Preclinical observations strongly support the antitumor activity of IL-15 mediated by CD8+ T cells (127), and IL‐15 co-expression in CD19-CAR-T not only revealed a strong killing effect against leukemia cells, but most of the persistent T cells were phenotypically consistent with Tscm that drive long‐term persistence (128). The gene discussed is IL15; the disease is leukemia.