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[Leukocyte adhesion on a fibrinogen-coated surface under static conditions: experimentation and creation of a model]
V Labrador1, S Legrand, S Muller
1Laboratoire d'Angiohématologie-Hémorhéologie, LEMTA UMR CNRS 7563, Faculté de Médecine, F-54500 Vandoeuvre-les-Nancy.
Abstract:
The adhesion of polymorphonuclear leukocytes (PMNs) on the vascular endothelium is a complex process that occurs during different biological and pathological events and involves numerous molecules. The adhesion cascade is induced after PMN stimulation by various molecular or cellular signals. Fibrinogen is one of the substrates for CD11b/CD18 B2-integrins expressed at the PMN surface; fibrinogen-neutrophil binding is induced by inflammatory reactions. In order to understand this process, we have carried out studies on the basis of preliminary experiments on red blood cells and synthetic particles. The modelization of quiescent PMNs adhesion on a fibrinogen substrate was investigated with a sedimentation cell chamber. Two different physiological conditions were tested: the activated state of PMN by a synthetic pro-inflammatory activator (FMLP). The activated state of PMNs was both quantified by flow cytometry and controlled by fluorescence microscopy. The results suggest that quiescent neutrophils deposit in accordance with the ballistic deposition model. This random adsorption model differs from random sequential adsorption (RSA) in that the cells arriving at the surface are able to roll along cells previously adsorbed introducing the notion of gravitational attraction of cells. The preliminary results obtained with stimulated PMN do not allow to choose between one of this two deposition models. Nevertheless, the qualitative and quantitative effects of FMLP on neutrophils were demonstrated by modifications of adhesion molecules expression.
Insights
Quiescent neutrophils adhere to fibrinogen substrates following a ballistic deposition model, unlike random sequential adsorption. Activated neutrophils show altered adhesion molecule expression, but their deposition model remains unclear.
Area of Science:
- Cellular Biology
- Biophysics
- Immunology
Background:
- Polymorphonuclear leukocyte (PMN) adhesion to vascular endothelium is crucial in biological and pathological processes.
- Fibrinogen-neutrophil binding, mediated by CD11b/CD18 integrins, is induced by inflammatory signals.
- Understanding PMN adhesion dynamics is essential for comprehending inflammatory responses.
Purpose of the Study:
- To model the adhesion of quiescent and activated polymorphonuclear leukocytes (PMNs) onto a fibrinogen substrate.
- To investigate the deposition mechanisms of PMNs under different physiological conditions.
- To quantify the effects of pro-inflammatory activators on PMN adhesion molecule expression.
Main Methods:
- Utilized a sedimentation cell chamber to study PMN adhesion to fibrinogen.
- Investigated quiescent PMNs and PMNs activated by N-formylmethionyl-leucyl-phenylalanine (FMLP).
- Quantified PMN activation using flow cytometry and fluorescence microscopy.
Main Results:
- Quiescent neutrophils exhibited deposition consistent with the ballistic deposition model.
- This model differs from random sequential adsorption by incorporating cell rolling and gravitational effects.
- Activated PMNs showed significant changes in adhesion molecule expression, but their deposition model was not definitively determined.
Conclusions:
- The ballistic deposition model accurately describes quiescent neutrophil adhesion to fibrinogen.
- Inflammatory activation alters PMN adhesion molecule expression, impacting their behavior.
- Further research is needed to elucidate the deposition model for activated PMNs.