Flow cytometric analysis of isolated microparticles from platelets activated with HIT sera, thrombin, and calcium ionophore.

Very few microparticles were observed in control reactions, in which platelets were incubated with patient serum that tested negative for (E) heparin-induced thrombocytopenia or heparin alone (data not shown). Microparticles (lower row) were identified using fluorescence (FL1, FITC anti-GPIbα) (y-axis) and size (FSC) (x-axis) characteristics. Microparticles isolated from platelets incubated with (F) heparin-induced thrombocytopenia serum, (G) thrombin, and (H) calcium ionophore demonstrated similar light scatter profiles as microparticles in unfractionated platelet reactions (upper row). The results of a representative experiment are shown.