The NBT (Nitroblue Tetrazolium) activity of neutrophil granulocytes in patients with influenza A infection

Trypanosoma lewisi-induced immunosuppression: The effects on alveolar macrophage activities against Cryptococcus neoformans

The immunosuppressive effect of Trypanosoma lewisi infection on alveolar macrophage (AM) activities against Cryptococcus neoformans was studied in an animal model. Two groups of rats were treated with T. lewisi and killed after 4 (4d-rats) and 7 days (7d-rats), respectively. A third group not given T. lewisi, served as control. AM were challenged in vitro with C. neoformans. Phagocytosis was assessed with a fluorescence method. Superoxide anion production was evaluated with the nitroblue tetrazolium (NBT) test. The survival of cryptococci was estimated by counting colony-forming units. The numbers of detached AM from culture plates were determined using a Bürker chamber. The NBT response, adhesion to plate surface and killing activity, but not the phagocytosis of AM from 4d-rats were significantly impaired compared to control or 7d-rats. Thus, T. lewisi causes transitory immunosuppressive effects on AM activities. This rapid T. lewisi immunosuppression model may be useful to study new approaches to anticryptococcal therapy.

Monocytes and neutrophils from tuberculosis patients are insensitive to anti-inflammatory effects triggered by the prototypic formyl peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP)

Tuberculosis is a chronic infectious disease caused by Mycobacterium tuberculosis where formyl peptides, which are cleavage products of bacterial and mitochondrial proteins, are present. In this study, we demonstrated that interferon gamma (IFN)-gamma and interleukin (IL)-10 induced the overexpression of the receptor for the Fc portion of IgG I (FcgammaRI) in monocytes from tuberculosis (TB) patients, showing that these cells respond to IFN-gamma and IL-10 signals. We also demonstrated that lower doses of IL-10 render monocytes from TB patients less responsive to higher doses of the cytokine. Although the prototypic formyl peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP) is a well-known proinflammatory agonist, we have demonstrated previously that preincubation of monocytes with FMLP inhibited the up-regulation of FcgammaRI induced by IFN-gamma or IL-10. This effect was not observed in monocytes from TB patients. FMLP also induced the down-regulation of the expression of FcgammaRI in monocytes that had been activated already with IFN-gamma. However, this effect of FMLP was not observed in monocytes from TB patients and supernatants from monocytes obtained from these patients were incapable of inducing the down-regulation of FcgammaRI. In contrast to normal donors, supernatants from FMLP-treated neutrophils from TB patients did not modify the basal level of expression of FcgammaRI in monocytes from normal donors. In conclusion, in this study we demonstrated the existence of two novel mechanisms that may contribute to the pathological effects generated by M. tuberculosis: the enhancement of FcgammaRI in response to IFN-gamma and IL-10, and the unresponsiveness to the anti-inflammatory effects induced by formyl peptides.

Hydroxyl radical scavengers inhibit TNF-alpha production in mononuclear cells but not in polymorphonuclear leukocytes

The hydroxyl radical (HO*) scavengers dimethylthiourea (DMTU), tetramethylthiourea (TMTU), dimethylsulfoxide (DMSO) and deferoxamine (DFX), the latter being an iron chelator which prevents HO* formation by blocking the Fenton reaction, were found to inhibit TNF-alpha production in LPS-stimulated human PBMC but not in PMN. Furthermore, this effect was not LPS-specific, as TNF-alpha production was reduced by HO* radical scavengers to a similar extent upon stimulation of PBMC with immune complexes (IC), concanavalin A (Con A) and phorbol myristate acetate (PMA). Other scavengers such as glutathione (GSH), N-acetylcysteine (NAC), ascorbic acid (ASC) and mannitol (MAN) do not have effect on the production of TNF-alpha either in PBMC or PMN. These results provide evidence that the participation of ROI in the regulation of TNF-alpha production differ in different cell types. Particularly, the data presented in this work indicate that HO* radicals have a central role in the production of this inflammatory cytokine by human PBMC.

