Nitric oxide synthase, inducible is an enzyme which is encoded by the NOS2 gene in humans and mice. Three related pseudogenes are located within the Smith-Magenis syndrome region on chromosome 17. Alternative splicing of this gene results in two transcript variants encoding different isoforms. Nitric oxide synthase is expressed in epithelial cells of the liver, lung and bone marrow. It is inducible by a combination of lipopolysaccharide and certain cytokines. Nitric oxide is a reactive free radical mediating in neurotransmission, antimicrobial and antitumoral activities. In mice, the function of Nos2 in immunity against a number of viruses, bacteria, fungi, and parasites has been well characterized, whereas in humans the role of NOS2 has remained elusive and controversial. Nos2 is important for protective immunity against CMV. Caveolin 1 has been shown to interact with Nitric oxide synthase 2A. and Rac2.