Expression of β-Defensin Genes in Bovine Alveolar Macrophages

Bovine alveolar macrophages (BAM) were examined for the expression of beta-defensins and to determine whether their expression could be upregulated by bacterial lipopolysaccharide (LPS), as observed with beta-defensins expressed in bovine tracheal epithelial cells. Four beta-defensins were expressed constitutively in BAM, with bovine neutrophil beta-defensin (BNBD)-4 and BNBD-5 being the most predominant. This is the first evidence of beta-defensin gene expression in a mature myeloid cell. LPS had no effect on beta-defensin expression in BAM, even though tumor necrosis factor alpha (TNF-alpha) production was induced. Nonbacterial inflammatory particles had little effect on beta-defensin gene expression or TNF-alpha production in BAM. We hypothesize that constitutively expressed beta-defensins of alveolar macrophages may have a role in lung host defense.