Overall, two important conclusions influencing the future combination of radioimmunotherapy targeting CCR8+ ti-Tregs and immune checkpoint inhibitors can be derived from these experiments: (1) whole anti-CCR8 IgG shows higher uptake in both CT26 and MC38 tumors and no uptake in the kidneys and should be used in combination with anti-CTLA4 and anti-PD1 immunotherapy; (2) the highest uptake of the antibody in the tumor is reached at 24 h post-injection. Here, CTLA4 is linked to neoplasm.