Application of γδ-TCR–expressing effector cells in immunotherapy of cancer patients. αβ T cells from a cancer patient are genetically modified to stably express optimized, high-avidity γδ-TCRs with broad range tumor cell killing activity. After expansion during in vitro culture and infusion into the cancer patient, circulating γδ-TCR effector cells home to the tumor and kill tumor cells. The ligand on tumor cells that is recognized by engineered γδ-TCRs is not known. Professional illustration by Alice Y. Chen.