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David A Raftos - One of the best experts on this subject based on the ideXlab platform.

  • the sea urchin complement homologue spc3 functions as an Opsonin
    The Journal of Experimental Biology, 2004
    Co-Authors: L A Clow, David A Raftos, Paul S Gross, Courtney L Smith
    Abstract:

    The purple sea urchin Strongylocentrotus purpuratus expresses a homologue of complement component C3 (SpC3), which acts as a humoral Opsonin. Significantly increased phagocytic activity was evident when yeast target cells were opsonized after incubation with coelomic fluid containing SpC3. SpC3 could be detected on the surface of yeast, and phagocytic activity could be inhibited by an anti-SpC3 antibody. This indicates that SpC3 promotes phagocytosis by physically tagging target cells for ingestion. Confocal microscopy showed that opsonized yeast were phagocytosed by a single coelomocyte type (polygonal phagocytes), presumably because these cells express SpC3 receptors. Overall, these data indicate that SpC3 is a major humoral Opsonin in S. purpuratus coelomic fluid.

  • a humoral Opsonin from the solitary urochordate styela clava
    Developmental and Comparative Immunology, 1993
    Co-Authors: Karen L Kelly, Edwin L Cooper, David A Raftos
    Abstract:

    Opsonins play a key role in invertebrate humoral immune systems. An Opsonin for yeast was identified in the plasma of the tunicate, Styela clava. In vitro cultures of hemocytes with homologous plasma-incubated yeast exhibited significantly higher levels of phagocytosis than controls. Studies indicated that the opsonic activity of Styela clava plasma increased the overall capacity for phagocytosis. Opsonization was inhibited by the carbohydrates mannan, N-acetyl-D-galactosamine, and galactose, and by the divalent cation chelator, EDTA. These data suggest that the Styela clava Opsonin may share some functional similarities with a C-type lectin. Incubation of yeast with Styela clava and Styela plicata plasma prior to phagocytosis by hemocytes from both species indicated the Styela clava Opsonin is species specific.

  • purification and characterization of a humoral Opsonin from the solitary urochordate styela clava
    Comparative Biochemistry and Physiology B, 1992
    Co-Authors: Karen L Kelly, Edwin L Cooper, David A Raftos
    Abstract:

    1. We have previously identified opsonic activity in the plasma of the solitary urochordate, Styela clava. 2. Here, we report the purification and further characterization of the opsonic molecule. 3. Two purification methods were employed. 4. Gel filtration yielded one strongly opsonic fraction that contained a single, electrophoretically-resolved protein. 5. Opsonic activity was dose-dependent and sensitive to tryptic digestion and heat denaturation. 6. SDS-PAGE and calibrated gel filtration indicated the opsonic protein was a 17.5 kDa monomer while isoelectrofocusing indicated a single pI of 7.0. 7. In an alternative procedure, a similar opsonic activity and protein were isolated by affinity purification using whole yeast cells.

Marvin Lesser - One of the best experts on this subject based on the ideXlab platform.

  • lipopolysaccharide induced stimulation of alveolar macrophage Opsonin independent phagocytosis
    Journal of Surgical Research, 1992
    Co-Authors: Christopher Cardozo, Jonathan Edelman, Marvin Lesser
    Abstract:

    Alveolar macrophage (AM) Opsonin-independent phagocytosis may be an important process by which bacteria are cleared from the airspaces. Although it has been shown that clearance of bacteria from the lung is altered in association with endotoxemia, the effect of endotoxemia on Opsonin-independent phagocytosis is unknown. Because alterations in AM Opsonin-independent phagocytosis could potentially influence bacterial clearance in the lung, we studied the effects of the intravenous injection of Escherichia coli lipopolysaccharide (LPS) into rats on AM Opsonin-independent phagocytosis of latex particles. AM obtained by bronchoalveolar lavage (BAL) 2 or 4 hr after injection of LPS demonstrated phagocytosis comparable to AM from control animals. In contrast, AM obtained 12 hr after injection of LPS demonstrated a nearly threefold increase in phagocytosis. Depletion of serum complement with Naja naja cobra venom factor (CVF) did not alter LPS-induced augmentation of phagocytosis. Furthermore, phagocytosis of AM obtained by BAL 2 or 12 hr after activation of complement by injection of CVF was not significantly different from that of AM from control animals, indicating that complement activation alone was not sufficient to stimulate Opsonin-independent phagocytosis. These observations suggest that Opsonin-independent phagocytosis may represent an important route of bacterial uptake by AM following endotoxemia, and that LPS-induced stimulation of AM Opsonin-independent phagocytosis may occur independently of activation of complement by LPS.

James D Bryers - One of the best experts on this subject based on the ideXlab platform.

