Immunization with peptide-loaded DCs elicits a potent CTL response in mast-cell–deficient mice.Kit^W-sh/Kit^W-sh or Kit⁺/Kit⁺ mice were immunized intraperitoneally with 1 × 10⁶ DCs that had been activated with the TLR3 ligand poly(I:C) overnight, and peptide-loaded with the immunodominant H2-Kb peptide SIINFEKL. DCs were derived from either mast-cell–deficient or wild-type mice. At day 6, the blood was monitored for the presence of SIINFEKL-tetramer⁺ CD8⁺ T cells (data not shown). Seven days after immunization, cytolytic activity against SIINFEKL-loaded CFSE^low or non–peptide-loaded CFSE^high syngeneic splenocytes was evaluated after 20 hours; target cells had been injected intravenously at day 6. Negative controls show no lysis, while the other groups of mice lysed the target cells 94% to 98%. One representative graph for each group is shown; the experiment was performed 2 times independently, using 3 mice per group.