Investigation of lipopolysaccharide binding protein in the bovine mammary gland

Abstract

This study investigated the presence of LBP in the bovine mammary gland during varying stages of development and infection. The project was initiated by the discovery of an EST in a mastitic mammary cDNA library which bore homology to lipopolysaccharide binding protein (LBP). The results add to the understanding of the innate immune defences of the gland and the biological regulation of LBP. The expression profile of LBP in bovine mammary tissue was characterised by northern blot analysis which showed that LBP levels were increased in infected and involuted tissues. This is supported by the results from in situ hybridisation which detected local expression of LBP in epithelia surrounding ducts and alveoli in infected tissue. LBP was also shown to be increased in mammary secretions of whey and skim milk from infected and involuted glands by western blotting with an antibody that was raised against a peptide of LBP. These results were quantified by ELISA. The LPS-binding activity of the native protein was confirmed by ligand blotting, immunoprecipitation and ELISA. Attempts were made to investigate the immuno-stimulatory activity of LBP using a recombinant protein in a cytokine induction assay. Due to problems encountered with the expression system the results from this can not be accurately analysed and further optimisation is required. This is the first report of local expression of LBP in the mammary gland and taken together, these results suggest an important role for LBP in the local innate defence of the gland.