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At least 847 records · Page 47Linked to original sources
PubMed1987

Influence of antibiotics on fibronectin binding and phagocytosis of staphylococci by human polymorphonuclear leukocytes.

The effect of subbactericidal concentrations of cell wall and protein synthesis-inhibiting antibiotics on fibronectin-staphylococcal interactions was examined. Exposure of staphylococci to protein synthesis inhibitors resulted in a dose-dependent decrease in fibronectin's ability to bind to and promote the phagocytosis of treated organisms by human polymorphonuclear leukocytes. Cell wall inhibitors, on the other hand, had little or no effect on fibronectin binding or phagocytosis. Serum remained an effective opsonin despite antibiotic modulation of fibronectin binding site expression.

Anti-Bacterial Agents↗
PubMed1981

Digestion of the fifth component of complement by eosinophil lysosomal enzymes. Production of eosinophil specific chemotactic activity.

Recently our laboratory has shown that neutrophils contain enzymatic activity within their lysosomal granules which will generate chemotactic activity for neutrophils and tumor cells from the fifth component of complement (C5). We have now expanded this initial observation and have demonstrated that eosinophils can release enzymatic activity from their lysosomal granules upon stimulation with immune complexes or opsoninized zymosan, but not with C5a or synthetic chemotactic peptides. Furthermore, the enzymatic activity released from the eosinophil lysosomal granules can cleave C5 into eosinophil-specific chemotactic activity. The generation of the eosinophil chemotactic activities from C5 is blocked by prior treatment of the eosinophil preparations with a number of protease inhibitors. The eosinophil-derived C5 cleaving activity possesses a pH optimum of 7.2, thus suggesting the enzymatic activity is a neutral protease. The demonstration that enzyme activities derived from eosinophils have the ability to generate eosinophil chemotactic factor(s) from C5 may explain why eosinophils are the predominant inflammatory cell in both nasal polyps and in the nasopharynx and bronchi of patients with allergic conditions such as hay fever and asthma.

Animals↗
PubMed1997

A controlled study of leukocyte activation in septic patients.

OBJECTIVE: Qualitative and quantitative evaluation of leukocyte activation in septic patients in comparison to two control groups. DESIGN: A prospective clinical study in which the leukocyte oxidative output of whole blood was measured in three groups of patients. Two chemiluminescence markers (luminol or lucigenin), indicative of either total oxidant output or superoxide production, and three stimuli (opsonized zymosan, formyl-methionyl-leucyl-phenylalanine (fMLP), phorbol myristate acetate) (PMA), representing different pathways of leukocyte activation, were used. Tumor necrosis factor, interleukin-6 and C-reactive protein (TNF, IL-6, and CRP) were determined to evaluate the severity of the inflammatory process. SETTING: Intensive care and surgical units of a university hospital. PATIENTS: Seventy-four healthy patients, ten ICU patients without signs of sepsis or systemic inflammatory response syndrome and 19 septic patients were studied. MEASUREMENT AND MAIN RESULTS: With all three stimuli, whole blood total oxidative output and superoxide production were generally increased in septic patients. This was most likely due to the increased leukocyte numbers in these patients. When the chemiluminescence values were normalized per phagocyte (granulocytes and monocytes), the total oxidative output of septic phagocytes decreased with opsonin and fMLP but increased with PMA, while superoxide output decreased regardless of the stimuli used. TNF, IL-6 and CRP, although increased in septic patients as compared to ICU controls, correlated weakly with oxidant output. CONCLUSIONS: The oxidative output of whole blood was increased in septic patients compared to controls because of elevated leukocyte numbers. However, oxidant output normalized for phagocyte numbers generally decreases during sepsis for most stimuli. Cytokines and CRP do not appear to be associated with the extent of oxidant output during sepsis.

Adult↗
PubMed2006

Contrasting evolutionary patterns in Drosophila immune receptors.

