FasL pathway is important for GVHD activity by donor CD4⁺ and CD8⁺ T cells but is not required for GVL activity by donor CD8⁺ T cells.

(A) All C3FeB6F1/J recipients underwent transplantation, as illustrated in Figure 1, with 10⁶ purified donor CD4⁺splenic T cells (see “Materials and methods”) and a leukemia dose of 5000 cells/mouse. Survival is depicted as a Kaplan-Meier curve. We determined by necropsy that all recipients of B6 CD4⁺ T cells (■) and of B6.pfp^−/− CD4⁺ T cells (▪) died of GVHD, whereas only one recipient of B6.gldCD4⁺ T cells (●) developed lethal GVHD. All other deaths in recipients of B6 BM only (○) or B6.gld CD4⁺T cells were from leukemia. (B) All C3FeB6F1/J recipients underwent transplantation, as illustrated in Figure 1, with 4 × 10⁶ purified donor CD8⁺ splenic T cells (see “Materials and methods”) and a leukemia dose of 5000 cells/mouse. Survival is depicted as a Kaplan-Meier curve. We determined by necropsy that 5 of 6 deaths in recipients of B6 CD8⁺ T cells (■) were from GVHD. One of the 8 recipients of B6.pfp^−/− CD8⁺ T cells (▪) and one recipient of B6.gld CD8⁺ T cells (●) died of GVHD, whereas all other deaths could be attributed to leukemia. All deaths among recipients of B6 BM only (○) were from leukemia. (C) Weight loss (as a measurement of GVHD morbidity) was determined weekly in all recipients of B6 CD8⁺ T cells (■) and B6.gld CD8⁺ T cells (●) from the BMT experiment described in panel B. Recipients of B6.gldCD8⁺ T cells had significantly less weight loss than recipients of B6 CD8⁺ T cells (P < .007). All experimental groups consisted of 8 animals, and representative results of 3 experiments with CD4⁺ T cells and 5 experiments with CD8⁺ T cells are shown.