LAG3 and neoplasm: Although the expression of the T‐cell inhibitory receptors PD‐1 and Lag‐3 on tumour‐infiltrating PTPN2‐deficient OT‐1 T cells at 9 days post‐transfer was not altered (Appendix Fig S3D), by 21 days post‐transfer relative PD‐1 and LAG‐3 levels were reduced and CD44 was increased on PTPN2‐deficient tumour‐infiltrating and draining lymph node OT‐1 T cells when compared to Ptpn2fl/fl controls (Appendix Fig S3E–G), consistent with decreased T‐cell exhaustion.