Genetic deficiencies resulting in the loss of IFN-γ production or signaling in mice lead to increased susceptibility to infections by other intracellular pathogens, such as L. monocytogenes (see below), Salmonella typhimurium and some viruses (Huang et al., 1993; Harty and Bevan, 1995; Jouanguy et al., 1999). Here, IFNG is linked to infection.