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PubMed1968

Phagocytosis in subacute bacterial endocarditis. Localization of the primary opsonic site to Fc fragment.

The opsonic properties of immune gammaG-globulins isolated from patients with chronic septicemic conditions, principally subacute bacterial endocarditis were studied. Opsonic capacity as well as complement-fixing properties of gamma-globulins appeared to be closely associated with integrity of Fc structures. Progressive pepsin digestion of immune gammaG-globulins, as monitored by successive loss of Gm(a) and Gm(b) antigens, abolished opsonic activity. Colostral gammaA, containing agglutinating antibacterial antibodies but no demonstrable complement-fixing activity, was devoid of opsonic capacity. Reduction of gamma-globulin opsonins with 0.01 or 0.1 M mercaptoethanol progressively abolished opsonic activity in parallel with loss of ability of treated gamma-globulins to fix complement with bacteria. Treatment of gamma-globulin opsonins with 0.01 M sodium metaperiodate also produced complete loss of opsonic capacity in parallel with loss of Gm(b) Fc antigens. These findings, together with antiopsonic effects demonstrable with anti-gamma-globulin factors showing primary reactivity with Fc structures, indicate that the opsonic property of immune gamma-globulins requires the participation of structures integral to the Fc region of gamma-globulin.

Agglutination Tests↗
PubMed1976

2-Deoxyglucose selectively inhibits Fc and complement receptor-mediated phagocytosis in mouse peritoneal macrophages II. Dissociation of the inhibitory effects of 2-deoxyglucose on phagocytosis and ATP generation.

Macrophages incubated in 2-deoxy-D-glucose (2-dG)-containing medium showed a marked decrease in cellular ATP content, and were unable to ingest IgG- and complement-coated erythrocytes via the corresponding membrane receptors for these ligands. However, the inhibitory effects of 2-dG on Fc- and C3 receptor-mediated phagocytosis were not a consequence of lowered macrophage ATP levels since addition of glucose or mannose to the culture medium restored the capacity of the macrophages to ingest IgG- and C3-coated particles without increasing ATP levels. These results indicate that Fc- and C3 receptor-mediated phagocytosis (opsonin dependent) differs qualitatively from the ingestion of latex and zymosan particles (opsonin independent); they suggest that the same regulatory molecules govern the responses of phagocytic cells to signals initiated by both the Fc and C3 receptors. The possibility that these molecules are regulated by glycosylation is discussed.

Adenosine Triphosphate↗
PubMed1977

The role of membrane receptors for C3b and C3d in phagocytosis.

In this paper we re-examine the roles of particle-bound IgG and C3 in phagocytosis of sheep erythrocytes (E) by monolayers of purified human monocytes and polymorphonuclear leukocytes (PMN). We conclude that two fragments of the C3 molecule, that is, C3b and C3d, can function as opsonins if the phagocyte has the appropriate membrane receptors. Monocytes, that bind both C3b and C3d, respond to both as opsonins. PMN, which do not bind C3d, respond only to particles opsonized with C3b. C3 and IgG have separate roles in phagocytosis. IgG, through its Fc fragment, directly stimulates particle ingestion, but is relatively inefficient at inducing particle binding. On the other hand, C3 primarily mediates the binding of the particle via complement receptors. A marked synergy exists between C3 and IgG in inducing phagocytosis. Thus, opsonization of the particle with C3 can be a necessary condition for particle ingestion, although by itself C3 does not trigger phagocytosis. The opsonic effect of C3 can be mimicked by a variety of nonimmunologic agents which enhance binding of the particle to the phagocyte without directly stimulating ingestion. The contact-inducing agents used include centrifugation of particle and phagocyte, high molecular weight dextran, protamine, and treatment of E with neuraminidase. These results suggest that the role of C3 in opsonization is mainly or exclusively one of establishing contact between particle and phagocyte.

