Neutrophil and platelet activation in equine recurrent airway obstruction is associated with increased neutrophil CD13 expression, but not platelet CD41/61 and CD62P or neutrophil-platelet aggregate formation.
Recurrent airway obstruction (RAO) in mature horses is characterized by reversible airway obstruction and neutrophilic inflammation; there is also functional activation of circulating platelets and neutrophils. This study was undertaken to determine if changes in activation marker expression and heterotypic aggregate formation can be used as an indicator of this increased functional responsiveness. In vitro conditions for flow cytometric measurement of CD13, CD41/61 and CD62P expression on activated cells and heterotypic aggregate formation were established. Values were then compared before and after antigen challenge of RAO and healthy horses. Platelet adhesion to serum-coated plastic was measured as a functional marker of platelet activation. In vitro activation resulted in increased expression of neutrophil CD13 and platelet CD41/61 and CD62P. Activation of both cell types caused a significant increase in neutrophil-platelet aggregates. In horses with RAO, but not controls, there was a significant increase in the percentage of CD13 positive neutrophils at 10h and 24h and in the mean fluorescence intensity at 10h. This was accompanied at 24h by an increased mean platelet side scatter and thrombin-stimulated platelet adhesion. In conclusion, CD13 expression can be used as an indicator of equine neutrophil activation both in vitro and in vivo. Equine platelet activation in vitro can be detected by measuring CD41/61 or CD62P expression, and PAF-activated platelets and neutrophils form aggregates. However, despite evidence of circulating platelet activation, neither a change in expression of platelet activation markers, nor heterotypic aggregate aggregate formation could be detected.
Department of Veterinary Basic Sciences, The Royal Veterinary College, North Mymms, Herts AL9 7TA, UK. bdunkel@rvc.ac.uk
B
B
Dunkel
K J
KJ
Rickards
D
D
Werling
C P
CP
Page
F M
FM
Cunningham
D000402:Airway Obstruction / Q000097:blood / Q000276:immunology / Q000662:veterinary*; D000818:Animals; D018826:CD13 Antigens / Q000032:analysis*; D002449:Cell Aggregation; D006734:Horse Diseases / Q000276:immunology*; D006736:Horses; D039661:Integrin beta3 / Q000032:analysis*; D009504:Neutrophils / Q000502:physiology*; D019007:P-Selectin / Q000032:analysis*; D015539:Platelet Activation; D010973:Platelet Adhesiveness; D010974:Platelet Aggregation; D040201:Platelet Membrane Glycoprotein IIb / Q000032:analysis*; D012008:Recurrence
D039661:Integrin beta3; D019007:P-Selectin; D040201:Platelet Membrane Glycoprotein IIb; D018826:CD13 Antigens