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Results for “OPSONINS”

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PubMed1998

Flow cytometric quantitation of human opsonin-dependent phagocytosis and oxidative burst responses to meningococcal antigens.

A one-step flow cytometric (FCM) assay has been developed to quantify both opsonin- and antigen-dependent phagocytosis and intraphagocyte oxidative burst responses. Meningococcal outer membrane structures (OMV) were adsorbed to fluorescent polystyrene beads, opsonized with serum, and exposed to leukocytes. FCM parameters of phagocytosis were evaluated in combinations with oxidative burst indicators. Rhodamine-123 was the most sensitive indicator and was compatible with quantitation of phagocytosis. The phagocytosis and oxidative burst responses induced by OMV beads were dependent on both antigens and opsonins. Increased human opsonic responses against OMV were induced during clinical meningococcal disease. A dissociation was noted between phagocytosis and oxidative burst in individual cells, indicating that functional opsonins against OMV components may differ in their ability to stimulate phagocytosis and oxidative burst responses. The method facilitates evaluation of purified bacterial structures as mediators of opsonin-dependent phagocytosis and intracellular oxidative microbicidal mechanisms, which is of interest in the complex process of selecting bacterial antigens as constituents of certain vaccines.

Adult↗

PubMedDate not supplied

A humoral opsonin from the solitary urochordate Styela clava.

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.

Animals↗

PubMed1993

Distinction between the depletion of opsonins and the saturation of uptake in the dose-dependent hepatic uptake of liposomes.

Opsonins play a role in the hepatic uptake of particles such as bacteria, lipid emulsion, and liposomes. The objective of this study was to distinguish between opsonin depletion and uptake saturation in the dose-dependent hepatic uptake of liposomes. The uptake of opsonized and unopsonized liposomes was determined in the isolated perfused liver. Serum (2.9 mL) was required to opsonize 1 mumol liposomes fully, indicating that a rat (250 g with 10 mL of serum) can opsonize 3.5 mumol liposomes. Next the dose effect on hepatic uptake of opsonized and unopsonized liposomes was examined. Saturation of uptake was found only for the opsonized liposomes. On the other hand, the hepatic uptake clearance decreased dose dependently from 4.31 to 0.79 (mL/min), with increasing doses from 0.075 to 17 mumol/250 g, respectively, after i.v. administration. Thus, the decrease in the hepatic uptake clearance at the medium dose was due to the saturation of uptake alone, and at the high dose it was due to opsonin depletion as well. These results show that the saturation of liposomal uptake in the liver and the depletion of opsonins occurred at different liposome dosage levels.

Animals↗

PubMed1979

Requirement of heat-labile opsonins for maximal phagocytosis of Candida albicans.

The requirement for heat-labile opsonins for phagocytosis of 2 serologically distinct strains and a number of clinical isolates of Candida albicans was examined by a previously described radiometric technique. The results indicated that both strains and all 10 isolates of C. albicans examined required heat-labile opsonins for maximal phagocytosis. The data suggest that heat-labile opsonins play an important role in immunity to C. albicans. However, the possibility that some strains of C. albicans may not utilize heat-labile opsonins cannot be excluded.

Candida albicans↗

PubMed1993

Heat-stable opsonins in tuberculosis and leprosy.

We have examined heat-stable opsonins to 4 species of gamma-irradiated mycobacteria (M. tuberculosis (H37Rv), M. avium (28A), M. scrofulaceum and M. leprae (cd 103)) in complement-depleted sera collected from Indonesian subjects with tuberculosis (106 patients),-leprosy (24 patients) and controls (40 hospital workers and 41 factory workers) indirectly by microtitre plate chemiluminescence (CL) assay and compared the results with antibody levels. The results indicate that there is a wide range of opsonic capacity for mycobacteria in complement-depleted sera. There was a poor correlation between the opsonic capacity as measured by CL and the anti-mycobacterial antibody content of sera measured by ELISA, suggesting that anti-mycobacterial antibody has little influence on the uptake of mycobacteria. However, a non-specific heat-stable opsonin appears to be present in some sera. Conversely, some sera from tuberculosis or leprosy patients suppress the production of reactive oxygen species from normal phagocytes in vitro when stimulated with M. tuberculosis. The relevance of this inhibition and the presence of heat-stable opsonins to the pathogenesis of tuberculosis have yet to be determined, but it is possible that the presence of opsonins may inhibit dissemination of tubercle bacilli to other organs.

Adolescent↗

PubMed1984

The effect of serum opsonins on the phagocytosis of Staphylococcus aureus and zymosan particles, measured by flow cytometry.

