SAA-induced G-CSF production correlates with neutrophilia in mice. (A) SAA or HSA was injected subcutaneously into C57BL/6 mice (n = 8) at a dose of 120 μg/kg per day in 0.2 mL phosphate-buffered saline at 24-hour intervals. Blood samples were collected before (0 hours) and at 48, 120, and 168 hours after the initial SAA injection. Neutrophil numbers in whole blood were determined and presented as fold changes. (B) The plasma concentration of G-CSF in SAA-injected mice was determined using ELISA at 0 hours and 168 hours after the initial administration as in panel A, and shown as fold changes (maximum, 97 pg/mL). (C) SAA was injected subcutaneously into age- and sex-matched WT and Csf3^−/− mice (n = 5), and peripheral blood neutrophil count was determined at the indicated time points as described in panel A. Statistical analysis was performed to compare neutrophil counts in Csf3^−/− mice with those in WT mice and marked whenever there is a statistically significant difference. *P < .05, **P < .005, ***P < .001, compared with control mice (A,B) or WT mice (C). In all panels, there is a significant difference between treatment and pretreatment samples at each time point (P < .05).