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Updated: May 12, 2026

Quantitative In vitro Assay to Measure Neutrophil Adhesion to Activated Primary Human Microvascular Endothelial Cells under Static Conditions
Published on: August 23, 2013
Acute-phase concentrations of soluble fibrinogen inhibit neutrophil adhesion under flow conditions in vitro through
J Pillay1, V M Kamp, M Pennings
1Department of Respiratory Medicine, University Medical Center Utrecht, Utrecht, The Netherlands.
Background:
Immobilized fibrinogen and fibrin facilitate leukocyte adhesion, as they are potent ligands for leukocyte MAC-1 (CD11b/CD18). However, fibrinogen in its soluble form also binds to MAC-1, albeit with low affinity. The level of soluble fibrinogen is increased during chronic and acute inflammation, but the function of this increase is unknown.
Objectives:
To study the effect of soluble fibrinogen in concentrations found in severe acute inflammation on leukocyte adhesion.
Methods:
Isolated leukocytes and soluble fibrinogen were studied in various in vitro settings under static and under flow conditions.
Results:
Soluble fibrinogen functioned as a natural antagonist of neutrophil functions that are dependent on MAC-1, such as the respiratory burst induced by unopsonized zymosan and adhesion to ICAM-1 and heparin. In addition, soluble fibrinogen inhibited lymphocyte function-associated antigen 1-dependent lymphocyte binding to ICAM-1 through a direct interaction with ICAM-1. Soluble fibrinogen reduced MAC-1-dependent binding of interleukin-8-activated neutrophils to ICAM-1-expressing cells under flow conditions. Importantly soluble fibrinogen in acute-phase concentrations (4-10 mg mL(-1) ) dose-dependently reduced neutrophil firm adhesion to tumor necrosis factor-α-activated endothelium to 40% under flow conditions.
Conclusions:
We propose a model in which the increased circulating concentrations of soluble fibrinogen found during the acute-phase response can act as a natural antagonist of leukocyte recruitment, and therefore might contribute to the resolution of inflammation.
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