Granulocyte colony-stimulating factor (G-CSF) is needed to regulate the production of neutrophils to meet the need for an increased number of neutrophils during infection, but G-CSF is not absolutely necessary for granulopoiesis; in G-CSF knockout mice, approximately 25% of the normal number of residual granulocytes is generated, and mature neutrophils are produced (65). Here, CSF3 is linked to infection.