Absence of γδ T cells in allogeneic BM transplant recipients reduces GVHD severity. B6 γδ^-/- mice (γδ^-/-: ▴, n = 24) or wild-type (wt: •, n = 38) mice received 1100 cGy TBI and underwent transplantation with 5 × 10⁶ BM cells and 2 × 10⁶ T cells from BALB/c or syngeneic B6 donors (syn: ○, n = 21) and evaluated for survival (A) and clinical GVHD score (B) as detailed in “Materials and methods.” Data from 4 similar experiments are combined. Error bars represent standard error. ▴ vs •, ^**P < .01 by Wilcoxon rank test. ▴ vs •, ^*P < .05 by Mann-Whitney U test.