IL15 and cancer: Because PD-1 pathway blockade acts mainly on Tpex cells, causing them to generate Ttrex cells with strong cytolytic activity (11), an administration of IL-15 that increases the population of Tpex cells combined with αPD-1 therapy could lead to a powerful synergistic effect that might be applied to more patients and different types of cancer that are resistant or refractory to current therapies.