Early B-cell development is blocked in Notch2IC//mb1Cre^+/− mice. (A) Flow cytometric analysis of BM single-cell suspensions. Numbers display the percentages and SD of lymphocyte-gated pro- and large pre-B cells (B220⁺CD43⁺), immature and small pre-B cells (B220⁺CD43⁻), and mature, recirculating B cells (B220^highCD43⁻; top) or of lymphocyte, B220⁺CD43⁺-gated Hardy Fraction A (BP1⁻CD24^low)//early pro-B, Fraction B (BP1⁻CD24⁺)//late pro-B, Fraction C (BP1⁺CD24^low), and Fraction C′ (BP1⁺CD24⁺)//early pre-B²⁰  (bottom). Values were calculated from 10 analyzed mice per genotype. (B) Notch2IC//mb1Cre^+/− mice display an aberrant T-cell population in the BM. BM single-cell suspensions were stained and analyzed with flow cytometry for the expression of indicated surface markers. Histograms show overlays of surface expression of the indicated molecules on lymphocyte-gated, hCD2⁺ BM cells from Notch2IC//mb1Cre^+/− (black line) and lymphocyte-gated BM cells from control (gray line) mice. Mean percentages and SDs were calculated from 10 independent experiments. (C) In the BM of Notch2IC//mb1Cre^+/− mice, absolute T-cell numbers are increased, whereas B-cell numbers are decreased. Absolute numbers of total counted cells, lymphocyte-gated, B220⁺ B cells and Thy1.2⁺ T cells in the BM of Notch2IC//mb1Cre^+/− (○) and control (●) mice. Points represent data from individual mice, and horizontal bars mark the mean value.