Sensing of coliforms by the bovine mammary gland and epithelial cells
Résumé
Despite continuous efforts to reduce its incidence, mastitis remains a major disease in dairy cows. Main mastitis pathogens include Gram-positive as well as Gram-negative bacteria such as Escherichia coli, Klebsiella pneumonia and Serratia marcescens. Mammary Epithelial Cells (MEC) are likely key players in the initial response of the udder to intra-mammary bacterial infections. In this study we describe how these cells can sense the presence of mastitis pathogens. Our data show that MECs are equiped with Pattern-Recognition Receptors (PRR) that allow them to respond to LPS as well as to lipoproteins and peptidoglycan degradation products but, surprisingly, not to flagellin. These data are in agreement with in vivo data showing that infusion in the udder of these molecules, with the notable exception of flagellin, triggers an inflammatory response. In order to investigate how expression of PRR and reponse to purified bacterial agonists translate in terms of response to live bacteria, we compared the innate immune response of bovine mammary epithelial cells to infection by different strains of Enterobacteriacae. The response was analyzed in terms of IL-8 production. Altogether, our results will allow a better understanding of the initial steps of the interaction between mammary epithelial cells and Gram-negative mastitis pathogens.