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At least 991 records · Page 55Linked to original sources
PubMed2001

Hereditary human complement C3 deficiency owing to reduced levels of C3 mRNA.

An 8-year-old son (L.A.S.) of consanguineous parents, presented recurrent bacterial infections, vasculitis and extremely low levels of serum C3 (0.15 microg/ml). The classical and alternative pathway haemolytic activities and the generation of opsonins and chemotactic factors derived from the activation of the complement system were markedly affected in the proband's serum. An in vitro addition of purified C3 restored the classical pathway-dependent haemolytic activity of his serum. Autoradiographs of the proband's lipopolysaccharide (LPS)-stimulated and 35S-labelled fibroblast supernatants after that the SDS-PAGE revealed no C3 alpha or beta chains. The amount of C3 mRNA synthesized by the proband's fibroblasts, as evaluated by reverse transcription-polymerase chain reaction (RT-PCR) assays, was greatly reduced.

Cell Migration Inhibition↗
PubMed2002

Structural, quantitative and functional comparison of amyloid P component in sera from patients with systemic lupus erythematosus and healthy donors.

Serum amyloid P component (SAP) is a serum protein that has a function as opsonin and is known to bind nuclear material with high affinity. Quantitative and/or qualitative deficiencies in SAP may possibly lead to the impairment of normal homoeostatic mechanisms of tissue turnover. Thus, SAP knockout mice display systemic lupus erythematosus (SLE)-like manifestations such as nephritis and circulating antinuclear antibodies. In the present study, we investigated whether there are changes in the structure, function or serum levels of SAP in serum from SLE patients as compared with those from healthy donors. We found that SAP in SLE sera has the same molecular mass as that of in the sera of normal individuals, when analysed by online immunoaffinity reversed phase mass spectrometry. Also, the serum levels of SAP did not differ significantly between the two groups. Finally, as an estimate of function, SAP from SLE patients appeared to have the same affinity for heparin and nucleosomes as SAP from normal individuals, when analysed by crossed affinity immunoelectrophoresis and enzyme-linked immunosorbent capture assay (ELISA). In conclusion, the data do not support alterations in the levels, structure or function of SAP circulating in SLE patients.

Blood Donors↗
PubMed2003

Increased hydrogen peroxide generation by neutrophils from patients with acne inflammation.

BACKGROUND: Reactive oxygen species generated by neutrophils are closely correlated with the pathogenesis of a variety of inflammatory skin diseases. The aim of this study was to investigate the possible role of reactive oxygen species generated by neutrophils in the mediation of acne inflammation. METHODS: Bacterial phagocytotic stimuli, mediated by opsonin activity, were applied to whole blood, and neutrophil hydrogen peroxide production was measured. RESULTS: Patients with acne inflammation showed a significantly increased level of hydrogen peroxide produced by neutrophils compared to patients with acne comedones and healthy controls. There were no marked differences in the level of hydrogen peroxide produced by neutrophils between patients with acne comedones and healthy controls. In addition, patients with acne inflammation treated by oral administration of minocycline hydrochloride, a drug that inhibits hydrogen peroxide generation by neutrophils, showed a significant decrease in the ability of neutrophils to produce hydrogen peroxide in accordance with a decrease in the inflammatory activity of acne lesions. CONCLUSIONS: The present study seems to suggest that acne inflammation is mediated in part by hydrogen peroxide generation by neutrophils.

Acne Vulgaris↗
PubMed1999

Lipopolysaccharide stimulates HepG2 human hepatoma cells in the presence of lipopolysaccharide-binding protein via CD14.

