Bcl-2 overexpression results in reduced cardiomyocyte apoptosis and immune cell infiltration in cardiac allografts during acute rejection. At 8 days after transplantation, the cardiac allografts were harvested, and histologic sections and lysates from the cardiac allografts were prepared as described in “Materials and methods.” (A) The number of apoptotic cells in cardiac allografts was counted by ISOL TUNEL staining, (B) the activity of caspase-3, and (C) the level of Fas ligand in heart lysates were measured by ELISA. Histologic sections were also stained with anti-CD3, -CD4, -CD8a, -CD11c, -Mac-1, and -B220 antibodies, as described in “Materials and methods.” The number of positive cells in each cardiac allograft was manually counted by 2 investigators who were blinded to the experimental conditions. Cells were counted in 6 animals (4 fields each) at 200 × magnification. (D) The percentage of positively stained cells—that is, the number of labeled cells divided by total number of cells—was recorded. Filled columns show the data from WT heart grafts (n = 6), and open columns show data from the Bcl-2 Tg heart grafts (n = 6). Mean ± SD values are shown. NS indicates not significant.