Deregulation of endogenous IL-15 increases Bcl-2 expression in CD8⁺ T lymphocytes after allogeneic BMT. Spleens were harvested from recipients of IL-15 tg B6 or wt B6 allogeneic BM cells 12 or 13 days after transplantation. (A) Flow cytometry histogram showing Bcl-2 protein expression in gated CD8⁺ or CD8^- splenocytes taken from recipients of wt B6 allogeneic (open histogram) or IL-15 tg B6 allogeneic (solid histogram) BM cells. Mean fluorescence intensity (MFI) values for each group (mean ± SE) are indicated. (B) MFI values for Bcl-2 were obtained from gated CD8⁺ lymphocyte populations. Mean Bcl-2 MFI values ± SE for recipients of wt B6 or IL-15 tg B6 allogeneic BM cells are shown. Data are representative of 2 independent experiments involving a total of 13 mice.