Expression of IL-7Rα on Treg cells. (A) Surface IL-7Rα versus intracellular Foxp3 were evaluated in cells from thymus, spleen, and lymph nodes of normal C57BL/6 mice. IL-7Rα was variably expressed on Foxp3-positive cells. (B) Effect of overnight culture on expression of IL-7Rα. The level of IL-7Rα increased on some cells from thymus spleen and lymph node of normal C57BL/6 mice. On Treg cells (CD4⁺CD25⁺) from thymus, the IL-7Rα level increased, but it did not rise on Treg cells from spleen or lymph node. Culture with IL-7 down-regulated IL-7Rα expression on Treg cells as well as other T cells. (C) Foxp3 down-regulates IL-7Rα expression. The IL-7–dependent T-cell line D1 was infected with the retrovirus MigR1 expressing Foxp3, or with an empty MigR1 vector. After 24 hours, cells were analyzed for expression of IL-7Rα. The result is representative of 3 separate experiments. (D) Subsets of thymocytes were analyzed for expression of Foxp3 versus IL-7R. Cells were sorted according to expression of CD4, CD8, and CD25, then assayed by real-time PCR.