Mycobacterium tuberculosis (MTB)- stimulated production of nitric oxide by human alveolar macrophages and relationship of nitric oxide production to growth inhibition of MTB

Setting Although nitric oxide (NO) is a major proximate mediator of microbicidal activity in murine macrophages against intracellular pathogens including mycobacteria, its production by and effector role in human macrophages is not clear. Objective To determine the capacity of Mycobacterium tuberculosis (MTB) to stimulate NO in human monocytes (MN) and alveolar macrophages (AM) and to assess the relationship between NO production and intracellular growth of MTB. Design NO production (measured as nitrite) by MTB (H37Ra)-infected macrophages and intracellular growth of MTB were measured in cells from 17 healthy subjects. Results MTB (5:1, MTB:cells) stimulated little to no NO by MN, but induced NO in AM at days 4 and 7 after infection. There was, however, variability in the response by…