Possible relationship between IKDCs and other lineages in bone marrow. Lymphoid progenitors can be conveniently resolved on the basis of c-Kit, Sca-1, and RAG-1 densities⁶  as depicted here. Our new findings suggest that CD62L/L-selectin⁺ progenitors (LSPs) are the most effective source of IKDCs. In contrast, NK cells are normally produced from c-Kit^Lo RAG-1⁺ prolymphocytes (including IL-7Rα⁺ common lymphoid progenitors [CLPs]). Although IKDCs do not express RAG-1, they could be made under experimental conditions from progenitors that express RAG-1 (not illustrated; see Figure 2A). Among other distinctions from pDCs, IKDC development was insensitive to Notch and dependent on the Id-2 transcriptional repressor (not illustrated).