Platelet-induced expression of tissue factor procoagulant activity in freshly isolated human mononuclear cells: implications for experimental use

Clin Lab Haematol. 2003 Oct;25(5):321-5. doi: 10.1046/j.1365-2257.2003.00544.x.

Abstract

Monocytes express tissue factor (TF) as a result of cytokine stimulation or endothelial adherence. We evaluated monocyte-platelet interaction in vitro as another trigger for monocyte TF enhancement in human mononuclear cells isolated by density gradient centrifugation from peripheral blood. Cell TF procoagulant activity (TF-PCA) was quantitated by a one-stage recalcification clotting time assay. Platelets were counted and identified by whole blood flow cytometry as CD61 positive particles, activated platelets were characterized by P-Selectin (CD62) expression, and monocytes by surface CD14 expression. A significant correlation between normalized TF-PCA of isolated mononuclear cells and platelet count was shown (r = 0.43, P < 0.001). Percentage of activated platelets in baseline samples was 4.2 +/- 3.5 while adenosine diphosphate (ADP) increased platelet positivity to 34 +/- 17% (P < 0.001). After isolation, 52 +/- 12% of platelets within suspensions were activated (P < 0.0001). Percentage of CD62-positive monocytes (CD14+ particles) increased from baseline 5% to 13 +/- 6% in ADP-stimulated samples to 53 +/- 17% after isolation (P < 0.001). These findings suggest that density gradient centrifugation activates platelets and that an adhesive interaction between monocytes and platelets may promote TF-PCA expression in isolated mononuclear suspensions. Enhanced monocyte TF expression as a result of an activated platelet-monocyte interaction seems to be an important laboratory effect requiring consideration when utilizing this technique in an experimental setup.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blood Platelets / physiology*
  • Cell Communication
  • Centrifugation, Density Gradient
  • Humans
  • Lipopolysaccharide Receptors / analysis
  • Monocytes / metabolism*
  • P-Selectin / analysis
  • Platelet Aggregation
  • Thromboplastin / metabolism*

Substances

  • Lipopolysaccharide Receptors
  • P-Selectin
  • Thromboplastin