UNIPROT:P43026 - FACTA Search

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Query: UNIPROT:P43026 (lipopolysaccharide)
62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Interleukin-1 (IL-1) and other monocyte products have several important effects on the systemic response to infection in addition to their roles in lymphocyte stimulation. The present studies were carried out to determine whether products of stimulated monocytes activated circulating neutrophils (PMN) to increase expression of receptors for C3b (CR1) and C3bi (CR3), which are necessary for optimal margination, migration, and phagocytosis. Supernatants of human mononuclear cells that had been stimulated with lipopolysaccharide (LPS) or purified protein derivative (PPD) contained both tumor necrosis factor (TNF) and IL-1 and increased CR1 and CR3 expression on isolated PMNs. Supernatants of unstimulated cultures, media alone, or LPS or PPD alone had little or no effect. Supernatant effects were detectable at 1:3,000 final dilution and appeared to have a characteristic slow time course. These supernatants also caused dose- and time-dependent secretion of PMN granular constituents, but maximal receptor expression was accompanied by secretion of less than 10% of the cells' content of lysozyme and less than 16% of the B12 binding protein. Immunoadsorption studies showed that the supernatant's activity could be removed by anti-TNF but not by anti-IL-1. Recombinant IL-1 had no effect on receptor expression, but recombinant TNF increased CR1 and CR3 expression with kinetics similar to the supernatants. These results thus indicate that TNF is the major monocyte product that increases CR1 and CR3 expression on mature blood neutrophils. This would result in increased margination and phagocytic activity and may be an important systemic effect that would help the host eradicate infection.
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PMID:Tumor necrosis factor is the major monocyte product that increases complement receptor expression on mature human neutrophils. 296 77

Treatment of patients with septic shock using monoclonal antibodies (mAbs) to endotoxin is still controversial. Clinical trials of E5, one of the mAbs directed against the lipid A moiety of lipopolysaccharide (LPS), are currently in progress. The mechanisms of action of this, and other antibodies under clinical evaluation, are, however, poorly understood. In this study we examined in vitro the ways in which E5 interacted with Gram-negative bacteria, complement, erythrocytes and monocytes. By fluorescence-activated cell sorter (FACS) analysis we showed direct, dose-dependent binding of E5 to Escherichia coli (E. coli) and Salmonella minnesota (S. minnesota). Antibody binding to S. minnesota was enhanced by treatment with the beta-lactam antibiotic amoxycillin, but not by treatment with the aminoglycoside gentamicin. Immune complexes formed between E5 and both species of Gram-negative bacteria activated both classical and alternative complement pathways, but only in the case of S. minnesota did this facilitate binding to erythrocyte CR1 and monocyte CR3. Bacterial C3b and iC3b fixation by E5 was quantified using specific mAbs. These observations suggest that E5 may enhance bacterial clearance in several ways: (1) by facilitating direct complement fixation; (2) by facilitating the binding of opsonized bacteria to cells of the mononuclear phagocyte system; (3) by enabling bacteria to bind to erythrocyte CR1 (CD35), allowing safe carriage in the circulation to the fixed macrophages of the liver and spleen; (4) by acting synergistically with beta-lactam antibiotics.
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PMID:The anti-lipid A monoclonal antibody E5 binds to rough gram-negative bacteria, fixes C3, and facilitates binding of bacterial immune complexes to both erythrocytes and monocytes. 779 40