Human leukocyte phagocytosis of S. aureus and zymosan particles was measured by flow cytometry (FCM). Killing of bacteria was measured by a standard microbiological method. When pooled human serum was heated to 56 degrees C for 30 min, the percentage of phagocytosing polymorphonuclear neutrophilic leukocytes (PMNLs), the rate of phagocytosis and killing of S. aureus by the whole leukocyte population were reduced to about 50% of the control values. The results indicate that the impaired phagocytosis and killing were due to the lack of attachment of bacteria opsonized with heat-stabile serum opsonins, mainly IgG, to 50% of the PMNLs. A prey-predator model was used to compare phagocytosis of S. aureus in heated and control serum. The rate of phagocytosis by those PMNLs that were active in heated serum was the same as that of all the leukocytes in control serum, suggesting that heat-labile serum opsonins did not affect the rate of phagocytosis by these PMNLs. PMNLs and monocytes phagocytosed zymosan particles in control serum, but in heated serum only a fraction of the leukocytes, corresponding to the fraction of monocytes phagocytosed. Thus, all PMNLs seem to be capable of phagocytosis by heat-labile serum opsonins. The combined use of S.aureus and zymosan particles may be of advantage in rapid screening of serum opsonin activities and phagocyte function in infectious and haematological disorders.

Adhesiveness↗

PubMed1984

Human opsonins to meningococci after vaccination.

Two groups of volunteers were immunized with either a serogroup A plus C meningococcal polysaccharide vaccine or a combined serogroup B polysaccharide-serotype 2 protein vaccine. Serum opsonin responses were measured by chemiluminescence of polymorphonuclear leukocytes exposed to opsonized live meningococci. Two of the six volunteers immunized with the A plus C vaccine had an increase in serum opsonins to group A meningococci, four responded to group C meningococci, and none to group B meningococci. Five other volunteers who were immunized with the combined group B polysaccharide-serotype 2 protein vaccine responded with an increase in serum opsonins to group B meningococci of two different protein serotypes, as well as to a group C-serotype 2 meningococcal strain. Although no booster effect was observed after a second dose of the combined vaccine, both the polysaccharide and the protein components appear to be able to stimulate an opsonin response.

Bacterial Vaccines↗

PubMed1978

A new semiquantitative radiometric opsonin assay. Selective measurement of opsonizing capacity of the alternative pathway.

A new semiquantitative radiometric opsonin assay is described. It was found that the opsonin activity generated by incubating brewer's yeast, Saccharomyces cerevisiae, in medium containing less than 5% human serum was exclusively complement dependent. In contrast, C. albicans was effectively opsonized in the absence of complement. Antibodies and the early classical complement pathway did not contribute to the opsonization of S. cerevisiae and neither did C5-9. The brewer's yeast assay can therefore be used for measuring selectively the opsonizing capacity of the alternative pathway. Sera from approximately 7% of apparently healthy adult controls consistently failed to generate significant opsonin activity while 8 out of 26 patients with suspected immune deficiency of unknown cause were defective in this assay. All opsonin deficient sera so far tested had haemolytically normal alternative pathway and Factor B activity.

Adult↗

PubMed1997

Bispecific antibodies overcome the opsonin-receptor mismatch of cystic fibrosis in vitro: restoration of neutrophil-mediated phagocytosis and killing of Pseudomonas aeruginosa.

Inflammation and infection associated with bacterial pathogens, primarily Pseudomonas aeruginosa (Pa), are the primary causes of morbidity and mortality for cystic fibrosis (CF) patients. CF patients may be predisposed to these bacterial infections by a defect in phagocytosis due to "opsonin-receptor mismatch," in which a complement receptor (CR1) and an important opsonin (iC3b) are destroyed by proteolytic enzymes. We show that opsonin-receptor mismatch can be mitigated in vitro using a bispecific Ab (bsAb) to cross-link neutrophils via the beta-chain of leukocyte integrins (CD18) to bacterial epitopes or C3d on opsonized Pa. Two chemically cross-linked bsAb were constructed with mAb specific for C3d (or the O-specific side chain of Fisher Devlin Immunotype 1 Pa) and CD18. Using an in vitro model of elastase-mediated opsonin-receptor mismatch, these bsAb specifically enhanced Pa phagocytosis and killing, with the anti-C3d-containing bsAb restoring the levels of phagocytosis to approximately those for the non-elastase-treated opsonic control. These results encourage the further investigation of bsAb as therapeutic agents for bacterial infection in the lungs of CF patients.

Antibodies, Bispecific↗

PubMed1990

Immunorecognition in the freshwater bivalve, Corbicula fluminea. II. Isolation and characterization of a plasma opsonin with hemagglutinating activity.

