Ccl22^−/− mice have excessive T cell responses upon vaccination. Ccl22^−/− and WT C57BL/6 mice were injected with OVA protein two times at a 7-d interval, and CpG together with Alum were used as adjuvant. (A and B) 1 wk after the last injection, the frequency of OVA-specific cytotoxic T cells (CD19^negCD3⁺CD8⁺) in the peripheral blood was determined by pentamer (H-2Kb OVA_257–264) staining (A) and intracellular IFN-γ staining (B) upon restimulation with OVA_257–264 peptide (n = 11 mice per group treated with OVA and n = 4 mice per group without treatment). Data are shown as mean ± SEM and are pooled from two independent experiments. In total, three experiments with similar results were performed. **, P < 0.01 (two-sided Student’s t test).