Compromised allo-CTL and GVHD generation in LIGHT-KO donor T cells. (A) BDF1 mice were injected intravenously with 5 × 10⁷ spleen cells from WT (▪) or LIGHT-KO (□) B6 mice. Ten days later, spleen cells from the recipient mice were harvested and analyzed for CTL activity against P815 (H-2^d) and EL4 (H-2^b) tumor cells by ⁵¹Cr-release assay. (B) T cells (2 × 10⁷ cells) and non–T cells (4 × 10⁷ cells) purified from spleen cells of WT or LIGHT-KO B6 mice were mixed in the following combinations: WT T cells plus WT non–T cells (□), WT T cells plus LIGHT-KO non–T cells (▪), LIGHT-KO T cells plus WT non–T cells (○), LIGHT-KO T cells plus LIGHT-KO non–T cells (•). These combined cells were injected intravenously into BDF1 mice. Ten days later, anti–host CTL activity from recipient spleen cells were analyzed as in panel A. (A-B) Data representative of 3 independent experiments. (C) BDF1 mice (n = 5 in each group) were exposed to lethal-dose irradiation (12 Gy) followed by intravenous injection of 5 × 10⁶ T cell–depleted B6 BM cells alone (○) or together with 2 × 10⁶ B6 WT (▪) or LIGHT-KO (▴) T cells. The survival of recipient mice is shown. *P = .049. (D) BALB/c mice (n = 7 in each group) were exposed to lethal-dose irradiation (10 Gy) followed by intravenous injection of 5 × 10⁶ T cell-depleted B6 BM cells alone (▪) or together with 1 × 10⁶ B6 WT (•) or LIGHT-KO (○) T cells. Survival (left panel) and body weight changes (right panel) were monitored. *P = .0008. (C-D) Results are representative of 2 independently performed experiments.