DC migration toward CCL21 occurs with apoptotic and not with necrotic cells and does not depend on the cell line or on the maturation stimulus used. (A) Immature DCs were exposed for 4 hours to UVB-treated ApoC (UVB) or to necrotic (Nec) Jurkat cells at a DC/dead cell ratio of 1:8 before the addition of TNF-α (250 U/mL). (B) DCs were exposed to apoptotic Jurkat cells (Jurkat UVB) or M44 cells (M44 UVB) before the addition of TNF-α (250 U/mL). (C) DCs were stimulated with apoptotic Jurkat cells (apoptotic cells) before the addition of TNF-α (250 U/mL) or LPS (5 μg/mL). Specific migrating DC numbers represent the numbers of DCs migrating toward CCL21 minus the numbers of DCs migrating toward medium. Nonspecific migration accounted for 342 ± 180 DCs in the TNF-α condition and 1618 ± 834 DCs in the LPS condition compared with 421 ± 403 DCs in the absence of treatment (not shown).