Inverse relationship between CD4⁺FOXP3⁺ and CD4⁺CD25⁺ T cells and acute GVHD. We compared CD4⁺, CD4⁺FOXP3⁺, and CD4⁺CD25⁺ T cells in donors of patients with no or grade 1 GVHD (n = 12) (○) and donors of patients with GVHD (n = 18) (•). We also examined CD4⁺, CD4⁺FOXP3⁺, and CD4⁺CD25⁺ T cells at days 30 to 45 after SCT in patients with grade 0 to 1 GVHD (n = 6) (□) and patients with grade 2 to 4 GVHD (n = 13) (▪). (A) The absolute CD4⁺ T-cell count was not significantly different in donors and patients with or without GVHD. (B) Donors of patients who did not develop GVHD had increased numbers of CD4⁺FOXP3⁺ T cells. Similarly, in patients with GVHD, after SCT, the absolute CD4⁺FOXP3⁺ T-cell count was significantly lower, whereas the absolute CD4⁺CD25⁺ T-cell count was significantly higher than those who did not develop GVHD (B-C). In addition, the proportion of CD4⁺CD25⁺ T cells that were FOXP3⁺ was significantly lower in patients with GVHD, indicating expansion of CD4⁺CD25⁺FOXP3^– effector T cells (D). Bars indicate median values. Symbols for patient-donor pairs are color matched.