Development and incidence of GVHD. (A) Relationship between donor lymphocyte dose, timing after transplantation, and development of GVHD. Sibling donor DLIs are represented as circles and unrelated donor DLIs as squares. Open symbols represent cases without GVHD. Filled symbols represent those with GVHD: gray with grade I GVHD, black with grades II-IV. Four doses of DLI were given beyond the maximum time point illustrated. (B) Incidence of GVHD according to DLI dose and donor type. □ indicates sibling DLI; ▪, unrelated donor DLI.