Reactive nitrogen intermediates and the pathogenesis of Salmonella and mycobacteria

Over the past decade, reactive nitrogen intermediates joined reactive oxyge n intermediates as a biochemically parallel and functionally non-redundant pathway for mammalian host resistance to many microbial pathogens. The past year has brought a new appreciation that these two pathways are partially redundant, such that each can compensate in part for the absence of the oth er. In combination, their importance to defense of the murine host is great er than previously appreciated. In addition to direct microbicidal actions, reactive nitrogen intermediates have immunoregulatory effects relevant to the control of infection. Genes have been characterized in Mycobacterium tu berculosis and Salmonella typhimurium that may regulate the ability of path ogens to resist reactive nitrogen and oxygen intermediates produced by acti vated macrophages.