Combined effects of SDF-1 and SLF on CB CD34⁺ (A), BM CD34⁺ (B) and CB HPC cells. Cells migrated into the lower chamber were counted (A and B) or assayed for HPC (C) after the indicated chemoattractants (SDF-1 at 100 ng/mL for part A and B, 50 ng/mL for part C; SLF at 50 ng/mL for part A, B, and C) or control medium were added singly or in combination to either the upper or lower chambers. *Significant difference from controls (second bar to the left for part A and B, and medium for part C,P < .05). **Significant change from migration induced by either SLF or SDF-1 alone, P < .005.