Donor CD4⁺CD25⁺ cells affect cGVHD. Combined data from 3 experiments. On day 0, WT recipient mice were lethally irradiated and reconstituted with 8 × 10⁶ BM cells alone (n = 15), BM plus 1.5 × 10⁶ to 2 × 10⁶ (unfractionated) CD4⁺ T cells (CD4) (n = 33), BM plus 1.5 × 10⁶ to 2 × 10⁶ CD25-depleted CD4⁺ T cells (CD4/CD25^-) (n = 41), or BM plus 1.5 × 10⁶ to 2 × 10⁶ (unfractionated) CD4⁺ cells plus 3 × 10⁵ CD4⁺CD25⁺ T cells (CD4 + CD25⁺) (n = 13). (A) Incidence of cGVHD. †P < .01 for CD4 + CD25⁺ versus CD4. (B) ^*P < .05, †P < .01 for CD4/CD25^- or CD4 + CD25⁺ recipients compared with CD4. BM control mice did not get cGVHD and are represented on the graph as scoring “0.” (C) Pathology score for representative mice. Mean score is indicated by a horizontal bar. †P < .01, CD4/CD25^- or CD4 + CD25⁺ as compared with CD4. Pathology samples were taken on day 33 or 45. (D-F) Clinical scores for individual mice; 5 representative mice per group (D) CD4, (E) CD4/CD25^-, and (F) CD4 + CD25⁺. Each line represents an individual mouse, and lines are given at varying patterns for clarity.