CTLA4 and neoplasm: It is expressed in most circulating effector cell memory CD8(+) T cell subsets, and the knockout of TOX in human tumor‐infiltrating CD8(+) T cells can lead to down‐regulation of PD‐1, TIM‐3, TIGIT, and CTLA‐4, suggesting that the TOX can promote T cell failure by up‐regulating immune checkpoint proteins in tumors.