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PubMed1988

Opsonin-dependent stimulation of bovine neutrophil oxidative metabolism by Brucella abortus.

Nonopsonized Brucella abortus and bacteria treated with fresh antiserum, heat-inactivated antiserum, or normal bovine serum were evaluated for their ability to stimulate production of superoxide anion and myeloperoxidase-mediated iodination by neutrophils from cattle. Brucella abortus opsonized with fresh antiserum or heat-inactivated antiserum stimulated production of approximately 3 nmol of O2-/10(6) neutrophils/30 min. Similarly treated bacteria also stimulated the binding of approximately 4.3 nmol of NaI/10(7) neutrophils/h to protein. Significant (P less than 0.05) production of O2- and iodination activity by neutrophils were not stimulated by nonopsonized bacteria or organisms treated with normal bovine serum. Seemingly, B abortus stimulated oxidative metabolism in bovine neutrophils; however, the stimulation was dependent on the presence of bacterial associated opsonins.

Animals↗
PubMed1986

Immune opsonin-independent phagocytosis by pulmonary macrophages.

The uptake of albumin-coated latex particles by hamster pulmonary macrophages (PM) in vitro was investigated by using a new technique that combined flow cytometry and fluorescence microscopy to differentiate and quantitate bound vs ingested particles. In the absence of serum, PM avidly bound and ingested particles, whereas phagocytosis by hamster polymorphonuclear leukocytes (PMN) was less marked. In the presence of serum, phagocytosis by PM was slightly depressed, whereas phagocytosis by PMN was stimulated more than 10-fold. The binding of particles to PM in the absence of serum was pH, temperature, and trypsin sensitive and was dependent on the presence of extracellular Ca++ but not Mg++. The ingestion of particles by this immune opsonin-independent pathway was also temperature sensitive but was not affected by either pH or extracellular Ca++. Particle ingestion, but not binding, was inhibited by cytochalasin D and the divalent cation ionophore A23187.

Albumins↗
PubMed1987

Molecular regulation of phagocyte function. Evidence for involvement of a guanosine triphosphate-binding protein in opsonin-mediated phagocytosis by monocytes.

Although many functions of phagocytes are known to be regulated by guanosine triphosphate (GTP)-binding proteins, phagocytosis itself has not been considered one of these. However, previous studies have examined only unstimulated neutrophil phagocytosis. Motivated by our previous work, which showed that stimulated neutrophil phagocytosis is regulated by GTP-binding proteins (H. D. Gresham, M. G. Peters, and E. J. Brown. 1986. J. Cell Biol. 103:215a), we have examined the effect of pertussis toxin (PT) on monocyte receptor-mediated phagocytosis. PT inhibited unstimulated and fibronectin-stimulated IgG-mediated phagocytosis and also inhibited C3b-mediated phagocytosis stimulated by fibronectin or phorbol dibutyrate. Cholera toxin (CT) had no effect on unstimulated or stimulated phagocytosis mediated by IgG or C3b. PT inhibition of phagocytosis was not mediated via increases in cellular cAMP levels or by inhibition of the respiratory burst. Inhibition of phagocytosis did not result from decreased numbers of plasma membrane opsonin receptors nor decreased ability to bind opsonized targets. Although phorbol ester-stimulated phagocytosis was inhibited by PT, ligand-independent internalization of CR1 stimulated by phorbol dibutyrate proceeded normally in PT-intoxicated cells. We conclude that a PT-sensitive GTP-binding protein does regulate phagocytic function in monocytes. This protein operates on a molecular mechanism specific to the process of ingestion in both unstimulated monocytes and in cells stimulated to increase phagocytosis. Because unstimulated neutrophil phagocytosis is unaffected by PT or CT, and stimulated neutrophil phagocytosis is inhibited by both PT and CT, our data also demonstrate that monocytes and neutrophils have distinct mechanisms for regulation of phagocytic function.

Catalase↗
PubMed1977

The role of easily released substances (ERS) from bacteria in physiologic solution in natural immunity. VI. Induction of opsonins for different genera of bacteria by ERS from Staph. aureus oxford.

