Differential roles of CD40 and CD80/86 on donor and host APCs in cGVHD. (A) Incidence of cGVHD in CD40^-/- (CD40) recipients. One representative experiment is shown. On day 0, recipient mice were lethally irradiated and reconstituted with 8 × 10⁶ WT BM cells alone; both recipient types (n = 9); or WT BM plus 10⁷ WT spleen cells as a source of CD4 cells, WT recipients (n = 15), CD40 recipients (n = 14). (B) Clinical disease in CD40 recipients. Average clinical score for mice affected with cGVHD (unaffected mice are excluded). BM control mice did not get cGVHD and are represented on the graph as scoring “0.” (C) Incidence of cGVHD in CD80/86^-/- recipients. Combined data from 2 experiments are shown. On day 0, recipient mice were lethally irradiated and reconstituted with 8 × 10⁶ WT BM cells alone; both recipient types (n = 19); or WT BM plus 10⁷ WT spleen cells as a source of CD4 cells, WT recipients (n = 27), CD80/86^-/- recipients (n = 29). †P < .01 for CD80/86^-/- recipients versus WT recipients of spleen cells. (D) Clinical disease in CD80/86^-/- recipients. Average clinical score for mice affected with cGVHD (unaffected mice are excluded). BM control mice did not get cGVHD and are represented on the graph as scoring “0.” ^*P < .05 for CD80/86^-/- recipients as compared with WT recipients of spleen cells. (E) Incidence of cGVHD in CD80/86^-/- recipients of CD40^-/- BM. Combined data from 2 experiments are shown. On day 0, recipient mice were lethally irradiated and reconstituted with 8 × 10⁶ WT or CD40^-/- BM cells alone; both BM types (n = 22), WT BM plus 2 × 10⁶ purified CD4 cells, WT recipients (n = 15), CD80/86^-/- recipients (n = 32); or CD40^-/- BM plus 2 × 10⁶ purified CD4 cells, CD80/86^-/- recipients (n = 34). †P < .01 for CD80/86^-/- recipients of CD40^-/- BM + CD4 cells versus WT BM + CD4 cells. (F) Clinical disease in CD80/86^-/- recipients of CD40^-/- BM. Average clinical score for mice affected with cGVHD (unaffected mice are excluded). BM control mice did not get cGVHD and are represented on the graph as scoring “0.” (G) Incidence of cGVHD in WT recipients of CD40^-/- BM. One representative experiment of 2 is shown. On day 0, recipient mice were lethally irradiated and reconstituted with 8 × 10⁶ WT or CD40^-/- BM cells alone; both BM types (n = 10), WT BM plus 2 × 10⁶ purified CD4 cells (n = 15), or CD40^-/- BM plus 2 × 10⁶ purified CD4 cells (n = 15). †P < .01 for recipients of CD40^-/- BM + CD4 cells versus WT BM + CD4 cells. (H) Clinical disease in WT recipients of CD40^-/- BM. Average clinical score for mice affected with cGVHD (unaffected mice are excluded). BM control mice did not get cGVHD and are represented on the graph as scoring “0.”