The assembly of peptide/MHC complexes within the cDC population is impaired during GVHD. (A) C3H/Hej grafts were transferred into B6 recipients as described in “Methods.” On day 10 after transplantation, DCs were sort-purified and pulsed with whole hen-egg lysosyme protein, and IA^k-HEL levels were measured. Data are representative of 3 replicate experiments. Black solid line indicates non-GVHD; gray solid line, GVHD; and dotted lines, respective isotype controls. (B) Day 10 post-BMT DCs (B6 → BALB/c model) were assessed for expression of the YAe complex. Data are representative of 2 replicate experiments. Black solid line indicates non-GVHD; gray solid line, GVHD; and dotted lines, respective isotype controls. (C) BALB/c mice were transplanted and treated with Flt3L after transplantation. Data are combined from 2 replicate experiments, with n = 4 to 8/group shown. ##P = .01 to .001. (D) DC subset profiles of Flt3L-treated animals on day 10. (E) B6 DCs were generated in vitro as described in “Methods” and had the phenotype shown. (F) These cells were subsequently injected (day 6), followed by TEa T cells (day 7), as described. n = 9, 5, or 4/group. Data are representative of 2 replicate experiments in which either 10 or 20 × 10⁶ BM DCs were transferred. *P = .05 to .01. **P = .01 to .001.