Vertebrate immune system molecules that bind directly to parasites are commonly subject to strong directional natural selection, probably because they are engaged in an evolutionary arms race with parasites. We have investigated whether similar patterns of evolution are seen in components of the Drosophila immune system that bind parasite-derived molecules. In insects, TEPs (thioester-containing proteins) function as opsonins, binding to parasites and promoting their phagocytosis or encapsulation. The Drosophila melanogaster genome encodes four TEPs, three of which are upregulated after an immune challenge. We report that two of these three Drosophila genes evolve rapidly under positive selection and that, in both TepI and TepII, the "bait-like region" (also known as the variable region) shows the strongest signature of positive selection. This region may be the site of proteolytic cleavage that leads to the activation of the molecule. It is possible that the proteolytic activation of TEPs is a target of host-parasite coevolution, with parasites evolving to prevent proteolysis, which in turn favors mutations in the bait-like region that restore the response. We also sequenced three gram-negative binding proteins (GNBPs) and two immune-induced peptides with strong homology to the GNBPs. In contrast to the Tep genes, the GNBP genes are highly conserved. We discuss the reasons why different components of the immune system have such different patterns of evolution.

Animals↗
PubMed2000

The homologue of mannose-binding lectin in the carp family Cyprinidae is expressed at high level in spleen, and the deduced primary structure predicts affinity for galactose.

Mannose-binding lectin (MBL) participates in the innate immune system as an activator of the complement system and as an opsonin after binding to certain carbohydrate structures on microorganisms. We isolated and characterized cDNA transcripts encoding an MBL homologue from three members of the carp family Cyprinidae, the zebrafish Danio rerio, the goldfish Carassius auratus, and the carp Cyprinus carpio. The carp and zebrafish transcripts contain two polyadenylation sites and RT-PCR on mRNA from carp tissues revealed the carp transcript to be most prominently expressed in the spleen. The deduced mature proteins contain 228 or 233 amino acids with a short N-terminal segment containing a single conserved cysteine expected to form interchain disulfide bridges, a collagen domain interrupted by four amino acids between two glycine residues, a neck region predicted to form an alpha-helical coiled-coil structure, and a C-terminal carbohydrate recognition domain (CRD). Several of the structurally important residues in the CRD are conserved, but the residues known to interact with the calcium ion and hydroxyl groups of the carbohydrate ligand are different. The amino acid motif EPN, important for mannose specificity, was QPD in the Cyprinidae homologue, suggesting specificity for galactose instead. The identity between the deduced amino acid sequences is more than 90% between the carp and the goldfish and 68% and 65% between these two species, respectively, and the zebrafish. The identity with bird and mammalian MBLs ranges from 28 to 33%.

Amino Acid Sequence↗
PubMed2005

Emerging roles and new functions of CD46.

In the past 20 years, our understanding of the workings of complement regulatory protein, CD46 (membrane cofactor protein), has grown as has the impressive list of pathogens interacting with this membrane-bound complement inhibitor. Referred to as a "pathogen magnet," CD46 serves as a receptor for seven human pathogens. Initially discovered as a widely expressed C3b- and C4b-binding protein, it was subsequently shown to be a cofactor for the serine protease factor I to inactivate by limited proteolysis these two opsonins and components of the convertases. The involvement of CD46 in reproductive processes continues to be an emerging story. It is a protector of placental tissue, but it may also play a more direct role in reproduction through its expression on the inner acrosomal membrane of spermatozoa. Cross-linking CD46 with antibodies or natural or pathogenic ligands induces rapid turnover and signaling events. In this regard, much attention is currently focused on generating human T lymphocyte regulatory cells by cross-linking CD46. Finally, highlighting its importance in protecting cells against excessive complement activation is the discovery that even a heterozygous deficiency of CD46 predisposes to hemolytic uremic syndrome.

Amino Acid Sequence↗
PubMed2000

Early diagnosis of postoperative infection: assessment of whole blood chemiluminescence.

