Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “OPSONINS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 865 records · Page 48Linked to original sources
PubMed1991

Phagocytosis of opsonized oil droplets by neutrophils. Adaptation to a microtiter plate format.

A previously described assay for neutrophil phagocytosis of oil droplets labeled with the lipophilic red dye, oil red O, has been adapted to a microtiter plate format. Oil laden neutrophils are fixed to the plate with glutaraldehyde, washed free of uningested oil, and evaluated for degree of oil red O uptake by direct determination of light absorption at 540 nm in a microtiter plate reader. Advantages of the modified procedure include the ability to determine rates of phagocytosis (multiple determinations) under diverse conditions, simultaneously and with greater facility. Multiple centrifugation steps are eliminated and the requirement for extraction of oil red O from each cell pellet prior to quantitation becomes optional. The system has been evaluated for oil droplets emulsified with lipopolysaccharide alone or with lipopolysaccharide together with bovine serum albumin. For droplets emulsified with lipopolysaccharide alone, efficient opsonization was accomplished with fresh serum alone, through heat labile, presumably complement-dependent, pathways. For droplets emulsified with lipopolysaccharide and bovine serum albumin, specific antiserum to bovine serum albumin was a considerably more efficient opsonin than non-immune fresh serum. A third system is described in which tetanus toxoid was introduced into oil droplets that had been previously emulsified with lipopolysaccharide. Inclusion of toxoid antigens rendered the oil droplets susceptible to opsonization with tetanus immune globulin, making the assay system possibly applicable to evaluation of immunoglobulin function in humans.

Azo Compounds↗
PubMed1983

Plasma fibronectin concentration in animal models of sepsis and endotoxemia.

Plasma fibronectin is a nonspecific opsonin which mediates phagocytosis of particulate matter by macrophages. Fibronectin depletion results in depression of reticuloendothelial system phagocytic function. This may potentiate microvascular embolization and sludging in critical illness. It has been hypothesized that sepsis is a major cause of fibronectin depletion. To explore this hypothesis, plasma fibronectin concentrations were measured in rats with intraabdominal abscesses and in rabbits subjected to the generalized Shwartzman reaction (spaced doses of endotoxin). In both groups of animals there was a significant increase (P less than 0.05) rather than decrease in fibronectin concentrations at times when sepsis and disseminated intravascular coagulation were manifest. This study does not support the hypothesized relationship between sepsis and fibronectin depletion. Until the kinetics of fibronectin production and utilization are further delineated, caution must be exercised in the interpretation of immunoreactive plasma fibronectin levels.

Abdomen↗
PubMed1990

Lipopolysaccharide enhances monocyte adherence to matrix-bound fibronectin.

Fibronectin (Fn), an extracellular matrix glycoprotein with binding sites for collagen, fibrin, heparin, and cell surfaces, is a nonimmune opsonin which up-regulates phagocytic function and facilitates adherence of human monocytes. We have developed a simple assay to study adherence of peripheral blood monocytes to Fn on a gelatin matrix. While cell adherence was enhanced by the presence of Fn in a dose-dependent manner, it was inhibited by peptides containing the Arg-Gly-Asp (RGD) cell attachment sequence or by coating the matrix with antibodies directed against Fn. Preincubation of monocytes for 30 min with Escherichia coli lipopolysaccharide (LPS) at doses of 1-50 micrograms/ml increased adherence to Fn-gelatin but not to gelatin alone, while longer preincubation (24 hr) resulted in similar changes at lower doses (0.01-1.0 micrograms/ml). Enhanced Fn adherence may be essential for monocyte localization to sites of inflammation.

Antineoplastic Agents↗
PubMed1992

Effect of Pseudomonas aeruginosa elastase and alkaline protease on serum complement and isolated components C1q and C3.

