HLA-C and neoplasm: Acting as toxic immune cells, activated NK cells managed by a suite of activating, co-stimulatory and inhibitory receptors [36], can directly kill tumor cells, especially those that lack major histocompatibility complex (MHC; also known as human leukocyte antigen (HLA)) class I [37], such as tumor cells from metastatic and blood tumors, and indirectly improve the response of antibodies and T cells [38].