Survival (30 days) of lethally irradiated recipients (B10) transplanted with mobilized PB from donor mice (B10.BR). Donors were treated once daily with FL alone (▴), G-CSF alone (◊), FL + G-CSF (□), or carrier only (•). PBMC were obtained from donors after 7 days (A and B) or 10 days (C and D) of growth factor administration and pooled for each group. Recipients were injected with 1 × 10⁶ or 2.5 × 10⁶ PBMC 3 to 5 hours after irradiation (4 to 7 mice per group). There was a significantly greater survival of mice reconstituted with PBMC from FL- and FL + G-CSF–treated donors when compared with unmobilized or G-CSF–mobilized PBMC. Differences between groups that reached statistical significance are marked (a: FL + G-CSF v control,P <0.05; b: FL + G-CSF v G-CSF, P < .05; c: FL v control, P < .05; d: FL + G-CSF vcontrol P < .005; e: FL + G-CSF v G-CSF, P<0.05; f: FL v control, P < .005; g: FL vG-CSF, P < .05).