KLRK1 and plasma cell myeloma: In particular, an increased number of NK cells expressing higher levels of the activating receptors NKG2D, NKp30 and NKp44 has been observed in MM patients during IMiDs therapy [23, 24]; moreover, IMiDs enhance NK cell antibody-dependent cell-mediated cytotoxicity (ADCC) activity toward MM cells [25], and can sensitize myeloma cells to NK cell cytotoxicity by inhibiting the expression of PD-L1 [26].