Agglutination↗
PubMed1997

In vivo effects of recombinant human granulocyte colony-stimulating factor on neutrophil oxidative functions in normal human volunteers.

The effect of daily in vivo granulocyte colony-stimulating factor (G-CSF) treatment on neutrophil function was studied over a 14-day period using a luminescence system for differential measurement of oxidase and myeloperoxidase (MPO) dioxygenation activities in whole blood. Opsonin receptor-mediated phagocyte functions were also measured with this system. G-CSF produced a dose-dependent neutrophil leukocytosis and a proportional increase in oxidase activity per volume of blood. The oxidase activity per neutrophil remained relatively constant throughout the test period. However, both chemical- and opsonin-stimulated MPO oxygenation activities per neutrophil were greatly increased by treatment with maxima correlating temporally to initial G-CSF exposure during the early mitotic phase of neutrophil development. The possibility that peroxynitrite contributes to this maximum luminol-dependent activity was tested, but neither superoxide dismutase, a competitive inhibitor of peroxynitrite production, nor N-methyl-L-arginine, an inhibitor of nitric oxide synthase, exerted a significant inhibitory effect.

Adult↗
PubMedDate not supplied

Interactions of polymorphonuclear leukocytes with anaerobic bacteria.

The interactions of anaerobic bacteria with polymorphonuclear leukocytes (PMNs) are reviewed. Anaerobes, including species of Propionibacterium, Fusobacterium, and Bacteroides, produce serum-independent chemotactic factors capable of attracting PMNs. In addition, these bacteria produce chemoattractants by complement activation and possibly by interaction with host lipids. Bacteroides species are optimally phagocytosed by PMNs when opsonized by both immunoglobulin and complement although the latter appears to provide the critical opsonin. As is the case with several aerobic bacteria, the polysaccharide capsule of Bacteroides fragilis interferes with PMN phagocytosis and antibody to the capsule partially overcomes this virulence property. The presence of Bacteroides species may also inhibit PMN phagocytosis and killing of aerobic gramnegative bacteria either by competing for limited opsonins or by decreasing intracellular killing. Bactericidal activity of PMNs against anaerobes appears to proceed primarily through oxygen-independent mechanisms, although the relevant microbicidal components have not been identified. Some antibiotics with activity against anaerobic bacteria penetrate PMNs, and antibiotic pretreatment of B. fragilis, with levels below the minimal inhibitory concentration, facilitates PMN phagocytosis of these organisms.

Anti-Bacterial Agents↗
PubMed1980

Interactions of phagocytic and bacterial cells in patients with bacteremia caused by gram-negative rods.

The phagocytic and bactericidal functions of polymorphonuclear leukocytes and monocytes and the opsonic activity of serum from patients with gram-negative bacteremia were compared with those of cells and serum from healthy donors and control patients. Leukocytes from five of 20 patients showed diminished phagocytic capacity. Leukocytes from three of 12 patients had decreased chemotactic activity. Eleven of 37 blood culture isolates were inefficiently phagocytized after opsonization in homologous patient serum. However, in no instance was the opsonic capacity of patient serum significantly lower than that of control serum. In the serum of some patients, an increase in heat-stable opsonins was found during the course of infection. Resistance to opsonization of strains of Escherichia coli correlated with the presence of K capsular polysaccharide. It was concluded that both impaired leukocyte function and ineffective opsonization play a role in the pathogenesis of gram-negative bacteremia. Heat-stable opsonins (presumably specific antibodies) appear to be necessary for effective phagocytosis of bacilli that cause gram-negative bacteremia.

Antigens, Bacterial↗
PubMed1981

Phagocytosis and algicidal activity of human polymorphonuclear neutrophils against Prototheca wickerhamii.