The soluble form of complement receptor type 1 in human plasma (sCR1) might correspond to the shedding of the receptor by proteolytic cleavage at the cell surface. A new enzyme-linked immunosorbent assay (ELISA) was established to specifically measure membrane-bound CR1 using a rabbit polyclonal antibody against a 19-amino acid peptide corresponding to the C-terminal sequence of the intracellular domain of CR1 (mCR1-ELISA). This ELISA measured CR1 from solubilized erythrocyte membranes, polymorphonuclear leukocytes (PMN), a B lymphocyte cell line and renal podocyte-derived urinary vesicles in a dose-dependent manner. In contrast, and similarly to recombinant soluble CR1 which lacks the intracellular domain of CR1, plasmatic sCR1 was not recognized, suggesting that sCR1 corresponds to an extracellular fragment of whole CR1. In vitro, PMN were shown to release a soluble form of CR1 which was also not recognized in the mCR1-ELISA, and whose size was smaller (5 kDa) than the CR1 of PMN cell membranes. The release of soluble CR1 was highest for PMN and HL60 cells, followed by U937 cells and three different B lymphocyte cell lines, whereas T lymphocyte cell lines did not release soluble CR1. The levels of CR1 gene expression were also higher in PMN compared to remaining blood leukocytes and the different cell lines tested above. Incubation of PMN with formyl-methionyl-leucyl-phenylalanine, tumor necrosis factor-alpha or lipopolysaccharide accelerated the release of soluble CR1, and incubation with granulocyte/macrophage colony-stimulating factor resulted in sustained CR1 gene expression and higher total soluble CR1 release. Our results suggest that soluble CR1 is produced by cleavage of cell surface CR1, and that a large fraction of human plasma sCR1 is cleaved from PMN. The release of sCR1 by leukocytes may play a role in the control of complement activation at sites of inflammation.
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PMID:Soluble complement receptor type 1 (CD35) is released from leukocytes by surface cleavage. 795 65

Several functions of polymorphonuclear cells (PMNs) require adhesion to occur. Various membrane proteins' functions such as CD18 (beta 2 chain of integrin), CD35 (CR1) and CD16 (F c gamma Receptor III) participate in adhesion. In vivo treatment with Ribomunyl (R), an immunomodulating agent, was shown to enhance adhesion and migration of PMNs. To explore the direct effect of R on PMNs, cells from healthy subjects were treated in vitro with R. A significant increase of PMN adhesion and expression of CD18 and CD35 molecules were observed with 50 and 100 micrograms/ml of R after 2 h incubation. However, R-treatment decreased the PMN reactivity towards anti-CD16 (F c gamma RIII) monoclonal antibody. The effect of R on adhesion and membrane molecule expression was independent of the presence of serum and of polymixin B. Thus, this effect cannot be due to lipopolysaccharide (LPS) contaminants and does not require interactions with serum components. In previous studies, it was shown that in vitro amoxicillin increased some PMN functions whereas josamycin decreased them. The in vitro incubation of PMNs with R and amoxicillin (100 micrograms/ml) potentiated the positive effect of amoxicillin on adhesion and the antibiotic counterbalanced the negative effect of R on CD16 expression. In addition, R compensated the negative effect of josamycin (100 micrograms/ml) on PMN adhesion and on CD18 and CD35 expression. This study indicates: (1) the direct effect of R on PMN adhesion and on expression of molecules involved in adhesive-mediated functions, and (2) the beneficial effect of the association of R with antibiotics which can stimulate PMN activity.
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PMID:In vitro stimulation of polymorphonuclear cell adhesion by ribomunyl and antibiotic + ribomunyl combinations: effects on CD18, CD35 and CD16 expression. 809 33

HA-1A is a human monoclonal IgM antibody which recognizes the lipid A component of lipopolysaccharide (LPS). This antibody has reduced mortality in the septic shock syndrome resulting from Gram negative bacteria, in which many of the manifestations are considered to be due to cellular activation and secretion of cytokines, most notably TNF-alpha. However HA-1A does not directly neutralize LPS effectively in vitro, and studies reported to date have not defined its mechanism of action. Here we demonstrate that HA-1A, which in the presence of complement promotes immune adherence, may inhibit LPS action by facilitating its sequestration on red blood cells and clearance to an extent that cytokine production is reduced. Incubation of LPS at clinically significant (pg/ml) does with HA-1A at therapeutic levels (e.g. 10 micrograms/ml) and complement resulted in LPS association with erythrocyte CR1 receptors. This reduced the ability of the residual, free LPS by 50-70% to induce the secretion of TNF-alpha, IL-1 beta and IL-6 from normal blood mononuclear cells. This mechanism is likely to be operative in vivo, and could account for the protective effect of HA-1A, and its reduction of TNF-alpha production in vivo.
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PMID:Antilipid a monoclonal antibody HA-1A: immune complex clearance of endotoxin reduces TNF-alpha, IL-1 beta and IL-6 production. 826 Jun 1

