Accelerated clearance of non–host-reactive donor (Ly5.2⁺Thy1.1⁺) T cells when coinjected with host-reactive (Ly5.1⁺Thy1.2⁺) T cells. (A) Numbers of CD4⁺ and CD8⁺non–host-reactive T cells found in the spleen of B6AF1 recipients on day 12. Host-reactive and non–host-reactive cells were prepared as described for Fig 3A. Non–host-reactive T cells (20 × 10⁶) were injected alone or with either 40 × 10⁶ host-reactive T cells or 40 × 10⁶syngeneic (B6.SAF1) T cells. N = 3; *P < .05 when compared with results 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. (B) Non–host-reactive grafted CD4⁺ T cells overexpress Fas when coinjected with host-reactive T cells (right panel), but not when injected alone (left panel). Fas expression was assessed on day 8 as described in Fig 5. Results from one representative experiment of three are shown. (C) Downregulation of Thy1 expression was observed on CD4⁺ and CD8⁺ non–host-reactive grafted T cells when coinjected with host-reactive T cells (right panel), but not when injected alone (left panel). Two- and three-color staining was performed with the following fluorochrome-conjugated antibodies: anti-Ly5.2 or anti-Thy1.1, anti-Fas, and anti-CD4 or anti-CD8. Results from one representative experiment of three are shown.