CD4 and CD8 T_Ms home to tissues that supply them with their favored homeostatic cytokines. (A) Cytokine receptor expression on the MP CD4 and CD8 T_Ms (gated as CD4⁺CD25⁻CD44^hi and CD8⁺CD44^hi, respectively) in the spleen of 1-year-old B6 mice measured by flow cytometry. Representative histogram plots and mean fluorescence intensity (MFI) measurements are shown (n > 4). (B) Proliferation of CD4 and CD8 T_Ms in response to cytokine stimulation (100 ng/mL) for 3 days in vitro measured by cell counts. T_Ms were purified from 1-year-old B6 mice. Representative data are presented as mean of triplicates ± SEM (n = 4). (C,D) Proliferation of CD4 and CD8 T_Ms in response to cytokine stimulation in vivo measured by BLI. MFG-labeled OT2 (CD4) or OT1 (CD8) T_Es (1 × 10⁶) were adoptively transferred into each albino B6 recipient mouse. Six months later, the recipients harboring the OT2 or OT1 T_Ms received administration (IP) of either IL-7 or IL-15 daily (10 μg) for 5 sequential days. (C) Time-course tracking of the TBL change of the indicated recipient mice receiving either IL-7 or IL-15. Data are presented as mean ± SEM. (D) Representative BLI images of the indicated mice right before the 1st cytokine administration (day 1) and 1 day after the last cytokine administration (day 6; n = 3-4). (E) Tissue expression of IL-7 and IL-15 in 1-year-old B6 mice measured by Taqman Q-PCR. Representative data are presented as mean of triplicates ± SEM (n = 4).