CD4 and neoplasm: We observed long-term survival after treatment (>150 d) in 50% of tumor-bearing WT mice treated with Ad-TK + Ad-Flt3L (*, p < 0.05 versus saline; MSR 4.1; Figure 1A) and failure to improve survival in Rag1−/−, CD4−/−, or CD8a−/− mice (all on C57BL/6 background) compared with WT controls (Figure 1B), indicating T cell-dependent tumor regression.