MRP4 down-regulation hampers mLC migration toward CCL19 and CCL21. (A) MUTZ3-vector control and MUTZ3-shMRP4 cells were differentiated into LCs and matured by addition of a cytokine cocktail (see “Methods”). Phenotypic analysis (n = 4) is depicted and shows no abnormal differentiation due to the absence of MRP4. Mature LCs were allowed to migrate in a transwell assay toward the chemokines CCL19 and CCL21 either immediately (B) or after (C) preincubation with typical MRP4 substrates (PGE₂, 1 μg/mL; LTB₄ and LTD₄, 200 nmol/L; 8-Br-cGMP, 50 μmol/L). The percentages migrated cells are given relative to the vector control migrated cells (n = 3 for panels B and C; mean ± SD).