ERS obtained from Staph. aureus by mild extraction with physiologic saline solution possess activity of inducing nonspecific opsonins which react with homologous bacteria and with related Gram-negative bacteria. ERS from Staph. aureus weakly stimulated precipitins and antibodies active in passive hemagglutination and induced a marked rise in agglutinin titers especially for the homologous strain and Gram-negative S. typhimurium bacilli. N-acetyl-D-glucosamine absorbed the opsonizing factor for various bacteria with heterologous activity.

Acetylglucosamine↗
PubMed1979

The interaction of opsonins with human polymorphonuclear leucocytes (PMN). I. The influence of human complement (C) and IgG on ingestion and digestion of C-resistant E. coli.

The influence of opsonization on ingestion and digestion of C-resistant E. coli was tested in a phagocytic system consisting of a monolayer of human PMN to which was added E. coli opsonized in different ways. At the end of the phagocytosis, noningested bacteria were separated and the monolayer was removed. The cells were then fractionated. The number of bacteria at different time intervals and the amount and distribution of lysosomal enzymes in the cell fractions were determined. It became apparent that the ingestion of cell-attached bacteria was independent of opsonins. However, the intracellular destruction was enhanced following opsonization with C only, although this was not the result of a greater discharge of lysosomal enzymes into the phagosome. We postulate that sublethal damage of E. coli by C renders the bacteria more sensitive to the bactericidal activity of the phagocytes.

Bacteriolysis↗
PubMed1986

[Possible role of opsonins in adsorption and transport of biological membranes and viruses by Staphylococci].

Electron microscopy of ultrathin sections of Staphylococcus aureus cells, Wood-46 strain, opsonized by the blood serum has revealed deposition of blood serum components on the bacterial cell walls. The bacteria opsonized by the blood serum absorbed biological membranes and the influenza virus virions. Staphylococcus-opsonin-virus complexes were digested by polymorphonuclear leukocytes. In mixed infection models staphylococci and influenza virus virions were detected in different parts of the phagocyte cytoplasm.

Adsorption↗
PubMed1986

Inhibition of immune opsonin-independent phagocytosis by antibody to a pulmonary macrophage cell surface antigen.

Unlike other hamster phagocytes, hamster pulmonary macrophages (PM) avidly ingest albumin-coated latex particles in the absence of serum. They also possess a highly specific cell surface antigen. To evaluate the relationship between these two characteristics, PM were incubated with mouse monoclonal antibody directed against the PM antigen. After unbound antibody was removed, the amount of bound antibody and the phagocytic capability of PM were measured by flow cytometry and fluorescence microscopy. Maximum antibody binding produced a 25% inhibition of ingestion. Particle attachment was not affected. This effect was antigen specific, since neither a nonspecific mouse myeloma protein of the same subclass nor a mouse antibody that bound to another hamster surface antigen had any effect on binding or ingestion. If antigen-specific F(ab')2 fragments were introduced both before and during the period of phagocytosis, the inhibition of particle ingestion approached 100%. Particle binding increased at low F(ab')2 concentrations but declined at higher concentrations. Because calcium may play a role in the ingestion process, the effect of antibody on 45Ca uptake was evaluated. It was observed that antigen-specific F(ab')2 fragments stimulated 45Ca uptake, whereas control antibodies did not. These results suggest that the antigen reacting with our anti-hamster PM monoclonal antibody is involved in immune opsonin-independent phagocytosis and that calcium participates in this phagocytic process.

Animals↗
PubMed1977

[Opsonins and erythrophagocytosis].

The author studied the capacity of granulocytes and reticular cells of rat bone marrow to phagocytize mouse red blood cells in the action of opsonins against them. A comparative assessment of phagocytosis of fresh and formaldehyde-treated mouse red blood cells was conducted. A moderate phagocytosis observed with the use of fresh erythrocytes and immune noninactivated rat serum was less pronounced when inactivated serum was used. No phagocytosis occurred with rat nonimmune serum. On the contrary, when formaldehyde-treated erythrocytes were used with the same sera phagocytosis was much stronger.

Animals↗
PubMed1984

Interaction between human polymorphonuclear leucocytes and Staphylococcus aureus in the presence and absence of opsonins.

