Evaluation of structural and functional alterations of circulating neutrophils in calves with experimentally induced pneumonic pasteurellosis.
OBJECTIVE
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.


METHODS
10 healthy, 2- to 4-week-old male Holstein calves.


METHODS
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
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.
McClenahan
D J
DJ
Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Minnesota, St Paul 55108, USA.
Fagliari
J J
JJ
Evanson
O A
OA
Weiss
D J
DJ
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000097:blood / Q000382:microbiology; D007962:Leukocytes / Q000502:physiology; D016177:Macrophage-1 Antigen / Q000097:blood; D008297:Male; D016978:Mannheimia haemolytica; D009504:Neutrophils / Q000473:pathology / Q000502:physiology*; D010326:Pasteurella Infections / Q000097:blood / Q000662:veterinary*; D012766:Pasteurellosis, Pneumonic / Q000097:blood*; D018410:Pneumonia, Bacterial / Q000097:blood / Q000662:veterinary*; D012016:Reference Values
D016177:Macrophage-1 Antigen