IFNAR1 and neoplasm: Moreover, compared to isotype control antibody treatment, treatment with systemic anti‐IFNAR1 and anti‐IL‐1β antibodies significantly decreased the frequency of the granzyme B+‐ and perforin+ PD1+CD8+ T cells in tumors of mice bearing the Arf1‐ablated tumor cells (Figure 6i,k and Figure S12e, Supporting Information), indicating that the type I IFNs and IL‐1β cytokines are responsible for enhanced tumor killing ability of the CD8+ T cells in mice bearing the Arf1‐ablated tumor cells.