Pathogen-specific loss of host resistance in mice lacking the IFN-γ-inducible gene IGTP

Interferon-γ (IFN-γ) is critical for defense against pathogens, but the molecules that mediate its antimicrobial responses are largely unknown. IGTP is the prototype for a family of IFN-γ-regulated genes that encode 48-kDa GTP-binding proteins that localize to the endoplasmic reticulum. We have generated IGTP-deficient mice and found that, despite normal immune cell development and normal clearance of Listeria monocytogenes and cytomegalovirus infections, the mice displayed a profound loss of host resistance to acute infections of the protozoan parasite Toxoplasma gondii. By contrast, IFN-γ receptor-deficient mice have increased susceptibility to all three pathogens. Thus, IGTP defines an IFN-γ-regulated pathway with a specialized role in antimicrobial resistance.