Progenitors that arise before CLPs are the IL-6 targets. Bone marrow cells from wild-type, B6.Sle1.Yaa, and B6.Sle1.Yaa.IL-6^−/− mice were selected as Lin⁻ (NK1.1, CD3, CD8, CD19, B220, Mac-1, Gr1, TER-119), c-Kit^lo, and Flt3⁺. The selected population was divided according to surface expression of IL-7Rα. IL-7Rα⁺ cells were considered as CLPs. (A) CLPs from the bone marrow of each strain are shown; unstained shows the cells not stained with anti–IL-7Rα. The results are representative 5 separate animals. The percentage of total cells meeting CLP criteria is indicated. The squares show IL-7⁺ CLP cells; the numbers next to them show the percentage of CLPs in total bone marrow. (B,C) Cell numbers and percentages of CLPs in each strain are shown. The data were obtained from 5 mice and are shown as and average (mean ± SD). Cell numbers are shown as number from one femur and one tibia. *P < .001 compared with the wild-type and B6.Sle1.Yaa.IL-6^−/− mice.