IMMUNOBIOLOGY Derivation of 2 categories of plasmacytoid dendritic cells in murine bone marrow

competent to make type I interferon were rigorously defined as a Ly-6C and CD11cLo subset of the B220CD19 CD43CD24Lo bone marrow (BM) Frac-tion A. Otherwise similar Ly6C cells expressed the natural killer (NK) mark-ers DX5 and NK1.1. pDCs represented a stable, discrete, and long-lived popula-tion. Stem cells and early lymphoid pro-genitors (ELPs), but not prolympho-cytes, were effective precursors of pDCs, and their differentiation was blocked by ligation of Notch receptors. Furthermore, pDCs were present in the BM of RAG1/, CD127/IL-7Ra/