More importantly, the improved production of IFN‐γ by tumor‐infiltrating CD8+ T cells in Tipe2ΔNK/ΔNK mice was compromised by further deletion of Prf1 in Tipe2ΔNK/ΔNK; Prf1ΔNK/ΔNK mice, while both cell numbers and IFN‐γ production of tumor‐infiltrating CD8+ T cells were comparable between Tipe2ΔNK/ΔNK; Prf1ΔNK/ΔNK mice and Prf1ΔNK/ΔNK mice (Figure 4F), indicating that the improved help of Tipe2−/− NK cells for the antitumor function of CD8+ T cells was dependent on NK cell antitumor effector functions. The gene discussed is PRF1; the disease is neoplasm.