Phagocytosis of Staphylococcus aureus by human polymorphonuclear leucocytes (PMN) in the presence and absence of opsonins was studied with an assay which allows interaction between PMN and bacteria on a surface. The kinetics of uptake, the activity of the metabolic burst, and the degranulation during phagocytosis of opsonized and unopsonized bacteria were compared. Uptake of unopsonized S. aureus proceeded at a slower rate, but unopsonized staphylococci induced metabolic activity and degranulation in the PMN to the same extent as opsonized bacteria. Treatment of PMN with a metabolic inhibitor (2-deoxy-D-glucose) or with an inhibitor of microfilament function (cytochalasin B) totally inhibited the capacity of PMN to ingest unopsonized S. aureus, whereas uptake of opsonized bacteria was much less affected. Treatment of the PMN with pronase prevented uptake of unopsonized bacteria, but had no effect on the uptake of opsonized bacteria. Uptake was not inhibited by mannose. Recognition of S. aureus by the PMN was not dependent on the presence of the cell wall components protein A or teichoic acid. The presence of a capsule inhibited uptake.

Cell Wall↗
PubMed1984

Human fibronectin is an opsonin for IgG antibody-coated sheep erythrocytes.

We studied the effect of human fibronectin on the binding and phagocytosis of IgG antibody-coated sheep erythrocytes (EA) by human monocytes. EA were preincubated with or without fibronectin (100 micrograms/ml) at 37 degrees C for 3 hours and both EA and EA-fibronectin were subsequently exposed to monocyte monolayers. A significantly higher percent of monocytes formed rosettes and phagocytosed EA-fibronectin than EA. To determine if the enhancing effect of fibronectin was on the EA or on the monocytes, several experiments were performed. EA were preincubated with or without fibronectin for 3 hours, washed, and added to monocyte monolayers. Percent rosettes and phagocytosis was significantly higher in monocytes incubated with EA-fibronectin than with EA. By contrast, preincubation of monocytes with soluble fibronectin at 37 degrees C for 15 minutes had no significant effect on their ability to bind or phagocytose EA. Thus fibronectin affects EA and enhances its binding to the monocytes. Both monocyte-EA and EA-fibronectin rosettes were completely inhibited by preincubation of monocytes with large concentrations of heat-aggregated IgG. However, below this maximal inhibitory concentration, heat-aggregated IgG produced significantly less inhibition of EA-fibronectin than EA rosettes. Our results suggest that EA-fibronectin binds exclusively to the monocyte Fc receptor and that fibronectin enhances the affinity of EA for the receptor. We did not demonstrate any effect of fibronectin on the interaction of monocytes with IgM antibody-coated or heat-damaged sheep erythrocytes. In conclusion under our test conditions, fibronectin acts as a opsonin for EA.

Animals↗
PubMed1978

Opsonins in human serum for the phagocytosis of complexes between IgG and protein A of Staphylococcus aureus.

The phagocytosis of complexes between staphylococcal protein A and 125I-labelled IgG is enhanced by fresh human serum and to a somewhat lesser extent by heat-inactivated serum. Opsonizing activity is detected in two distinct peaks by Sephadex G-200 column chromatography. One peak corresponds to the excluded material and the other to the ascending limb of the second protein peak. The active material in serum is retained on a protein A-Sepharose but not on an IgG-Sepharose column. Active material eluted from a protein A-Sepharose column and run on a Sephadex G-200 column again shows two activity peaks corresponding to those obtained on chromatography of whole serum. The first peak contains mainly IgA nd IgM but very little total protein material. The second peak contains mainly IgG but also IgA. Purified normal IgA, but not one myeloma IgA preparation tested, has the capacity to enhance phagocytosis of protein A-IgG complexes. Possible examinations for the opsonin activity are discussed.

Chromatography, Gel↗
PubMed1993

Conglutinin acts as an opsonin for influenza A viruses.

