Analysis of B lymphopoiesis in Lyl-1 KO mice. (A) Quantification of B cells in total BM from wt, Lyl-1^+/– and Lyl-1^–/– mice. The proportion of CD19⁺ cells among B220⁺ cells is shown. (B) Quantification of pro–B (B220⁺ CD19^–D43⁺ IgM^–), pre–B (B220⁺ CD19⁺ CD43⁺ IgM^–), and immature B (B220⁺ CD19⁺ CD43^–IgM⁺) cells in BM from wt, Lyl-1^+/–, and Lyl-1^–/– mice. (A-B) Mean ± SEM of 3 independent experiments (*P < .05). (C) Comparison of the quantity of CLPs in the BM of wt and Lyl-1–deficient mice. BM cells were incubated with a cocktail of biotin anti-Lin, PE–anti–IL-7R, FITC–anti–Sca-1, and APC–anti–c-Kit mAb in a first step and were stained with streptavidin-PE–Cy-7 in a second step. Shown are representative flow cytometric profiles determining the frequency of CLP cells obtained (Lin^–, IL7R⁺, sca-1^+/low, c-Kit^+/low).