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Multiparticle adhesive dynamics: hydrodynamic recruitment of rolling leukocytes
1Departments of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA.
Summary
Hydrodynamic collisions can recruit leukocytes to blood vessel walls during inflammation. This "hydrodynamic recruitment" mechanism, observed in experiments and simulations, enhances cell adhesion and may be crucial in vivo.
Area of Science:
- Biophysics
- Immunology
- Fluid Dynamics
Background:
- Leukocyte rolling along blood vessel walls is critical for inflammatory responses.
- This process occurs in postcapillary venules across various shear stresses and vessel sizes.
- Specific receptor-ligand interactions mediate leukocyte adhesion.
Purpose of the Study:
- To investigate how hydrodynamic collisions influence leukocyte capture on selectin-bearing surfaces under shear flow.
- To understand the mechanism of "hydrodynamic recruitment" in cell adhesion.
- To validate theoretical predictions with in vivo experimental data.
Main Methods:
- Utilized a cell-free assay with carbohydrate-coated spherical beads as model leukocytes.
- Performed experimental studies to observe bead attachment following collisions.
- Employed direct numerical simulations incorporating multiparticle hydrodynamic interactions.
Main Results:
- Model leukocytes attached to the adhesive wall 4-5 cell diameters upstream or downstream of stationary or rolling beads.
- Downstream attachment resulted from glancing, indirect collisions near the wall plane.
- Numerical simulations accurately reproduced experimental observations.
Conclusions:
- Hydrodynamic recruitment is a viable mechanism for leukocyte capture, independent of buoyancy.
- This mechanism operates across a range of shear rates, suggesting in vivo relevance.
- In vivo hamster cheek pouch model measurements support the proposed hydrodynamic recruitment theory.