Recipient Langerhans cells are not required for clinical or histologic GVHD in the B6^bm12→B6 model. Tg⁺ and Tg⁻ hosts were irradiated and reconstituted with B6^bm12 BM with or without B6^bm12 splenocytes containing 10⁶ CD4 cells. (A) Percentage weight change in 2 independent experiments. P > .07 comparing Tg⁺ and Tg⁻ CD4 recipients at all time points; P < .05 comparing each CD4 group to its respective BM-alone control from day +13 onward. (B) Pathology scores from the 2 experiments combined; P values are shown in the figure. Serum samples collected from predesignated mice on day +7 after BMT were analyzed for cytokine levels (C; 3 samples per group; *P = .05 comparing BM-alone to CD4 recipients; P = .7 comparing CD4-recipient groups; data from 1 of 2 experiments with similar results).