The participation of natural cytotoxicity in the control of malignant disease

Natural killer (NK) cells participate together with T cells in the control of the primary tumor growth and metastatic disease. Since natural cytotoxicity is mostly down-regulated by high levels of self major histocompatibility complex (MHC) antigens, the primary role of NK cells may be to eliminate cells which fail to express these molecules. The NK cell activity clearly correlates with clinical stage and progression of malignant disease: in most patients with disseminated tumors NK cells are lytic incapable and cannot respond to interferon stimulation properties.