CUTTING EDGE - CD19(-B CELLS CAN GIVE RISE TO DENDRITIC CELLS IN-VITRO() PRO)

Dendritic cells (DC) have the specific capacity of initiating primary T cell responses and ultimately derive from precursors in bone marrow. DC were originally thought to be only of myeloid origin, and myeloid precursor cells could be induced to differentiate into functional DC i n response to granulocyte-macrophage (GM)-CSF. However, early CD4(low) precursor cells from the thymus can also develop into DC when culture d in IL-1 beta, IL-3, IL-7, TNF-alpha, stem cell factor, and Flt-3L. I n that case, GM-CSF was not required. We now show that CD19(+) pro-B c ells develop into DC with T cell stimulatory properties when cultured under similar conditions. These pro-B cells acquired the DC-related ma rkers CD11c and NLDC145/DEC205, along with CD80/B7-1, CD86/B7-2, and a high density of MHC class II Ags. The marrow-derived DC did not expre ss CD4 or CD8 alpha, which are markers related to thymic DC. These fin dings are consistent with a new pathway through which DC are generated from H lymphoid precursors.