Pneumococcal pneumonia-derived sepsis-induced emergency granulopoiesis requires CXCL1. WT and Cxcl1^−/− mice were infected intratracheally with S pneumoniae 6303 strain (5 × 10⁴ CFU). (A) Flow cytometric analysis of granulopoiesis. First, bone marrow cells that had lost the potential to give rise to granulocytes were removed from the target population. The remaining cells (R5) were then analyzed for expression of c-Kit and Ly-6G. Populations R2 and R4 represent eosinophilic and megakaryocyte-erythroid progenitors, respectively. FACS dot plot (B), percentage (C), and number (per femur/tibia) (D) of subpopulations #1 to #5 within the granulopoietic compartment at 48 hours postinfection (n = 5-6 mice/infection group; n = 3 mice/control group). All experiments were performed 3 times. Statistical significance was determined by unpaired Student t test (C-D). *P < .05; **P < .01.