Protothecosis is an uncommon infection due to Prototheca wickerhamii. Recently, a patient with progressive cutaneous protothecosis and an apparent defect in the ability of her polymorphonuclear neutrophils (PMNs) to kill P. wickerhamii was successfully treated. Therefore, the role of PMNs and serum opsonins in host defense against tissue invasion by this organism was evaluated. The results show that human PMNs ingested and kill P. wickerhamii. Ultrastructural studies revealed digestion of the organism by PMNs 60 min after ingestion. Optimal phagocytosis and killing of P. wickerhamii by PMNs required the presence of both specific IgG antibody and heat-labile opsonins.

Antibodies↗
PubMed1992

Binding of unopsonized Cryptococcus neoformans by human bronchoalveolar macrophages: inhibition by a large-molecular-size serum component.

Infection with Cryptococcus neoformans usually begins after inhalation of airborne organisms. Since levels of opsonins in the alveolar space may be low, the ability of human bronchoalveolar macrophages to bind C. neoformans in the presence and absence of opsonins was studied. Bronchoalveolar macrophages bound unopsonized C. neoformans. Surprisingly, component(s) in pooled human serum (PHS) inhibited binding, as evidenced by 26% and 71% inhibition of binding when 20% PHS and heat-inactivated PHS (HI-PHS), respectively, were added to the system. Separation of PHS by molecular size revealed that the inhibitory component had an apparent molecular weight greater than 10(6) and was inhibitory at nanomolar concentrations. PHS stimulated and HI-PHS had no effect on binding of acapsular C. neoformans and zymosan particles to bronchoalveolar macrophages. These data demonstrate that bronchoalveolar macrophages can bind unopsonized, encapsulated C. neoformans, but that serum component(s) inhibits binding.

Bacterial Adhesion↗
PubMed1993

Function of uterine and blood-derived polymorphonuclear neutrophils in mares susceptible and resistant to chronic uterine infection: phagocytosis and chemotaxis.

In vitro phagocytosis and chemotaxis of uterine and blood-derived polymorphonuclear neutrophils (PMNs) were compared in mares with different resistance to chronic uterine infection (CUI). Both the primary in vitro function of PMNs and the role of uterine environmental factors on PMN function were investigated. The uteri of mares susceptible to (n = 6) and resistant to CUI (n = 5) were inoculated with 5 x 10(6) Streptococcus zooepidemicus when the mares were in estrus. Uterine secretions in addition to uterine and blood-derived PMNs were sampled at 5 and 24 h later. During a subsequent estrus, bacterial inoculation of the uterus was repeated, and samples were removed from the mares 12 and 36 h later. Neither the phagocytic nor the chemotactic capacity of PMNs changed over time in any of the groups. However, chemoattractive properties of uterine secretions declined over time in both resistant (p < 0.0007) and susceptible mares (p < 0.01). Significantly higher phagocytosis (p < 0.03) and chemotaxis (p < 0.05) by uterine derived PMNs were found in the susceptible mares compared to resistant mares when a standardized opsonin (pooled plasma) was used. However, uterine secretions from susceptible mares demonstrated a poorer opsonizing capacity (p < 0.00002) but were more chemoattractant (p < 0.004) than secretions from resistant mares. When opsonins and chemoattractants were provided by plasma, no differences were detected in phagocytosis between blood-derived and uterine PMNs. In contrast, chemotaxis of uterine PMNs were superior to blood-derived PMNs in both resistant (p < 0.007) and susceptible mares (p < 0.0001) under these conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1978

Opsonic alpha2 surface binding glycoprotein therapy during sepsis.

