Continuous infusion of rGM-CSF alone, or in combination with rIL-4, increased spleen cellularity and the percentage of CD11c⁺ DCs.

C57BL/6 mice were treated for 7 days with rGM-CSF (GM, 10 μg/d) or the combination of rGM-CSF and rIL-4 (GM/IL-4, 10 μg each per day) by subcutaneous osmotic pump. (A) Total number of viable splenic leukocytes was determined by hemocytometer count on day 7. Treatment with GM alone produced an average 4.4-fold increase in cell number, whereas combination rGM/rIL-4 produced an average 2.0-fold increase in cellularity. Values represent mean ± SE of 3 experiments. (B) Single-cell spleen suspensions were stained with anti-CD11c-FITC mAbs, and the effects of cytokine treatment on the percentage of CD11c⁺ DC were determined by FACS analysis. Three percent to 7% of control cells expressed CD11c, whereas 6% to 22% of cells from GM-treated mice expressed CD11c and 8% to 25% of cells from rGM/rIL-4–treated mice expressed CD11c. Values represent mean ± SE of 3 experiments. *P ≤ .05 compared with control; †P ≤ .05 compared with GM; ‡P ≤ .1 compared with control.