Ex vivo generation of mature equine monocyte-derived dendritic cells

Dendritic cells (DCs) are innate immune cells specialized in antigen detection and presentation. They perform an essential role in initiating and guiding the immune response, the direction of which largely depends upon the activation state of the DCs. The objective of this study was to generate mature equine monocyte-derived DCs and, in doing so, to develop a method for measuring the activation state of these cells. Equine DCs were stimulated with UV-inactivated Escherichia coli (E. coli), and the activation status was measured by analyzing cell surface marker expression, cytokine production, and endocytic capacity. Comparisons for each parameter measured were performed between macrophages, non-stimulated DCs and stimulated DCs. Equine monocyte-derived DCs may be distinguished from macrophages based on cell surface expression of MHC class II (p < 0.0001) and CD206 (p < 0.0001), their capacity for endocytosis of FITC-dextran (p < 0.05), and production of TNF-α upon stimulation (p < 0.001). Furthermore, stimulated DCs can be distinguished from non-stimulated DCs based on increased cell surface expression of MHC class II (p < 0.0001) and upregulation of pro-inflammatory cytokine mRNA, particularly IL-12/IL-23p40 (p < 0.05) and IL-23p19 (p < 0.05). The ability to measure DC activation state will facilitate future investigations of equine DC function.