  • artificial Opsonin enhances bacterial phagocytosis oxidative burst and chemokine production by human neutrophils
    Pathogens and Disease, 2017
    Co-Authors: Kristy N Katzenmeyer, Luisa Mayorga Szott, James D Bryers
    Abstract:

    Here, we describe the application of an 'artificial Opsonin' to stimulate the innate immune response against Gram-positive bacteria. The artificial Opsonin comprises a poly(L-lysine)-graft-poly(ethylene glycol) backbone displaying multiple copies of vancomycin and human IgG-Fc. The vancomycin targets bacteria by recognizing d-Ala-d-Ala-terminated peptides present in the bacterial cell wall. The human IgG-Fc antibody fragments serve as phagocyte recognition moieties that recognize the Fcγ cell surface receptors expressed by professional human phagocytes. Staphylococcus epidermidis RP62A, a biofilm-forming, methicillin-resistant strain, was utilized to investigate the effects of opsonization on phagocytosis, oxidative burst and IL-8 chemokine production by human neutrophils. Results show that opsonization of S. epidermidis RP62A with the artificial Opsonin resulted in an ∼2-fold increase in neutrophil phagocytosis. Analysis of the cell supernatant found a 2- to 3-fold increase in neutrophil IL-8 secretion. The neutrophil oxidative burst was investigated using the oxidation-sensitive fluorophore dihydrorhodamine-123. Bacterial opsonization resulted in a 20% increase in fluorescence intensity, indicating a significant increase in the production of reactive oxygen species by the neutrophils. These studies suggest that artificial Opsonins may be a novel immunostimulation therapeutic strategy to control infections caused by Gram-positive bacteria, particularly those that are known to be immune evasive and/or antibiotic resistant.

  • multivalent artificial Opsonin for the recognition and phagocytosis of gram positive bacteria by human phagocytes
    Biomaterials, 2011
    Co-Authors: Kristy N Katzenmeyer, James D Bryers
    Abstract:

    Abstract Hospital-acquired infections (HAIs) remain a leading cause of death in the United States. Unfortunately, treatment of HAIs is complicated by the emergence of antibiotic-resistant bacterial strains. In an effort to enhance the body’s natural immune response to infection, we have developed an artificial Opsonin to promote the recognition, phagocytosis, and destruction of pathogenic bacteria by human phagocytes. The artificial Opsonin is constructed from multivalent conjugates of poly( l -lysine)-graft-poly(ethylene glycol) with vancomycin and human IgG-Fc. Our approach utilizes vancomycin’s inherent ability to bind to d -Ala- d -Ala terminated peptides present in the cell wall of Gram-positive bacteria. Here, we show that conjugation of vancomycin to PLL-g-PEG prevents its action as an antibiotic and allows vancomycin to function solely as a recognition molecule. Human IgG-Fc antibody fragment serves as a phagocyte recognition molecule and is recognized by the Fcγ cell surface receptors expressed on professional human phagocytes. Using flow cytometry, we found that a polysaccharide-encapsulated, methicillin-resistant strain of Staphylococcus epidermidis is efficiently recognized by the artificial Opsonin (nearly 100% of cells were opsonized) and that Opsonin binding is specific since it can be inhibited by the soluble cell wall peptide analog acetyl-Lys- d -Ala- d -Ala. Opsonization of S. epidermidis resulted in an approximate 2-fold increase in phagocytosis by a human neutrophil cell line. Notably, Enterococcus faecalis VanB, a bacterial strain with inducible vancomycin resistance, was used to show that the artificial Opsonin does not unintentionally induce antibiotic resistance mechanisms.

Yutaka Atomi - One of the best experts on this subject based on the ideXlab platform.

  • effect of granulocyte colony stimulating factor on Opsonin receptor expression in cerulein induced acute pancreatitis
    Pancreas, 2005
    Co-Authors: Hongfang Tuo, Masanori Sugiyama, Takashi Watanabe, Masanobu Nakashima, Nobutsugu Abe, Yutaka Atomi
    Abstract:

