Donor pretreatment with peg-G-CSF is more effective than standard G-CSF in preventing GVHD. (A) Survival was determined by Kaplan-Meier analysis. Donor B6 mice received either control diluent, standard human G-CSF 2 μg/animal/d for 6 days, 3 μg peg-G-CSF, or 12 μg peg-G-CSF as a single injection on day -6. Lethally irradiated B6D2F1 recipient mice received transplants as in Figure 1 (control syngeneic recipients, n = 6; control allogeneic, n = 6; peg-G-CSF 3 μg, n = 12; peg-G-CSF 12 μg, n = 12; human standard G-CSF 2 μg/d, n = 18). P = .82, 3 μg peg-G-CSF versus 12 μg peg-G-CSF; P = .0001, 2 μg G-CSF (for 6 days) versus 3 μg, and 12 μg peg-G-CSF (single dose).