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Vet. Res.
Volume 38, Number 1, January-February 2007
Page(s) 95 - 108
Published online 08 December 2006
How to cite this article Vet. Res. (2007) 95-108
Vet. Res. 38 (2007) 95-108
DOI: 10.1051/vetres:2006052

Shedding of sCD14 by bovine neutrophils following activation with bacterial lipopolysaccharide results in down-regulation of IL-8

Eun J. Sohna, Max J. Paapeb, Douglas D. Bannermanb, Erin E. Connorb, Raymond H. Fettererc and Robert R. Petersa

a  Department of Animal and Avian Sciences, University of Maryland, College Park, MD 20742, USA
b  Bovine Functional Genomics Laboratory, USDA-ARS, Beltsville, MD 20705, USA
c  Animal Parasitic Diseases Laboratory, USDA-ARS, Beltsville, MD 20705, USA

(Received 1 June 2006; accepted 3 October 2006; published online 8 December 2006)

Abstract - CD14, the leukocyte co-receptor for lipopolysaccharide (LPS), is important in the response of bovine polymorphonuclear neutrophil leukocytes (PMN) to Gram-negative bacteria. In other species, the expression of CD14 on the surface of PMN was shown to increase after exposure to inflammatory stimuli. These newly expressed molecules may originate from either an intracellular pool or through new gene expression. We sought to characterize bovine PMN cell surface expression and shedding of CD14 molecules, and CD14's effect on secretion of the chemoattractants IL-8 and IL-1$\beta $ by PMN. Bovine PMN were incubated in RPMI for 20 h at 37 $^{\circ}$C with LPS (1, 10, 100 $\mu $g/mL). IL-8 release increased with treatment of 1 $\mu $g/mL LPS, but decreased 41.5 and 95% at the 10 and 100 $\mu $g/mL concentrations of LPS, respectively. In contrast, shedding of CD14 from the surface of PMN only increased at the highest concentration of LPS (100 $\mu $g/mL). Secretion of IL-1$\beta $ was similar regardless of the LPS concentration used to stimulate PMN. The effect of PMN concentration ( $1 \times 10^{7}$, $2.5\times 10^{7}$, $5\times 10^{7}$, and $10\times 10^{7}$/mL) on CD14 cell surface expression and shedding of IL-8 and IL-1$\beta $ were also determined. Shedding of CD14 by PMN increased with increasing concentration of PMN after exposure to 0.1 and 10 $\mu $g/mL of LPS, while secretion of IL-8 decreased. IL-1$\beta $ increased at the highest concentration of PMN. The use of real time polymerase chain reaction showed that CD14 mRNA expression was not different between control and LPS-stimulated cells, indicating that the sCD14 came from either membrane bound CD14 or a preformed pool. Our results demonstrate that release of CD14 from PMN suppresses secretion of IL-8, and may be an important regulatory mechanism for controlling excessive migration of PMN into the bovine mammary gland.

Key words: CD14 / IL-8 / LPS / neutrophil / bovine

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© INRA, EDP Sciences 2007