Levels of functional Numb correlate with thymus cellularity. (A) Western blot analysis, using an anti-Myc tag antibody, of dnNb and p71 Numb expression in thymus of WT, Numb TG, dnNb TG, and dnNb × Numb TG mice. (B) Western blot analysis, using an anti-Myc tag (left) or anti-Numb (right) antibody, of dnNb and Numb expression in DN thymocytes of WT, dnNb, and Numb TG mice. (C) Absolute numbers of DN and DP cell subsets in thymus of WT (black) and Numb TG (gray) mice; N = 5 (WT), 7 (Numb TG). (D) Absolute numbers of DN and DP cell subsets in thymus of WT (black) and dnNb TG (gray) mice; N = 5 (WT), 6 (dnNb TG). (E) CD25 and CD44 expression in Lin⁻ thymocytes of 4-week-old WT, Numb TG, dnNb TG, and dnNb × Numb TG mice. Quadrants represent DN1, DN2, DN3, and DN4 subpopulations (clockwise from top left to bottom left). (F) Total cell numbers in dnNb TG (gray), dnNb × Numb TG (white), WT (black), and Numb TG (light gray) adult thymi; N = 12 (Numb TG), 7 (dnNb × Numb TG), 12 (WT), 12 (Numb TG). Means ± SD of at least 3 independent experiments are plotted.