In the steady-state lymphoid organ, dendritic cells (DCs) are classified into two major subsets, plasmacytoid DC (pDC) and conventional DC (cDC). A standing question was whether a common progenitor for plasmacytoid and conventional dendritic cells exists during the sequential differentiation from hematopoietic stem cells to dendritic cells. We have recently identified such a common clonogenic plasmacytoid and dendritic cell progenitor (CDP) from mouse bone marrow using antibodies for c-kit, Flt3, and M-CSFR. CDPs generated almost exclusively pDC and cDC in vitro and upon transfer in irradiated and steady-state mice in vivo. Single-cell analysis revealed the existence of clonal progenitors giving rise to both pDC and cDC within the CDP population. Thus, these results prove the existence of a common developmental pathway for at least some pDCs and cDCs in lymphoid organs in vivo.
