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Phagocyte NADPH oxidase: a multicomponent enzyme essential for host defenses

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El-Benna J., Dang P. M.-C., Gougerot-Pocidalo A.-M., Elbim C.
Archivum Immunologiae et Therapiae Experimentalis
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2005
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vol. 53
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issue 3
199-206
EN
Phagocytes such as neutrophils and monocytes play an essential role in host defenses against microbial pathogens. Reactive oxygen species (ROS), such as superoxide anion, hydrogen peroxide, the hydroxyl radical, and hypochlorous acid, together with microbicidal peptides and proteases, constitute their antimicrobial arsenal. The enzyme responsible for superoxide anion production and, consequently, ROS generation, is called NADPH oxidase or respiratory burst oxidase. This multicomponent enzyme system is composed of cytosolic proteins (p47phox, p67phox, p40phox, and rac1/2) and membrane proteins (p22phox and gp91phox, which form cytochrome b558) which assemble at membrane sites upon cell activation. The importance of this enzyme in host defenses is illustrated by a life-threatening genetic disorder called chronic granulomatous disease in which the phagocyte enzyme is dysfunctional, leading to life-threatening bacterial and fungal infections. Also, because ROS can damage surrounding tissues, their production, and thus NADPH oxidase activation, must be tightly regulated. This review describes the structure and activation of the neutrophil NADPH enzyme complex.
2

Mannose-binding lectin enhances the attachment and phagocytosis of mycobacteria in vitro

100%
Bonar A., Chmiela M., Rudnicka W., Rozalska B.
Archivum Immunologiae et Therapiae Experimentalis
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2005
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vol. 53
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issue 5
437-441
EN
Phagocytosis is the critical first step in the Mycobacterium (M.) tuberculosis-phagocyte interaction. The process involves microbial ligands and phagocyte surface receptors. It is known that serum mannose-binding lectin (MBL), an innate immune system component, may enhance the uptake of microbes by phagocytic cells and activate the complement system. Since phagocytes are the replicative environment for mycobacteria and, as we described earlier, tuberculosis patients differ from controls in serum MBL level, we asked whether MBL plays a role in promoting M. tuberculosis access to phagocytic cells. To estimate the influence of MBL on the phagocytic process, FITC-labeled Mycobacterium bovis BCG was used as a model bacterium. Neutrophils from healthy individuals were used as phagocytes. Phagocytosis was performed in the presence or absence of recombinant MBL (rMBL; 2 or 20 g/ml). The activation of complement was determined by dot-blot immune assay with monoclonal antibodies against C5b-C9. We showed that phagocytosis of the bacteria was more intensive in the presence of human rMBL. Both attachment and ingestion of mycobacteria were enhanced when MBL and active complement components (fresh serum) were present in the medium. The dot-blot method showed that the bacteria slightly activated complement by themselves. This effect was enhanced in the phagocyte-bacteria co-cultures containing rMBL.It is possible that MBL may serve in vivo as one of the factors facilitating the entry of mycobacteria into phagocytes, pathogen spread, and the establishment of infection.
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