Migration of different B-cell subsets from adult bone marrow to human SDF-1β. Chemotaxis of FACS-sorted B cells (A) or B cells from total bone marrow (B) in response to serial dilutions of SDF-1β (1 to 1,000 ng/mL) or medium alone is shown. In (B), early lineage B cells define a cell population that includes both pro-B (CD19⁺, κ⁻/λ⁻, CD34⁺) and pre-B (CD19⁺, κ⁻/λ⁻, CD34⁻) cells. Results are expressed as the migration index, which is defined as the number of cells migrated to the lower compartment in the presence of the chemokine divided by the number of cells that have migrated to the lower compartment in the presence of medium alone. A migration index 1 indicated the migration of 1.1% of total input cells and a migration index of 20 equaled 35% migration of total input cells. The results are representative of 4 experiments with primary B cells from total bone marrow and 2 with sorted bone marrow B cells.