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Evaluation of structural and functional alterations of circulating neutrophils in calves with experimentally induced
D J McClenahan1, J J Fagliari, O A Evanson
1Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Minnesota, St Paul 55108, USA.
Objectives:
To determine the structural and functional alterations in circulating neutrophils that may lead to sequestration in lung microvasculature and endothelial injury in calves with experimentally induced pneumonic pasteurellosis.
Animals:
10 healthy, 2- to 4-week-old male Holstein calves.
Procedures:
Holstein calves were anesthetized and inoculated intrabronchially with Dulbecco phosphate buffered saline (0.9% NaCl) solution (DPBSS; 5 control calves) or 1 x 10(9) Pasteurella haemolytica organisms (5 infected calves). Blood samples were collected before and 1, 2, 4, and 6 hours after inoculation. Total and differential WBC count, dilute whole blood leukocyte deformability, neutrophil size distribution, and neutrophil surface CD11b expression were measured in blood samples.
Results:
A progressive decrease in leukocyte deformability and increase in neutrophil size was detected 1, 2, 4, and 6 hours after inoculation of P haemolytica. Neutrophil surface CD11b expression was greater than baseline values at 6 hours after inoculation of P haemolytica. Two populations of neutrophils with an increase in size were detected in P haemolytica-infected calves. Both subpopulations had increased CD11b expression, compared with neutrophils that were typical in size.
Conclusions And Clinical Relevance:
Neutrophils circulate in an activated and nondeformable state in calves with experimentally induced pneumonic pasteurellosis. A decrease in neutrophil deformability and neutrophil aggregation may contribute to neutrophil trapping in the lung microvasculature during pneumonic pasteurellosis in calves.