Opsonizing and agglutinating activities of plasma from the freshwater clam, Corbicula fluminea, were found to be inhibited by the sugars, 2-deoxy-D-glucose (deoxy-Glu) and N-acetyl-D-galactosamine (GalNAc). The plasma opsonin/agglutinin was subsequently isolated by a two-step separation procedure. Aldehyde-fixed rabbit erythrocytes (RRBC) were used as a solid-phase plasma opsonin affinity absorbant, and deoxyGlu and GalNAc were used in the eluting buffer to desorb several RRBC-binding plasma proteins. The second step involved the further separation of sugar-eluted proteins by Sephacryl S-200 gel filtration. A plasma protein with an apparent molecular weight of 40 kd on SDS-PAGE under nonreducing conditions was found to possess both agglutinating and opsonizing activities. It was further shown to be composed of two identical 20 kd subunits associated through disulfide linkage(s). Although this protein shares some structural similarity with other bivalve opsonins, differences in native molecular size or subunit structure, agglutinating properties and/or sugar binding specificity support the current hypothesis that naturally occurring plasma opsonins of molluscs represent a heterogeneous group of proteins unified primarily through their lectin-like characteristic of binding specific carbohydrate determinants.

Animals↗

PubMed1969

Natural immunity to bacterial infections: the relation of complement to heat-labile opsonins.

Heat-labile opsonins to pneumococci in normal mammalian sera, unlike antibodies, fail to interact with the bacteria at 0 degrees C and require Ca(++) and/or Mg(++). They are readily removed from serum by antigen-antibody complexes that fix complement (C) and are inhibited by reagents that inactivate various C components. The principal heat-labile opsonin to pneumococci is activated C3 (C3(b)), but a slight enhancing effect is exerted by one or more of the late-reacting components of the hemolytic complement system (C5-C9). Since heat-labile opsonins are immunologically polyspecific, they presumably play a broad protective role in the early (preantibody) phase of acute bacterial infections.

Animals↗

PubMed1961

The role of opsonins in the clearance of living and inert particles by cells of the reticuloendothelial system.

An investigation of the clearance of bacteria and colloids from the blood stream of mice has shown that both living and inert particles require serum factors (opsonins) in order that they may be phagocytosed by the macrophages of the reticuloendothelial system. It has been demonstrated that after the injection of a large dose of colloid there is a depletion of these serum opsonins which appears to account for the reduced rate of clearance of a second dose of colloid or living bacteria, since replacement of these factors leads to normal clearance. The significance of these results is discussed and it is suggested that in "blockaded" animals there is a depletion of serum opsonins rather than a saturation of phagocytic cells.

Animals↗

PubMed1983

Peritoneal macrophages and opsonins: antibacterial defense in patients undergoing chronic peritoneal dialysis.

The antibacterial activity of phagocytic cells and opsonins in peritoneal dialysis effluents from 21 patients undergoing chronic peritoneal dialysis (CPD) was studied. Effluents contained an average of 12 x 10(6) cells per liter that were predominantly macrophages. Macrophages phagocytized and killed opsonized Staphylococcus epidermidis, Staphylococcus aureus, and Escherichia coli as efficiently as did polymorphonuclear neutrophils (PMNs) from healthy donors. Macrophage chemiluminescence was one-third of that observed with donor PMNs. In the absence of opsonins, macrophages efficiently phagocytized and killed S. aureus by binding S. aureus cell wall protein A to macrophage surface IgG. Nine (43%) of 21 effluents failed to opsonize S. epidermidis, and none opsonized E. coli. When present, titers of S. epidermidis opsonins were 50- to 100-fold lower than that of normal serum. IgG and C3 concentrations in effluent reflected its opsonic capacity. Macrophages from patients undergoing CPD thus have intact phagocytic and bactericidal functions. However, the low level of opsonic molecules and inadequate numbers of macrophages in the peritoneal cavity may predispose patients undergoing CPD to peritonitis.

Ascitic Fluid↗

PubMed1997

Phagocytosis of viable Candida albicans by alveolar macrophages: lack of opsonin function of surfactant protein A.

Surfactant protein A (SP-A) contributes to host defense by opsonizing microbial organisms for phagocytosis by alveolar macrophages (AM). The role of SP-A as opsonin for phagocytosis of Candida albicans was analyzed. AM in suspension exhibited no phagocytosis of nonopsonized yeast. This was not increased by SP-A, whether provided for preincubation of AM or yeast or present during coincubation. However, the engulfment of serum-opsonized yeast by AM in suspension was inhibited by SP-A. This inhibitory effect was mimicked by complement subcomponent C1q and concanavalin A but not by type IV collagen. SP-A did not interfere with phagocytosis of serum-opsonized yeast by adherent AM, monocytes, neutrophils, or peritoneal macrophages. SP-A lacks function as an opsonin for the phagocytosis of C. albicans by AM but interferes with binding of yeast to AM, inhibiting subsequent ingestion. The role of SP-A as an alveolar space opsonin may thus critically depend on the microbial species involved.

