Immune Control of Tuberculosis by IFN-γ-Inducible LRG-47

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Abstract
Interferon-γ (IFN-γ) provides an essential component of immunity to tuberculosis by activating infected host macrophages to directly inhibit the replication of Mycobacterium tuberculosis (Mtb). IFN-γ–inducible nitric oxide synthase 2 (NOS2) is considered a principal effector mechanism, although other pathways may also exist. Here, we identify one member of a newly emerging 47-kilodalton (p47) guanosine triphosphatase family, LRG-47, that acts independently of NOS2 to protect against disease. Mice lacking LRG-47 failed to control Mtb replication, unlike those missing the related p47 guanosine triphosphatases IRG-47 or IGTP. Defective bacterial killing in IFN-γ–activated LRG-47–/– macrophages was associated with impaired maturation of Mtb-containing phagosomes, vesicles that otherwise recruited LRG-47 in wild-type cells. Thus, LRG-47 may serve as a critical vacuolar trafficking component used to dispose of intracellular pathogens like Mtb.
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