86,591 research outputs found
Induction of CD69 activation molecule on human neutrophils by GM-CSF, IFN-γ, and IFN-α
No full textThe CD69 glycoprotein is an early activation antigen of T and B lymphocytes but it expression is induced in vitro on cells of most hematopoietic lineages, including neutrophils after stimulation with PMA or fMLP. In this study, we investigated whether CD69 expression on human neutrophils could be modulated by inflammatory or anti-inflammatory cytokines (IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-18, G-CSF, GM-CSF, TNF-α, TGF-β, IFN-α, IFN-γ). Resting neutrophils from healthy subjects did not express CD69 on the cell surface; moreover, a preformed intracellular pool of CD69 was not evident in these cells. CD69 was barely detectable on these cells after overnight incubation in medium while overnight incubation with GM-CSF, IFN-γ or IFN-α significantly induced CD69 expression on neutrophils with GM-CSF appearing to be the most potent inducer. This induction was dependent on a new protein synthesis as it was significantly inhibited by cycloheximide (about 50% inhibition). CD69 cross-linking on GM-CSF-primed neutrophils sinergized with LPS and increased TNF-α production and secretion suggesting a role for CD69-positive neutrophils in the pathogenesis and maintenance of different inflammatory diseases
The effect of cytokines on human neutrophil Fc receptor-mediated phagocytosis
No full textThe recombinant (r) cytokines interferon-γ (rIFN-γ), granulocyte/macrophage-colony stimulating factor (rGM-CSF) and tumor necrosis factor-α (rTNF-α) all activate neutrophils. The aim of this work was to determine the effect of these cytokines on neutrophil Fc-receptor (FcR)-mediated phagocytosis and membrane expression of FcR, particularly FcRII and FcRIII. A short treatment (≥ 15 min) of neutrophils with rGM-CSF and rTNF-α at concentrations ≥ 62.5 U/ml significantly increased their ability to bind and phagocytize IgG-coated erythrocytes (EA). Both cytokines also showed more enhancing activity when suboptimally sensitized EA were used for binding and ingestion assays. A similar treatment of neutrophils with rIFN-γ at doses up to 500 U/ml was ineffective. The effect of rGM-CSF and rTNF-α was blocked by a monoclonal anti-GM-CSF antibody and by a polyclonal anti-TNF-α antibody respectively, thus establishing that the cytokines were responsible for the activity of the recombinant preparations. The cytokine-induced enhancement of FcR-mediated phagocytosis did not correlate with an enhancement of FcRII membrane expression on treated neutrophils; rGM-CSF significantly increased FcRIII expression, but rTNF-α and rIFN-γ were both ineffective in this respect. Since different roles of FcRII and FcRIII have been reported on ligand binding and ingestion, we also studied the effect of rGM-CSF and rTNF-α on the functional properties of these FcR, using specific monoclonal antibodies (mAbs). In the blocking experiments the pretreatment of neutrophils with rGM-CSF and rTNF-α did not modify the blocking properties of either anti-FcRII or anti-FcRIII mAbs, suggesting that cytokine-pretreatment does not affect the individual contribution of each type of FcR to ligand binding and internalization. Our data point to a new activity for both rGM-CSF and rTNF-α in augmenting FcR-mediated phagocytosis on neutrophils, but the mechanism of this enhancement remains to be elucidated
Effect of adalimumab on neutrophil function in patients with rheumatoid arthritis
No full textNeutrophils are known to be targets for the biological activity of tumour necrosis factor (TNF)- alpha in the pathogenensis of rheumatoid arthritis (RA). Therefore, these cells may be among the targets of anti-TNF- alpha therapy. In this study we evaluated the effect of therapy with adalimumab (a fully human anti-TNF- alpha mAb; dosage: 40 mg subcutaneously every other week) on certain phenotypic and functional aspects of neutrophils obtained from 10 selected patients with RA and 20 healthy control individuals. Peripheral blood neutrophils were obtained at baseline and during anti-TNF- alpha therapy (2, 6 and 12 weeks after the first administration of adalimumab). All patients had been receiving a stable regimen of hydroxychloroquine, methotrexate and prednisone for at least 3 months before and during the study. Baseline neutrophil chemotaxis was significantly decreased in RA patients when compared with control individuals (P < 0.001). Two weeks after the first administration of adalimumab, chemotactic activity was completely restored, with no differences noted between patients and control individuals; these normal values were confirmed 6 and 12 weeks after the start of anti-TNF- alpha therapy. Phagocytic activity and CD11b membrane expression on neutrophils were similar between RA patients and control individuals; no modifications were observed during TNF- alpha neutralization. The production of reactive oxygen species, both in resting and PMA (phorbol 12-myristate 13-acetate)-stimulated cells, was significantly higher in RA patients at baseline (P < 0.05) and was unmodified by anti-TNF- alpha mAb. Finally, we showed that the activation antigen CD69, which was absent on control neutrophils, was significantly expressed on neutrophils from RA patients at baseline (P < 0.001, versus control individuals); however, the molecule was barely detectable on cells obtained from RA patients during adalimumab therapy. Because CD69 potentially plays a role in the pathogenesis of arthritis, our findings suggest that neutrophils are among the targets of anti-TNF- alpha activity in RA and may provide an insight into a new and interesting mechanism of action of anti-TNF- alpha mAbs in the control of inflammatory arthritis
Development of phagocytic function of cultured human monocytes is regulated by cell surface IL-10.