HA-1A has been shown clinically to decrease mortality in septic patients with gram-negative bacteremia. In this study, the ability of HA-1A to augment the serum complement-dependent immune adherence of 125I-labeled Escherichia coli J5 lipopolysaccharide (LPS) to human erythrocytes (RBC) and polymorphonuclear leukocytes (PMNL) was evaluated. In vitro studies indicated three things: HA-1A mediates immune adherence of 125I-J5 LPS to human RBC and PMNL in a dose-dependent manner; under these conditions, high concentrations of LPS (400 ng/mL) could be specifically bound. Immune adherence occurs via the classical complement pathway as demonstrated by its calcium dependence; HA-1A-J5 LPS-C' immune complexes bound to CR1 on human RBC and PMNL. PMNL binding and internalization of immune complexes was demonstrated by trypsin stripping of externally bound immune complexes. These studies support the proposal that HA-1A can lower the bioavailability of endotoxin by mediating binding and potential clearance of LPS via human RBC through the reticuloendothelial system or via direct internalization by peripheral blood PMNL.
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PMID:Human anti-endotoxin antibody HA-1A mediates complement-dependent binding of Escherichia coli J5 lipopolysaccharide to complement receptor type 1 of human erythrocytes and neutrophils. 845 Feb 52

MoAbs to bacterial cell wall lipopolysaccharide are currently under evaluation for the treatment of Gram-negative sepsis. The mode of action of these reagents remains poorly understood. In this study we examined the ability of radiolabelled HA-1A (an IgM anti-lipid A MoAb) to bind in vitro to Salmonella minnesota (Re 595), Escherichia coli, and Streptococcus pyogenes. HA-1A was able to bind specifically to the 'rough' mutant Salm. minnesota, but not to a 'smooth' E. coli, or Strep. pyogenes. Binding to Salm. minnesota led to complement fixation which resulted in bacterial adherence to erythrocyte CR1, suggesting a possible mechanism whereby the antibody might enhance clearance of bacteria by facilitating delivery to the fixed mononuclear phagocytic system. We were not able to demonstrate the formation of immune complexes between free lipopolysaccharide and HA-1A in the presence of serum, nor the enhancement of complement-mediated binding of HA-1A:Salm. minnesota immune complexes to erythrocytes by antibiotic treatment. Binding of HA-1A to small bacterial fragments was, however, demonstrable after in vitro treatment with a beta-lactam antibiotic, which disrupts the bacterial cell wall, but not with gentamicin, an aminoglycoside antibiotic which blocks protein synthesis.
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PMID:The anti-lipid A antibody HA-1A binds to rough gram-negative bacteria, fixes complement and facilitates binding to erythrocyte CR1 (CD35). 848 8