Lipopolysaccharide (LPS)-binding protein (LBP), an opsonin for activation of macrophages by bacterial LPS, is synthesized in hepatocytes and is known to be an acute phase protein. Recently, cytokine-induced production of LBP was reported to increase 10-fold in hepatocytes isolated from LPS-treated rats, compared with those from normal rats. However, the mechanism by which the LPS treatment enhances the effect of cytokines remains to be clarified. In the present study, we examined whether LPS alone or an LPS/LBP complex directly stimulates the hepatocytes, leading to acceleration of the cytokine-induced LBP production. HepG2 cells (a human hepatoma cell line) were shown to express CD14, a glycosylphosphatidylinositol-anchored LPS receptor, by both RT/PCR and flow cytometric analyses. An LPS/LBP complex was an effective stimulator for LBP and CD14 production in HepG2 cells, but stimulation of the cells with either LPS or LBP alone did not significantly accelerate the production of these proteins. The findings were confirmed by semiquantitative RT/PCR analysis of mRNA levels of LBP and CD14 in HepG2 cells after stimulation with LPS alone and an LPS/LBP complex. In addition, two monoclonal antibodies (mAbs) to CD14 (3C10 and MEM-18) inhibited LPS/LBP-induced cellular responses of HepG2 cells. Furthermore, prestimulation of HepG2 cells with LPS/LBP augmented cytokine-induced production and gene expression of LBP and CD14. All these findings suggest that an LPS/LBP complex, but not free LPS, stimulates HepG2 cells via CD14 leading to increased basal and cytokine-induced LBP and CD14 production.

Acute-Phase Proteins↗
PubMed2000

Interleukin-1 and cutaneous inflammation: a crucial link between innate and acquired immunity.

As our primary interface with the environment, the skin is constantly subjected to injury and invasion by pathogens. The fundamental force driving the evolution of the immune system has been the need to protect the host against overwhelming infection. The ability of T and B cells to recombine antigen receptor genes during development provides an efficient, flexible, and powerful immune system with nearly unlimited specificity for antigen. The capacity to expand subsets of antigen-specific lymphocytes that become activated by environmental antigens (memory response) is termed "acquired" immunity. Immunologic memory, although a fundamental aspect of mammalian biology, is a relatively recent evolutionary event that permits organisms to live for years to decades. "Innate" immunity, mediated by genes that remain in germ line conformation and encode for proteins that recognize conserved structural patterns on microorganisms, is a much more ancient system of host defense. Defensins and other antimicrobial peptides, complement and opsonins, and endocytic receptors are all considered components of the innate immune system. None of these, however, are signal-transducing receptors. Most recently, a large family of cell surface receptors that mediate signaling through the NF-kappaB transcription factor has been identified. This family of proteins shares striking homology with plant and Drosophila genes that mediate innate immunity. In mammals, this family includes the type I interleukin-1 receptor, the interleukin-18 receptor, and a growing family of Toll-like receptors, two of which were recently identified as signal-transducing receptors for bacterial endotoxin. In this review, we discuss how interleukin-1 links the innate and acquired immune systems to provide synergistic host defense activities in skin.

Antibody Formation↗
PubMed2001

A comparison of foal and adult horse neutrophil function using flow cytometric techniques.

Flow cytometric assays were used to compare phagocytic and oxidative burst activity of neutrophils from healthy foals less than 7 days of age with the activity of cells from healthy adult horses. The phagocytosis of Staphylococcus aureus by foal neutrophils was less than that observed for adult neutrophils when autologous serum was used as the source of opsonins in the assay. The use of adult serum did not significantly improve the ability of foal neutrophils to attach bacteria. The oxidative burst activity of foal neutrophils was equivalent to that of adult cells. However, when serum or plasma was incorporated into the oxidative burst assay, foal neutrophils demonstrated greatly reduced autofluorescence and a suppressed response to phorbol myristate acetate (PMA), relative to that demonstrated by adult cells. These results suggest that peripheral blood neutrophils from foals have a reduced ability to phagocytose bacteria relative to that exhibited by adult horse neutrophils and that the oxidative burst activity of foal neutrophils is down-regulated in response to an unidentified serum factor(s). Such changes may contribute to the increased susceptibility of foals to septic disease.

Age Factors↗
PubMed1997

The role of collectins in host defense.

