Although IAV-PR8 infection failed to increase blood neutrophil numbers or CXCL12 expression by endothelial cells (Figure 7, B–D), the involvement of the CXCL12/CXCR4 axis in regulating neutrophil, especially LDN, accumulation in the lungs and bone marrow deserves further investigation. The gene discussed is CXCL12; the disease is infection.