The present study was undertaken to examine and compare the direct effect of two Pseudomonas enzymes, elastase and alkaline protease, on the serum hemolytic complement as a whole, and on the two recognition molecules of complement, C1q and C3 in particular. The results of our study show that incubation of serum with 0-50 micrograms/ml elastase or protease (60 min, 37 degrees C) resulted in a dose-dependent depletion of hemolytic complement with the protease being 3-4 times more efficient than elastase. Incubation of highly purified C3 (20 hr, 37 degrees C) with protease (2% w/w) resulted in the conversion of the 190-kDa molecule to a 120-kDa fragment. When analyzed by SDS-PAGE under reducing conditions, the 120-kDa piece yielded three distinct bands: an intact 75-kDa beta-chain and two alpha-chain pieces of approximately 41- and 26-kDa. NH2-terminal end sequence analysis localized the 26-kDa fragment within the cysteine-rich 41-kDa, COOH-terminal piece. This in turn suggests that the 70-kDa fragment which is not accounted for on SDS-PAGE is derived from the NH2-terminal end of the alpha-chain molecule which is completely degraded into small fragments. While the degradation pattern obtained with elastase is similar to that of protease, the latter enzyme was found to be more efficient. Exposure of C1q (0-5 hr, 37 degrees C) to protease or elastase on the other hand appears to reveal preferential sensitivity of the 28-kDa A-chain and 24-kDa C-chain, of the C1q molecule, with the protease being more potent than the elastase. Since both C1q and physiologic fragments of C3 (C3b, iC3b, and C3dg) are important opsonins of varying efficiencies, degradation of these molecules by Pseudomonas enzymes may, in part, facilitate the survival and proliferation of the organism in plasma. Furthermore, degradation of the key recognition molecules of complement, C1q and C3, would enhance the virulence of this organism by aborting complement-mediated bacterial killing. In addition the results imply that during Pseudomonas bacteremia, PaAP may be a much more destructive enzyme than PaE with regards to C3 and C1q but combined, the synergistic effect may overwhelm not only the proteins of the complement system, but other proteins of the humoral immune defense system as well.

Amino Acid Sequence↗
PubMed1993

A novel divalent cation-binding site in the A domain of the beta 2 integrin CR3 (CD11b/CD18) is essential for ligand binding.

A recombinant peptide encoding the CD11b A domain bound 54Mn2+ with a high affinity. Other divalent cations, including Mg2+, Zn2+, Ni2+, Co2+, and Cd2+, but not Ca2+ or Ba2+, competed effectively for Mn2+ binding. Amino acid substitutions within two conserved and noncontiguous regions in the recombinant peptide abolished 54Mn2+ binding. When these substitutions were introduced independently in complement receptor type 3 (CR3), each abolished the metal-dependent binding of the receptor to the major C3 opsonin iC3b, without impairing subunit association or surface expression of the receptor. These findings identify an unsuspected and novel metal-binding site within the A domain of CR3 that is required for metal-dependent ligand binding and also identify a good target for designing drugs aimed at countering the inflammatory potential of this key receptor.

Amino Acid Sequence↗
PubMed1984

Uterine defense mechanisms in the mare: The use of intrauterine plasma in the management of endometritis.

Twenty-nine mares with either active or subclinical endometritis were treated with intrauterine infusions of their own plasma in one of two treatment schemes. Twenty-six mares actively infected, with an average of 2.4 years barren, were treated with combinations of saline irrigations and plasma infusions. Twenty-four showed clinical improvement and were bred, resulting in 15 pregnancies. Three mares with subclinical endometritis were treated post-breeding with a single plasma infusion and all became pregnant. The response to plasma infusions supports in-vitro observations which implicate serum-derived opsonins, particularly complement, as enhancers of phagocytic function.

Journal Article↗
PubMed1996

Effect of PEO surface density on long-circulating PLA-PEO nanoparticles which are very low complement activators.

The rapid uptake of injected nanoparticles by cells of the mononuclear phagocytes system (MPS) is a major obstacle when a long blood circulation time is needed. Whereas nanoparticles made from PLA and stabilized by surfactants (PLA-F68) are rapidly phagocytized, the rate of phagocytosis is strongly reduced in case of nanoparticles made from a diblock copolymer (PLA-PEO). Because of the role of the complement system in opsonization, this difference of phagocytosis was hypothesized to be related to this system. An important complement consumption was obtained in 5 min in the presence of PLA-F68 particles. In the presence of a higher surface area of PLA-PEO particles possessing a high PEO surface density, the consumption remained very low. When the average PEO surface density was decreased on such particles below a given threshold, a fast and strong complement consumption occurred again. These experimental data support the concept of steric repulsion towards proteins, by surfaces covered with terminally attached PEO chains and emphasize the prime importance of PEO surface density in such an effect. The major, but probably not exclusive, role of complement as an opsonin capable of inducing a fast phagocytosis by MPS should be taken into account concerning the in vitro evaluation of nanoparticles as candidates for a long blood circulation.

Biocompatible Materials↗
PubMed1984

Activation of vertebrate complement by Helix pomatia haemolymph.

Haemolymph plasma from the pulmonate snail Helix pomatia contains a constituent, not yet identified, which causes activation of vertebrate complement via the alternative complement pathway in fluid phase. The activation of vertebrate complement by snail plasma is closely analogous to the activation caused by cobra venom factor (CVF), the snake's C3b, with one notable exception; the snail factor requires vertebrate C3 for the formation of C3 convertase which cobra venom factor does not. Our results do not allow any definite conclusion on the exact mechanism but we favour the idea that the haemolymph contains a complement-like protein which functions as an opsonin in the snail, and which can interact with vertebrate alternative complement pathway components.