A rapid (30 min) whole blood assay for the detection of lipopolysaccharide (LPS) is described. This chemiluminescent (CL) assay utilizes the CR1 and CR3 receptor-induced oxidant production of polymorphonuclear leucocytes as a detection platform. The differential priming of neutrophils in whole blood by LPS-antibody complexes allows the specificity of the assay to be achieved. Oxidant released in response to complement opsonized zymosan results in luminol oxidation and subsequent light emission. This is dependent on heat labile putative complement proteins in the plasma. The assay consists of a control which measures baseline whole blood neutrophil oxidant production. The test assay contains murine monoclonal IgM antibody against the Lipid A epitope of LPS and measures the enhanced chemiluminescent response of the neutrophils in the presence of LPS-antibody complexes. Maximal sensitivity of the CL assay is dependent upon optimal antigen-antibody equivalence and duration of pre-incubation with the whole blood sample. The quantification of LPS is possible by inclusion of a positive control containing a maximally reactive LPS dose (800 pg/ml Escherichia coli 055:B5 LPS at an antibody concentration of 0.8 microg/assay). The CL assay is insensitive to variations in patient neutrophil concentration over a minimum range of 0.5 to 20 x 10(9) cells/l. The CL assay is widely reactive with the LPS of many strains of gram negative bacteria but not with the cell wall products of gram positive bacteria or Candida and Aspergillus. In comparison to acid extraction chromogenic LAL, the CL assay demonstrates superior recovery precision and accuracy in in vitro studies. This was reproducible over a wide range of LPS concentrations (0.017-1.6 EU/ml or 20-2000 pg/ml). This assay may be a clinically useful tool for the diagnosis of infection or endotoxin in patients.
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PMID:A rapid assay of endotoxin in whole blood using autologous neutrophil dependent chemiluminescence. 967 5

Expression of membrane-bound CX3CL1, a CX(3)C chemokine, can be strongly induced by inflammatory cytokines in primary endothelial cells, mediating capture and tight adhesion of cells, such as monocytes, that carry the CX(3)CR1 receptor. Here, we measured CX3CL1 mRNA and protein induction by human aortic smooth muscle cells (SMCs), another major component of vessel walls, in response to inflammatory stimuli, and analyzed the effect of membrane-bound CX3CL1 on monocyte adhesion, tissue factor (TF) expression, and tumor necrosis factor-alpha (TNF-alpha) released. In human vascular SMCs, CX3CL1 transcripts were induced after 4h of stimulation with a combination of TNF-alpha and interferon-gamma. Cell-associated and shedded CX3CL1 were measured with a specific ELISA, showing that only 30% of the protein was cleaved from the membrane. Expression of CX3CL1 by SMC increased adhesion of monocytic cells, an effect, which was blocked by soluble CX3CL1. Interestingly, monocyte adhesion to CX3CL1-coated plates partially inhibited lipopolysaccharide-induced TF expression and TNF-alpha release. Thus, CX3CL1, in addition to its adhesive/chemotactic functions, directly promotes monocyte antiinflammatory and antiprocoagulant responses. This could have important implications in clinical settings such as atherosclerosis, in which SMCs and monocytic cells are in close proximity.
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PMID:Fractalkine/CX3CL1 production by human aortic smooth muscle cells impairs monocyte procoagulant and inflammatory responses. 1282 4

Complement-opsonized particles become immune adherent to complement receptor 1 (CR1 or CD35) on human erythrocytes, allowing particles to be ingested by phagocytes in the liver and the spleen. We investigated the role that immune adherence plays in the uptake and killing of Salmonella montevideo by human neutrophils. Exposure to serum induced loss of flagella and facilitated immune adherence, which was followed by more-efficient phagocytosis and killing, compared with that after exposure to serum-opsonized, free bacteria. One correlate of bacterial killing is the fusion of phagosomes with lysosomes, which can be monitored by Lyso-Tracker or lysosomal-associated membrane protein 2 colocalization with the intracellular bacteria. At 5 min, phagolysosmal fusion was significantly faster for immune-adherent bacteria than for non-immune-adherent bacteria, but, by 35 min, the difference between the 2 groups was minimal. Immune adherence also facilitated the ingestion of antibody complement-opsonized fluorescent microspheres, but, unlike bacteria, most internalized microspheres failed to fuse with lysosomes. However, addition of lipopolysaccharide, a Toll-like receptor ligand, to microspheres directed their intracellular trafficking, resulting in rapid lysosomal fusion. Thus, immune adherence facilitates phagocytosis, but the route of intracellular processing depends on the molecular nature of the target and is independent of host complement and antibody.
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PMID:Phagocytosis of Salmonella montevideo by human neutrophils: immune adherence increases phagocytosis, whereas the bacterial surface determines the route of intracellular processing. 1596 14

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