Since the 1940's, non-Ig inhibitors of influenza A virus (IAV) hemagglutination activity and infectivity have been recognized in mammalian sera. Recently, the heat labile (beta) inhibitor of this type was identified by indirect methods as the lectin, conglutinin. In support of this hypothesis, we found that purified conglutinin strongly inhibited hemagglutination activity and infectivity of IAV. By using IAV strains with specific variations in glycosylation of the hemagglutinin molecule, we showed these effects to be mediated by binding of conglutinin to high mannose carbohydrate attachments on the viral hemagglutinin. Through the same mechanism conglutinin caused aggregation of IAV particles. Human neutrophils produce hydrogen peroxide upon exposure to IAV. Also, after a brief period of exposure to IAV, neutrophils exhibit depressed responsiveness (deactivation) upon exposure to other stimuli (e.g., chemotactic peptides). These phenomena may be related to the in vivo inflammatory response during IAV infection, and to the propensity of IAV-infected subjects to suffer bacterial superinfection. Pre-incubation of IAV with conglutinin markedly potentiated human neutrophil hydrogen peroxide production in response to the virus. This effect correlated with the ability of conglutinin to aggregate the virus. IAV treated with conglutinin also caused significantly less neutrophil deactivation than did the unopsonized virus. These enhancements of neutrophil respiratory burst responses by conglutinin were again mediated by binding of the lectin to viral carbohydrates. The mammalian C-type lectin family includes conglutinin, mannose-binding protein, and surfactant proteins A and D. These lectins may be important constituents of the initial host response to IAV, by inhibiting IAV infectivity directly, causing viral aggregation, and acting as opsonins to enhance phagocyte responses to the virus.

Animals↗
PubMed1993

Killing of Staphylococcus aureus by tumor necrosis factor-alpha-activated neutrophils. The role of serum opsonins, integrin receptors, respiratory burst, and degranulation.

We have examined the effects of TNF priming on the killing of Staphylococcus aureus by human neutrophils. In the absence of serum opsonins, neutrophils failed to kill S. aureus, and TNF priming did not induce the cells to become bactericidal. Normal human serum, containing complement activity, promoted the killing of the bacteria by neutrophils. Pretreatment of neutrophils for 30 min with TNF significantly enhanced their bactericidal activity. The effects of TNF on neutrophil bactericidal activity was dependent on serum concentration and the degree of enhancement induced increased up to a concentration of 1%. The kinetics of bacterial killing showed that TNF-only enhanced the initial rate of killing, over the first 30 min. Little killing of bacteria occurred in the presence of complement-inactivated serum, and TNF did not stimulate this killing. These results suggest that TNF enhances the neutrophil complement-dependent killing of S. aureus. TNF increased the expression of CR3 (CD11b/CD18) and CR4 (P150, 95; CD11c/CD18) adhesion receptors but not LFA-1 (CD11a/CD18); and mAb against the alpha-chain of either CR3 or CR4 but not LFA-1 prevented the enhancing effects of TNF on the neutrophil bactericidal activity.

Animals↗
PubMedDate not supplied

Comparison of the effect of different opsonins on the phagocytosis of fluorescein-labeled staphylococcal bacteria by chicken heterophils.

Heterophil phagocytosis of fluorescein-labeled staphylococcal bacteria was analyzed by flow cytometry. Opsonization with two types of normal pooled sera and staphylococcal antisera significantly increased bacterial phagocytosis compared to samples without an opsonin. The staphylococcal antisera did not significantly increase bacterial phagocytosis compared to the normal pooled sera. Opsonization appears to increase bacterial phagocytosis but specific antisera may not increase phagocytosis beyond that caused by pooled normal sera.

Animals↗
PubMed1986

Opsonin independent interaction of Klebsiella strains with human polymorphonuclear leukocytes.

Nine encapsulated Klebsiella strains with different types of fimbriation and their nonencapsulated mutants were tested for their stimulatory potency for human polymorphonuclear leukocytes in the absence of opsonins. The luminol chemiluminescence assay was used for these experiments. It could be shown that the interaction between Klebsiella bacteria and human leukocytes is rather complex depending not only on the presence of capsules but also on the hydrophobicity of Klebsiella surface and on the type of fimbriation existing.

Fimbriae, Bacterial↗
PubMed1997

Hepatitis B virus binding to leucocyte plasma membranes utilizes a different region of the preS1 domain to the hepatocyte receptor binding site and does not require receptors for opsonins.

A quantitative assay of hepatitis B virus (HBV) binding to hepatocyte plasma membranes was adapted to show that leucocyte plasma membranes bind serum-derived HBV saturably, and that this binding is inhibited using synthetic peptides representative of the large envelope protein of HBV. Using a panel of ligand-blocking monoclonal antibodies (mAb) to opsonin receptors, it was shown that the three classes of Fc gamma R and CR3 are not major receptors for HBV on leucocytes or hepatocytes. It was also shown that HBV does not utilize the receptor for IgA, Fc alpha R, for attachment to leucocytes, despite reported sequence homology between the large envelope protein of HBV and the Fc portion of human IgA. Evidence is presented that the receptor for HBV on leucocytes may differ from the hepatocyte receptor(s), based on synthetic peptide inhibition assays of HBV binding. Furthermore, it was observed that glycosaminoglycans influence the HBV-liver and leucocyte interactions, providing evidence that HBV attachment may be a multi-stage process.

