To evaluate the synergistic effects of vaccination and PD-1Ab21, B16-OVA-bearing mice, which were adoptively transferred with OT-1 cells 1 day before tumor inoculation, were first vaccinated by intradermal (i.d.)injection of poly I:C and OVA peptide and then treated with PD-1Ab21, anti-PD-1 antibody, or a combination of PD-1Ab and IL-21. Here, IL21 is linked to neoplasm.