Association among filamentous actin content, CD11b expression, and membrane deformability in stimulated and unstimulated bovine neutrophils.
OBJECTIVE
To investigate rheologic properties of bovine neutrophils that may result in adhesion molecule-independent sequestration of neutrophils in inflamed lungs of cattle.


METHODS
Healthy 2- to 4-week-old male Holstein calves.


METHODS
Neutrophil deformability, filamentous actin (F-actin) content, and CD11b expression was determined for unstimulated bovine neutrophils and bovine neutrophils incubated with the inflammatory mediators tumor necrosis factor-alpha (TNF), platelet-activating factor (PAF), interleukin-8 (IL-8), zymosan-activated plasma (ZAP), Pasteurella haemolytica-derived lipopolysaccharide (LPS), and P haemolytica leukotoxin. Neutrophils were separated into 3 subpopulations on the basis of size. The Factin content and CD11 b expression were evaluated by use of flow cytometry. Leukocyte deformability was evaluated by filtration of dilute whole blood.


RESULTS
The subpopulation of the smallest-sized neutrophils (>90% of neutrophils) contained little F-actin. A subpopulation of slightly larger neutrophils had a profound increase in F-actin content and CD11 b expression. The subpopulation of the largest neutrophils had increased F-actin content and CD11b expression, compared with those for both subpopulations of smaller neutrophils. Incubation of neutrophils with PAF and ZAP but not TNF, IL-8, LPS, or leukotoxin, resulted in decreased neutrophil deformability and increased F-actin content. Incubation with PAF and TNF induced an increase in size of neutrophils.


CONCLUSIONS
Size can be used to identify subpopulations of large and rigid neutrophils in blood samples from healthy calves. Platelet-activating factor and activated complement fragments are potent inducers of F-actin formation and neutrophil rigidity. Physical changes in neutrophils may impede their transit through lung microvasculature and result in leukocyte trapping independent of adhesion molecule interactions with endothelial cells.
McClenahan
D J
DJ
Department of Veterinary PathoBiology, College of Veterinary Medicine, University of Minnesota, St Paul 55108, USA.
Evanson
O A
OA
Walcheck
B K
BK
Weiss
D J
DJ
D000199:Actins / Q000032:analysis*; D000818:Animals; D001769:Blood; D002417:Cattle / Q000097:blood*; D002462:Cell Membrane / Q000187:drug effects; D005098:Exotoxins / Q000494:pharmacology; D007249:Inflammation / Q000097:blood*; D016209:Interleukin-8 / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D016177:Macrophage-1 Antigen / Q000096:biosynthesis*; D008297:Male; D016978:Mannheimia haemolytica; D009504:Neutrophils / Q000737:chemistry / Q000187:drug effects*; D010972:Platelet Activating Factor / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015054:Zymosan / Q000378:metabolism
D000199:Actins; D005098:Exotoxins; D016209:Interleukin-8; D008070:Lipopolysaccharides; D016177:Macrophage-1 Antigen; D010972:Platelet Activating Factor; D014409:Tumor Necrosis Factor-alpha; C018579:leukotoxin; D015054:Zymosan