Apoptosis of non–host-reactive T cells when coinjected with host-reactive T cells. Non–host-reactive cells were injected alone or with either host-reactive T cells or syngeneic T cells as described in Fig 7. (A) The proportion of non–host-reactive cells stained by Annexin-V was evaluated in fresh uncultured spleen cell suspensions from day-8 B6AF1 hosts. Three-color staining was performed with the following antibodies: PE-labeled anti-Ly5.2, Cy-chrome–labeled anti-CD4 or anti-CD8, and FITC-labeled Annexin-V. Results from one representative experiment of three are shown. (B) Annexin-V staining was performed after culturing recipient spleen cells during 40 hours in the presence of Con A. Results are expressed as the mean ± SD (N = 3) in the lower panel, and results from one representative experiment are depicted in the upper panel. **P< .01, ***P < .005 when compared with the results obtained in mice transplanted with non–host-reactive T cells alone or non–host-reactive T cells + syngeneic T cells. No differences were found between mice transplanted with non–host-reactive T cells alone versus non–host-reactive T cells + syngeneic T cells.