Functional analysis of recombinant bovine CD14Report as inadecuate

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Abstract : Studies in mice and humans indicate that membrane CD14 mCD14 on the surface of monocytes, macrophages and polymorphonuclear neutrophils PMN mediate activation of these cells by lipopolysaccharide LPS. Soluble CD14 sCD14, in the circulation, binds to LPS and blocks LPS binding to mCD14. The role of bovine CD14 in cellular activation by LPS is undefined. Changes in CD18 expression on PMN and steady state levels of mRNA for tumor necrosis factor-$\alpha$ TNF-$\alpha$, interlukin-6 IL-6 and IL-8, sensitive markers for activation of leukocytes by LPS, were used to measure functional activity of recombinant bovine sCD14 rbosCD14. Whole blood n = 3 cows treated with LPS alone caused CD18 expression on PMN to increase by 12% $P < 0.02$, whereas pre-incubation of LPS with 10 or 100 $\mu$g-mL of rbosCD14 completely inhibited increase in CD18 expression. After treating whole blood with LPS at concentrations of 1, 100 or 10$^{4}$ ng-mL for 2 h, level of mRNA for TNF-$\alpha$, IL-6 and IL-8 in leukocytes and concentration of TNF-$\alpha$ in plasma increased. However, pre-incubation of LPS with rbosCD14 inhibited the increase in TNF-a mRNA, but not the increase in IL-6 and IL-8 mRNA. Excess amount of anti-human CD14 monoclonal antibody MAB also inhibited LPS-induced increase in TNF-$\alpha$ mRNA. Preincubation of LPS with rbosCD14, or rbosCD14 plus MAB did not affect LPS-induced increase in TNF-$\alpha$ in plasma. Collectively, results indicate that rbosCD14 inhibit LPS-induced increase in CD18 expression and TNF-$\alpha$ mRNA. However, secretion of TNF-$\alpha$ was not inhibited by pre-incubation of LPS with rbosCD14. The TNF-$\alpha$ in plasma may partially induce transcription of IL-6 and IL-8, which contribute to the CD14-independent increase in level of mRNA for IL-6 and IL 8.

Keywords : CD14 LPS TNF-$\alpha$ bovine PMN

Author: Yan Wang Dante Zarlenga Max Paape Geoffrey Dahl Grant Tomita



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