Whole blood chemiluminescence (CL), which allows for the evaluation of both the oxygen radical release by phagocytes and the serum opsonin activity using very small amounts of blood, is considered to be a useful means of assessing the host defense against infection. We measured the whole blood chemiluminescence in 59 patients before and after open surgery (surgery by a laparotomy) for gastrointestinal disease. Early postoperative infection was detected in 12 (20.3%) of the 59 patients. These 12 patients all had significantly higher white blood cell counts compared with the noninfected patients on the third and subsequent days after surgery (P < 0.01). The peak CL in the early postoperative infected group was also significantly higher than that in the noninfected group on the day of surgery (P < 0.0001), 1 day after surgery (P < 0.0001), and 3 days after surgery (P < 0.01). Whole blood CL may therefore be a useful modality for the early detection of postoperative infection in the future.

Adult↗
PubMed2007

Identification of poly-reactive natural IgM antibody that recognizes late apoptotic cells and promotes phagocytosis of the cells.

UNLABELLED: Natural IgM can recognize apoptotic cells, but the molecular structure and the role in macrophage phagocytosis of apoptotic cells remain unclear. OBJECTIVES: (1) To examine the binding of previously isolated natural IgM (3B4) to apoptotic cells and its effects on phagocytosis of apoptotic cells. (2) To characterize the molecular structure of 3B4. METHODS: 3B4 binding to apoptotic thymocytes was examined by flow cytometry. Polyreactivity of 3B4 was assayed by ELISA. PKH26-labeled Macrophages were incubated with PKH67-stained apoptotic cells in the presence of 3B4. Macrophages phagocytosis of apoptotic cell was evaluated by flow cytometry. The DNA segments of 3B V(H) and V(K) were sequenced and analyzed. RESULTS: 3B4 IgM recognized late apoptotic cells. Polyreactive-recognitions of lysophosphatidylcholine (LPC) as well as some autoantigens were observed in 3B4. Phagocytosis of late apoptotic cells was increased in the presence of 3B4. The V(H) and V(K) genes of 3B4 showed a germline gene context, while N-sequences and nucleotide loss were observed in CDR3. CONCLUSION: 3B4 promotes macrophage phagocytosis of late apoptotic cells in a complement-independent process. 3B4 has a germline configuration and is possibly ligand-selected. Out experiments suggest an independent role of natural IgM as opsonin in clearance of late apoptotic cells.

Actins↗
PubMed2005

Immunology of apoptosis and necrosis.

A complex of reactions regulating the number of cells in organs and tissues under normal and pathologic conditions is one of the most important systems of multicellular organisms. In this system, which controls both cell proliferation and clearance, clearance has been given special attention during the last three decades. Some stages of the clearance are known (the choice of "unwanted" cells, their destruction not affecting the surrounding tissue, and, finally, removal of the corpses), and undeniable progress has been achieved in the understanding of the second stage mechanisms, whereas mechanisms of elimination per se of cells or their fragments still continue to be terra incognita. The clearance of such cells is mainly determined by different components of natural and adaptive immunity: phagocytes, complement, opsonins, antigen-presenting cells, etc. Recently specific "danger signals", such as hydrolases, DNA, heat shock proteins, and other potential immunogens released by cells during their elimination have been discovered. Entering the extracellular space, these signals induce inflammation and injury of the surrounding tissues, i.e., autoimmune reactions. Heat shock proteins, in addition to chaperon activity, act as signaling, costimulating, and antigen-carrying molecules in the interactions of dying cells and the immune system.

Animals↗
PubMed1983

Polymorphonuclear leukocytes: dedicated professional phagocytes.

Polymorphonuclear leukocytes are termed professional phagocytes because they are specially equipped to seek and destroy invading microorganisms. Polymorphonuclear leukocytes are formed in the bone marrow and released into the circulation, where they are transported to the tissues. At sites of tissue invasion by microorganisms, humoral factors are released that induce these cells to leave the bloodstream and enter the tissues. Chemotactic substances guide polymorphonuclear leukocytes to the infecting organisms. Antibody and complement can function as opsonins and enhance the ability of polymorphonuclear leukocytes to engulf microbes. Ingested organisms are killed by oxidative or nonoxidative systems. Defects in the various aspects of polymorphonuclear leukocyte function may be found in patients with recurrent, severe, or unusual infections. Evaluation of selected patients with recurrent infections should include tests of polymorphonuclear leukocyte function.

