Development and function of murine B220(+)CD11c(+)NK1.1(+) cells identify them as a subset of NK cells

Lymphoid organs contain a B220(+)CD11c(+)NK1.1(+) cell population that was recently characterized as a novel dendritic cell (DC) subset that functionally overlaps with natural killer (NK) cells and plasmacytoid DCs (PDCs). Using Siglec-H and NK1.1 markers, we unambiguously dissected B220(+)CD11c(+) cells and found that PDCs are the only professional interferon (IFN)-α–producing cells within this heterogeneous population. In contrast, B220(+)CD11c(+)NK1.1(+) cells are a discrete NK cell subset capable of producing higher levels of IFN-γ than conventional NK cells. Unlike DCs, only a minute fraction of B220(+)CD11c(+)NK1.1(+) cells in the spleen expressed major histocompatibility complex class II ex vivo or after stimulation with CpG. Consistent with being a NK cell subset, B220(+)CD11c(+)NK1.1(+) cells depended primarily on interleukin 15 and common cytokine receptor γ chain signaling for their development. In terms of function, expression of distinctive cell surface receptors, and location in lymphoid organs, NK1.1(+)B220(+)CD11c(+) appear to be the murine equivalent of human CD56(bright) NK cells.