Immunological features of bovine mammary epithelial cells: a meta-analysis

In vitro culturing of mammary epithelial cells (MECs) is an effective method to identify the mechanisms underlying bovine mammary immunity. Primary cultures of mammary epithelium (pbMEC), and BME-UV1 and MAC-T continuous cell lines are currently used for these studies. To date, it is still unclear which of the above cell lines should be considered as the best model to perform experiments on mammary immunity and mastitis pathogenesis. The aim of this retrospective study was to compare the immunological behavior of the different cell lines as reported in literature, and to predict what line is more suitable for mammary immunity experiments. This was done through a meta-analysis of all the articles found in Pubmed and Web of Knowledge databases accessed on February 2013. The initial database search was performed by using the query "bovine mammary epithelial cells", and as a result 429 candidate articles were selected. Out of them, 162 articles were further selected since reporting the use of MEC lines for studies on mammary immunity. The following selection step was done on the basis of cytokines expression, to a final set of 39 publications. The articles were then grouped according to the cell line used, the applied immunological stimulus, the type of immune response and the method used for the analysis. The present work provided for the first time a throughout comparison of the immune response of different bovine MECs, as a result of different studies. The analysis of data confirmed that both pbMEC and continuous cell lines are capable to produce several cytokines and cathelicidins even with large heterogeneity in the stimuli applied and in the assays performed. A more standardized approach for experimental condition and measurement methodologies is required to allow precise comparison of data obtained in different conditions.