Effect of SLPs and components on chemotaxis of CD34⁺ cells. (A) Chemotaxis of BM CD34⁺ cells toward medium alone (control), SDF-1 low (10 ng/mL) alone, SLPs (combined SLPs from 3 patients), SDF-1 low + SLP, and SDF-1 high (300 ng/mL). SDF-1 was always added to the lower chamber. Data are pooled from quadruplicate samples from 3 independent experiments (*P < .00001). (B) mPB CD34⁺ cells were kept in SLPs (solid line) or were washed out of SLPs and resuspended in control medium (dashed line). At set time points, cells were isolated from the samples and assayed for their responsiveness to a low dose of SDF-1 (30 g/mL) in chemotaxis assays. After chemotaxis, cells were collected from the lower chambers, cells were counted (left panel), and clonogenic CFU-GMs collected from the lower chambers were assayed in secondary methylcellulose cultures (right panel). Data are pooled from quadruplicate samples from 3 independent experiments (*P < .00001). (C) Chemotaxis of CD34⁺ cells to medium alone (control), SDF-1 low (10 ng/mL) alone, and SDF-1 low (10 ng/mL) + uPAR (1 μg/mL) or + ICAM (1 μg/mL) or + VCAM (1 μg/mL) or + fibronectin (2 μg/mL) or + fibrinogen (4 μg/mL) or + C3a (1 μg/mL). Data are pooled from quadruplicate samples from 3 independent experiments (*P < .00001).