NOS2 (iNOS, nitric oxide synthase 2, inducible) is a synthase for nitric oxide, a reactive free radical and messenger molecule that acts a biologic mediator in neurotransmission and antimicrobial/anti-cancer processes. In macrophages, nitric oxide mediates tumoricidal and bactericidal actions. It also has nitrosylase activity and mediates cysteine S-nitrosylation of cytoplasmic target proteins such COX2. In immunohistochemistry, NOS2 antibodies may be used to characterize epithelial injury and cells undergoing apoptosis in sites of inflammation. NOS2 may be useful in diagnosing liver diseases, as NOS2 has high expression in a number of pathologies and is involved in the etiology of liver fibrosis. Furthermore, antibodies to NOS2 may have utility in cancer: elevated levels of NOS2 have been found in cancers of the lung, colon, and prostate as well as in melanoma, glioblastoma and oral dysplasia, and high levels of NOS2 in cancers are generally correlated with poor prognosis. In normal tissue, NOS2 is positive in the gastrointestinal tract, appendix and urinary bladder. References: Proc Natl Acad Sci USA. 90 (8): 3491–5, PMID: 7682706; Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2000 Nov; 90(5):624-9, PMID: 11077387; Clin Cancer Res. 2000 Dec; 6(12):4768-75, PMID: 11156233; Med Oral Patol Oral Cir Bucal. 2014 May; 19(3): e242–e247, PMID: 24316703; Arch Pathol Lab Med. 2009 Jan;133(1):97-100, PMID: 19123745; Clin Mol Hepatol. 2015 Dec; 21(4): 319–325, PMID: 26770919;