MKI67 and neoplasm: In tumors of mice bearing the Arf1‐ablated tumor cells, the expression of Ki67 and T‐bet was significantly increased in the PD1+CD8+T cells, but this was abolished after treatment with anti‐IFNAR1 and anti‐IL1β antibodies (Figure 6g,h and Figure S12c,d, Supporting Information), suggesting that the type I IFNs and IL‐1β cytokines are responsible for maintenance of the effective CD8+T cells in mice bearing the Arf1‐ablated tumor cells.