Mannose-binding protein (MBP) belongs to a group of Ca(2+)-dependent lectins called collectins that play a role in first-line host defense. It recognizes specific carbohydrate residues (mannose and N-acetylglucosamine) on the surface of microorganisms and promotes the killing of microbes either by acting directly as an opsonin or by activating the lectin complement pathway. The collagenlike domain of MBP is important for the binding of MBP to the collectin receptors expressed on different phagocytes, and for activation of complement. The binding of MBP to bacteria, viruses, and parasites has been demonstrated in vitro. Three major mutations have been found in exon 1 of the MBP gene, which encodes the collagenous domain of the protein. These mutations cause low levels of serum MBP and have been linked with lifelong risk of infection. The homozygotes for these mutations are especially susceptible to severe infections.

Animals↗
PubMed1986

Neutrophil activation in thermal injury as assessed by increased expression of complement receptors.

We studied neutrophil activation in patients with burns by serial immunofluorescent measurement of neutrophil expression of the complement opsonin receptors CR1 and CR3. CR1-dependent fluorescence was initially (days 0 through 5 after the burn) elevated (mean +/- SEM, 294 +/- 42 vs. 63 +/- 6 in the controls; P less than 0.001) and gradually returned to normal (days 6 through 8, 270 +/- 62, P less than 0.001; days 9 through 13, 185 +/- 38, P less than 0.001; days 14 through 19, 143 +/- 27, P less than 0.001; and days 20 through 50, 93 +/- 5, P less than 0.04). CR3-dependent fluorescence paralleled that of CR1. Neutrophil chemotaxis in response to zymosan-activated serum, a source of C5a, was depressed (days 0 through 5, 77 +/- 4 percent of control, P less than 0.001; days 6 through 8, 70 +/- 4 percent, P less than 0.001; days 9 through 13, 74 +/- 3 percent, P less than 0.001; days 14 through 19, 90 +/- 4 percent, P less than 0.01; and days 20 through 50, 97 +/- 3 percent, P not significant) and inversely correlated with CR1- and CR3-dependent fluorescence (r = -0.559, P less than 0.001; and r = -0.709, P less than 0.001, respectively). Plasma C3a desArg levels were above normal (100 +/- 5 ng per milliliter) throughout (days 0 through 5, 305 +/- 42; days 6 through 8, 546 +/- 69; days 9 through 13, 490 +/- 72; days 14 through 19, 409 +/- 54; and days 20 through 50, 260 +/- 36; all P less than 0.005). Thus, neutrophils in burned patients were activated as indicated by increased expression of complement receptors. The correlation between this increase and the depression of chemotaxis in response to zymosan-activated serum suggests that C5a is responsible for systemic neutrophil activation, which may contribute to the increased susceptibility to infection of patients with burns.

Adult↗
PubMed1982

Complement activation by isolated myelin: activation of the classical pathway in the absence of myelin-specific antibodies.

Many pathological conditions of the central nervous system involve damage to and removal of myelin membrane. Very little is known about initiation of this membrane damage and the mechanisms of disposal of the damaged tissue. We are interested in the interaction between complement (the components of complement are designated C1, C2, C3, etc.) and myelin membranes and the possible role of complement in amplifying myelin damage and in the disposal of damaged myelin in vivo, because activation of complement generates both membrane-attack complexes and opsonin(s). In this study, we found that isolated rat or human myelin consumes complement in the absence of specific antibodies. Activation of complement was demonstrated by showing C3 cleavage in fresh serum incubated with myelin. Incubation of central nervous system myelin with C2-deficient serum produced no C3 consumption and only minor factor B conversion, thus excluding the alternative pathway of activation. Involvement of the classical pathway was shown directly by the C1 fixation and transfer assay. Myelin incubated with C2-deficient serum or with purified C1 and then washed contained C1 activity that could lyse sheep erythrocytes sensitized with anti-Forssman IgM antibody and carrying C4, together with C2 and C3-C9. Membranes in brain tissues other than myelin (heavy membrane fraction obtained on sucrose density gradient centrifugation) were unable to activate C1.

