Functional analysis of recombinant bovine CD14.

Area of Science:

• Immunology
• Veterinary Science
• Molecular Biology

Background:

• Membrane CD14 (mCD14) and soluble CD14 (sCD14) are key mediators of cellular activation by lipopolysaccharide (LPS).
• The function of bovine CD14 in LPS-induced cellular responses remains largely undefined.
• CD18 expression on neutrophils and mRNA levels of TNF-alpha, IL-6, and IL-8 are sensitive markers of leukocyte activation by LPS.

Purpose of the Study:

• To investigate the role of recombinant bovine soluble CD14 (rbosCD14) in modulating LPS-induced activation of bovine leukocytes.
• To determine if rbosCD14 can block LPS binding to membrane CD14 (mCD14) and inhibit downstream signaling.

Main Methods:

• Whole bovine blood was treated with LPS alone or in combination with varying concentrations of rbosCD14.
• Changes in CD18 expression on polymorphonuclear neutrophils (PMN) were measured.
• Steady-state mRNA levels for TNF-alpha, IL-6, and IL-8 in leukocytes were quantified.
• Plasma TNF-alpha concentrations were analyzed.

Main Results:

• rbosCD14 significantly inhibited the LPS-induced increase in CD18 expression on PMN.
• Pre-incubation with rbosCD14 blocked the LPS-induced increase in TNF-alpha mRNA, but not IL-6 or IL-8 mRNA.
• rbosCD14 did not inhibit the LPS-induced increase in plasma TNF-alpha concentration.
• Anti-human CD14 monoclonal antibody also inhibited LPS-induced TNF-alpha mRNA.

Conclusions:

• rbosCD14 effectively inhibits LPS-induced CD18 expression and TNF-alpha mRNA transcription in bovine leukocytes.
• The inhibition of TNF-alpha mRNA suggests a role for rbosCD14 in blocking LPS-mCD14 interaction.
• Secretion of TNF-alpha and subsequent induction of IL-6 and IL-8 may involve CD14-independent mechanisms.