Adoptive transfer of T cells to WT, KI, or KO host mice. (A) CFSE-labeled T cells from KO mice were injected into irradiated WT, KI, or KO mice (5 × 10⁶ cells each). On days 3 and 5, splenocytes from host mice were stained for CD4⁺/CD8⁺ subsets. Proliferation of transferred CD4⁺/CD8⁺ T cells was visualized by CFSE dilution. Data are representative of 4 mice/group. (B) CFSE-labeled T cells from WT, KI, or KO mice were injected into irradiated WT B6.SJL congenic mice (8 × 10⁶ cells each). On day 6, splenocytes were isolated from host mice and stained for CD45.2, CD4, and CD8. Cells were gated on CD45.2⁺ to exclude endogenous T cells. Proliferation of transferred CD4⁺/CD8⁺ T cells was visualized by CFSE dilution. Data are representative from 5 mice/group.