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  • Author or Editor: Christian Burvenich x
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Abstract

Objective—To determine whether proinflammatory mediators and glucocorticoids affect CD62L(L-selectin) expression on peripheral blood neutrophils from cows in various stages of lactation.

Animals—100 healthy dairy cows during early (13.1 ± 0.79 days after parturition; n = 31), peak (58.7 ± 1.64 days after parturition; 31), and mid (137.2 ± 2.59 days after parturition; 38) lactation.

Procedure—In vitro effects of relevant proinflammatory mediators that are released in response to mastitis caused by gram-negative bacteria such as lipopolysaccharide (endotoxin), tumor necrosis factor-α, and platelet-activating factor (PAF) on CD62L expression on bovine neutrophils were assessed by flow cytometry. Influences of cortisol and dexamethasone on CD62L expression on bovine neutrophils were also investigated.

Results—Basal CD62L expression on neutrophils from cows during early, peak, and mid lactation were similar. Lipopolysaccharide and tumor necrosis factor-α had no effect on CD62L expression on neutrophils from cows at any stage of lactation. Conversely, PAF elicited a time- and dose-dependent, down regulatory effect on CD62L expression. However, no differential shedding of CD62L from neutrophils of cows at any stage of lactation were detected. In addition, no effects on CD62L expression on bovine neutrophils after whole blood incubation with cortisol or dexamethasone were observed. Incubation with glucocorticoids did not prevent the down regulatory effect of PAF on CD62L expression.

Conclusions and Clinical Relevance—Comparable basal CD62L expression on bovine neutrophils and equal amounts of CD62L shedding from bovine neutrophils during all stages of lactation suggest that variations in CD62L density are not a likely cause of susceptibility of cows to coliform-induced mastitis during early lactation. (Am J Vet Res 2004;225:1421–1426)

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in American Journal of Veterinary Research

Abstract

Objective—To evaluate L-selectin (CD62L) and Mac-1 (CD11b) expression at the surface of blood and milk neutrophils during the early inflammatory response to Escherichia coli-induced mastitis in cows.

Animals—6 healthy Holstein heifers in early lactation.

Procedure—Blood and milk samples were collected before and after intramammary administration of 104 CFU's of E coli in the left mammary gland quarters. Bacterial counts and electrolyte concentrations in milk, rectal temperature, differential blood leukocyte counts, milk somatic cell counts, neutrophil viability, and the expression of CD62L and CD11b on blood and milk neutrophils were determined longitudinally.

Results—Bacteria grew during the first 6 hours after inoculation with a pronounced leukocytic influx. Coincident with neutrophil influx was an increase in CD62L+ and CD11b+ milk neutrophils, as well as an improved viability of milk neutrophils. The peak of the inflammatory reaction was reached approximately 12 hours after E coli inoculation. From that time forward, changes in CD62L and CD11b expression were opposed to each other, with a decrease in CD62L expression and an increase in CD11b expression on blood and milk neutrophils; the magnitude of the differences in CD62L and CD11b expression between blood and milk neutrophils decreased. Percentages of CD62L+ and CD11b+ milk neutrophils increased to percentages that were similar to blood neutrophils (ie, approx 92%).

Conclusions and Clinical Relevance—The presence of adhesion molecules on a large percentage of milk neutrophils during the acute inflammatory response, together with the changes in receptor density, suggest a major role for CD62L and CD11b in neutrophil function during coliform mastitis. (Am J Vet Res 2004;65:1164–1171)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether apoptosis of neutrophils was accelerated during mastits experimentally induced by use of Escherichia coli or E coli endotoxin and whether differences were apparent in the response to E coli or endotoxin.

Animals—11 healthy lactating Holstein cows.

Procedure—Blood samples were collected from cows at various intervals after intramammary inoculation with E coli or endotoxin. Percentage of apoptotic neutrophils detected after in vitro incubation for 3 hours was determined. Fluorescein isothiocyanatelabeled annexin-V in combination with propidium iodide was used to distinguish apoptosis and necrosis of neutrophils. Total and differential circulating leukocyte counts and rectal temperature were determined at the time of collection of blood samples. Milk yield and milk somatic cell counts were determined at the time of milking.

Results—Inoculation of endotoxin did not accelerate in vitro induction of neutrophil apoptosis. However, inoculation of E coli increased the percentage of apoptotic neutrophils. At 18 hours after inoculation, 20% of the neutrophils were apoptotic, compared with 5% before inoculation. Milk somatic cell count and rectal temperature increased, milk production and total leukocyte count decreased, and percentage of immature neutrophils increased after inoculation with E coli or endotoxin. However, kinetics of the responses were more rapid, more severe, and of shorter duration during endotoxininduced mastitis.

Conclusions and Clinical Relevance—In vitro induction of apoptosis of neutrophils was accelerated only during E coli-induced mastitis and not during endotoxin- induced mastitis. Endotoxin inoculation as a model for studying coliform mastitis in dairy cows should be viewed with caution. (Am J Vet Res 2002;63:448–453)

Full access
in American Journal of Veterinary Research