Mono-methylated arginine (MMA) is well-known inhibitor of inducible nitric oxide synthase (iNOS) and has been extensively used for studying NO’s mechanistic roles during macrophage activation, cardiovascular diseases, hypercholesterolemia, nervous system disorders, lung diseases, autoimmunity, and viral/bacterial infections, including tuberculosis (7, 73–76). The gene discussed is NOS2; the disease is lung disorder.