Bacterial Infections↗
PubMed1983

Genetic deficiency of C4 presenting with recurrent infections and a SLE-like disease. Genetic and immunologic studies.

A young girl presenting with recurrent pulmonary infections and atypical lupus erythematosus was totally deficient in C4. In one sister, also deficient in C4, the same symptoms developed. Results of family studies were consistent with an autosomal recessive mode of transmission and with linkage of the genes determining C4 deficiency to those of the major histocompatibility complex. The patient's serum and red cells were Chido- and Rodgers-negative. Humoral and cellular immunity were normal, except for a low lymphocyte response in mixed lymphocyte culture. The cellular function of the patient's polymorphonuclear leukocytes was normal, for both phagocytosis and bactericidal activity using Candida albicans. However, in the presence of C4-deficient serum, opsonin generation and bactericidal indexes were diminished. These defects were completely reversible upon addition of purified C4.

Child, Preschool↗
PubMed1996

Fate of cationic liposomes and their complex with oligonucleotide in vivo.

The present studies describe the biodistribution of cationic liposomes and cationic liposome/oligonucleotide complex following intravenous injection into mice via the tail vein. (111)In-diethylenetriaminepentaacetic acid stearylamide ((111)In-DTPA-SA) was used as a lipid-phase radiolabel. Inclusion of up to 5 mol% DTPA-SA in liposomes composed of 3beta-(N-(N',N'-dimethylaminoethane)carbamoyl)cholesterol (DC-Chol) and dioleoylphosphatidylethanolamine (DOPE) did not influence liposome formation or size, nor the binding/uptake or fusion of the cationic liposomes with CHO cells in vitro. Moreover, nuclear delivery of oligonucleotide to CHO cells was unaffected by the probe. The biodistribution of liposomes with increasing concentration of DC-Chol (1:4-4:1, DC-Chol/DOPE, mol/mol) at 24 h post-injection revealed no dependence on lipid composition. Uptake was primarily by liver, and accumulation in spleen and skin was also observed. Comparatively little accumulation occurred in lung. Clearance of injected liposomes by liver was very rapid (approximately 84.5% of the injected dose by 7.5 h post-injection). Liposome uptake by liver and spleen were equally efficient in the dose range of 3.33 to 33.33 mg/kg body weight, yet possible saturation of liver uptake at a dose of 66.80 mg/kg may have allowed for increased spleen accumulation. Preincubation of cationic liposomes with phosphorothioate oligonucleotide induced a dramatic yet transient accumulation of the lipid in lung which gradually redistributed to liver. Similar results were observed when monitoring iodinated oligonucleotide in the complex. Immuno-histochemical studies revealed large aggregates of oligonucleotide within pulmonary capillaries at 15 min post-injection, suggesting the early accumulation in lung was due to embolism. Immuno-histochemical studies further revealed labeled oligonucleotide to be localized primarily to Kupffer cells at 24 h post-injection. Immuno-electron microscopy revealed localization of oligonucleotide primarily to the lumen of pulmonary capillaries at 15 min post-injection. Immuno-electron microscopy revealed localization of oligonucleotide primarily to the lumen of pulmonary capillaries at 15 min post-injection, and to phagocytic vacuoles of Kupffer cells at 24 h post-injection. By these methods, nuclear delivery of oligonucleotide in vivo was not observed. Increasing concentration of mouse serum inhibited cellular binding/uptake of cationic liposomes in vitro, without or with complexed oligonucleotide. We therefore postulate that interaction with plasma components, including opsonin(s), inhibits cellular uptake of the injected liposomes as well as the liposome/oligonucleotide complex, and mediates rapid uptake by Kupffer cells of the liver. These results are relevant to the design of cationic liposomes for efficient delivery of nucleic acid in vivo.

