CD8A and neoplasm: Moreover, tumour‐infiltrating PTPN2‐deficient CD4+ and CD8+ effector/memory T cells were significantly more active, as assessed by the PMA/ionomycin‐induced production of markers of T‐cell cytotoxicity ex vivo, including interferon (IFN)‐γ and tumour necrosis factor (TNF) (Fig 1E).