DCs polarize the MTOC in antigen-specific synapses. (A) DCs were stimulated with a combination of TLR agonists (CpG and LPS) and loaded (Ag) or not (no Ag) with OVA class I peptide before mixing to OVA-specific CD8⁺ T cells (OT-I). Confocal sections showing the MTOC position detected by staining with anti–α-tubulin antibodies (left) or using DCs differentiated from centrin-GFP knock-in mice (right) mixed with carboxylic acid, succinimidyl ester (SNARF)–labeled T cells (red). (B) DC–T cell conjugates were formed using TLR-stimulated DCs loaded with the indicated doses of peptide. The percentage of DCs with the MTOC polarized toward the DC–T cell interface was quantified as described in the experimental procedure. Values are plotted as means ± SEM of >100 conjugates/condition. (C) DCs were treated with TLR agonist for the indicated periods and loaded with 1 nM peptide before synapse formation. The percentage of polarized DCs was scored in at least 50 conjugates for each condition in 3 independent experiments.