Infiltration of CD8+T cells can reduce tumor cell metastasis and is associated with higher survival rate and lower risk of recurrence in patients with biliary tract cancer.[19,27] High FoxP3+ Tregs/CD8+T cell value was found to be associated with poor OS and disease-free survival in lung adenocarcinoma, pancreatic cancer and other tumors.[28,29] It can be seen that the increase of FoxP3+ Tregs infiltration and the decrease of CD8+T cell infiltration contribute to the formation of immunosuppressive TME and lead to poor prognosis. This evidence concerns the gene CD8A and biliary tract cancer.