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Platelet microparticles bind, activate and aggregate neutrophils in vitro
1William J. Harrington Sr., Center for Blood Diseases, Dept of Medicine, School of Medicine, University of Miami.
Blood Cells, Molecules & Diseases
|January 1, 1995
Summary
Platelet microparticles (PMP) bind to neutrophils, activating them and potentially mediating inflammatory and thrombotic conditions. This interaction is calcium-dependent and enhanced compared to whole platelets.
Area of Science:
- Biomedical research
- Hematology
- Immunology
Background:
- Activated platelets interact with leukocytes, contributing to ischemic reperfusion injury and thrombosis.
- Platelet microparticles (PMP) are shed upon platelet activation, expressing markers like CD62P that mediate adhesion.
Purpose of the Study:
- To investigate the interaction between PMP and leukocytes, specifically neutrophils.
- To characterize the binding kinetics, dependence on calcium, and functional consequences of PMP-neutrophil interactions.
Main Methods:
- Incubation of isolated PMP with leukocytes (neutrophils and lymphocytes).
- Assessment of binding using flow cytometry (FITC-labeled anti-CD41) and fluorescence microscopy.
- Evaluation of inhibition by antibodies (anti-CD62P, anti-sialyl Lewis X) and calcium chelation (EGTA).
- Measurement of CD11b expression and phagocytic activity on neutrophils post-PMP incubation.
Main Results:
- PMP preferentially bound to neutrophils over lymphocytes in a calcium-dependent manner.
- Binding was time- and concentration-dependent, with PMP forming bridges between neutrophils.
- PMP binding to neutrophils increased CD11b expression and phagocytic activity.
- PMP binding was significantly inhibited by anti-sialyl Lewis X, more so than by anti-CD62P.
Conclusions:
- PMP actively engage and activate neutrophils, suggesting a role beyond platelet factor 3.
- PMP may act as mediators in ischemic injury, thrombosis, and inflammation by modulating neutrophil function.