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Routine Screening Method for Microparticles in Platelet Transfusions
Published on: January 31, 2018
Glycoprotein IIb-IIIa on platelet-derived microparticles, and microparticle structures studied by electron
Abstract:
Shedding of microparticles from the platelet surface is usually associated with exposure of platelet procoagulant activity. Platelet-derived microparticles have been detected in blood in various disease states. In vitro, platelet stimulation with a number of different agonists results in formation of microparticles. In the present study, microparticles induced by platelet stimulation by calcium ionophore or by membrane incorporation of the terminal complement complex C5b-9 were studied using electron microscopy, confocal laser microscopy, flow cytometry and radio-immunoelectrophoresis. When studied by electron microscopy, microparticle morphology was found to be dependent upon the induction method. Platelet stimulation with the calcium ionophore resulted in smaller, more homogeneous and electron dense microparticles than those induced by insertion of the terminal complement complex. With flow cytometry and confocal laser immunofluorescence microscopy, microparticle GPIIb-IIIa was demonstrated using a FITC-conjugated antibody to GPIIIa. Surface-bound GPIIb-IIIa was demonstrated on the microparticles by immunoelectron microscopy. Crossed immunoelectrophoresis of detergent-solubilized microparticles visualized a very prominent GPIIb-IIIa immunoprecipitate arc, and binding of [(125)1]fibrinogen to microparticle GPIIb-IIIa was demonstrated by radio-immunoelectrophoresis. This suggests that the activated GPIIb-IIIa complex is preserved intact during the shedding of microparticles from the platelet surface.
Insights
Platelet microparticle formation differs based on induction method. Activated platelet GPIIb-IIIa complex remains intact on shed microparticles, suggesting preserved function in disease states.
Area of Science:
- Hematology
- Cell Biology
- Immunology
Background:
- Platelet microparticles are observed in various diseases.
- Microparticle shedding is linked to platelet procoagulant activity.
- Platelet stimulation in vitro generates microparticles.
Purpose of the Study:
- To investigate microparticle morphology and GPIIb-IIIa complex presence.
- To compare microparticles induced by calcium ionophore versus complement C5b-9.
- To assess the integrity of GPIIb-IIIa on microparticles.
Main Methods:
- Electron microscopy for morphology.
- Confocal laser microscopy and flow cytometry for GPIIb-IIIa detection.
- Radio-immunoelectrophoresis for fibrinogen binding to GPIIb-IIIa.
Main Results:
- Microparticle morphology varied with induction method (calcium ionophore vs. C5b-9).
- GPIIb-IIIa was detected on microparticles using flow cytometry and microscopy.
- Activated GPIIb-IIIa complex and fibrinogen binding were confirmed on microparticles.
Conclusions:
- Platelet microparticle characteristics depend on the induction stimulus.
- The activated GPIIb-IIIa complex is preserved on shed microparticles.
- This suggests retained functionality of platelet microparticles in pathological conditions.