Animals↗
PubMed1988

Elevation of plasma fibronectin and serum amyloid P in autoimmune NZB, B/W, and MRL/1pr mice.

The acute-phase proteins, fibronectin (Fn) and serum amyloid P (SAP), are opsonins which by virtue of their adhesive properties may be involved in the glomerular nephritis associated with splenic lupus erythematosus (SLE). Because of their possible involvement in the pathophysiology of lupus, plasma Fn and SAP levels from three strains of autoimmune mice were measured over time to determine if Fn and SAP rose as the mice sickened and renal function degenerated. Baseline levels of Fn and SAP were measured when the mice were between 1.5 and 3 months of age. The characteristic rapid onset of autoimmune disease in MRL/1pr mice was accompanied by a two- to threefold increase in plasma Fn and SAP by Day 100. The B/W mice, which develop autoimmune disease more slowly, did not have a significant increase in plasma Fn and SAP until Day 240. The NZB mice, with the most delayed onset of disease, exhibited a modest but significant elevation of plasma Fn and SAP by Day 360. Histologic examination of the kidneys of B/W and NZB mice indicated that pathological abnormality of the glomeruli and tubules coincided with the elevation of plasma Fn and SAP levels. In contrast, blood samples taken over time from normal BALB/c mice did not possess abnormal levels of Fn or SAP. It appears that elevation of plasma Fn and SAP in the MRL/1 pr, B/W, and NZB mice is related to the onset and severity of autoimmune disease and the subsequent loss of renal function.

Age Factors↗
PubMed1986

Tritrichomonas foetus: preparation of monoclonal antibodies with effector function.

Monoclonal antibodies were prepared against Tritrichomonas foetus and characterized with regard to binding and immune effector activities. Nine of 27 monoclonal antibodies which reacted with T. foetus appeared to bind to the surface of live parasites. Immunoelectron microscopy confirmed the surface binding of two of these. At least six of these surface reactive monoclonal antibodies facilitated complement mediated lysis of T. foetus and one acted as an opsonin for phagocytosis by peripheral blood bovine monocytes. Five surface reactive monoclonal antibodies identified a molecule of approximately 150,000 relative molecular weight on Western blots of whole parasite preparations. These results collectively suggest the 150,000 relative molecular weight molecule may be an important target antigen for the immune response to T. foetus.

Agglutination↗
PubMed1987

Bacterial lectins, cell-cell recognition and infectious disease.

Numerous bacterial strains produce surface lectins, commonly in the form of fimbriae that are filamentous assemblies of protein subunits. Among the best characterized of these are the type 1 (mannose specific) fimbrial lectins of Escherichia coli that consist almost exclusively of one class of subunit with a molecular mass of 17 kDa. They possess an extended combining site corresponding to a trisaccharide and preferentially bind carbohydrate units of oligomannose or hybrid type. Type 1 fimbriae also possess a hydrophobic region close to the carbohydrate-binding site, since aromatic alpha-mannosides inhibit strongly (up to 1000-times more than methyl alpha-mannoside) the agglutination of yeasts by the bacteria and the adherence of the latter to pig ileal epithelial cells. The combining sites of type 1 fimbriae of the salmonellae and of other enteric bacteria are different from those of E. coli in that they are smaller and do not possess a hydrophobic region. The various bacterial surface lectins appear to function primarily in the initiation of infection by mediating bacterial adherence to epithelial cells, e.g. in the urinary and gastrointestinal tracts. The mannose specific lectins also act as recognition molecules in lectinophagocytosis (i.e. phagocytosis of the bacteria in the absence of opsonins) by mouse, rat and human peritoneal macrophages, and human polymorphonuclear leukocytes. Affinity chromatography of membrane lysates from human polymorphonuclear leukocytes on immobilized type 1 fimbrial lectin, using methyl alpha-mannoside as eluent, showed that glycoproteins with apparent molecular masses of 70-80, 100 and 150 kDa act as receptors for the bacteria. Inhibition experiments with monoclonal antibodies suggest that the glycoprotein bands of 100 and 150 kDa may be identical with the alpha and beta subunits of leukocyte complement receptors and adhesion glycoproteins involved in complement-mediated opsonophagocytosis. The systems described serve as a fine illustration for the biological role of lectin-carbohydrate interactions. Further studies of these systems will lead to a deeper understanding of the molecular basis of infectious diseases, and perhaps also to new approaches for their prevention.

