Thrombotic activity of exosomes and MVs from MDA-MB-231 cell line. The thrombotic activity of exosomes and MVs was tested using pure fibrin clots or clots produced in platelet-poor plasma. A total of 30 μg of exosomes or MVs was added to pure fibrinogen or platelet-poor plasma. The OD was measured at 350 nm every 2 minutes for 1 hour at 37°C. α-Thrombin was added to the fibrinogen or platelet-poor plasma as a positive control. Thrombotic activity in the presence of fibrinogen is shown for MVs (Ai) and exosomes (Bi) from MDA-MD-231 cells. The thrombotic activity with human plasma is shown for MVs (Aii) and exosomes (Bii) from MDA-MD-231 cells. Representative photographs of the experiment are presented in the lower panels. *P ≤ .05, **P ≤ .01, ***P ≤ .001, Mann-Whitney U test (1 tailed).