Animals↗
PubMed1988

The chicken macrophage response to carbohydrate-based irritants: temporal changes in peritoneal cell populations.

Temporal changes in the recruitment and functional activation of Cornell K strain chicken peritoneal macrophages elicited by starch and dextrans were determined. During a 72-hr period following intraperitoneal injection, Sephadex (cross-linked dextran) elicited a gradually increasing number of peritoneal exudate cells (PECs) which contained greater than or equal to 78% macrophages in the adherent cell population. In contrast, starch tended to elicit higher numbers of PECs early in the stimulation process, with heterophils comprising a major proportion of the adherent cells. Later in the time course, macrophages were the predominant adherent cell type. Comparisons of PEC recruitment using Sephadex vs. low molecular weight dextrans demonstrated that the low-molecular weight dextrans elicited fewer PECs than did Sephadex; unlike Sephadex, however, the low molecular weight dextrans generated a significant peak of heterophil infiltration that was similar, although delayed, to that produced with starch. Sephadex-stimulated peritoneal macrophages exhibited time-dependent functional acquisitions for 1) the phagocytosis of sheep erythrocytes, 2) the engulfment of opsonized sheep erythrocytes, and 3) opsonin-erythrocyte rosetting. Acquisition of phagocytic activity for uncoated vs. opsonized erythrocytes occurred under very different rates during the time course. The results suggest that both the nature of the irritant and the time point of cell harvest can be appropriately selected to provide the particular cell population and functional status desired for subsequent in vitro analyses.

Animals↗
PubMed1989

Immunoproteins in evolution.

All vertebrates respond to antigenic challenge by specific cellular reactions and by producing circulating antibodies, and they also contain recognition molecules that are evolutionary relics of primitive non-immune recognition. One such ancient recognition molecule is C-reactive protein (CRP), a member of the pentraxin family, that has homologs occurring in species as diverse as vertebrates, tunicates and the horseshoe crab (an ancient arachnoid). This molecule has lectin-like properties, can act as an opsonin and interact with complement and cells in a manner paralleling immunoglobulins (Igs). The horseshoe crab lectin and CRP, although unrelated to Igs, share functional idiotopes with classical antibodies. This finding reflects either an evolutionary convergence or a mechanism of "mini gene insertion" that allows molecules of distinct evolutionary histories to react to the same ligands. Serum antibodies of all vertebrates are polydisperse in charge and are composed of polypeptide chains comparable in mass to those of mammalian light and heavy chains. Molecular genetic studies of placoderm derived vertebrates are incomplete but are sufficient to allow the conclusion that Igs of these species are specified by variable (V), joining (J) and constant (C) gene segments and that rearrangement are an essential feature for the generation of antibody diversity. Here we present new evidence following from the use of antibodies directed against synthetic joining region peptides as probes in the study of rearranging Igs in evolution, the use of recombinant DNA technology to study T cell receptor V beta genes in a goldfish genomic library and the isolation and characterization of a gene fragment specifying sandbar shark light chain C region. We reached the following conclusions: (1) J region segments are the most conserved in evolution, and this most probably reflects the essential requirements for these gene segments in the formation of intact Ig genes by rearrangement; (2) the framework segments of V regions are highly conserved in vertebrate evolution for both T cell receptors and classical Igs; and (3) although C region segments of light chains of lower vertebrates are homologous to their mammalian counterparts, the degree of conservation of C region structure in phylogeny is apparently less than that for V regions. Essentially, phylogenetic trees can be built using C regions but not V regions. We have identified a molecule of approximate mass of 26 kDa in the hemolymph of the tunicate, Boltenia ovipera, that is serologically cross-reactive with shark heavy chain and with J region peptides.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1995

Human microglia mediate anti-Cryptococcus neoformans activity in the presence of specific antibody.

