Granulocyte-macrophage colony-stimulating factor, interleukin-3 (IL-3), and IL-5 greatly enhance the interaction of human eosinophils with opsonized particles by changing the affinity of complement receptor type 3

Abstract Eosinophil functions can be modulated by several cytokines such as granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin- 3 (IL-3), and IL-5. We have investigated the modulatory role of these cytokines on the interaction of human eosinophils with opsonized particles (serum-treated zymosan [STZ]). Addition of STZ to eosinophils isolated from the peripheral blood of normal human donors resulted in an interaction of the STZ particles with only 15% to 25% of the cells. Treatment of the eosinophils with GM-CSF, IL-3, or IL-5 strongly enhanced both the rate of particle binding and the percentage of eosinophils binding STZ. The effect of the cytokines is most likely mediated by a change in affinity of the complement receptor type 3 (CR3) on the eosinophils for the complement fragment iC3b on the STZ particles. This is indicated by the observation that (1) the effect of the cytokines on STZ binding was prevented by a monoclonal antibody against the iC3b-binding site on CR3 and (2) the enhanced binding was already apparent before upregulation of CR3 on the cell surface was observed. In a previous study, similar results were obtained with platelet-activating factor (PAF)-primed eosinophils. Because we found that the cytokines strongly enhanced the STZ-induced PAF synthesis, we investigated the role of both released PAF and cell-associated PAF in the priming phenomenon by the cytokines. Cytokine priming appeared to be largely independent of the synthesis of PAF.</jats:p

Release of platelet-activating factor is important for the respiratory burst induced in human eosinophils by opsonized particles

Abstract The respiratory burst induced in human eosinophils by serum-treated zymosan (STZ) was found to be almost completely prevented by preincubation of the cells with WEB 2086, an antagonist of platelet- activating factor (PAF). When eosinophils were primed by the addition of 1 mumol/L PAF, subsequent addition of WEB 2086 had only a minor effect on the STZ-induced respiratory burst. These results suggest a role for PAF synthesis and PAF release in the activation of the respiratory burst by STZ. Indeed, supernatant of STZ-stimulated eosinophils was able to prime fresh eosinophils (as did PAF itself), and this effect was again inhibited by WEB 2086. This indicates that eosinophils synthesize and release PAF during STZ stimulation. Measurements of total PAF and PAF release showed that most of the PAF synthesized by eosinophils was released in the extracellular medium. This study shows that synthesis and release of PAF is important for respiratory burst activity induced in human eosinophils by STZ.</jats:p

Release of platelet-activating factor is important for the respiratory burst induced in human eosinophils by opsonized particles

The respiratory burst induced in human eosinophils by serum-treated zymosan (STZ) was found to be almost completely prevented by preincubation of the cells with WEB 2086, an antagonist of platelet- activating factor (PAF). When eosinophils were primed by the addition of 1 mumol/L PAF, subsequent addition of WEB 2086 had only a minor effect on the STZ-induced respiratory burst. These results suggest a role for PAF synthesis and PAF release in the activation of the respiratory burst by STZ. Indeed, supernatant of STZ-stimulated eosinophils was able to prime fresh eosinophils (as did PAF itself), and this effect was again inhibited by WEB 2086. This indicates that eosinophils synthesize and release PAF during STZ stimulation. Measurements of total PAF and PAF release showed that most of the PAF synthesized by eosinophils was released in the extracellular medium. This study shows that synthesis and release of PAF is important for respiratory burst activity induced in human eosinophils by STZ.</jats:p

Membrane surface antigen expression on neutrophils: a reappraisal of the use of surface markers for neutrophil activation

Neutrophil research relies largely on studies with highly purified cells. Yet the isolation procedures induce changes in surface expression of several proteins. We used a large panel of monoclonal antibodies (MoAbs) to characterize in detail the phenotypic changes during isolation and stimulation of human neutrophils. Centrifugation on density gradients appears to be the crucial step that causes an increase in expression of antigens not detectable on neutrophils in whole blood samples (cytochrome b558 recognized by MoAb 7D5; and CD10) or expressed at significantly lower levels (CD11a, CD11b, CD11c, CD13, CD16, CD45, and CD67). Other antigens were unaffected by the density gradient centrifugation step (CD32, CD54, CD58, Leu-8, HLA class I). Upregulation of antigens was also determined by stimulation of purified neutrophils. Upregulation of CD63 was an excellent marker for release from azurophil granules. We subsequently related the surface antigen expression to functional activities of purified neutrophils. From these experiments, we concluded that 7D5-as “early activation” marker--does not necessarily discriminate between primed or resting neutrophils with respect to NADPH oxidase activity.</jats:p

Membrane surface antigen expression on neutrophils: a reappraisal of the use of surface markers for neutrophil activation

Abstract Neutrophil research relies largely on studies with highly purified cells. Yet the isolation procedures induce changes in surface expression of several proteins. We used a large panel of monoclonal antibodies (MoAbs) to characterize in detail the phenotypic changes during isolation and stimulation of human neutrophils. Centrifugation on density gradients appears to be the crucial step that causes an increase in expression of antigens not detectable on neutrophils in whole blood samples (cytochrome b558 recognized by MoAb 7D5; and CD10) or expressed at significantly lower levels (CD11a, CD11b, CD11c, CD13, CD16, CD45, and CD67). Other antigens were unaffected by the density gradient centrifugation step (CD32, CD54, CD58, Leu-8, HLA class I). Upregulation of antigens was also determined by stimulation of purified neutrophils. Upregulation of CD63 was an excellent marker for release from azurophil granules. We subsequently related the surface antigen expression to functional activities of purified neutrophils. From these experiments, we concluded that 7D5-as “early activation” marker--does not necessarily discriminate between primed or resting neutrophils with respect to NADPH oxidase activity.</jats:p

