RAG1 and neoplasm: To begin testing whether T cell maturation was necessary for the cooperative anti-tumor effect of the combination of [212Pb]VMT01 and ICIs, this treatment combination was administered to B6.129S7-Rag1tm1Mom/J mice (i.e., Rag1 KO mice) bearing B16-F10 tumors (n = 7), where 4.1 MBq [212Pb]VMT01 was administered as a single injection on day 0, as this regimen showed most significant anti-tumor effectiveness.