DN T cells from DLI-treated mice can suppress antidonor CD8⁺ T cells.

(A,B) A group of (2C × dm2)_F1 mice were given DLI (▪) or left untreated (▾) and then given transplants. At 1 week after transplantation, splenocytes (A) or lymph node cells (B) were collected from recipient mice and the proportion of DN T cells was determined by flow cytometry. Various numbers of lymphocytes (up to 7.0 × 10⁴ total cells) containing the indicated numbers of DN T cells were used as putative suppressor cells and cultured with 1000 naive 1B2⁺CD8⁺ T-cell–responder cells and irradiated splenocytes from (B6 × BALB/c)_F1 mice. Three days later, 1 μCi (0.037 MBq) tritium-thymidine was added to each well. The plate was incubated overnight, and cells were harvested 18 hours later. Shown is the mean proliferation ± SD in counts/minute for 3 replicates in 2 independent experiments. (C) Naive 1B2⁺CD8⁺ T cells were stimulated for 4 days with irradiated (B6 × BALB/c)_F1 cells, labeled overnight with 10 μCi (0.37 MBq) tritium-thymidine, and used as target cells. Various numbers of lymph node cells from DLI-treated (▪) and untreated (▾) mice were used as effector cells. Shown is the mean percentage of specific killing ± SD for 3 replicates in 2 independent experiments. (D) DN T cells were purified from the lymph nodes of DLI-treated mice 3 days after transplantation and used as effector cells. Activated anti-L^d+ (▪) or anti-H-2^s (▾) CD8⁺ T cells were used as targets at the ratios indicated. Shown is the mean percentage of specific killing ± SD for 3 replicates in 2 independent experiments.