Animals↗
PubMed1991

Expression of a soluble and functional form of the human beta 2 integrin CD11b/CD18.

Polymorphonuclear cells and monocytes (phagocytes) are a critical component of host defense against infections. However, these cells also play a significant role in host tissue damage in many noninfectious diseases, such as ischemia-reperfusion injury syndromes and rejection of transplanted organs. The leukocyte adhesion molecule family CD11/CD18 (beta 2 integrins) is critical to the function of polymorphonuclear cells and monocytes in inflammation and injury. Inherited deficiency of CD11/CD18 impairs phagocyte chemotaxis, adhesion and transmigration across endothelium, and clearance of invading microorganisms through phagocytosis and cell-mediated killing. Furthermore, murine monoclonal antibodies directed against the CD11b/CD18 (CR3) heterodimer have been shown to reduce, by 50%-80%, phagocyte-mediated ischemia-reperfusion injury in several organ systems, such as the myocardium, liver, and gastrointestinal tract and to inhibit development of insulin-dependent diabetes mellitus in nonobese diabetic (NOD) mice. Expression of CD11b/CD18 in a soluble and functional form might therefore be potentially useful as an anti-inflammatory agent. We have now expressed a recombinant soluble heterodimeric form of this human beta 2 integrin, normally expressed as two noncovalently associated membrane-bound subunits. The secreted receptor exhibited direct and specific binding to its ligand, iC3b, the major complement C3 opsonin, and inhibited binding of polymorphonuclear cells to recombinant interleukin 1-activated endothelium.

Amino Acid Sequence↗
PubMed1999

Antitumor activity of mannan-binding protein in vivo as revealed by a virus expression system: mannan-binding proteindependent cell-mediated cytotoxicity.

Mannan-binding protein (MBP), a Ca2+-dependent mammalian lectin specific for mannose and N-acetylglucosamine, is an important serum component associated with innate immunity. MBP activates complement and functions as a direct opsonin on binding to mannooligosaccharide-bearing pathogens. We have found that MBP recognizes and binds specifically to oligosaccharide ligands expressed on the surfaces of a human colorectal carcinoma. Interestingly, the recombinant vaccinia virus carrying human MBP gene was demonstrated to possess a potent growth-inhibiting activity against human colorectal carcinoma cells transplanted in KSN nude mice when administered by intratumoral or subcutaneous injection. Moreover, a significant prolongation of life span of tumor-bearing mice resulted from the treatment. This effect appears to be a consequence of local production of MBP. Unexpectedly, the mutant MBP, which had essentially no complement-activating activity, was nearly as active as wild-type MBP. These results indicated that MBP has a previously undescribed cytotoxic activity, which we propose to term MBP-dependent cell-mediated cytotoxicity(MDCC). In addition, this study provides a model for the development of an effective and specific host defense factor for cancer gene therapy.

Animals↗
PubMed2006

Lectin from the Manila clam Ruditapes philippinarum is induced upon infection with the protozoan parasite Perkinsus olseni.

Glycan-binding proteins (lectins) are widely expressed in many invertebrates, although the biosynthesis and functions of the lectins are not well understood. Here we report that Manila clam (Ruditapes philippinarum) synthesizes a lectin termed Manila clam lectin (MCL) upon infection with the protozoan parasite Perkinsus olseni. MCL is synthesized in hemocytes as a approximately 74-kDa precursor and secreted into hemolymph where it is converted to 30- and 34-kDa polypeptides. The synthesis of MCL in hemocytes is stimulated by one or more factors in Perkinsus-infected hemolymph, but not directly by Perkinsus itself. MCL can bind to the surfaces of purified hypnospores and zoospores of the parasite, and this binding is inhibitable by either EDTA or GalNAc. Fluorescent beads coated with purified MCL were actively phagocytosed by hemocytes from the clam. Immunohistochemistry showed that secreted MCL is concentrated within cyst-like structures. To define the glycan binding specificity of MCL we examined its binding to an array of biotinylated glycans. MCL recognizes terminal non-reducing beta-linked GalNAc as expressed within the LacdiNAc motif GalNAcbeta1-4GlcNAcbeta1-R and glycans with terminal, non-reducing beta-linked Gal residues. Our results show that the synthesis of MCL is specifically up-regulated upon parasite infection of the clams and may serve as an opsonin through recognition of terminal GalNAc/Gal residues on the parasites.

