Generation and characterisation of an equine macrophage cell line (e-CAS cells) derived from equine bone marrow cells

Macrophages play a pivotal role in the pathophysiology of many diseases by mediating the host immune response to infections and intoxications. The species-specific activation of macrophages and the differential response in cytokine production impedes the extrapolation of results between species. Therefore, the aim of this study was to isolate and immortalise macrophages from equine bone marrow (BM) cells in order to study equine-specific signalling pathways. The isolated BM-derived macrophages (referred to as e-CAS cells) showed proliferation kinetics similar to that of standardised cell lines and were maintained in culture for >76 passages. To characterise the cells, a number of typical parameters of macrophages were tested. Morphological evaluation (May-Grünwald Giemsa staining) and non-specific esterase activity indicated the e-CAS cells to be macrophages. The presence of CD14 and their ability to phagocytose Escherichia coli bioparticles further confirmed their identity, as did their ability to produce cytokines, reactive oxygen and nitrogen intermediates in response to LPS. These data show that the established cell line (e-CAS) shows the characteristics of equine macrophages and may, therefore, prove to be a unique in vitro model for studying the cellular biology of equine inflammation.