Roles of IL-15 and DCs in CD8 T-cell proliferation. (A) Expression of membrane bound IL-15 on the splenic CD11c⁺ DCs of Rag1^−/− mice, TCRβ^−/− mice, and TCRβ^−/− mice treated with anti-Thy1.2 Ab every 4 days for 2 weeks before sacrifice was examined as described in“Methods.” Cells were washed with acid PBS to strip off membrane bound IL-15. IL-15 staining was repeated to validate the staining. The results are representative from 3 independent experiments. (B) BMDCs (wild-type or IL-15^−/−) were generated as described in “BMDCs” and adoptively transferred (5 × 10⁶ DCs) together with 10⁶ Thy1.1 naive T cells into TCRβ^−/− recipients. Dot plots are representative of 6 to 7 individually tested mice from 2 independent experiments. (C) Total CD4 and CD8 T-cell recovery was calculated from the indicated tissues 7 days after transfer. Each symbol represents individual recipient. (D) Intracellular bcl-2 expression of CD8 T cells was determined at 14 days after transfer of naive T cells and BMDCs derived from wild-type or IL-15^−/− mice into TCRβ^−/− recipients. *P < .05; **P < .01. Shown are the mean ± SD of individually tested mice (n = 3 to ∼ 4).