Activation of human neutrophils by oleic acid involves the production of reactive oxygen species and a rise in cytosolic calcium concentration: a comparison with N-6 polyunsaturated fatty acids

Contains fulltext : 95617.pdf (publisher's version ) (Open Access)BACKGROUND: There is a growing body of evidence showing that dietary constituents and lipids in particular, influence the function of the human immune system. However, although the beneficial effects of oleic acid (OA) are clear, its mechanism of action at the molecular level is poorly understood. AIMS: To evaluate neutrophil activation under the influence of OA and compare this with several n-6 PUFAs. METHODS: Two key aspects of neutrophil activation were investigated: oxygen radical (ROS) production and intracellular Ca(2+) signaling. RESULTS: OA and the n-6 PUFA arachidonic acid (AA) both induced ROS production in a dose-dependent manner, although AA was the more potent stimulus. When looking for the mechanisms behind these effects, we found that both FA induce increases in cytosolic calcium concentration [Ca(2+)](i)), but whereas OA-induced ROS production is totally mediated through Ca2+ signaling, this is not the case for AA since ROS generation by AA is only partly inhibited in BAPTA-treated cells. We also found evidence for the involvement of protein kinase C (PKC) in the OA-induced ROS generation; by contrast, other enzymes apart from PKC seem to be implicated in n-6 PUFA-induced ROS production. In addition, our results argue against the involvement of a pertussis toxin-sensitive receptor activated by OA. CONCLUSIONS: OA differs from the n-6 PUFA AA in the activation of human neutrophils and these differences may be related to their distinct inmunomodulatory properties

Dénoncer le lobbying pour dénoncer l'Europe sur Twitter? Lobbying et transparence dans les discours des candidats à l'élection européenne

Cette proposition s’inscrit dans l’axe 3 sur la production du discours des candidats à l’élection européenne. Dans la suite de notre recherche sur la construction des identités discursives des candidats à l’élection européenne (conduite dans le cadre du projet TEE2014), nous souhaitons explorer une dimension spécifique du discours politique des candidats sur Twitter : la manière dont ceux-ci parlent du fonctionnement des institutions européennes à travers la question du lobbying et de la transparence. Pour ce faire, nous prenons comme point de départ les discussions autour de TAFTA (Traité Nord-Atlantique de Libre Echange) accusées par certains d’opacité et d’illégitimité démocratique (Gadrey, 2014). La question du lobbying est particulièrement prégnante dans l’espace politique européen du fait notamment de la place importante des groupes d’intérêt dans le fonctionnement institutionnel de l’UE (Saurugger, 2003). Devant le nombre de lobbyistes évoluant au sein de « la bulle européenne », leur rôle dans les négociations politiques et leur puissance économique, des revendications en terme d’encadrement et de transparence des procédures de lobbying ont émergé, portées par des associations du type « Alter-EU » ou « Corporate Europe Observatory », mais également par un certain nombre d’acteurs politiques européens. Qu’en est-il des candidats en campagne ? Sur la base d’un corpus de tweets collectés d’octobre 2013 à juin 2014, nous proposons une analyse à la fois discursive et communicationnelle des messages des candidats à l’élection européenne qui comportent une référence à la problématique du lobbying et de la transparence. Notre approche est comparative, puisque nous nous intéressons aux candidats belges, britanniques, espagnols et français pour tenter de comprendre comment le discours sur le lobbying traverse les frontières. Au vu de l’importance des concepts de lobbying et transparence dans le cadre d’un discours plus général sur l’Europe, nous analysons également les messages des candidats pour le poste de président de la Commission européenne ainsi que les messages publiés sur les comptes des groupes politiques. Ceci nous permet de montrer si et comment les groupes politiques participent aux discussions d’une manière distincte des candidats individuels. Nous formulons l’hypothèse que le discours sur le lobbying s’accompagne généralement d’une remise en cause plus globale du fonctionnement des institutions, voire de l’UE en tant que telle. En effet, dans un contexte institutionnel européen dans lequel la « rhétorique du déficit communicationnel » (Aldrin, 2009) et celle du « déficit démocratique » (Meyer, 1999 ; Spanier, 2012 ; etc.) sont prégnantes, nous voudrions voir comment l'idéal démocratique est mobilisé par les candidats à l’élection européenne. Cette interrogation nous semble d’un intérêt particulier puisque les discours étudiés sont diffusés sur un dispositif socionumérique lui-même souvent célébré pour ses vertus démocratiques et participatives (voir par exemple Vergeer, 2012). Comment les candidats se l’approprient-ils pour aborder la question du lobbying et du fonctionnement des institutions européennes? Leur discours est-il de nature plutôt informative, dénonciative ou mobilisatrice ? Une telle approche invite à interroger la présence ou non des publics, souvent imaginés (Marwick & boyd, 2010 ; Litt, 2012) dans les messages: nous posons en effet l’hypothèse que ces messages visent davantage des publics acquis (sympathisants, militants) que des publics profanes. Nous prenons bien sûr en compte les spécificités d’un dispositif médiatique comme Twitter, que nous présentons en amont de l’analyse. Nous montrons ainsi comment le discours sur la transparence et le lobbying se construit sur le dispositif Twitter dans le contexte spécifique des élections européennes