P815 leukemia is resistant to GVL mediated by donor-derived TNF and LTα3. Leukemia relapse by Kaplan-Meier analysis in lethally irradiated (1100 cGy) B6D2F1 recipients transplanted with grafts from B6.WT or B6.Lta^−/− donors, containing 5 × 10⁶ BM cells, and (A) 2 × 10⁶ CD3⁺ T cells with 2.5 × 10⁴ P815 tumor cells, (P = .60, Lta^−/− vs WT; P = .25, Tnf^−/− vs WT, T cell–replete groups), or (B) 0.5 × 10⁶ CD3⁺ T cells with 5.0 × 10⁴ P815 tumor cells. P = .42, Lta^−/− vs WT; P = .98, Tnf^−/− vs WT, T cell–replete groups. For panels (A) and (B), data is combined from a minimum of 2 experiments, n ≥ 18, BM + T arms; n = 10, TCD control arm. (C) Lethally irradiated (1100 cGy) B6D2F1 recipients received B6.Tnf/Lta^−/− or B6.WT grafts (0.5 × 10⁶ T and 5 × 10⁴ tumor cells). Experiment is 1 of 3 replicate experiments, n = 16, Tnf/Lta^−/− group; n = 8, WT BM + T group; n = 5, WT TCD group. P = .65, Tnf/Lta^−/− vs WT, T cell–replete groups. (D) Representative biophotonic imaging at day 7 and 14 after BMT confirming leukemia development irrespective of donor-derived LTα, TNF, or both.