A pronounced depletion of an opsonic protein for hepatic reticuloendothelial (RE) phagocytosis has been demonstrated in critically ill trauma patients. This opsonic alpha(2) surface binding (SB) glycoprotein has immunologic identity and a similar amino acid composition to cold insoluble globulin (CIg). Since CIg can be concentrated in cryoprecipitate, it was utilized as a readily available source of opsonic alpha(2)SB glycoprotein for replacement therapy after injury with documented hypoopsonemia. Six septic patients (2 multiple trauma, 2 thermal burn, and 2 intra-abdominal abscess) were studied to test whether cryoprecipitate infusion would restore this humoral component. Pre- and posttherapy opsonin levels were determined by bioassay and electroimmunoassay. In all patients, severe opsonin depletion was reversed following cryoprecipitate infusion. All patients had a rapid improvement in febrile state, normalization of leukocyte levels, and improvement in pulmonary function as evidenced by decreasing requirements for end expiratory pressure at lowered levels of inspired oxygen. One patient was studied more extensively and demonstrated an increase in cardiac output, limb blood flow, total body and limb oxygen delivery, total body and limb oxygen consumption and a progressive decrease in pulmonary shunt fraction. Thus, opsonic alpha(2)SB glycoprotein deficiency can be reversed by cryoprecipitate infusion in critically ill septic injured patients. Replacement of this humoral factor may be an important therapeutic modality in prevention of multiple organ failure, but it should be administered only after documentation of hypoopsonemia in traumatized patients.

Adult↗
PubMed1989

Interaction of Candida albicans with neutrophils: effect of phenotypic changes in yeast cell-surface composition.

The susceptibility of four strains of Candida albicans to phagocytosis and intracellular killing by rabbit peritoneal neutrophils was investigated. Two of the strains, isolated from active infections, were known to synthesize a surface layer of mannoprotein fibrils in response to growth on 500 mm-galactose; the other strains, from asymptomatic carriers, lacked this capability. The presence of serum opsonins greatly enhanced phagocytosis of all four strains and, following opsonization, phagocytosis of an infective strain was equally rapid after growth on either 500 mm-galactose or 50 mm-glucose. In the absence of opsonins, galactose-grown infective strains were phagocytosed faster than either glucose-grown infective strains or galactose-grown carrier strains. These differences in phagocytic uptake were paralleled by differences in neutrophil chemiluminescence response. Intracellular killing of galactose-grown infective strains was only half that of glucose-grown infective strains or galactose-grown carrier strains after incubation for 60 min. Pretreatment of neutrophils with extracellular polymeric material, which contains the surface fibrils, completely inhibited intracellular killing. These results indicate that production of the fibrillar layer promotes yeast virulence by increasing resistance to intracellular killing, although it may enhance phagocytosis in locations where opsonic activity is poor.

Animals↗
PubMed1979

Phagocytosis measured as inhibition of uridine uptake: a method that distinguishes between surface adherence and ingestion.

Polymorphonuclear leucocytes selectively inhibited the incorporation of 14C-uridine by intracellular staphylococci. Within specified limits, the amount of radiolabel incorporated by extracellular staphylococci was related to bacterial concentration. The incorporation of labelled uridine can thus be exploited to assay the extent to which association between staphylococci and polymorphonuclear leucocytes reflects surface adherence as opposed to ingestion. A comparison of the new method with a conventional viable-count determination of leucocyte-associated bacteria shows it to be comparable in efficiency when non-immune serum is used as opsonin and superior when specific opsonin is used.

Cell Membrane↗
PubMed1995

Non-opsonic phagocytosis of Trichophyton mentagrophytes arthroconidia by human neutrophils in vitro.

A non-opsonic mechanism of binding and phagocytosis by human neutrophils of Trichophyton mentagrophytes arthroconidia is described. This was in direct contrast to the complement dependency of Candida albicans phagocytosis. Both serum complement and specific antibody to T. mentagrophytes promoted maximal phagocytosis (61% and 40% of neutrophils, respectively, contained arthroconidia). Increasing the ratio of arthroconidia to neutrophils did not increase non-opsonic phagocytosis (18-26%). Phagocytosis of arthroconidia exposed to trypsin in the absence of opsonin was not affected (18%). However, proteinase and chitinase reduced the level of non-opsonic and opsonic phagocytosis to negligible levels (6.3% and 4.5%, respectively). When mannose was added to neutrophils, mannose receptors on the phagocyte membrane were partially blocked when arthroconidia were opsonised, but this did not reduce the level of non-opsonic phagocytosis. The non-opsonic mechanism proposed here may have direct relevance in skin sites poor in opsonins.

