KLRK1 and plasma cell myeloma: Because high tumor-associated expression of ligands MICA, MICB and ULBPs, the stimulatory receptor NKG2D strongly contributes to NK cell response against solid and hematologic cancers (4, 5), including multiple myeloma (MM) (6), a neoplasia caused by accumulation of malignant plasma cells (PCs) in the bone marrow (BM).