We previously described the production of tumor-reactive or activated-by-cytokine killer (TRACK) NK cells expanded from umbilical cord blood (UCB) NK cells, transduced with a retroviral vector encoding soluble IL-15 (sIL15), which were further cytokine-activated to induce PD-L1 expression and then cryopreserved (24). The gene discussed is IL15; the disease is neoplasm.