Cells, Cultured↗
PubMed1989

Platelet-dependent induction and amplification of polymorphonuclear leucocyte lysosomal enzyme release.

Degranulation of human polymorphonuclear leucocytes induced by opsonized zymosan (OpZ) was studied in the presence or absence of platelets, either resting or stimulated by thrombin. Lysozyme secretion from polymorphonuclear leucocytes stimulated with OpZ increased in the presence of platelets. A further increase was observed when platelets had been stimulated with thrombin. The effect was dependent on platelet concentration (10-80 platelets/polymorphonuclear leucocytes). Resting polymorphonuclear leucocytes could be activated by platelets that had been stimulated with thrombin with an optimal effect observed at 0.1 U/ml of thrombin. Substitution of platelets with platelet-released products only resulted in significant stimulation of polymorphonuclear leucocytes at concentrations above those used in the coincubations experiments. Zymosan coated with various opsonins showed a gradient in the relative intensity of polymorphonuclear leucocytes degranulation. Platelet-dependent enhancement of polymorphonuclear leucocytes degranulation was higher with opsonins that were poorer at inducing lysosomal secretion. The role of platelets as helper cells in the activation of polymorphonuclear leucocytes appears to be dominant when polymorphonuclear leucocytes are challenged in suboptimal conditions. Positive interactions between platelets and polymorphonuclear leucocytes may be relevant in vivo at the site of inflammation where platelets could enhance effector functions of polymorphonuclear leucocytes.

Blood Platelets↗
PubMed2006

Non-opsonising aggregates of IgG and complement in haemoglobin C erythrocytes.

Haemoglobin C (HbC) differs from normal HbA by a lysine for glutamate substitution at position 6 of beta-globin. Heterozygous AC and homozygous CC phenotypes are associated with shortened erythrocyte life spans and mild anaemia. AC and CC erythrocytes contain elevated amounts of membrane-associated haemichromes, band 3 clusters, and immunoglobulin G (IgG) in vivo. These findings led us to investigate whether AC and CC erythrocytes might expose elevated levels of IgG and complement, two opsonins that have been implicated in the phagocytic clearance of senescent and sickle erythrocytes. Surprisingly, we found IgG, complement, and other plasma proteins co-localised in aggregates beneath the membrane of circulating AC and CC erythrocytes. These observations, and our finding of similar aggregates in erythrocytes heterozygous or homozygous for haemoglobin S (sickle-cell haemoglobin), suggest that the vast majority of membrane-associated IgG and complement detected in these abnormal erythrocytes is intracellular and does not contribute to the eventual opsonic clearance of these cells. Phagocytosis studies with macrophages provide evidence in support of this suggestion. Studies of erythrocyte clearance that involve the detection of membrane-associated IgG and complement as putative opsonins should investigate the possibility that these plasma proteins reside in the erythrocyte interior, and not on the cell surface.

Anemia, Sickle Cell↗
PubMed1979

Opsonization of Cryptococcus neoformans by human immunoglobulin G: role of immunoglobulin G in phagocytosis by macrophages.

