CD4 and neoplasm: In addition to the fact that effector CD8+ T cells can be used as the main killing effector cells of recombinant TCR-T cells, CD4+T cells have also been shown to excrete cytokines IFN-γ and tumor necrosis factor (TNF) through a variety of mechanisms, thus eliminating tumor cells in vivo independently of CD8+ T cells to play an anti-tumor effect (26–32).