Expression of H60 on host nonhematopoietic cells diminishes T_MH60-mediated GVL. B6.H60 or B6.H60 → actH60 chimeras were irradiated and reconstituted with T cell–depleted C3H.SW BM, B6.H60 mBC-CML with no T cells or with 5 × 10⁴ or 5 × 10⁵ CD8⁺ T_M from DEC-H60–vaccinated C3H.SW donors. Cohorts of mice were killed on day +14 for analysis of EGFP⁺NGFR⁺ mBC-CML cells and Tet^H60+ CD8 cells. (A) Survival. All deaths were from leukemia. P < .0001 comparing B6.H60 and B6.H60 → actH60 T_MH60 recipients (both T_MH60 doses). The survival difference was reflected in the number of EGFP⁺NGFR⁺ cells at day +14. P = .1, P = .05, and P < .0001 comparing the numbers of mBC-CML cells in B6.H60 and B6.H60 → actH60 T_MH60 recipients in BM, spleen, and peripheral blood, respectively. Peripheral blood data include counts from mice not killed. Fewer Tet^H60+ CD8 cells were generated in B6.H60 → actH60 chimeras. (C) Representative flow cytometry. (D) Quantitation at days +7 and +14 in BM and spleen. P = .05 comparing B6.H60 recipients of 5 × 10⁴ T_MH60 with B6.H60 → actH60 recipients of either 5 × 10⁴ or 5 × 10⁵ T_M H60 in spleen and BM at day +14. P = .05 comparing B6.H60 and B6.H60 → actH60 recipients of 5 × 10⁴ T_MH60 in spleen and BM at day +7. (E) Quantitation of Tet^H60+ cells in peripheral blood. P ≤ .02 comparing B6.H60 recipients of 5 × 10⁴ T_MH60 with B6.H60 → actH60 recipients of either 5 × 10⁴ or 5 × 10⁵ T_MH60. Data are representative of 2 experiments with similar results.