Characterization of IL-2- and IL-15-dependent mouse bone marrow-derived cultures enriched in NK1.1⁺ cells. Freshly harvested bone marrow from C57Bl/6 mice was immediately analyzed by fluorescence activated cell sorting (FACS) (A) or after cytokine treatment (B-E). Cultured cells were first treated with IL-15 for 3 days (culture initiation). Cells were then washed and cultured further in the presence of IL-15 for an additional 7 days (B) or 11 days (C), or else IL-2 for a period of 7 days (D) or 11 days (E), as indicated at the top of each panel. Cells from each culture were analyzed for side scatter (SSC-H) and forward scatter (FSC-H) and by 2-color FACS using mAbs to the surface markers NK1.1, Ly49G2, CD3, and CD8. The number in the upper right corner of each quadrant indicates the percentage of cells in that quadrant.