Characterization of TLR9 responsiveness in cell subsets derived from in vitro pDC differentiation of hematopoietic stem and progenitor cells

Plasmacytoid dendritic cells are multifunctional immune cells that play roles in both the innate and adaptive immune systems. Their hallmark function is the production of large amounts of type I interferons in response to viral infections. Moreover, they are also capable of producing various other cytokines, presenting antigens, and displaying cytotoxic activity. The potential of plasmacytoid dendritic cells as an immunotherapy for cancer and infectious diseases is being explored, but their broad application is limited by their low frequency in the blood and reduced viability during ex vivo culture. We previously developed an efficient in vitro differentiation protocol to generate plasmacytoid dendritic cells from CD34 hematopoietic stem and progenitor cells, providing a scalable and reliable source of plasmacytoid dendritic cells. Here, based on the surface markers CD123 and CD303, we characterize distinct cell subsets derived from in vitro plasmacytoid dendritic cell differentiation, identifying a unique population with high CD123 expression. Cells within this population are the primary producers of interferon-alpha in response to TLR9 stimulation and exhibit a transcriptomic profile closely resembling that of circulating blood plasmacytoid dendritic cells.