During infection and inflammation, an array of cytokines, including Interleukin (IL)-1β (17, 18), IL-3 (19, 20), IL-6 (21–23), Tumor necrosis factor-α (TNF-α) (24–27) and Interferon (IFN) (28, 29) together with hematopoietic growth factors (HGFs) such as M-CSF, G-CSF and GM-CSF (17, 30), orchestrates the switch from steady-state to emergency hematopoiesis (31–33). Here, IL3 is linked to infection.