Adult↗
PubMed1995

Neisserial porins inhibit human neutrophil actin polymerization, degranulation, opsonin receptor expression, and phagocytosis but prime the neutrophils to increase their oxidative burst.

Porins are trimeric proteins that constitute water-filled pores that allow transmembrane diffusion of small solutes through the outer membrane layer of gram-negative bacteria. The porins are capable of inserting into the membranes of eucaryotic cells, and in the present study we have examined the in vitro effects on neutrophil functions of the following purified porins: meningococcal outer membrane protein classes 1 and 3 and gonococcal outer membrane protein 1B (P1B). The neisserial porins inhibited human neutrophil chemoattractant-induced actin polymerization and degranulation of both primary and secondary granules. The neutrophil expression of immunoglobulin G (IgG) Fc receptors II (Fc gamma RII; CDw32) and III (Fc gamma RIII; CD16), as well as the activation-dependent downregulation of Fc gamma RIII, were reduced by the meningococcal and gonococcal porins. The neisserial porins impaired the upregulation of complement receptors 1 (CD35) and 3 (CD11b) and inhibited the phagocytic capacity of neutrophils, as evaluated by the uptake of meningococci (strain 44/76) in the presence of patient serum containing known amounts of IgG against meningococcal porins. The porins also primed neutrophils to increase their intracellular hydrogen peroxide production in response to FMLP, whereas no such priming was observed if the neutrophil protein kinase C was stimulated directly with phorbol myristate acetate. The neisserial porins influenced neutrophil functions in a time- and concentration-dependent manner. The meningococcal class 1 outer membrane protein and the gonococcal P1B tended to alter neutrophil functions more than the meningococcal class 3 protein. Thus, the neisserial porins inhibited human neutrophil actin polymerization, degranulation, opsonin receptor expression, and phagocytosis but primed the neutrophils to increase their oxidative burst. It remains to be determined whether these in vitro observations reflect mechanisms that may be of importance for the interaction between neutrophils and Neisseria species in vivo.

Actins↗
PubMed2003

Dendritic cells as host cells for the promastigote and amastigote stages of Leishmania amazonensis: the role of opsonins in parasite uptake and dendritic cell maturation.

In their mammalian hosts, Leishmania are obligate intracellular parasites that mainly reside in macrophages. They are also phagocytosed by dendritic cells (DCs), which play decisive roles in the induction and shaping of T cell-dependent immune responses. Little is known about the role of DCs in the Leishmania life cycle. Here, we examined the ability of mouse bone marrow-derived DCs to serve as hosts for L. amazonensis. Both infective stages of Leishmania (metacyclic promastigotes and amastigotes) could be phagocytosed by DCs, regardless of whether they had previously been experimentally opsonized with either the complement C3 component or specific antibodies. Parasites could survive and even multiply in these cells for at least 72 hours, within parasitophorous vacuoles displaying phagolysosomal characteristics and MHC class II and H-2M molecules. We then studied the degree of maturation reached by infected DCs according to the parasite stage internalised and the type of opsonin used. The cell surface expression of CD24, CD40, CD54, CD80, CD86, OX40L and MHC class II molecules was barely altered following infection with unopsonized promastigotes or amastigotes from nude mice or with C3-coated promastigotes. Even 69 hours post-phagocytosis, a large proportion of infected DCs remained phenotypically immature. In contrast, internalisation of antibody-opsonized promastigotes or amastigotes induced DCs to mature rapidly, as shown by the over-expression of costimulatory, adhesion and MHC class II molecules. Thus, in the absence of specific antibodies (e.g. shortly after infecting naive mammals), infected DCs may remain immature or semi-mature, meaning that they are unable to elicit an efficient anti-Leishmania T cell response. Absence of DC maturation or delayed/incomplete DC maturation could thus be beneficial for the parasites, allowing their establishment and amplification before the onset of immune responses.

Animals↗