IL2 and neoplasm: NK cells are activated by various stimuli such as contact with dendritic cells (DC), MHC-I-negative cells, binding of IgG-containing immune complexes, direct engagement of NK receptors by stress-induced tumor-associated molecules or pathogen-derived products, and several cytokines such as interleukin (IL)-2, IL-12, IL-15, IL-18, IL-21, and interferon (IFN)-α/β (Vivier et al., 2008).