KLRK1 and neoplasm: Since there is evidence that leukaemia/lymphoma cells can downregulate such ligand expression (e.g., ULBPs [151,160]), and that leukaemic stem cells do not express NKG2D ligands [161], allowing them to evade recognition by cytotoxic lymphocytes, understanding γδ T-cell target recognition and killing mechanisms will be important to establish biomarkers of potential patient sensitivity or resistance to γδ T-cell-mediated anti-tumour function.