Neutrophil function and glutathione-peroxidase (GSH-px) activity in healthy individuals after treatment with N-acetyl-L-cysteine

The objective of this study was to evaluate the effect of N-acetyl-L-cysteine (NAC) on neutrophilic functions and as an antioxidant. NAC, 600 mg daily, given orally to healthy individuals for a period of 2 weeks, affected some functions of human neutrophilic granulocytes when tested in vitro. NAC treatment caused a decrease in the production of superoxide anions by stimulated neutrophils and the improvement of their phagocytic capacity although it did not affect their random or chemotactic migration. The level of glutathione peroxidase (GSH-px) in thrombocytes of the NAC-treated individuals was increased in comparison with the activity before treatment. These results suggest that NAC might act as a scavenger of oxygen-derived free radicals released by stimulated neutrophils and thereby protect the tissue against the radical caused injury as well as optimize phagocytosis.

Oxygen radical release by neutrophils of HIV-infected patients

Neutrophils from asymptomatic HIV-infected patients have an increased Nitroblue tetrazolium (NBT) reduction, that is an increased production of oxygen radicals. Plasma from these patients can activate normal neutrophils to an increased NBT-reduction and the neutrophil activating factor thus seems to be mainly plasma bound. Further, the patients also have increased levels of plasma malondialdehyde and thus an increased lipid peroxidation. Plasma cysteine levels are low, a sign of increased consumption of antioxidants. Treatment of the asymptomatic HIV-infected patients with N-acetylcysteine corrected the plasma cysteine levels and had some beneficial effects, but did not inhibit the increased radical production by the neutrophils.

Lymphocyte and granulocyte function in nutritionally depleted patients. The effect of 2 weeks of total parenteral nutrition

Parenteral nutrition has been reported to restore impaired immune function in nutritionally depleted patients. Lymphocyte and granulocyte function were studied before and after 2 weeks of total parenteral nutrition (TPN) in 9 depleted patients, 5 with gastrointestinal cancer and 4 with benign gastrointestinal disorders. The ability of purified blood lymphocytes to incorporate (14)C-labelled thymidine spontaneously and following mitogenic and antigenic stimulation was studied. Before TPN spontaneous lymphocyte activity was significantly increased and mitogen and antigen responsiveness significantly decreased in comparison to healthy controls. These abnormalities were more pronounced in patients with malignant disorders while the remaining patients showed a moderate impairment. No improvement in lymphocyte capacity was observed following 2 weeks of TPN. Granulocyte function measured as chemotaxis, phagocytosis, NBT-reduction and bactericidal capacity did not differ significantly between patients and controls and no changes were seen following nutritional treatment. These findings support the concept that the underlying disease and/or other factors rather than the secondary nutritional depletion are the main reasons for immune impairment. Furthermore, no immunomodulating effects of lipid emulsions on lymphocyte and granulocyte function, under these experimental conditions, were apparent.

The role of O-antigen polysaccharide in the activation of neutrophils by lipopolysaccharides of Salmonella species

Activation of neutrophils by lipid A, O-antigen polysaccharides (PS) and smooth lipopolysaccharides (LPS) isolated from Salmonella choleraesuis (O-6,7) and Salmonella typhimurium (O-4,5,12) was investigated. The methods used were assays for lysozyme release and for nitroblue tetrazolium (NBT) reduction which measures the level of oxidative metabolism of neutrophils. LPS from both species stimulated neutrophils to the same extent in the presence of autologous plasma. In the absence of plasma only the O-6,7 LPS activated neutrophils. Lipid A or PS isolated from both LPS either did not activate neutrophils or did so only at very high concentrations when tested in the presence of plasma; in the absence of plasma no activation occurred. The data indicate that both PS and lipid A segments of LPS are required for activation of neutrophils by LPS. We also deduce that plasma, probably complement, is required for the interaction of some LPS, e.g. O-4,5,12 with neutrophils whereas other LPS, e.g. O-6,7 can interact directly and activate neutrophils.

