Pre-TCR signaling in p45 Tg TCF-1-deficient mice. (A) Thymocytes from the indicated types of mice were stained with anti-CD44 and CD25 and the lin cocktail. Numbers depict the percentage of cells in the respective quadrants. (B) Bar graphs show the mean of the absolute number (± SD) of DN1, DN2, DN3, and DN4 cells among lin-negative cells. ^*Statistically significant difference (P < .05) as compared with TCF-1 knockout. (C) Thymocytes derived from the indicated types of mice were cultured at 37°C in the absence of growth factors. After collection they were stained with antibodies to the lineage cocktail, CD44, and CD25. For each time point the percentage of viable DN3 and DN4 cells was determined relative to a fixed number of added microspheres. The ratio at the onset of culture was arbitrarily set to 100%. The graphs show mean (± SD) percentage of surviving DN3 and DN4 cells relative to the onset of culture. ○ indicates TCF-1^+/-; ▵, TCF-1^-/-; •, TCF-1^-/- p45 Tg; and ▴, TCF-1^-/- p33 Tg.