Chemotactic activity of SDF-1 and CKβ-11/MIP-3β/ELC for DP thymocyte subsets defined by CD69 expression. Total thymocytes were added to the upper chambers and optimal concentrations of SDF-1 (300 ng/mL) and CKβ-11/MIP-3β/ELC (500 ng/mL) were added to the lower chambers. Input and migrated cells were stained with antibodies to CD4, CD8, and CD69. CD4⁺CD8⁺CD69⁺ cells and CD4⁺CD8⁺CD69⁻ cells were counted by FACscan for 30 seconds. Data are shown as the net mean percentage of migration after background subtraction for each subset (±SD of triplicated experiments). *Significant migration (P< .05) from background migration.