the anti-GPVI Fab 9O12. (A) Images are from 1 representative film in a total of 10. Bar, 20 µm. Fibrin is stained in red, platelets appear in orange, and platelets bound to fibrin in yellow. (B) A quantitative analysis was performed on images obtained after 5 minutes of perfusion and is presented as the ratio of the surface area of fibrin-associated platelets to the total fibrin surface area (n = 10). Mean ± SEM, ***P < .001, Student t test.