Animals↗
PubMed1986

Changes in plasma fibronectin during acute nutritional deprivation in healthy human subjects.

1. Plasma fibronectin, a glycoprotein, is an opsonin of the reticuloendothelial system. 2. In ten healthy volunteers starved for 4.5 d, daily measurements showed a rapid reduction in plasma fibronectin, no alteration in either C3 or plasma transferrin and, at the end of the starvation period, an elevated serum albumin. 3. On refeeding, plasma fibronectin rapidly returned to its prestarvation level but plasma transferrin was significantly reduced and did not recover by the end of the study. 4. Changes in plasma fibronectin may be a sensitive index of nutritional status. The reduction of plasma fibronectin in short-term starvation may compromise host defence tolerance of injury and sepsis.

Adult↗
PubMed2002

Phagocytic and candidacidal activities of macrophages from suckling and adult mice pretreated with concanavalin-A.

In this study, we investigated the effect of concanavalin-A (Con-A) on the activation of phagocytosis and killing of Candida albicans by peritoneal macrophages from suckling and adult mice. Pretreatment of adult mice with Con-A dose-dependently increased the percentage of macrophages phagocytosing C. albicans in vitro from 3.8 +/- 0.9 to 24.2 +/- 2.4 in the absence of serum opsonins. Addition of mannan (50 microg) and mannose (50 mM) to the incubation medium reduced phagocytosis from 21.5 +/- 1.3 to 4.7 +/- 1.9, suggesting that treatment with Con-A increased phagocytosis mediated by mannose receptors. Killing of C. albicans was also increased by increasing the dose of Con-A. Pretreatment of suckling mice with Con-A increased the macrophages' phagocytic and candidacidal activities by an amount similar to that observed in adult mice. Furthermore, suckling mice pretreated with Con-A survived an intraperitoneal inoculum of 5 x 10(7) C. albicans, whereas all control mice died within 24-48 h of infection. This suggested that increased phagocytosis and killing of C. albicans stimulated by the action of Con-A conferred early protection upon suckling mice experimentally infected with C. albicans.

Animals↗
PubMed1994

Integrin alpha v beta 3 differentially regulates adhesive and phagocytic functions of the fibronectin receptor alpha 5 beta 1.

The plasma protein fibronectin is an important opsonin in wound repair and host defense. To better understand the process of fibronectin-mediated phagocytosis, we have transfected K562 cells, which endogenously express alpha 5 beta 1, with alpha v beta 3. In these transfectants, antibodies to alpha v beta 3 block phagocytosis of fibronectin-opsonized beads completely, even though half the ingestion occurs through endogenous alpha 5 beta 1 receptors. alpha 5 beta 1-mediated adhesion to fibronectin-coated surfaces is unaffected by alpha v beta 3 ligation. Neither alpha v beta 5 nor alpha M beta 2 ligation affects alpha 5 beta 1 phagocytic function in transfectants expressing these receptors. Pharmacologic data suggest that alpha v beta 3 ligation suppresses the phagocytic competence of high affinity alpha 5 beta 1 receptors through a signal transduction pathway, perhaps involving protein kinase C. In addition to its significance for phagocytosis, alpha v beta 3 regulation of alpha 5 beta 1 function may be significant for its roles in cell migration, metastasis, and angiogenesis.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed2006

ATP-binding cassette transporter A7 enhances phagocytosis of apoptotic cells and associated ERK signaling in macrophages.