The interaction of the opportunistic fungus Cryptococcus neoformans with human microglia was studied in vitro in the presence and absence of capsule binding antibody. In the absence of capsule binding antibody there was little or no phagocytosis. Addition of the murine monoclonal antibody (mAb) 2H1 (IgG1, kappa) to the capsular glucuronoxylomannan (GXM) produced a dose-dependent enhancement of C. neoformans phagocytosis by microglia. Phagocytosis resulted in marked inhibition of fungal proliferation. Microglial antifungal activity was studied by colony forming unit assay, L-[3H]leucine incorporation assay, and phase contrast microscopy. At microglia: C. neoformans ratios of 10:1 to 80:1 fungal growth was reduced by 61-95%. Inhibitors of nitric oxide synthase and reactive oxygen intermediates did not prevent antifungal activity mediated by human microglia. Transmission electron microscopic studies revealed that although some internalized yeast cells were killed, the majority were intact consistent with fungistasis. Human microglia cells are potent effector cells against C. neoformans in vitro in the presence of specific antibody. Enhancement of microglial activity in vivo by opsonins may be a useful therapeutic strategy.

Antibodies, Fungal↗
PubMed1989

Effect of lentinan and mannan on phagocytosis of fluorescent latex microbeads by mouse peritoneal macrophages: a flow cytometric study.

Lentinan, an immunopotentiating beta-1,3-glucan polysaccharide stimulated the in vitro phagocytosis of BSA-coated, C3b- or monoclonal immunoglobulin (IgG2b)-coated fluorescent microspheres by resident or thioglycollate-elicited mouse macrophages in a dose-dependent manner. Analysis of flow cytometric data has shown that microbead phagocytosis of resident macrophages, which exhibit a lower basic phagocytic activity than the thioglycollate elicited ones, has been augmented by up to 900% due to lentinan. The percent ratio of phagocytes among peritoneal exudate cells, however, remained unchanged after short-term lentinan stimulation. Preincubation of the cells with lentinan resulted in increased ingestion of the microbeads. Activation of phagocytosis by lentinan is therefore due in part to the direct stimulation of the cells, however, lentinan also serves as supplementary opsonin for C3b-coated beads. Mannan inhibited the ingestion of C3b-coated microspheres by 75%, which was abolished in part when lentinan was also added to the cells. Mannan did not influence the phagocytosis of BSA-coated or IgG-coated beads. Our data, based solely on in vitro studies, suggest a beta-glucan receptor mediated activation of phagocytes by lentinan. These receptors are different from the C3b, Fc or mannose receptors. It is very likely that stimulation of phagocytic activity of macrophages by lentinan may contribute to the antitumor action of this immunopotentiating polysaccharide.

Animals↗
PubMed1990

Transcriptional regulation of hepatic angiotensinogen gene expression by the acute-phase response.

The acute-phase response is a protective physiological reaction to tissue injury manifested by the immediate increase in production and secretion of liver proteins the function of which is to re-establish the homeostasis altered by injury. Such proteins include blood coagulation factors, opsonins, protease-inhibitors and angiotensinogen, a precursor of the potent vasopressor peptide angiotensin II. The angiotensinogen gene is typical of genes regulated during the acute-phase response inasmuch as the promoter regulating its transcription rate is acutely responsive to three known mediators of the acute-phase response: glucocorticoids, and the cytokines interleukin-1 and tumor necrosis factor. We present a model, based on experimental evidence, for the mechanism by which angiotensinogen gene transcription is regulated in a graded fashion by the interplay of several hormonally-inducible transcription factors that bind a hormonally-inducible enhancer unit of the angiotensinogen promoter. These factors include the glucocorticoid receptor, nuclear factor kappa B and members of the CAAT/viral enhancer (C/EBP) family of DNA-binding proteins.

Acute-Phase Reaction↗
PubMed1982

Reversible depression of the reticuloendothelial system by liposomes.

The effect of various doses of different types (reverse phase evaporation vesicles and small unilamellar vesicles) of intravenously injected liposomes on reticuloendothelial activity, as measured by the blood clearance rate of intravenously injected carbon, was investigated. Also the effect of pretreatment with reverse phase evaporation vesicles on blood clearance and tissue distribution of a second dose of similar vesicles was determined. For all concentrations used reverse phase evaporation vesicles caused a reduction in reticuloendothelial activity at least up to 4 h after injection. 24 h after administration the rate of carbon clearance returned to the control level. On the contrary small unilamellar vesicles did not block reticuloendothelial activity. Pretreatment with reverse phase evaporation vesicles (250 mumol/kg) caused an increased blood level and a decreased hepatic uptake of a second dose of the vesicles, injected 1 h after the first dose. This seems to be due to a depression of reticuloendothelial activity and not to a depletion of opsonins. Pretreatment with small unilamellar vesicles (250 mumol/kg) had no significant influence on the tissue distribution of a second dose of vesicles. Our results clearly indicate that reverse phase evaporation vesicles cause a reversible depression of reticuloendothelial activity and this depression seems to be induced by a saturation of reticuloendothelial cells with liposomes.

