Reversible expression and function of the TreIL-7R transgene in F5 TreIL-7R mice. Groups of 6-week-old F5 TreIL-7R mice (n = 4) were taken off or maintained on dox food for 4 weeks, after which the phenotype of thymus and spleen was analyzed by FACS. Dot plots show CD4 versus CD8 expression in thymus (A) and TCR versus CD8 expression in spleen (B) of control F5, dox-fed, and dox-free F5 TreIL-7R mice. (C) Histograms show IL-7R expression by CD8⁺TCR^hi splenocytes from F5 controls (broken line), dox-fed F5 TreIL-7R mice (solid line), and dox-free F5 TreIL-7R mice (gray fill). Data are representative of at least 2 independent experiments.