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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The PTPase YopH of Yersinia is essential to the ability of these bacteria to block phagocytosis. Wild-type Yersinia pseudotuberculosis, but not the yopH mutant strain, resisted phagocytosis by J774 cells. Ingestion of a yopH mutant was dependent on tyrosine kinase activity. Transcomplementation with wild-type yopH restored the anti-phagocytic effect, whereas introduction of the gene encoding the catalytically inactive yopHC403A was without effect. The PTPase inhibitor orthovanadate impaired the anti-phagocytic effect of the wild-type strain, further demonstrating the importance of bacteria-derived PTPase activity for this event. The ability to resist phagocytosis indicates that the effect of the bacterium is immediately exerted when it becomes associated with the phagocyte. Within 30 s after the onset of infection, wild-type Y. pseudotuberculosis caused a YopH-dependent dephosphorylation of phosphotyrosine proteins in J774 cells. Furthermore, interaction of the cells with phagocytosable strains led to a rapid and transient increase in tyrosine phosphorylation of paxillin and some other proteins, an event dependent on the presence of the bacterial surface-located protein invasin. Co-infection with the phagocytosable strain and the wild-type strain abolished the induction of tyrosine phosphorylation. Taken together, the present findings demonstrate an immediate YopH-mediated dephosphorylation of macrophage phosphotyrosine proteins, suggesting that this PTPase acts by preventing early phagocytosis-linked signalling in the phagocyte.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-4935
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Rat peritoneal mast cells in vitro released [3H]-serotonin in the presence of halide (I-), myeloperoxidase (MPO), and a H2O2-generating system. The degranulation was partly inhibited with low concentrations of bovine serum albumin (BSA; 0.1–l% w/v), or polyethyleneglycols (PEG 600 or PEG 6000, 0.1% w/v). Furthermore, PEG 600 and PEG 6000 enhanced the stabilization achieved with 0.1% BSA. The results may provide a new aspect on antigenicity of PEG-modified allergens, and on mast-cell response at an inflammatory site.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-4986
    Keywords: HL 60 and U 937 cells ; phagocytosis ; IgG ; complement ; glycolipid ; liposome binding ; fluorescence microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Increased ability to recognize carbohydrate structures on particles was observed in promyelocytic HL 60 cells and histiocytic U 937 cells during differentiation inducedin vitro with dimethylsulfoxide (DMSO) or phorbol myristate acetate (PMA). The size of the cells and increased capacity to bind and ingest IgG-or complement-coated yeast particles were used as indicators of phagocytic maturation. Carbohydrate affinities were assessed by the binding of glycolipid-containing liposomes displaying mannose, galactose, lactose,N-acetylgalactosamine, fucose, inositol, or ganglioside residues. With DMSO, HL 60 cells showed greater affinity for mannose and ganglioside residues, and with PMA also for fucosyl ligands. U 937 cells displayed a slightly different pattern; mannose binding was present before induction and by DMSO affinity was clearly augmented for galactose, fucose, ganglioside and inositol residues. With PMA these effects were smaller except for increased binding of lactosyl liposomes. Subclones of cells derived from U 937 (Cl 1, Cl 2 and Cl 3) appeared more mature already in the absence of inducing agent, and the lectin activity was barely affected by DMSO or PMA. Incidentally, Cl 1 lacked mannose affinity, which was fully expressed in Cl 2. With respect to inositol and ganglioside residues the reverse pattern was observed. In conclusion, DMSO- or PMA-mediated maturation in HL 60 and U 937 cells is accompanied by increased carbohydrate binding similar to what has been found in mature macrophages and granulocytes, indicating that these cellular systems can be used for further assessment of the molecular origin of lectin-like membrane components in phagocytic cells.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-4986
    Keywords: HL60 and U937 cells ; phagocytosis ; lectin binding ; microfluorometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The display of carbohydrate structures was measured in promyelocytic HL60 cells and in histiocytic U937 cells induced to differentiate to phagocytic cellsin vitro during three to seven days of cultivation in the presence of dimethylsulfoxide (DMSO). It was assessed by micro-or spectrofluorometric quantification of the binding of fluorescent lectins. Changes in the cell size and the association and uptake of IgG-or complementopsonized yeast cells (Saccharomyces cerevisiae) were used as signs of phagocyte differentiation. The binding of wheat germ agglutinin (WGA), concanavalin A (Con A),Ricinus communis agglutinin-I (RCA-I) andUlex europaeus agglutinin-I (UEA-I) varied due to the presence of DMSO during cultivation, and without DMSO also on the number of days in culture and the type of cell.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-2576
