Exogenous IL-15 enhances CD8 T-cell expansion. (A) Groups of TCRβ^−/− mice that receive Thy1.1 naive T cells were implanted with a miniosmotic pump containing 5 μg rmIL-15. Mice were killed 3 weeks after pump implantation. Tissue cells were stained for Thy1.1 and CD4. Total T-cell recovery was determined by FACS analysis. Shown are the mean ± SD of 3 to approximately 4 individually tested mice. (B) Groups of Rag1^−/− mice received 3 × 10⁶ γδ T cells at day 0, 10⁶ naive T cells at day 14 together with a miniosmotic pump containing 5 μg rmIL-15. Mice were killed 14 days after the pump treatment. Total cell recovery of donor CD4 and CD8 T cells was determined by FACS analysis. (C) Total γδ T-cell recovery was also determined by FACS analysis. Each symbol represents individual mice. *P < .05.