Animals↗

PubMed1984

The role of plasma fibronectin as a nonantibody, noncomplement opsonin for Staphylococcus aureus.

The possible role of plasma fibronectin as a nonantibody, noncomplement opsonin for S. aureus was studied using peripheral blood leukocytes from healthy rabbits. Fibronectin depletion of normal rabbit serum by affinity absorption chromatography reduced the opsonic ability of that serum (p less than 0.05) and resulted in impaired bacterial killing of S. aureus in vitro. The addition of purified fibronectin to fibronectin-depleted serum significantly reversed the opsonic defect (p less than 0.01). The combination of complement inactivation, plus fibronectin depletion, resulted in a severe opsonic deficiency that was much worse than either deficiency alone (p less than 0.05). However, fibronectin alone in the absence of other serum factors was a poor opsonin for S. aureus, suggesting that its major role as an opsonin might be to augment or amplify other serum factors.

Animals↗

PubMed1991

Defective Candida opsonin and procidin function in patients with recurrent pyogenic infection: a common immunodeficiency.

Polymorphonuclear cell function tests were performed in 340 patients with recurrent unexplained infections. Serum-dependent defects in phagocytosis and intracellular killing of Candida albicans (Candida opsonin and procidin defects) were specifically associated with susceptibility to recurrent pyogenic infections, Candida opsonin defects occurring in 12.7% and Candida procidin defects in 20.8% of patients compared with 3.7% of healthy controls. Saccharomyces cerevisiae opsonin deficiencies were also found frequently in patients with recurrent infections, being present in 18.2% compared with 7.4% controls, although not specifically in those with pyogenic infection.

Adolescent↗

PubMed1998

Binding of the capsule-like serotype-specific polysaccharide antigen and the lipopolysaccharide from Actinobacillus actinomycetemcomitans to human complement-derived opsonins.

We investigated the molecular mechanism of resistance of Actinobacillus actinomycetemcomitans to complement-dependent chemiluminescence response by human polymorphonuclear leukocytes. Whole cells of serotype b-specific polysaccharide antigen-defective mutants ST2 and ST5 were constructed by inserting transposon Tn916 into A. actinomycetemcomitans strain Y4. These strains induced strong chemiluminescence response by human polymorphonuclear leukocytes and markedly bound to human complement-derived opsonins. In contrast, strain Y4 induced weak chemiluminescence response and weakly bound to complement-derived opsonins. The biosensor analysis revealed that lipopolysaccharide from strain Y4 strongly bound to human C3b, but serotype b-specific polysaccharide antigen did not. The serotype b-specific polysaccharide antigen molecule might sterically hinder the interaction between complement-derived opsonins and lipopolysaccharide to reduce complement-dependent chemiluminescence response by human polymorphonuclear leukocytes.

Adult↗

PubMed1999

Human opsonins induced during meningococcal disease recognize transferrin binding protein complexes.

Patient serum opsonins against transferrin binding protein A+B (TbpA+B) complexes from two Neisseria meningitidis strains (K454 and B16B6, with 85- and 68-kDa TbpB, respectively) were quantified by a functional phagocytosis and oxidative burst assay. TbpA+B complexes adsorbed to fluorescent beads were opsonized with individual acute and convalescent sera from 40 patients infected by a variety of meningococcal strains. Flow cytometric quantitation of leukocyte phagocytosis products (PP) demonstrated that disease-induced serum opsonins recognized TbpA+B, and the highest anti-TbpA+B serum opsonic activities were found between admission to hospital and 6 weeks later. The PP values obtained with TbpA+B from strain B16B6 (PP(B16B6)) were higher than those obtained with TbpA+B from strain K454 (PP(K454)), with both acute and convalescent sera (P < 0.0001), and correlated positively with higher immunoglobulin G enzyme-linked immunosorbent assay titers against TbpA+B from strain B16B6 than from strain K454 (P < 0.001). In spite of considerable variations between individuals, significant correlations were found between the PP(B16B6) and PP(K454) values, and the PP values did not depend on the variability of the TbpB proteins of the disease-causing strains. Simultaneously measured oxidative burst activity correlated closely with the PP values. We conclude that highly cross-reactive anti-TbpA+B serum opsonins are produced during meningococcal disease. The anti-TbpA+B opsonic activities were not affected by the variability of the TbpB proteins of the disease-causing strains, which further adds to the evidence for the vaccine potential of meningococcal TbpA+B complexes.

Adolescent↗