FLT3/ITD blocks B-lineage differentiation at the early pro-B stage. Flow cytometry analysis of the fraction of CLPs (A) and early B-cell differentiation (B) in whole BM from 2-month-old FLT3/ITD mice and wild-type littermate controls. (A) Far left panels: Cells are whole BM cells. (B) Cells are CD93⁺ cells in whole BM. Numbers shown on plots are percentages in whole BM. (C) The graph summarizes the differences in the fraction of CLPs and B-cell progenitors. Data are mean ± SEM (error bars) (n = 5). (D) Flow cytometry analysis for annexin V staining of B-cell compartments demonstrates increased apoptosis in late pro-B cells from FLT3/ITD mice. Data are representative of 3 independent experiments.