TGF-β, produced by MM cells and Tregs, downregulates NK-activating receptors and impairs cytotoxicity.71 MM cells produce IL-6, which inhibits NK cell function, and PGE2 from MDSCs also inhibits NK activation via the natural cytotoxicity regulators (NCR), NKG2D and CD16/ FcγRIIIA receptors (reviewed in72) (18). Here, KLRK1 is linked to Miyoshi myopathy.