Granulopoiesis is tightly regulated to meet host demands during both 
"steady-state" and "emergency" situations, such as infections. The transcription 
factor CCAAT/enhancer binding protein β (C/EBPβ) plays critical roles in 
emergency granulopoiesis, but the precise developmental stages in which C/EBPβ 
is required are unknown. In this study, a novel flow cytometric method was 
developed that successfully dissected mouse bone marrow cells undergoing 
granulopoiesis into five distinct subpopulations (#1-5) according to their 
levels of c-Kit and Ly-6G expression. After the induction of candidemia, rapid 
mobilization of mature granulocytes and an increase in early granulocyte 
precursors accompanied by cell cycle acceleration was followed by a gradual 
increase in granulocytes originating from the immature populations. Upon 
infection, C/EBPβ was upregulated at the protein level in all the granulopoietic 
subpopulations. The rapid increase in immature subpopulations #1 and #2 observed 
in C/EBPβ knockout mice at 1 d postinfection was attenuated. Candidemia-induced 
cell cycle acceleration and proliferation of hematopoietic stem/progenitors were 
also impaired. Taken together, these data suggest that C/EBPβ is involved in the 
efficient amplification of early granulocyte precursors during 
candidemia-induced emergency granulopoiesis.