Characterization of the PS Cells, a mammary epithelial cell line for the study of mammary gland immunity

Session : P14 - Immune responses in the mammary glandInternational audienceDecryption of diseases such as mastitis or breast cancer relies on our knowledge of the physiology of mammary epithelial cells. These cells produce milk, but they are also supposed to be sentinels for the detection of infections and the triggering of inflammation within the udder. Despite their pivotal role, none of the existing cell lines is sufficient to provide a steady and unfailing deciphering of the general physiology of mammary cells and their implication in immune responses against diseases. Here, we describe the PS cell line, especially its cellular purity and specificity, and its ability to respond to mastitis pathogens. Contrary to bovine primary cell cultures, the PS cell line is exclusively composed of luminal cytokeratin18-positive mammary epithelial cells. It expresses α and β-caseins, and it is able to secrete cytokines, chemokines (CCL20, CXCL8) and anti-microbial peptides (SAA3, TAP) in response to bacterial agonists in the absence of serum, unlike other mammary epithelial cell lines. This immune capacity is allowed by expression of functional receptors implicated in the recognition of components synthetized by mastitis pathogens, in particular lipopeptides (recognized by toll-like receptors (TLR) 1, 2 and 6). Other Microbe-Associated Molecular Patterns (MAMPs) such as peptidoglycan subunits (NOD 1 or NOD2), flagellin (TLR5), and LPS (TLR4-CD14-MD2 complex) induce weaker responses. This may result from a low expression of TLR5 and CD14, in keeping with some in vivo data but at variance with some data obtained with primary cells. The PS cell line will be useful to specify the part played by mammary epithelial cells in the innate defense against mastitis, and to investigate their interplay with the other cell populations constituting the udder during mastitis