The role of immunoglobulin G (IgG) as an opsonin in phagocytosis of Cryptococcus neoformans by macrophages was investigated. Labeling with 125I showed that IgG isolated from normal human serum bound to non-encapsulated C. neoformans. Furthermore, IgG-opsonized cryptococci were agglutinated by anti-serum to IgG heavy chains, indicating that normal human serum contains antibody that will bind to the yeast surface. The IgG isolated from normal serum accounted for all opsonizing activity found in normal human serum, since differences were not noted between the opsonizing activities of whole serum, heat-inactivated serum and purified IgG when these opsonins were compared at equivalent concentrations of IgG. Phagocytosis of IgG-opsonized cryptococci was inhibited by anti-macrophage IgG, a reagent known to block Fc-mediated attachment and ingestion, and by pepsin digestion of opsonizing IgG. Thus, IgG opsonization is an Fc-dependent process. Opsonizing IgG appears to play its major role during the attachment phase of phagocytosis, since antimacrophage IgG blocked attachment of cryptococci to macrophages but could not block ingestion of IgG-opsonized cryptococci that had been allowed to attach to macrophages. Ingestion of opsonized cryptococci was not blocked by 2-deoxy-D-glucose, a reagent known to block Fc-mediated ingestion, thus confirming that IgG has a primary role in attachment and suggesting that ingestion is mediated by a process that is not Fc dependent.

Agglutination↗
PubMed1979

Opsonic activity of normal human cerebrospinal fluid for selected bacterial species.

The opsonic activity of normal human cerebrospinal fluid (CSF) has not been well defined. In this study, the opsonic activity of normal CSF for laboratory and blood culture isolates of Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli, Hemophilus influenzae type b, and Neisseria meningitidis was measured by a quantitative assay employing radiolabeled bacteria and polymorphonuclear leukocytes. All isolates of S. aureus, except the Wood 46 strain, were opsonized in undiluted CSF (>50% uptake by polymorphonuclear leukocytes.) There was heat-stable and heat-labile opsonic activity in CSF for S. aureus. Only one blood culture isolate of E. coli was moderately well opsonized in undiluted CSF (26% uptake). None of the remaining laboratory or clinical isolates were opsonized in undiluted CSF. The S. aureus isolates were more readily opsonized in dilute normal serum than were the other bacterial species, and complement appeared to be the heat-labile opsonin in serum. However, complement may not be the heat-labile opsonin in normal CSF for S. aureus. In contrast to serum, complement C3 was not visualized on the staphylococcal cell surface by immunofluorescence microscopy and chelation of CSF did not diminish opsonic activity. This study demonstrates that normal CSF is opsonic for S. aureus but not for bacterial species that more commonly cause meningitis. These species differences in opsonic requirements may be important in the pathogenesis of meningitis.

Bacteria↗
PubMed1980

Opsonization of four Bacteroides species: role of the classical complement pathway and immunoglobulin.

Previous investigators have suggested that opsonization of two Bacteroides species is mediated exclusively by the alternative complement pathway and requires immunoglobulins. In this study, the nature of the opsonic factors in nonimmune human serum for four species of Bacteroides was investigated by measuring uptake of [(3)H]thymidine-labeled bacteria by human polymorphonuclear leukocytes. Normal human serum, C2-deficient serum, immunoglobulin-deficient serum, and serum chelated with ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetic acid (EGTA), MgEGTA, and ethylenediaminetetraacetic acid (EDTA) were used as opsonic sources. Heat inactivation of each of these sera significantly reduced its opsonic activity for all four Bacteroides species, suggesting that serum complement was essential for effective opsonization. All strains were opsonized in the absence of the classical complement pathway; however, kinetics studies revealed that opsonization proceeded at a significantly faster rate when the classical complement pathway was intact. Although two strains were opsonized in immunoglobulin-deficient sera, opsonization was less efficient and appeared to occur via the alternative complement pathway. Unexpectedly, all strains were well opsonized by the classical complement pathway in 10% serum which had been effectively chelated with EGTA or EDTA. The explanation for this finding is unknown; however, it is possible that cell wall cations of Bacteroides species may participate in the activation of complement in chelated serum, resulting in effective opsonization. It was also found that Bacteroides, when incubated with an Escherichia coli strain in normal serum, could compete for opsonins and thereby reduce phagocytosis of E. coli. It is possible that competition for opsonins among bacterial species contributes to the synergistic role these organisms share in mixed floral infections.

Bacteroides↗