Elevated CXCR4 expression and increased CXCR4-mediated chemotaxis toward SDF1α in BM CD34⁺ cells of patients with CN. (A) We measured CXCR4 surface expression in BM CD34⁺ cells from 4 patients with CN treated with G-CSF and 2 healthy volunteers treated with G-CSF with the use of rat anti–human CXCR4 antibody. Data presented as mean fluorescence intensity (MFI) of CXCR4 staining. Data represent means ± SDs of triplicates (*P < .05). (B) We analyzed chemotactic activity of BM CD34⁺ cells isolated from 4 patients with CN treated with G-CSF and 2 healthy volunteers treated with G-CSF with the use of Transwell migration assays, as described in “Methods.” The cells were additionally treated or not with 100 μg/mL of purified human NE. Results are expressed as the percentage of CD34⁺ cells loaded into the upper chamber that had migrated to the bottom well toward 10 ng/mL of SDF1α. Data represent means ± SDs of triplicates (*P < .05). (C) We assessed CXCR4 surface expression on BM CD34⁺ cells from 4 patients with CN treated with G-CSF which were incubated without or with NE and migrated in the low compartment of a Transwell chamber toward 10 ng/mL of SDF1α. Data presented as mean fluorescence intensity (MFI) of CXCR4 staining. Data represent means ± SDs of triplicates (*P < .05).