KLRK1 and neoplasm: Treg are believed to inhibit NKG2D-mediated NK cell killing [15], and in accordance with this observation, both tumour cell lines (B16F10 and B16FasL) used in these experiments express the NK2GD ligand Rae-1 (Fig. 2C), in contrast to other studies in which NKG2D ligands were transfected into tumour cells [14], [15].