IL-15 produced by BM-derived or non-BM-derived cells can mediate memory CD8 T-cell proliferation. Combinations of BM chimeras were generated using IL-15^-/- and B6 mice as a source of BM or as hosts. Ten weeks after reconstitution, mice were infected with VSV. Forty days after infection, mice were given BrdU in their drinking water for 4 weeks. Mice were killed and spleen cells were stained with anti-BrdU, N-tetramer, and anti-CD8. Panel A shows the BrdU intensity of N-tetramer-positive, CD8⁺ gated cells (^*P < .05). (B) The total number of N-tetramer-positive cells recovered from spleens 10 weeks after VSV infection. (C) The percentage of CD8 T cells present in the spleen of each type of BM chimera. The values above each bar represent the percentage of control (Wt → Wt). Error bars indicate standard deviation.