Vet. Res. 34 (2003) 413-421
DOI: 10.1051/vetres:2003012

Functional analysis of recombinant bovine CD14

Yan Wang^a, Dante S. Zarlenga^b, Max J. Paape^b, Geoffrey E. Dahl^c and Grant M. Tomita<sup>d

a</sup>  Department of Animal and Avian Sciences, University of Maryland, College Park, MD-20742, USA
^b  Immunology and Disease Resistance Laboratory, USDA-ARS, Beltsville, MD-20705, USA
^c  Department of Animal Sciences, University of Illinois, Urbana, IL-61801, USA
^d  Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, PQ, J2S 7C6, Canada

(Received 23 October 2002; accepted 25 February 2003)

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- (TNF- ), 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 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- , IL-6 and IL-8 in leukocytes and concentration of TNF- 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- mRNA. Preincubation of LPS with rbosCD14, or rbosCD14 plus MAB did not affect LPS-induced increase in TNF- in plasma. Collectively, results indicate that rbosCD14 inhibit LPS-induced increase in CD18 expression and TNF- mRNA. However, secretion of TNF- was not inhibited by pre-incubation of LPS with rbosCD14. The TNF- 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.

Key words: CD14 / LPS / TNF- / bovine / PMN

Correspondence and reprints: Max J. Paape Tel.: (1) 301 504 8302; fax: (1) 301 504 9498;
    e-mail: mpaape@anri.barc.usda.gov

© INRA, EDP Sciences 2003