ERK1/2 phosphorylation in nonactivated monocyte-derived dendritic cells and ERK1/2 importance in CCL2-driven MDDC transmigration. (A) Nonactivated (left panel) and activated (right panel) monocyte-derived dendritic cells (MDDCs) and peripheral blood lymphocyte (PBLs) were either untreated or treated with 100 ng/ml chemokine ligand 2 (CCL2). Expression of p38-MAPK and ERK1/2 and their phosphorylated forms was determined by western blotting. (B) Nonactivated (top panel) and activated (bottom panel) MDDCs and PBLs (2×105 cells) were left untreated or treated with p38 (SB203580) or ERK1/2 (U0126) inhibitors at the indicated doses. Transmigration assays in the presence or absence of CCL2 were performed and cells were counted at 24 hours. Data are representative of at least two independent experiments each performed in duplicate. Statistical significance (*P ≤0.05, **P ≤0.005, ***P ≤0.0005) between the control (no inhibitor) and each inhibitor-treated sample in the presence of CCL2 was determined by Student’s t test.