CD4 and neoplasm: In line with the aforementioned results (Fig. 3b), anti-4-1BB indeed resulted in a significant decrease in the percentage of CD73+ cell in both transferred CD4+ and CD8+ T cells in the tumor (Fig. 4j) and spleen (Supplementary Fig. 5) from tumor-bearing Rag1−/− hosts, indicating again a specific potent downregulation of CD73 expression on T cells by the 4-1BB-mediated costimulation.