CXCL12α protein and functional CXCR4 expression on HPCs following G-CSF treatment. Wild-type or NE × CG-deficient mice were treated with saline or G-CSF (n = 3-4, each). (A) The amount of CXCL12α protein in the bone marrow extracellular fluid was measured by ELISA. (B) The chemotaxis of CFU-Cs to CXCL12α was measured; the percentage of CFU-Cs migrating in response to CXCL12α is shown. Data represent the mean ± SD.