IFNG and infection: When these cells are stimulated by cytokines or bacterial components, such as lipopolysaccharide (LPS), superantigens of gram-positive bacteria, or streptococcal derivatives, they play important roles in the defense against tumors and infections; i.e., both NKT and NK cells exert cytotoxic activity simultaneously or differentially by releasing cytotoxic mediators, such as perforin and granzyme, and/or by producing proinflammatory cytokines, including interferon-gamma (IFN-γ), depending on the type of stimuli [10].