CD4 and neoplasm: Neoantigen-directed CD4+ adoptive T cell therapy, where reactive T cells are selected from tumor-infiltrating lymphocytes, also clearly has clinical activity, for instance, in cholangiocarcinoma with a clone directed against a mutation in ERBB2-interacting protein and in urothelial carcinoma with a clone directed against mutated C-terminal binding protein 1 (Tran et al., 2014; Leko et al., 2019).