CD8A and neoplasm: Meanwhile, the percentage of CD8+ TCR-T rather than CD4+ TCR-T showed more increase within the tumor in mice receiving IL-21R-TCR-T than conventional TCR-T treatment (Fig. 5n, o and Supplementary Fig. 9b), demonstrating the superior proliferation and infiltrating capacity of CD8+ IL-21R-TCR-T within the tumor microenvironment.