TNF is required for maximum graft-versus leukemia activity of donor T cells.

Lethally irradiated C3HxB6 mice were given transplants as described in “Materials and methods” with B6 TCD BM with or without the addition of 2 × 10⁶ splenic T cells from B6 wt or TNF^−/− mice. Some animals also received 2 × 10⁴ 32Dp210 murine leukemia cells on day 0. Survival was monitored daily and cause of death is determined by necropsy as described in “Materials and methods.” Groups consisted of 4 (BM-only group) and 8 to 12 (all other groups) animals per group. Survival is plotted as a Kaplan-Meier curve. Recipients of wt T cells survive longer, and die mostly of GVHD, while recipients of bone marrow (BM) only and of BM + TNF^−/− T cells succumb rapidly to tumor, indicating an important role for donor T cell–derived TNF in GVL activity.