1,721,002 research outputs found
Killing by neutrophil extracellular traps: fact or folklore?
No full textNeutrophil extracellular traps (NETs) are DNA structures released by dying neutrophils and claimed to constitute a new microbicidal mechanism. Killing by NET-forming cells is ascribed to these structures since it is prevented by preincubation with DNase, which has been shown to dismantle NETs, before addition of the target microorganisms. Curiously, the possibility that the microorganisms ensnared in NETs are alive has not been considered. Using Staphylococcus aureus and Candida albicans blastospores we demonstrate that the microorganisms captured by NETs and thought to be killed are alive, since they are released and recovered in cell medium by incubation with DNase. It is concluded that NETs entrap but do not kill microbes.
Submitted July 1, 2011.
Accepted December 17, 201
Role of myeloperoxidase in the bactericidal activity of human polymorphonuclear leukocytes. Studies with myeloperoxidase-deficient subjects
No full textCommon methodology is inadequate for studies on the microbicidal activity of neutrophils.
No full textMicrobicidal activity of neutrophils is usually measured by colony-counting techniques after cell lysis in distilled water. While studying the effect of the reduced nicotinamide adenine dinucleotide phosphate-oxidase inhibitor diphenyleneiodonium (DPI) on the staphylocidal activity of neutrophils, we obtained inconsistent results: various degrees of inhibition in some experiments and no effect in others. The lysis step, i.e., dilution of neutrophils in distilled water, was the source of error. Cell-associated microorganisms were not dispersed effectively by this treatment. We overcame this problem by using water at pH 11 for cell lysis. Under these conditions, killing was inhibited completely and reproducibly by DPI. Here, we show that cell lysis in distilled water is incomplete and leads to an overestimate of microbial killing. This hinders identification of partial defects and makes complete defects appear as partial. We found that DPI-treated neutrophils and chronic granulomatous disease neutrophils were completely defective in killing of Staphylococcus aureus and Candida albicans and partially defective in killing of Escherichia coli after lysis with water pH 11, whereas after lysis in distilled water, killing of S. aureus and C. albicans was approximately 60% and approximately 70% of control killing, respectively, and killing of E. coli was normal. Likewise, killing of S. aureus by myeloperoxidase-deficient neutrophils was severely impaired after lysis in water pH 11 but appeared normal after lysis in distilled water. As most studies about neutrophil microbicidal activity have been performed using distilled water, our findings indicate that previous data about killing defects and the effects of agents that modulate microbicidal activity of neutrophils should be re-evaluated
Effect of a standardized liver and spleen fraction of peptides on the differentiation of human monocyte derived macrophages.
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Differential biochemical properties of myeloperoxidase- hydrogen peroxide-halide system and eosinophil peroxidase-hydrogen peroxide-halide system
No full textHuman eosinophil peroxidase enhances TNF and hydrogen peroxide release by human monocyte-derived macrophages
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Effect of biological surfaces on neutrophil O2- production and its relationship to the CD11b/CD18 integrin-dependent adherence.
No full textThe production of O2- in response to LPS, PAF, FMLP, TNF and PMA by human neutrophils in suspension and residing on surfaces coated with fetal calf serum (FCS), fibronectin (FN), laminin (LM), collagen types I and IV (CI and CIV), fibrinogen (FBG) or fibrin (FBN) was studied. Of the agonists used, PAF and LPS failed to induce a response in any of the above conditions; FMLP and PMA stimulated neutrophils to produce similar amounts of O2- either in suspension or on biological surfaces; TNF induced O2- production only by cells residing on FN, FBG and FBN. These results indicate that production of oxygen-derived free radicals by neutrophils depends on the type of agonist and the nature of the surface they interact with. The relationship between the respiratory burst and adherence was studied by measuring O2- release and adherence of neutrophils residing on FN, LM, CIV, and FBG, in the absence and in the presence of the monoclonal antibody 60.3 that recognizes the common beta-chain of CD11/CD18 integrins. FMLP, PMA and TNF increased neutrophil adherence on all these surfaces except CIV. The monoclonal antibody markedly inhibited the FMLP and PMA-induced adherence but had no effect on the O2- release elicited by these two agonists. In contrast, the monoclonal antibody inhibited both the increased adherence and O2- release induced by TNF on FN and FBG. The TNF-induced increase in adherence to LM, that was not accompanied by an increase in O2- release, was also inhibited by the monoclonal antibody. We conclude that the respiratory burst of neutrophils residing on surfaces is not necessarily correlated with adherence
IMPATTO DI UN CORSO DI FORMAZIONE A DISTANZA SULLA SEGNALAZIONE SPONTANEA DI REAZIONI AVVERSE DA FARMACI
No full textObiettivo del lavoro: verificare l'eventuale impatto di un corso di formazione a distanza accreditato sul sistema della segnalazione spontanea di reazioni avverse da farmac
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