Both αβ and γδ T-cell developments are impaired in the ATM^−/− thymus. (A) Dot plots for TCR-β and TCR-γδ expression gated on CD3-positive cells from ATM^+/+ and ATM^−/− thymi. Data are representative of 3 independent experiments. (B) Absolute numbers of TCR-β (left) and TCR-γδ (right)–positive T cells from ATM^+/+ (n = 4) and ATM^−/− (n = 6) thymi. Data are mean ± SE. ***P < .001. (C) BM progenitors were cultured with OP9-DLL1 cells supplemented with 5 ng/mL of Flt3L and 1 ng/mL of IL-7 for 18 days. Differentiated cells were harvested on indicated days and stained for surface TCR-β and TCR-γδ. Dot plots are gated on CD45-positive cells from ATM^+/+ and ATM^−/− BM progenitors at the indicated time points. Data are representative of 3 independent experiments. (D) Percentages of TCR-β and TCR-γδ-positive cells at the indicated time points. Data are mean ± SE. *P < .05. **P < .01.