Local production of nitric oxide in patients with tuberculosis.

Nitric oxide (NO), produced by the inducible nitric oxide synthase (iNOS), is important in host defence against Mycobacterium tuberculosis in rodents, but the presence of high-output NO production in human tuberculosis has been controversial. We investigated iNOS and nitrotyrosine (Ntyr) expression in pleural (n = 7), pulmonary (n = 5) and lymph node biopsies (n = 5) from untreated, newly diagnosed tuberculosis patients. Many iNOS and Ntyr reactive macrophages were observed in granulomas, including Langhans giant cells, indicating high-output NO production at the primary site of disease in tuberculosis.