Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract only
Publication Acceptance Date: 4/16/2007
Publication Date: 7/8/2007
Citation: Ibeagha-Awemu, E.M., Lee, J.W., Ibeagha, A.E., Bannerman, D.D., Paape, M.J., Zhao, X. 2007. Escherichia coli lipopolysaccharide upregulates the expression of both toll like receptor 4 and 2 (TLR4 and TLR2) in cultured bovine mammary epithelial cells. [abstract]. Journal of Dairy Science 90(Supl. 1):471 Interpretive Summary:
Technical Abstract: Bovine mammary epithelial cells contribute to the innate immune response to intramammary infection. Their ability to mount such a response is dependent upon mammary epithelial recognition of the invading pathogen by specialized receptors. Toll-like receptor 4 (TLR4) is one such receptor that recognizes and is specifically activated by lipopolysaccharide (LPS), a component of the outer envelope of gram-negative bacteria. Recently, it was shown that Staphylococcus aureus, a gram-positive bacteria, initiated the upregulation of both TLR2 and TLR4 in the bovine mammary gland. Because the mammary gland is known to elicit a robust innate immune response to Escherichia coli, we hypothesized that LPS could similarly induce upregulation of TLR4. To evaluate this, MAC-T cells (a bovine mammary epithelial cell line) were incubated in the presence or absence of 1 ug/ml LPS for 24 hrs. Expression of TLR2 and TLR4 were analyzed at both the mRNA and protein levels by quantitative real time PCR and flow cytometry, respectively. The mRNA for both receptors in treated cells was upregulated by 2.0 (TLR4) or 2.2 (TLR2) fold (P<0.01) in comparison to untreated cells. Similarly, specific antibodies against TLR2 and TLR4 detected the increased surface expression of the toll proteins. The mean channel fluorescence in treated cells as compared to untreated cells was 1224 vs. 554 for TLR4 and 3394 vs. 1671 for TLR2, respectively. These results demonstrate that LPS upregulates both TLR4 and TLR2, similar to that reported with ligands from S. aureus. This suggests that the bovine mammary epithelium possesses the necessary immune repertoires required to mount a robust defense against E. coli. This may also indicate a positive adaptation by the mammary epithelial cells to effectively deal with different types of mastitis pathogens.