Mouse platelet aggregation test with whole blood. Platelets were labeled with CD9-APC or CD9-PE and mixed in 1:1 ratio before stimulation. Aggregation was measured by flow cytometry in time after stimulation with PMA, collagen, Aggretin A, and botrocetin. Average and standard error of the mean are depicted, n > 3. (A) An example of the gating strategy used after flow cytometry analysis. Ter119⁻ cells were selected to calculate double-colored events by plotting them against PE/APC channels. The same dot plot is shown for total events. Note the increase in events in Q2 after stimulation with collagen. Q1-Q4 and RBC populations are plotted against the forward and side scatter and indicated by colored arrowheads. PLT, platelets; RBC, red blood cells. (B) Time course of double-colored events upon stimulation with PMA, collagen, Aggretin A, and botrocetin. Nonstimulated labeled platelets are shown as baseline for spontaneous aggregation. Colored asterisks at each data point indicate statistical significance with the unstimulated control (P < .05).