A distinct subset of plasmacytoid dendritic cells induces activation and differentiation of B and T lymphocytes.

Plasmacytoid dendritic cells (pDCs) are known mainly for their secretion of type I IFN upon viral encounter. We describe a CD2CD5CD81 pDC subset, distinguished by prominent dendrites and a mature phenotype, in human blood, bone marrow, and tonsil, which can be generated from CD34 progenitors. These CD2CD5CD81 cells express classical pDC markers, as well as the toll-like receptors that enable conventional pDCs to respond to viral infection.