Effects of growth factor administration on WBC numbers. Mice were injected SC with 1 μg MSA or MSA plus growth factor (each at 10 μg) daily for up to 10 days. Four mice per group were killed after 2, 4, 6, and 10 days growth factor treatment, as well as 7 days postcessation of treatment. The following symbols were used to represent each growth factor–treated group of mice: FL (•); G-CSF (▪); GM-CSF (▾); FL plus G-CSF (□); and FL plus GM-CSF (▿). The average WBC count in MSA control mice was 4.4 ± 1.7 × 10⁶/mL blood. This experiment was performed twice giving very similar results (only differing in the route of injection [IP] and dosage of G-CSF and GM-CSF [5 μg/mouse/d]). Data are expressed as mean ± standard error of mean (SEM). WBC counts that differed significantly (P < .005) from MSA controls are marked (*).