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Leukocyte-leukocyte interactions mediated by platelet microparticles under flow
S B Forlow1, R P McEver, M U Nollert
1School of Chemical Engineering and Materials Science, University of Oklahoma, Norman, Oklahoma 73019, USA.
Blood
|February 9, 2000
Summary
Platelet microparticles (PMPs) bridge leukocytes, promoting cell aggregation and interaction under flow conditions. These PMPs enhance leukocyte accumulation, particularly in disease states with elevated concentrations.
Area of Science:
- Hematology
- Cellular Biology
- Immunology
Background:
- Platelet microparticles (PMPs) are released from activated platelets and express P-selectin.
- Elevated PMP concentrations are observed in various disorders.
- The role of PMPs in leukocyte aggregation remains undefined.
Purpose of the Study:
- To investigate the role of P-selectin-expressing PMPs in mediating leukocyte-leukocyte interactions.
- To determine if PMPs bridge leukocytes expressing P-selectin glycoprotein ligand-1 (PSGL-1) under flow.
Main Methods:
- PMPs were isolated from platelet-rich plasma or generated from activated platelets.
- Flow chamber experiments assessed the adhesion of HL-60 cells or neutrophils to prebound cells.
- L-selectin function was blocked to isolate PMP-mediated effects.
Main Results:
- PMPs significantly increased transient adhesion of flowing leukocytes to bound leukocytes.
- PMP-mediated aggregation occurred even when L-selectin function was blocked.
- Microparticle-mediated interactions occurred at lower shear stresses compared to L-selectin.
Conclusions:
- PMPs enhance leukocyte aggregation and interaction under flow conditions.
- PMPs may contribute to leukocyte accumulation on selectin-expressing substrates.
- This mechanism is particularly relevant in diseases with increased PMP levels.