Effect of Brucella abortus lipopolysaccharide on oxidative metabolism and lysozyme release by human neutrophils

Both Brucella abortus lipopolysaccharide (LPS) and lipid A were low activators of nitroblue tetrazolium reduction and lysozyme release in human neutrophils. The stimulation was dose dependent and was higher in the presence of autologous plasma than in its absence. The comparison between Brucella LPS and lipid A versus Salmonella LPS revealed that at least 100 times more LPS and 1,000 times more lipid A of the former genus were required to induce significant nitroblue tetrazolium reduction and a corresponding lysozyme release in neutrophils. Low Brucella LPS-mediated superoxide and lysozyme production might contribute to the survival of these facultative intracellular bacteria in phagocytic cells.

Influence of HIV antigens on functional activity of neutrophilic granulocytes in

The effect of nine HIV antigens, including eight synthetic peptides, on the functional activity of granulocytes was studied using the reduction of nitroblue tetrazolium test (NBT test). Some peptides partly suppressed the functional activity of granulocytes. The most pronounced suppression was caused by ImVL (HIV-1 lysate immobilized on plates for ELISA) and SP-7 (a synthetic peptide from the gp41 protein of HIV-1). The degrees to which the functional activity of granulocytes was suppressed by ImVL and SP-7 was in inverse proportion to the specific antibody concentrations. No correlation was found between the reduction in the NBT test value and the amount of CD4+, CD8+ cells on CD4/8 ratio.

Intralipid decreases the bacterial lipopolysaccharide induced release of oxygen radicals and lysozyme from human neutrophils

Human neutrophils were incubated either with purified cell envelope lipopolysaccharides (LPS) of salmonella or with different concentrations of LPS combined with Intralipid. Incubation of neutrophils with LPS alone increased their oxidative metabolism with increased release of oxygen radicals as measured by the nitroblue tetrazolium (NBT) test and chemiluminescence response. The amount of lysozyme released by the cells also increased during incubation with LPS. However, when the neutrophils were incubated with LPS together with Intralipid, the LPS induced stimulation of the neutrophil NBT reduction, chemiluminescence and lysozyme release was significantly decreased. Intralipid might substitute for plasma high density lipoproteins (HDL), which are known to inhibit the LPS effects on the neutrophils in the acute stage of an infection with Gram-negative bacteria.

Quartz-dust-induced production of reactive oxygen metabolites by human granulocytes

We studied the effect of quartz on the production of reactive oxygen species by human polymorphonuclear leukocytes (PMN) in vitro by a chemiluminescence (CL) assay. Quartz caused a rapid dose-dependent CL response in the cells. Diamond dust used as an inert control did not stimulate the production of reactive oxygen metabolite by PMN. The quartz-induced activation of oxygen metabolism was also demonstrated by measuring oxygen consumption, nitroblue tetrazolium reduction, and superoxide and hydrogen peroxide production by PMN. Poly-vinyl-pyridine N-oxide (a quartz surface modifying agent) completely abolished the quartz-induced response, but had no effect on opsonized zymosan-induced CL response of PMN. The effect of N-acetylcysteine (a known antioxidant) was inhibitory to the CL formation induced by both quartz and opsonized zymosan. Our results are in agreement with the hypothesis that quartz-induced production of reactive oxygen metabolites is a possible mechanism by which quartz dust produces chronic inflammation and tissue injury of the lung. Agents interfering with the generation of reactive oxygen metabolites may provide a rationale for treatment of mineral-dust-induced pulmonary disease.

Selenium effects on human neutrophilic granulocyte function in vitro

The effects of an inorganic selenium salt on phagocytic functions of human neutrophilic granulocytes from donors with a low activity of glutathione peroxidase have been investigated. Granulocytes were exposed for 60 min in vitro to sodium selenite in two physiological concentrations (100 and 200 ng Se/ml) and one unphysiologically high concentration (2000 ng/ml). The spontaneous and chemotactic migration, the nitroblue tetrazolium reduction, the phagocytosis of fluorescein-labeled yeast particles and the intracellular killing of staphylococci were then studied in such granulocytes and compared to control cells, which had not been exposed to selenium. The migration and nitroblue tetrazolium reduction abilities of granulocytes were not affected by selenium exposure. The phagocytic and bactericidal activities were significantly increased in granulocytes exposed to selenium in physiological concentrations. However, at 2000 ng Se/ml these activities were found to be equal to or lower than control levels. Thus selenium supplementation might enhance phagocytic and bactericidal functions of human granulocytes, thereby improving the host defense against bacterial infections.

