Figure 2.

Granulocyte colony-stimulating factor (G-CSF) and ELR (Glu-Leu-Arg motif) + CXC chemokines act in a co-ordinated manner to mobilize and recruit neutrophils to the site of inflammation. G-CSF (blue arrows) and the ELR + CXC chemokines macrophage inflammatory protein (MIP)-2 and KC (green arrows) act to mobilize neutrophils from the bone marrow into the circulation; however, only MIP-2 and KC recruit neutrophils from the blood to the site of inflammation. KC and MIP-2 act via chemokine CXC receptor 2 (CXCR2) on neutrophils, whereas G-CSF down-regulates the expression of CXCR4 on neutrophils, thus reducing retention via the CXCR4/stromal cell-derived factor (SDF-1α) axis and mobilizing neutrophils into the circulation.