Migratory ability of CD40-activated B cells. 5 × 105 CD40-B cells were added to the upper chamber transwell plates. Varying amounts of the chemokines SDF-1α and SLC (R&D Systems) were added to the lower chamber. After 2 hours the cells that had migrated into the lower chamber were counted with a hemacytometer. The migration index is calculated relative to vehicle-treated controls. Shown are the means of 4 independent experiments ± SD.