The mammalian ATP-binding cassette transporters A1 and A7 (ABCA1 and -A7) show sequence similarity to CED-7, a Caenorhabditis elegans gene that mediates the clearance of apoptotic cells. Using RNA interference or gene targeting, we show that knock down of macrophage ABCA7 but not -A1 results in defective engulfment of apoptotic cells. In response to apoptotic cells, ABCA7 moves to the macrophage cell surface and colocalizes with the low-density lipoprotein receptor-related protein 1 (LRP1) in phagocytic cups. The cell surface localization of ABCA7 and LRP1 is defective in ABCA7-deficient cells. C1q is an opsonin of apoptotic cells that acts via phagocyte LRP1 to induce extracellular signal-regulated kinase (ERK) signaling. We show that ERK signaling is required for phagocytosis of apoptotic cells and that ERK phosphorylation in response to apoptotic cells or C1q is defective in ABCA7-deficient cells. These studies reveal a major role of ABCA7 and not -A1 in the clearance of apoptotic cells and therefore suggest that ABCA7 is an authentic orthologue of CED-7.

ATP Binding Cassette Transporter 1↗
PubMed1983

Functional activity of enucleated human polymorphonuclear leukocytes.

Enucleated human polymorphonuclear leukocytes (PMN) were prepared by centrifuging isolated, intact PMN over a discontinuous Ficoll gradient that contained 20 microM cytochalasin B. The enucleated cells (PMN cytoplasts) contained about one-third of the plasma membrane and about one-half of the cytoplasm present in intact PMN. The PMN cytoplasts contained no nucleus and hardly any granules. The volume of the PMN cytoplasts was about one-fourth of that of the original PMN. Greater than 90% of the PMN cytoplasts had an "outside-out" topography of the plasma membrane. Cytoplasts prepared from resting PMN did not generate superoxide radicals (O2-) or hydrogen peroxide. PMN cytoplasts incubated with opsonized zymosan particles or phorbol-myristate acetate induced a respiratory burst that was qualitatively (O2 consumption, O2- and H2O2 generation) and quantitatively (per unit area of plasma membrane) comparable with that of intact, stimulated PMN. Moreover, at low ratios of bacteria/cells, PMN cytoplasts ingested opsonized Staphylococcus aureus bacteria as well as did intact PMN. At higher ratios, the cytoplasts phagocytosed less well. The killing of these bacteria by PMN cytoplasts was slower than by intact cells. The chemotactic activity of PMN cytoplasts was very low. These results indicate that the PMN apparatus for phagocytosis, generation of bactericidal oxygen compounds, and killing of bacteria, as well as the mechanism for recognizing opsonins and activating PMN functions, are present in the plasma membrane and cytosol of these cells.

Blood Bactericidal Activity↗
PubMed1959

Interactions between rabbit polymorphonuclear leucocytes and staphylococci.

A method has been described for the study in vitro of leucocyte-bacteria interactions which permits the simultaneous evaluation of both phagocytosis and intracellular bacterial inactivation. Employing this technique, the fate and localization of staphylococci in homogeneous suspensions of rabbit polymorphonuclear leucocytes have been studied. Coagulase-positive strains of S. aureus were not efficiently ingested in the presence of normal rabbit serum. In contrast, coagulase-negative strains of S. albus were rapidly engulfed and inactivated. Immune sera prepared against a coagulase-positive strain enhanced the the ingestion of the homologous organism as well as of three heterologous strains of S. aureus. Following phagocytosis, prompt intracellular killing of S. aureus occurred. The thermostable opsonins in immune sera reacted only with strains of S. aureus. A comparison between polymorphonuclear leucocytes obtained from normal and immune animals revealed no differences in their ability either to ingest or kill coagulase-positive staphylococci. Studies with other bacterial species are presented to illustrate: (a) phagocytosis followed by intracellular inactivation; (b) phagocytosis followed by intracellular survival; and (c) the absence of phagocytosis.

Animals↗