Chemotactic and chemokinetic activities of the BM plasma on CD34⁺ cells. (A) Comparison of chemotactic activity of plasma from BM, CB, and PB on migration of BM CD34⁺ cells from the upper to lower chamber. Each plasma sample was diluted 1:2 and added to lower chamber. SUP is conditioned medium from the mouse stromal cell line, M2-10B4. (B) Chemotactic activity of BM plasma for human CB HPC present in a CD34⁺ population of cells. (C) Chemotactic and chemokinetic activity of BM plasma against PB plasma on CB CD34⁺ cells. PB and BM plasma used were diluted 1:2. (D) Inhibitory effect of the negative gradient of BM plasma on BM CD34⁺ cell migration induced by SDF-1. Diluted PB plasma (1:2) containing SDF-1 (50 ng/mL) was added to the lower chamber to attract human BM CD34⁺ cells from the upper chamber containing the indicated diluted plasma. *Significant changes from controls (medium for part A, PB for part B, PB/PB for part C, and third bar (PB/PB+SDF) to the left), P < .01.