Lower dose of IL-7 induces CD4⁺_SPT proliferation. (A) Schematic representation of the experimental design where CD90.2⁺CD45.1⁺CD4⁺_PERI and CD90.1⁺CD45.2⁺CD4⁺_SPT were transferred simultaneously into the same congenic recipients (CD90.2⁺CD45.2⁺). Mice were treated daily with either PBS (vehicle) or different doses of IL-7 for 6 days (1, 2.5, 5, or 10 μg/d). (B) Representative flow cytometric analysis of CFSE dilution in CD90.2⁺CD45.1⁺CD4⁺_PERI and CD90.1⁺CD45.2⁺CD4⁺_SPT cells isolated from LNs of PBS- or IL-7–treated mice. (C) Graphic representation of the percentage of proliferating cells in function of IL-7 concentration for CD90.2⁺CD45.1⁺CD4⁺_PERI and CD90.1⁺CD45.2⁺CD4⁺_SPT at day 7 of IL-7 treatment. (D) Graphic summary of the absolute number of CD90.2⁺CD45.1⁺CD4⁺_PERI (white) and CD90.1⁺CD45.2⁺CD4⁺_SPT (black). The numbers inside the white boxes represent the proportion of CD90.1⁺CD45.2⁺CD4⁺_SPT cells recovered from LN of mice treated with indicated concentration of IL-7. Three mice per group were analyzed in this experiment.