Expression of inducible Nitric Oxide Synthase (iNOS) in monocytic cells from children with infections by intracellular pathogens

iNOS is expressed by murine macrophages upon infection by intracellular pathogens. However, it is still questioned whether the enzyme were expressed in human infections. Intracellular staining by an anti-iNOS mAb of IFN-γ activated monocytes derived from patients with mycobacterial infection demonstrated that IFN-γ alone was sufficient to induce expression of the enzyme. In addition, mitogen-activated lymphocytes derived from the same patients released measurable amounts of IFN-γ. In order to investigate whether iNOS were expressed 〈I〉in vivo〈/I〈, we used an immunohystochemical approach on fresh frozen tissue sections. In all lymph nodes derived from infectious conditions characterized by formation of epitheloid granulomas, we observed strong reactivity for iNOS in epithelioid and multinucleated giant cells. In reactive lymphoadenitis, instead, all macrophages and dendritic cells were completely negative for iNOS. As a whole these results suggest that iNOS protein is induced by IFN-γ human monocytes activated 〈I〉in vitro〈/I〉, as well as in granulomas of patients with infection by intracellular pathogens