CD8A and cholangiocarcinoma: When the expression of B7-H4 is inhibited by the lentiviral vector encoding shRNA, the decrease of B7-H4 in tumor cells can be directly observed, and stable tumor cell lines with low expression of B7-H4 can be screened, and CD8 + T cell-mediated cytotoxicity is increased, providing a new idea for the treatment of CCA 47.