Effect of inhibitors of fibrin generation and platelet function on αIIbβ3-independent platelet aggregation induced by collagen and purified coagulation factors VIIa/X/II/I. Aggregation of αIIbβ3-inhibited platelets was induced as described in Figure 1. When collagen alone was added to αIIbβ3-inhibited platelets full aggregation did not occur, when collagen was added together with coagulation factors VIIa/X/II/I full aggregation occurred after approximately 7 minutes (left). In the right part of the graph, aggregation induced by the combination of collagen and coagulation factors in the presence of the compound mentioned at the X-axes is indicated. In the middle part of the graph, the effect of antibodies or antagonists affecting platelet function on aggregation of αIIbβ3-inhibited platelets is depicted; on the right, the effect of compounds affecting coagulation on αIIbβ3-independent aggregation is shown. Antibodies were preincubated with the platelet suspension for 45 minutes at room temperature; the other compounds were added 5 minutes before aggregation was induced. The time to the start of the second wave of aggregation (Figure 1) was determined from the aggregation curves. Data shown are mean ± standard deviation of at least 3 independent experiments. *P < .01, #P < .05 versus collagen plus coagulation factors.