Chemotaxis of LTB₄-pretreated DCs. BM-derived WT DCs, both iDCs (A) and mDCs (B), were pretreated with LTB₄ as indicated for 30 minutes at 37°C. The chemotactic response toward a fixed concentration (100 ng/mL) of CCL3 and CCL19 (iDCs) and toward CCL19 and CCL21 (mDCs) was determined. Significant difference in chemotaxis levels between untreated and LTB₄-treated DCs was indicated (*P < .05, *P < .01 by t test). Data are the mean ± SE of cells from 3 individual fields for each concentration from a representative experiment of at least 3 repetitions. (C) Checkerboard analysis of DC migration across polycarbonate filters toward CCL19.