CCR8 and neoplasm: Mechanism of action experiments that designed to find an immunological explanation of RIT and immunotherapy revealed expansion of CD4+CD8+ double positive T cells, anti-tumor M1 macrophages, 4-1BB+ effector CD8+T cells and NK cells after administration of 225Ac-anti-CCR8 RIT (Figures 4, 5, S6–S8).