    OBJECTIVES Decreased levels of expression of Opsonin receptors (CD11b and CD32/16) on peritoneal exudate neutrophils may lead to susceptibility to infection. Granulocyte colony-stimulating factor (G-CSF) increases the expression levels of CD11b on neutrophils and prolongs neutrophil survival. The effects of G-CSF on neutrophils and Opsonin receptor expressions of neutrophils were investigated in cerulein-induced acute pancreatitis. METHODS Forty-two mice were randomly assigned to each group (n = 6). Mice received subcutaneous G-CSF (120 microg/kg body weight) before the induction of acute pancreatitis with cerulein. Saline was used for instead of G-CSF or cerulein solution in control groups. CD11b and CD32/16 expression levels on circulatory and peritoneal exudate neutrophils were investigated 6 and 24 hours after the induction of acute pancreatitis. RESULTS Treatment with G-CSF did not aggravate the inflammation of pancreatic tissue evaluated by plasma amylase, acinar necrosis. However, it significantly increased the number of peritoneal exudate neutrophils (P < 0.05) and the CD11b- (P < 0.05) and CD32/16-positive (P < 0.05) peritoneal exudate neutrophils in mice with cerulein-induced acute pancreatitis. The means of fluorescence intensity for CD11b and CD32/16 expressions on circulatory and peritoneal exudate neutrophils were also elevated in the G-CSF groups. CONCLUSION G-CSF administration increases the numbers of neutrophils and improves expression levels of Opsonin receptors on neutrophils in mice with cerulein-induced acute pancreatitis.

  • Opsonin receptor expression on peritoneal exudative and circulatory neutrophils in murine acute pancreatitis
    Pancreas, 2001
    Co-Authors: Nobuhiko Hatano, Masanori Sugiyama, Takashi Watanabe, Yutaka Atomi
    Abstract:

    Acute severe (necrotizing) pancreatitis is often associated with pancreatic or peripancreatic infection. Decreased bacterial clearance due to impaired immune defense may cause local infection. We investigated expressions of surface Opsonin receptors (CD11b, complement receptor 3; CD32/CD16, immunoglobulin G Fc receptor) on local and circulatory neutrophils, in murine acute pancreatitis. The mild and severe forms of acute pancreatitis were induced by seven and 13 subcutaneous injections of caerulein, respectively. Peritoneal exudative and circulatory neutrophils were counted and assayed for receptor expressions by flow cytometry, serially at 1-72 hours after pancreatitis induction. Histologically, mild and severe forms showed edematous and necrotizing pancreatitis, respectively. The peritoneal exudative neutrophil count was greater in mild than in severe pancreatitis. Expressions of CD11b and CD32/CD16 on local neutrophils were upregulated early in mild pancreatitis. This upregulation was attenuated in severe pancreatitis. The circulatory neutrophil count was elevated in severe pancreatitis but was unchanged in mild pancreatitis. Opsonin receptor expression on circulatory neutrophils showed a transient, modest upregulation in the early phase of mild pancreatitis. Receptor-positive circulatory neutrophils showed a marked elevation that persisted throughout the course of severe pancreatitis. In conclusion, severe (necrotizing) pancreatitis is associated with reduced Opsonin receptor expression on local neutrophils and enhanced expression on circulatory neutrophils, as compared with mild (edematous) pancreatitis. These changes may contribute to local infectious complications and multiple organ failure, in severe pancreatitis.

Karen L Kelly - One of the best experts on this subject based on the ideXlab platform.

  • a humoral Opsonin from the solitary urochordate styela clava
    Developmental and Comparative Immunology, 1993
    Co-Authors: Karen L Kelly, Edwin L Cooper, David A Raftos
    Abstract:

    Opsonins play a key role in invertebrate humoral immune systems. An Opsonin for yeast was identified in the plasma of the tunicate, Styela clava. In vitro cultures of hemocytes with homologous plasma-incubated yeast exhibited significantly higher levels of phagocytosis than controls. Studies indicated that the opsonic activity of Styela clava plasma increased the overall capacity for phagocytosis. Opsonization was inhibited by the carbohydrates mannan, N-acetyl-D-galactosamine, and galactose, and by the divalent cation chelator, EDTA. These data suggest that the Styela clava Opsonin may share some functional similarities with a C-type lectin. Incubation of yeast with Styela clava and Styela plicata plasma prior to phagocytosis by hemocytes from both species indicated the Styela clava Opsonin is species specific.

  • purification and characterization of a humoral Opsonin from the solitary urochordate styela clava
    Comparative Biochemistry and Physiology B, 1992
    Co-Authors: Karen L Kelly, Edwin L Cooper, David A Raftos
    Abstract:

    1. We have previously identified opsonic activity in the plasma of the solitary urochordate, Styela clava. 2. Here, we report the purification and further characterization of the opsonic molecule. 3. Two purification methods were employed. 4. Gel filtration yielded one strongly opsonic fraction that contained a single, electrophoretically-resolved protein. 5. Opsonic activity was dose-dependent and sensitive to tryptic digestion and heat denaturation. 6. SDS-PAGE and calibrated gel filtration indicated the opsonic protein was a 17.5 kDa monomer while isoelectrofocusing indicated a single pI of 7.0. 7. In an alternative procedure, a similar opsonic activity and protein were isolated by affinity purification using whole yeast cells.