IRGM belongs to a family of interferon-gamma inducible GTPases, belonging to the GTPase superfamily, and are selectively induced by IFN-gamma or bacterial lipopolysaccharide (LPS) stimulation. IRGM is primarily expressed in all cells derived from B-cell lineages, and is highly expressed in macrophages following IFN-gamma stimulation. IRGM has been shown to be required for host defences against a broad range of intracellular pathogens. Specifically, IRGM deficient mice show defects with intracellular microbial killing, phagosome maturation and autophagy. More recently IRGM has been shown to inhibit baseline hematopoietic proliferation and is required for a normal hematopoietic stem cell response to chemical and infectious stimuli.