ANXA1 transfection inhibits U937 cell transmigration in response to SDF-1α. A, Effect of endogenous ANXA1 as determined by WT U937 cell incubation with a neutralizing mAb (1 μg/ml) in relation to a control mAb or untreated cells, on cell transmigration promoted by 50 ng/ml SDF-1α using the Transwell system (see Materials and Methods). Data are mean ± SEM of three experiments performed in triplicate. *, p < 0.05 vs control mAb. B, Comparison of the migratory ability of U937 cell clones in the Transwell system using 0–50 ng/ml SDF-1α. Data are mean ± SEM of five experiments performed in triplicate. *, p < 0.05 vs CMV empty plasmid clone.