Cd11c⁺B220⁺Gr-1⁺ Cells in Mouse Lymph Nodes and Spleen Display Characteristics of Plasmacytoid Dendritic Cells

Human plasmacytoid dendritic cells (pDCs) are major producers of IFNα, are activated by CpG motifs, and are believed to enter lymph nodes (LNs) via L-selectin dependent extravasation across high endothelial venules. To identify a similar murine DC type, CD11c⁺ cells in the LNs of L-selectin–deficient and control BALB/c mice were compared, revealing a population of CD11c⁺CD11b⁻ cells that is reduced 85% in the LNs of L-selectin–deficient mice. These cells are Gr-1⁺B220⁺CD19⁻, either CD4⁺ or CD8⁺, and localize within T cell zones of LNs. Freshly isolated CD11c⁺Gr-1⁺ cells express major histocompatibility complex class II at low levels, display a plasmacytoid morphology, and survive poorly in culture. Their survival is increased and they develop a DC-like morphology in interleukin 3 and CpG. Like human pDCs, CD11c⁺Gr-1⁺ cells stimulate T cell proliferation after activation with CpG and produce IFNα after stimulation with influenza virus. These cells also display a strain-specific variation in frequency, being fivefold increased in the LNs of BALB/c relative to C57BL/6 mice. These CD11c⁺CD11b⁻B220⁺Gr-1⁺ cells appear to be the murine equivalent of human pDCs.