Pretransplantation vaccination of donors with host-type CD8α⁺ DCs attenuates GVHD. Recipient B6 mice were irradiated with 1000 cGy total body irradiation (TBI) and injected with 5 × 10⁶ TCD BM and 4 × 10⁶ CD90⁺ T cells from syngeneic (squares, solid line, n = 11), allogeneic WT control (circles with dotted line, n = 12), allogeneic recipients of host-type CD8⁺ DC–vaccinated (triangles with solid line, n = 10), and CD8⁻ DC–vaccinated (diamonds with dotted line, n = 12) donors. They were evaluated for (A) survival. Error bars represent SE. *P < .05 between diluent control (red line) and host-type CD8α⁺ DC-vaccinated (triangles) groups. (B) Clinical GVHD score. Error bars represent SE. *P < .05 between controls (circles) and host-type CD8α⁺ DC–vaccinated allogeneic animals (triangles). Data are combined from 2 of 4 similar experiments. (C) Small and large intestines and livers were obtained from each group (n = 4/group) for detailed histopathologic analysis on day 7 after BMT as described in “Methods.” Coded slides were scored semiquantitatively to assess GVHD-specific pathologic damage. Total GVHD score: mean ± SE of the sum of scores for gut (small and large bowels) and livers from individual animals in each group. Error bars represent SE. *P < .05 between allorecipients of diluent control and host-type CD8α⁺ DC–vaccinated donors. (D) Recipient B6 mice were irradiated with 1000 cGy TBI and injected with 5 × 10⁶ TCD BM and 3 × 10⁶ CD90⁺ T cells from syngeneic (black solid line, n = 6), allogeneic WT control (circles with dotted line, n = 8), allogeneic recipients CD8⁺ DC-vaccinated (triangles with solid line, n = 8), and host CD8⁻ DC–vaccinated (diamonds with dotted line, n = 8) donors and evaluated for survival. Data from 2 similar experiments are combined. P < .04, CD8⁺ DCs vs control and CD8⁻ DCs.