Impaired survival of host-reactive donor T cells by anti–HVEM mAb treatment. (A) BDF1 mice were injected intravenously with 5 × 10⁷ B6 spleen cells on day 0 and subsequently were treated with intraperitoneal administrations of 100 μg control hamster IgG (▪) or LBH1 (□) on days 0, 3, and 6. On day 10, spleen cells from the recipient mice were harvested and analyzed for CTL activity against P815 (H-2^d) and EL4 (H-2^b) by ⁵¹Cr-release assay. (B) Under the same conditions described for panel A, recipient spleen cells were stained on day 10 with anti–H-2K^d mAb, together with anti–CD4 or anti–CD8 mAb. Percentage of donor (H-2K^d-negative) CD4⁺ or CD8⁺ T cells as well as total host cells (H-2K^d-positive) are shown. (C) BDF1 mice were injected intravenously with CFSE-labeled B6 spleen cells (5 × 10⁷ cells) followed by intraperitoneal injections of 100 μg control hamster IgG or LBH1 on days 0 and 3. CFSE dilution of donor (H-2K^d-negative) CD4⁺ or CD8⁺ T cells in the spleen was examined on day 4. (D) BDF1 recipient mice were injected intravenously with a mixture of spleen cells from 2C TCR-transgenic mice (1 × 10⁷ cells) and WT B6 spleen cells (3 × 10⁷ cells). On days 0 and 4, 100 μg control hamster IgG or LBH1 was administered intraperitoneally to the recipient mice. On day 7, the presence of 2C T cells in the host spleen was assessed by a staining with 1B2 clonotypic mAb and anti–CD8 mAb. Percentages of 2C T cells in CD8⁺ T cells are indicated. Representative results from 3 independent experiments are shown.