IL-7 therapy preferentially expands CD4⁺ T cells with low affinity TCR for self-peptide–MHCII complexes. (A) Schematic representation where diluted and undiluted CFSE peaks from CD45.1⁺CD4⁺_PERI obtained after 6 days of IL-7 therapy were sorted and transferred into distinct Rag^−/− recipients for another 7 days. At the bottom, representative flow cytometric analysis 7 days after the transfer of each CFSE peaks into Rag^−/− recipients. Left histogram represents cells that have initially undergone proliferation induced by IL-7. Right histogram represents cells that have not initially undergone proliferation during IL-7 therapy. Experiment was repeated twice with 2 mice for each experiment. (B) Schematic representation of the experimental design where Rag^−/− mice were first transplanted with 1 × 10⁶ CD45.1⁺CD90.2⁺ T cells. Five weeks post transfer, mice received 1 × 10⁶ CFSE-labeled CD45.2⁺CD90.1⁺ T cells. Mice were then treated with either PBS or IL-7 for 8 days. Mice were then sacrificed and CD45.2⁺CD90.1⁺CD4⁺ T cells were analyzed for evidence of proliferation. Control consisted of empty Rag^−/− mice. (C) Flow cytometric analysis of CFSE dilution of cells described in (B). Data are representative of 6 to 9 mice per group pooled from 3 independent experiments. (D) Representative flow cytometric analysis of CFSE dilution of peripheral CD4⁺ T cells transferred into IL-7^−/− recipients treated with PBS or IL-7. Data are representative of 6 mice per group pooled from 2 independent experiments.