TreIL-7R expression restores thymic development in F5 Il7r^–/– mice. Single-cell suspensions were prepared from thymus and spleen of 6-week-old F5 control, F5 Il7r^–/–, and dox-fed F5 TreIL-7R mice. (A) Dot plots show CD4 versus CD8 expression in the thymus for representative mice of the indicated strain. (B) The bar chart shows total thymocyte (□) and CD8 SP thymocyte (▦) cell numbers of mice from panel A. (C) Dot plots show TCR versus CD8 expression by splenocytes from the corresponding mice in panel A. (D) The bar chart shows total spleen (□) and CD8⁺TCR^hi (▦) cell numbers. (E) The histograms show IL-7R expression by CD4⁺CD8⁺ SP (broken line) and CD4^–CD8⁺ DP (solid line) thymocytes from F5 TreIL-7R mice and CD4⁺CD8⁺ DP thymocytes from control F5 mice (gray fill) as negative control, because DP thymocytes are known not to express IL-7R. Data are representative of 3 or more independent experiments.