No full textMonocytes differentiating in vitro into macrophages increase their capacity to ingest particles via FcγR and CR3. Because human recombinant IL- 10 is a potent up-regulator of phagocytosis in human monocytes, we investigated whether spontaneously produced IL-10 could be a signal for the modulation of phagocytosis by cultured monocytes. We show here that culture of monocytes in the presence of anti-IL-10 mAb completely abolished up- regulation of phagocytosis of both EIgG and EIgMC3bi, suggesting a role for spontaneously produced IL-10 in the modulation of phagocytosis by cultured human monocytes. The inhibition exerted by anti-IL-10 mAb on the development of FcyR-mediated ingestion was dependent on the concomitant inhibition of FcγRIII induction in cultured cells. On the other hand, a similar down- regulation of CR3 expression was not involved in the inhibitory effect exerted by anti-IL-10 mAb on the development of CR3-mediated ingestion. Monocytes secreted detectable levels of IL-10 when cultured in medium but the concentrations of IL-10 in the supernatants decreased with length of time in culture, the decrease being completely reversed by anti-IL-10 mAb. In addition, we showed that monocytes expressed immunoreactive IL-10 on their surface and this expression increased during differentiation into macrophages. Whether this IL-10 was bound to specific membrane receptors or it was an integral membrane protein remains to be determined; however, this latter possibility is consistent with our observations that IL-10 did not elute with acid treatment and exogenous IL-10 did not increase surface staining of monocytes. Our data indicate that human mononuclear phagocytes express IL-10 on their membrane and suggest that this cytokine may represent an autocrine signal for the increased phagocytic function observed during differentiation of monocytes into macrophages
T cell defect in essential mixed cryoglobulinaemia
No full textPeripheral blood lymphocytes from untreated patients with essential cryoglobulinaemia were studied for their surface markers and for their in vitro mitogenic reactivity. No differences in lymphocyte subpopulations were observed between cryoglobulinaemic patients and normal controls. Cultures of separated lymphocytes were stimulated with different concentrations of phytohaemagglutinin, Con-A and pokeweed mitogen. Incorporation of [3H]-thymidine in patients' cultures was compared with that of normal controls. Significantly decreased reactivity to phytohaemagglutinin and Con-A, but not to pokeweed mitogen, was found in all patients studied. The depressed mitogenic reactivity to phytohaemagglutinin and Con-A might be referred to a qualitative T cell defect
Increased expression of C3b and C3bi receptors on human neutrophils and monocytes induced by a glycoprotein extract from Klebsiella pneumoniae (RU41740)
No full textRU41740 is a glycoprotein extract from Klebsiella pneumoniae with immunomodulating properties under different experimental conditions. In particular the compound is able to stimulate several functions of human phagocytes in vitro and ex vivo. Using monoclonal antibodies and flow cytometry, in this work we assessed the effect of RU41740 on surface expression of receptors for C3b (CR1) and C3bi (CR3) in human phagocytic cells in vitro. The incubation of whole blood with varying RU41740 concentrations led to a dose-dependent increase in surface expression of CR1 and CR3 on both neutrophils and monocytes when compared with control samples incubated in buffer alone. The maximal drug-induced enhancement of complement receptors was: 291% ± 13.4% for CR1 and 265% ± 8.5% for CR3 in neutrophils; 117% ± 4.5% for CR1 and 98% ± 4.1% for CR3 in monocytes. These peak effects were observed using RU41740 at a final concentration of 10 μg/ml and were similar to those induced by optimal concentrations of the activating compound N-formyl-methionyl-leucyl-phenylalanine (10-7M). Polymyxin B did not modify the RU41740-induced enhancement of CR1 and CR3 expression on phagocytes, suggesting no role for endotoxin in this activity. These results define, at least in part, the mechanism of action of RU41740 on human phagocytes in vitro and could be relevant to in vivo events during RU41740 treatment
Membrane expression and function of complement receptors CR1 and CR3 on neutrophils from HIV-infected subjects: modulation by rTNF- and rGM-CSF.
No full textWe evaluated membrane expression and function of complement receptors CR1 and CR3 on neutrophils from 27 HIV-positive (HIV+) subjects (14 in the CDC class III and 13 class IV) as well as their modulation in vitro by recombinant tumour necrosis factor-α (rTNF-α) and granulocyte-macrophage colony stimulating factor (rGM-CSF). While CR1 was expressed at similar levels on neutrophils from controls and HIV+ subjects CR3 expression was significantly higher in CDC class IV subjects than in healthy controls, CR1 and CR3 expression was significantly increased after treatment of neutrophils with both cytokines, without differences between controls and HIV+ subjects. Similarly, the superoxide anion (O 2 -) production in response to C3-coated zymosan (C3zy) was significantly enhanced on neutrophils from CDC class IV subjects when compared with controls. rGM-CSF and rTNF-α treatment significantly enhanced the spontaneous as well as C3zy-stimulated O 2 - production by neutrophils from controls and CDC class III subjects, and induced an upward trend in the CDC class IV group. These results indicate that the neutrophils of HIV+ patients are preactivated in vivo but they also indicate that these cells may correctly respond to a subsequent particulate stimulus as well as to activating cytokines. Our findings suggest that desensitization or functional exhaustion of complement receptors are not implicated in the abnormalities observed on neutrophils from HIV+ patient
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