NK cells exhibit cytotoxic activity against not only infected
cells but also cancer cells (119–121). IFN- produced by
activated NK cells suppresses the proliferation of cancer cells
and activates cytotoxic T cells and macrophages (122,123).
While NK cells kill cancer cells in an antigen non-specific
manner, cytotoxic T cells recognize specific antigens of cancer
cells for killing. Moreover, macrophages secrete molecules
toxic to cancer cells and induce the apoptosis of cancer cells
(124–126).