Flow Cytometric Techniques for Studying Plasmacytoid Dendritic Cells in Mixed Populations

Plasmacytoid dendritic cells (PDCs) are the natural interferon (IFN-α)-producing cells in human peripheral blood that produce vast quantities of IFN-α in response to viral infection and other stimuli. PDCs are a rare cell type, making up less than 0.5% of peripheral blood mononuclear cells. To date, these cells have not been successfully cultured in vitro and are very sensitive to selection via magnetic bead labeling, making them very difficult to study as a purified population. Therefore, our laboratory has developed techniques to study PDCs in mixed populations. Using flow cytometry to label specific cell-surface markers, PDCs can be easily identified from other peripheral blood mononuclear cells or in mononuclear cell suspensions of lymphoid tissue. PDCs can also be permeabilized and stained for intracellular proteins or cytokines. Using surface and intracellular flow cytometry, phenotypic and functional aspects can be combined to accurately study PDCs in a mixed population of cells.