Animals↗
PubMed1986

A reaction vessel for the measurement of oxygen consumption by small numbers of cells in suspension.

A reaction vessel is described that permits measurement of oxygen consumption in small numbers of cells in suspension. The assay permits accurate detection of changes in oxygen tension amounting to less than 0.016 nmol X min-1, and allows the continuous monitoring and calculation of oxygen consumption by as few as 3-6 X 10(5) blood granulocytes or mouse peritoneal macrophages. The results obtained with this assay are highly reproducible, and the values agree closely with those obtained in 10-15-fold larger samples with commercially available oxygraphs. The reaction vessel offers three basic advantages: (1) fewer cells are required per sample (at most 1/10 the number needed for conventional oxygraphs); (2) smaller volumes of test media are needed (i.e., cytokines, opsonins); and (3) the oxygen tension of the medium can be rapidly changed to any desired level at the start of or during experiments. The applications described include the oxygen consumption by human granulocytes and murine peritoneal macrophages before and after addition of both soluble and particulate stimuli. With the use of this technique it was found that the maximum oxygen consumption by human granulocytes after stimulation with phorbol myristate acetate is proportional to the oxygen tension of the medium during the addition of the triggering agent.

Animals↗
PubMed1987

Flow cytometric quantitative evaluation of phagocytosis by human mononuclear and polymorphonuclear cells using fluorescent nanoparticles.

The use of fluorescent polymethacrylic nanoparticles (0.3 micron) as a flow cytometric reagent in the quantitative evaluation of phagocytosis by human mononuclear and polymorphonuclear cells is described. The preparation of the nanoparticles, by emulsion copolymerization of methacrylic monomers, and their physicochemical properties are briefly summarized. Nanoparticles coupled with a fluorescent agent (ethidium bromide) were used in a flow cytometric assay to study opsonin-independent phagocytosis by human polymorphonuclear cells and by human monocytes. The phagocytosis of nanospheres by monocytes was determined by flow cytometry from the fluorescence distribution and ingestion was visualized by scanning and transmission electron microscopy. One possible application of the fluorescent nanoparticles is the simultaneous analysis of cell surface antigens and cell phagocytic activity.

Acrylates↗
PubMed1991

Mannan-binding protein in human liver.

Mannan-binding protein (MBP) is a Ca(2+)-dependent lectin which was first described in 1978 in rabbit liver, and subsequently in serum and liver tissue from humans and a range of animal species. MBP structurally resembles C1q, and may act both as a focus for complement activation on the surface of microorganisms and as an opsonin in its own right. Low serum levels of serum MBP have been described in a group of children known to suffer from severe recurrent infections. MBP has also been reported to behave as an acute phase reactant. This preliminary study has investigated the localisation of MBP in human tissues using material obtained both at post mortem and from diagnostic liver biopsies. Using the IgG fraction of rabbit anti-human MBP, immunoperoxidase staining showed no evidence of significant MBP in a wide range of normal tissues, including liver taken both at post mortem and needle biopsy. However, there was a significant degree of staining for MBP in liver biopsies showing a variety of different pathologies, in particular severely damaged alcoholic livers, and those harbouring metastatic tumour. Moderate degrees of staining were also seen in liver biopsies from patients suffering from chronic biliary disease. It is uncertain whether this localisation of MBP in abnormal liver is an acute phase response, or represents a more fundamental link with liver disease. This question could be the focus for future studies.

Adolescent↗