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Surface property changes of polymorphonuclear leukocytes (PMNL) as a result of development of functional receptors to f-Met-Leu-Phe and as a result of f-Met-Leu-Phe binding have been studied by aqueous biphasic partitioning of the cells in systems of dextran and polyethylene glycol (PEG) with part of the PEG exchanged for positively charged or hydrophobic PEG. The results indicated that the development of functional receptors for f-Met-Leu-Phe was associated with increased exposure of hydrophobic surface structures as well as of negatively charged groups on the PMNL surface. Binding of f-Met-Leu-Phe to the PMNL surface receptors caused hiding of hydrophobic and charged structures, indicating that these properties are of importance in the interaction between PMNL and the chemotactic peptide.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-2576
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A decreased expression of the β2-integrin CD11b molecules on peripheral neutrophils from patients with pustular psoriasis occurred during treatment with retinoid compounds. Since this effect could not be mimicked in vitro with isolated peripheral neutrophils, the effect of retinoid compounds on cell differentiation was investigated. The promyelocytic cell line, HL60, was used to study what effect different retinoid compounds had on the cell surface expression of CD11b and L-selectin (CD62L) molecules, complement-mediated phagocytosis, adhesion and the oxidative burst. Retinoid-differentiated cells showed a significantly lower expression of CD11b and CD62L, and a decreased phagocytosis and oxidative burst compared to DMSO-differentiated HL60 cells or peripheral blood neutrophils. The diminished expression of β2-integrins or L-selectin did not affect their adhesion to non-activated or lipopolysaccharide-activated endothelial cells in vitro but may however affect adhesion to vascular endothelium under shear forces during blood flow. These results suggest that retinoid treatment could affect several early steps in the inflammatory process.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-2576
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Integrin receptors on human neutrophils mediate adhesion and phagocytosis. These functions are linked to a signal-transduction cascade that rearranges the cytoskeleton. The intention of this study was to clarify how activation of phospholipase D (PLD) is coupled to the complement receptor three (CR3, CD18/CD11b)mediated ingestion process. Carbobenzyloxy-leucine-tyrosine-chloromethylketone (zLYCK) inhibited PLD activation induced by complement-opsonized yeast particles (COYP) by 39%. Phagocytosis of these particles was reduced by zLYCK to the same extent. Anti-CD18-antibodies bound to protein A-positiveStaphylococcus aureus bacteria induced a significant PLD activation. These particles were not ingested which implicates that CR-mediated ingestion per se is not required to induce PLD activity. Cytochalasin B-treatment, which blocks actin reorganization, partly reduced COYP-mediated PLD activity, but had no effect on activity caused by anti-CD 18-coated particles. This excludes activation of PLD to be a secondary event, but rather an early signal in the phagocytic uptake prior to actin reorganization. These data suggest an important and early role for PLD in integrin-mediated phagocytosis.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-2576
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The ability to respond metabolically to stimulation with both soluble and paniculate substances was investigated in human polymorphonuclear leukocytes (PMNLs) isolated from an aseptic inflammatory reaction. Exudate PMNLs isolated from skin chambers (E-PMNLs) and blood PMNLs isolated from the peripheral blood (B-PMNLs) of the same individual were investigated in parallel. E-PMNLs were primed, resulting in an increased chemiluminescence (CL) response to subsequent stimulation with the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (FMLP) (334%) and serum-opsonized yeast particles (C3 yeast) (201%), as compared to B-PMNLs. Phorbol myristate acetate (PMA) on the other hand, induced a CL response in E-PMNLs that was only 70% of the response obtained in B-PMNLs. A similar primed state resulting in enhancement of the CL response to FMLP and C3 yeast could be induced in B-PMNLs by pretreatment with a bacterial culture filtrate. Pretreatment of E-PMNLs with the bacterial culture filtrate, however, did not increase the CL response to FMLPs any further. The enhanced functional response to FMLPs in E-PMNLs was accompanied by an increased binding of the peptide, demonstrated by a doubling of the amount of bound f-Met-Leu-[3H]Phe (209%), as compared to B-PMNLs. The increased C3-yeast-induced CL generation in E-PMNLs was accompanied by an increased ingestion and attachment of C3-opsonized yeast particles. The enhancement of phagocytosis in E-PMNLs was, however, dependent upon the opsonin used, since IgG-opsonized yeast particles were phagocytosed to the same extent by E-PMNLs and B-PMNLs, thereby indicating that selective receptor modulation is also involved in the priming of E-PMNLs for an enhanced response to C3-yeast. These results show that exudate cells isolated from skin chambers are modulated with respect to receptor-mediated functions resulting in an increased metabolic response to FMLP coupled with an increased binding of the peptide and an increased phagocytosis of C3-coated yeast particles. Receptor modulation during exudation may be an important mechanism in regulating the inflammatory response by PMNLs.
    Type of Medium: Electronic Resource
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