Nitroblue tetrazolium (NBT) reduction by neutrophilic granulocytes in patients with HTLV-III infection

The NBT reduction of granulocytes was determined in 11 patients with HTLV-III infection. The reaction was measured in granulocytes both in resting state and after stimulation with Escherichia coli, as well as with and without addition of plasma. In 5 patients with AIDS, the NBT reduction was significantly decreased in all these types of experiments, when compared with 12 healthy controls. In 6 patients with the lymphadenopathy syndrome (LAS), the NBT reduction of resting granulocytes was significantly higher than that of the controls. The findings could in general not be explained by superinfections. The elevated NBT test during the long term LAS stage reflects a release of free oxygen radicals, against which treatment might be directed.

A simple method for the solubilisation of reduced NBT, and its use as a colorimetric assay for activation of human macrophages by gamma-interferon

We describe a simple method by which the insoluble blue formazan dye produced by the reduction of nitro blue tetrazolium can be dissolved without heating using potassium hydroxide and dimethyl sulphoxide. This modification enhances the sensitivity and increases the applications of tests performed using the microELISA method and removes variations caused by uneven cell monolayers. It also allows quantification of NBT reduced by cells adherent to coverslips or in larger wells or Petri dishes, and can be used as a sensitive assay for macrophage activation by gamma-interferon.

Functions of human neutrophilic granulocytes after in vivo exposure to interferon alpha

The ability of neutrophilic granulocytes to phagocytize yeast particles and to reduce Nitro Blue Tetrazolium at rest and on activation with bacterial stimuli was monitored in 32 patients receiving treatment with human interferon alpha. The ability of these cells to attach to and ingest yeast particles was not altered to any major extent during 1 year of interferon treatment. In most patients, the Nitro Blue Tetrazolium-reducing activity increased after the first injection of interferon. During prolonged treatment with interferon alpha, 1 week to 1 year, granulocytes activated with bacteria exhibited a reduced Nitro Blue Tetrazolium activity in most patients.

Influence of cardiopulmonary bypass on some host defence functions in man

Four different functions of the immune defence were studied in six men undergoing open-heart surgery with cardiopulmonary bypass (CPB). Pre-operatively, a few hours after and three days after surgery the following tests were performed: (I) in vivo phagocytic and metabolic functions of the reticuloendothelial system (RES), (II) haemolytic activity of blood monocytes, (III) nitroblue tetrazolium (NBT) reduction by granulocytes, and (IV) bactericidal capacity of granulocytes. Compared to the pre-operative values, the RES functions were unchanged postoperatively, whereas there was a significant increase in the haemolytic activity of monocytes and in the NBT reduction of granulocytes. The capacity of the granulocytes to kill bacteria was normal a few hours after surgery, but significantly increased on day 3. No infectious complications occurred and all patients recovered uneventfully. These results suggest that, at the present time, open-heart surgery under CPB is accompanied by an increased activity of granulocytes and monocytes in the early postoperative period.

Immunologic investigation in children with recurrent pneumonia

In vitro lymphocyte stimulation by phytohemagglutinin (PHA) and pokeweed mitogen (PWM) and tests for granulocyte function were performed in 12 children with recurrent pneumonia. Reduced lymphocyte stimulation was found at repeated tests in 2 children and transiently decreased lymphocyte stimulation in 6 more children. In 3 patients, reduced bactericidal capacity of granulocytes was demonstrated, and in 1 cast stimulation showed decreased NBT activity of granulocytes. One patient examined had immunoglobulin deficiency.