IFNG and cancer: IL-12 induces the secretion of IFN-gamma from naive and activated T and NK cells, enhances the cytotoxic activity of NK cells, cytotoxic T lymphocytes, lymphokine activated killer cells and increases the proliferation of preactivated T cells and NK cells; the IL-12 ability to induce differentiation of Th1 cells, and to produce cell-mediated immunity enhancing cytokines, underlines how this cytokine plays a key role in promoting host defence and protection against cancer [51,52].