Animals↗
PubMed1995

Mechanism of the effect of thermotherapy as applied to AIDS.

Artificially induced thermal intermittence using thermogenic agents was utilized to treat AIDS patients in an attempt to make an analogy with the sterilization process by tyndallization employed in laboratories. It is known that micro-organisms are more sensitive to discontinuous than to constant heat. The author believes that the AIDS virus may be either destroyed or weakened using this method which may also provoke an immune stimulus over the body's system of defense, especially over the bone marrow, with the consequent increase of the indexes of lymphocins, opsonins and hematogenesis.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Ingestion and killing of Pasteurella haemolytica A1 by bovine neutrophils in vitro.

In this study, various parameters affecting the ability of bovine neutrophils to ingest and kill a virulent strain of Pasteurella haemolytica A1 in vitro were examined. Ingestion of P. haemolytica was serum dependent (optimal serum concentration 10%) and was mediated principally by heat-stable opsonins, presumably antibodies, that could be removed by absorption with formalin-killed P. haemolytica. Ingested P. haemolytica were killed by neutrophils within 1-4 h incubation; the magnitude of killing being directly dependent on the number of neutrophils present. The number of viable P. haemolytica was reduced by approximately 1.5 log at bacterial concentrations of 0.01-100 P. haemolytica per neutrophil; a concomitant reduction in neutrophil viability was observed at the highest bacterial concentration (100:1). Bovine neutrophils underwent a vigorous luminol-enhanced chemiluminescence response after ingesting opsonized P. haemolytica, thus indicating that reactive oxygen intermediates were being formed that could have contributed to the intracellular killing of P. haemolytica.

Animals↗
PubMed1994

Affinity purification of a mannose-binding protein, a sensitive tool in the diagnostics of IgM, via site-directed phosphorylated mannan bound to alumina.

Ca2+ -dependent mannose-binding proteins (MBPs) belong to the family of animal lectins. They perform in vivo as defence molecules that act as opsonins by enhancing the clearance of mannose rich pathogens and have been used in vitro for the purification of IgM. MBPs have been previously isolated by methods based on binding the protein moiety of various mannan species to different matrices. However, the mannan-protein complexes did not have a constant protein content and the yield of the isolated MBPs was variable. In the present study we describe a new approach for the affinity purification of MBPs based on the main polysaccharide moiety of the complex. After removal of residual phosphate groups naturally occurring at the C-3 position of the sugar, which interfere with MBP recognition, the mannan was phosphorylated enzymatically at C-6, at which position the OH group is not required for lectin binding. The enzymatically phosphorylated mannan bound to an alumina column was used successfully for MBP separation from rabbit serum. The mannose-binding protein obtained was used in our study for diagnostic purposes in the identification and determination of very low concentrations of IgM.

Aluminum Oxide↗
PubMed1986

The role of complement in inflammation during experimental pneumococcal meningitis.

The mechanism whereby an effective bactericidal inflammatory reaction develops in the subarachnoid space is not clearly defined. While normal cerebrospinal fluid is deficient in complement, immunoglobulin and leukocytes, these serum components appear in cerebrospinal fluid (CSF) during the course of bacterial meningitis. Using a rabbit model of pneumococcal meningitis we examined the role of the alternate complement pathway in three early events important to the defense of the subarachnoid space: leukocyte chemotaxis, phagocyte mediated bacterial killing, and clearance of bacterial components from the cerebrospinal fluid space. Rabbits treated with cobra venom factor to deplete complement were inoculated intracisternally with encapsulated (type II or XIX) pneumococci. Following complement depletion, there was a dramatic (at least 100-fold) decrease in the LD50 for these strains. Nevertheless, complement depletion did not affect the magnitude of CSF leucocytosis or the rate of clearance of bacterial particles from CSF. A short delay in the appearance of leukocytes in CSF was found in the absence of complement. The major effect of complement depletion, however, was to diminish the efficiency of leukocyte mediated killing of encapsulated bacteria in the CSF. Although the short delay in the onset of leukocytosis in the complement depleted animals is consistent with a chemotactic role of complement in the normal animal, the quantitatively normal leukocytosis in the complement depleted rabbits clearly indicates that important chemotaxins other than complement function in CSF. Inhibition of leukocytosis by indomethacin and diclofenac suggests that metabolite(s) of the arachidonic acid pathway may perform such a chemotactic role. A major role of complement in the defense of the subarachnoid space appears to be as an opsonin needed for the effective bactericidal activity of leukocytes. It is the lack of this function that best explains the greatly decreased LD50 value of encapsulated pneumococci in the complement depleted animal.

Animals↗