Identification of plasmacytoid pre-dendritic cells by one-color flow cytometry for phenotype screening

Plasmacytoid pre-dendritic cells (pDCs) are able to prime and polarize naive T-cells, while also having an important effector function in antiviral immunity through the rapid and robust production of interferon-alpha. The main setback of pDCs investigation is the rarity and ex vivo fragility of these cells. Relative simple, reliable, and accurate methods for phenotypic analysis and functional studies of pDCs without isolation would be a great deal of interest. Fresh whole blood samples were analyzed by two-color and one-color flow cytometric pDC-identification assays. The changes in the surface expression of CD62L and HLA-DQ on pDCs in whole blood samples after 24-h treatment with imiquimod, a toll-like receptor 7 agonist, were analyzed. Our data demonstrate that the identification of pDCs in peripheral blood samples can be achieved by using only one fluorescent channel for blood dendritic cell antigen (BDCA)-4 staining combined with the light scatter parameters, thus leaving the other channels open for further phenotypic and/or functional analysis. Recently, several lines of evidence supported the involvement of pDCs in the development of several human diseases, so our new one-color identification approach may provide a useful tool for investigation of the pathomechanism of the relevant diseases by using common, 2-laser benchtop cytometers.