Lymphoid origin of a lineage of intrinsically activated plasmacytoid dendritic cell in mice and humans

We identified a novel mouse plasmacytoid dendritic cell (pDC) lineage derived from the common lymphoid progenitors (CLPs) that is dependent on expression of BCL11A. These CLP- derived pDCs, which we refer to as B-pDCs, have a unique gene expression profile that includes hallmark B cell genes, normally not expressed in conventional pDCs. Despite expressing most classical pDC markers such as SIGLEC-H and PDCA1, B-pDCs lack IFN-a secretion, exhibiting a distinct inflammatory profile. Functionally, induce T cell proliferation more robustly than canonical pDCs following Toll-like receptor 9 (TLR9) engagement. B- pDCs also display elevated levels of the cell-surface receptor tyrosine kinase AXL, mirroring human AXL+ transitional DCs in function and transcriptional profile. Murine B-pDCs therefore represent a phenotypically and functionally distinct CLP-derived DC lineage specialized in T cell activation and previously not described in mice. ### Competing Interest Statement The authors have declared no competing interest.