KLRK1 and neoplasm: After prolonged incubation with A549 cells, the reduced proportion of CD8+ NKG2D(z) cells may be related to the fact that CD8+ NKG2D(z) CAR-T cells were more easily lost, indicating that CD4+ and CD8+ NKG2D CAR-T cells should be prepared separately in the future to study the differences in target tumor cell lysis and cytokine secretion.