FoxO3a-deficient mice develop neutrophilia following 5-FU injection. (A) A drastic increase in WBC count was detected FoxO3a-deficient mice 18 days after 5-FU treatment. ■ indicates WBC counts in FoxO3a-deficient mice (n = 10); and ○, WBC counts in wild-type mice (n = 10). Data are mean counts (×1000/μL) plus or minus SD of WBCs in FoxO3a-deficient or wild-type mice. *P < .01. (B) (Top panels) Peripheral blood images stained with May-Gruenwald Giemsa obtained from 8- to 12-week-old FoxO3a-deficient or wild-type mice 18 days after 5-FU treatment (inset, high magnification). (Bottom panel) Data are mean frequency (%) plus or minus SD of neutrophils determined by May-Gruenwald Giemsa staining in peripheral WBCs from FoxO3a-deficient (■; n = 5) or wild-type (□; n = 5) mice 18 days after 5-FU (250 mg/kg) treatment. *P < .01. Bar represents 100 μm. (C) Peripheral blood mononuclear cells were isolated from 8- to 12-week-old FoxO3a-deficient (■; n = 4) or wild-type (□; n = 3) mice 17 days after 5-FU treatment, and the expression of Ly6G, Gr1, CD3, B220, and Mac1 was analyzed by FACS. Data are mean frequency (%) plus or minus SD of indicated population in peripheral blood mononuclear cells. (D) Peripheral WBC counts in 8- to 12-week-old FoxO3a-deficient or wild-type mice administered subcutaneously with indicated G-CSF concentrations. ■ indicates WBC counts in FoxO3a-deficient mice (n = 3); and □, WBC counts in wild-type mice (n = 3). Data are mean counts (×1000/μL) plus or minus SD of WBCs.