KLRK1 and neoplasm: Mononuclear Gr-1(+) CD11b (+) F4/80(+) MDSCs isolated from RMA-S tumor-bearing mice did not suppress but activated NK cells to produce high amounts of IFN‐γ, and NK-cell activation by MDSCs depended partially on the interaction of NKG2D on NK cells with NKG2D ligand RAE-1 on MDSCs (34).