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PubMed1993

Opsonin-independent adherence and intracellular development of Legionella pneumophila within U-937 cells.

Legionella pneumophila adhered to and multiplied intracellularly in the human histiocytic lymphoma U-937 cell line. The infectious process was evaluated by viable bacterial cell colony counts and documented by transmission and scanning electron microscopy. In the absence of opsonins, wash-resistant bacterial adherence to host cells occurred within 1 h and attachment of 1 or 2 organisms per U-937 host cell involved close surface interactions at the prokaryotic and eukaryotic membranes. Intracellular multiplication of bacteria was maximal by 24 h after inoculation of cell monolayers. Release of L. pneumophila from these cells appeared as a lytic process that resulted in an increase in the numbers of microorganisms in the extracellular fluids and a concomitant decline in the number of intracellular bacteria. The course of cellular infection was completed by 72 h. The cellular and ultrastructural events of L. pneumophila adherence and uptake by U-937 cells in the absence of antibody or complement have been defined. In addition, this work further establishes the U-937 cell as a suitable model for investigating Legionella--host cell interactions.

Bacterial Adhesion↗
PubMed1991

Surfactant protein A is opsonin in phagocytosis of herpes simplex virus type 1 by rat alveolar macrophages.

In the present study we used flow cytometry to investigate the phagocytosis of fluorescein isothiocyanate-labeled herpes simplex virus type 1 (FITC-HSV-1) by rat alveolar macrophages and the effects of surfactant protein A (SP-A) on this process. The phagocytosis of FITC-HSV-1 by alveolar macrophages, which was studied as a model for virus phagocytosis in general, was strongly enhanced in the presence of SP-A. The SP-A-mediated phagocytosis was time and concentration dependent, reaching a maximal level after 15 min of incubation and at an SP-A concentration of 5 micrograms/ml. Using a fluorescence quenching technique, we could show that at least 65% of the viruses were indeed internalized by the macrophages. The addition of SP-A to the system was sufficient for the phagocytosis of FITC-HSV-1 by the alveolar macrophages, suggesting that SP-A acts as an opsonin. This hypothesis was further strengthened by the observation that F(ab')2 fragments of immunoglobulin G directed against SP-A could abolish FITC-HSV-1 phagocytosis by alveolar macrophages preincubated with SP-A. Comparing the opsonic capacity of serum and SP-A, SP-A proved to be twice as potent as serum in stimulating phagocytosis of FITC-HSV-1 by alveolar macrophages. Complement factor C1q, which is known to possess a similar collagen-like domain as SP-A, did not stimulate phagocytosis of FITC-HSV-1 by alveolar macrophages nor did it inhibit SP-A-mediated HSV-1 phagocytosis. This study demonstrates that SP-A may play an important role in the antiviral defenses of the lung.

Animals↗
PubMed1994

Combined therapy of granulocyte transfusions, intravenous opsonins and antibiotics for gram-negative pneumonia in neutropenic cancer patients.

Four patients with hematological malignancies, following bone marrow transplantation, who developed documented gram-negative [Klebsiella pneumoniae (2), Pseudomonas aeruginosa or Acinetobacter calcoaceticus] pneumonia during absolute neutropenia, were treated with a combination of antimicrobial therapy, granulocyte transfusions, and high-dose intravenous immunoglobulin. The patients recovered following this regimen, including 2 who had septic shock and respiratory failure, necessitating intubation and mechanical ventilation. These data suggest that therapy combining antimicrobial agents, granulocyte transfusions and opsonins may be effective in neutropenic patients who develop gram-negative pneumonia.

Adult↗
PubMed1992

Assay for opsonin activity based on chemiluminescence of a Cypiridina luciferin analog.

Opsonin activity (OA) was investigated in serum samples from cord blood of 11 full-term newborn infants and 12 healthy adult volunteers by the method of luminol-dependent chemiluminescence (L-CL) and Cypiridina luciferin analog-dependent chemiluminescence (CLA-CL) together with the measurement of complement components (C3, C4, C3A and properdin). CL and complement components of cord samples were significantly lower than that of healthy adult blood. CLA-CL showed a significant correlationship to C3 and C3A. L-CL also displayed a significant correlationship to C3A but the relationship to C3 was not significant. From these results, when OA is measured by CL, CLA-CL is preferred to L-CL as a technique.

Adult↗
PubMed1982

Opsonin-independent phagocytosis by human alveolar macrophages: augmentation by human plasma fibronectin.

A trypsin-sensitive membrane recognition unit that mediates phagocytosis of particulate activators of the human alternative complement pathway is present on human alveolar macrophages. Fragmented human plasma fibronectin selected by affinity chromatography with a monoclonal antifibronectin antibody augments this capacity. These data suggest a nonimmune mechanism for the clearance of some microorganisms from the opsonin-deficient microenvironment of the lung in which the alveolar macrophage is the principal resident phagocyte.

Fibronectins↗
PubMed1981

Cystic fibrosis pseudomonas opsonins. Inhibitory nature in an in vitro phagocytic assay.

Pseudomonas aeruginosa infection plays a primary pathogenetic role in the chronic respiratory tract disease of cystic fibrosis (CF) patients. Despite pronounced humoral immune responses, reflected by high levels of antibodies against Pseudomonas in serum and in sputum, the antibodies do not eliminate this bacterium. In the present study we have used affinity chromatography with a lipopolysaccharide substituted immunoadsorbent gel to isolate high titers (meanCF = 1:256) of immunotype specific Pseudomonas IgG antibodies from the sera of nine CF subjects, and have evaluated the functional ability of these antibodies to promote phagocytosis and intracellular killing of P. aeruginosa in an in vitro human alveolar macrophage culture system. The phagocytic and intracellular bactericidal kinetics revealed that CF IgG antibodies function in an inhibitory fashion. Both the rate of phagocytosis (rateCF = 204 cpm/unit time) and absolute bacterial uptakes maximal at 120 min (uptakeCF = 18 x 10(3) 14C cpm) were inhibited compared with appropriate positive controls (hyperimmune serum, HIS; [rateHIS = 399; uptakeHIS = 29 x 10(3), P less than 0.005]). The ability of such CF-derived opsonins to potentiate macrophage intracellular bactericidal processes was mildly impaired (bacterial survivalCF = 15 x 10(3) colony forming units (CFU)/min, survivalHIS = 9 x 10(3)). Further characterization of this defect, assessed with functional studies of the Fab and Fc portions of the immunoglobulin molecule, revealed an impairment in the attachment of these specific antibodies to the alveolar macrophage membrane Fc gamma receptors. Preliminary studies of the physical-chemical properties of these immunoglobulins were normal. The expression of this inhibitory activity in vivo may facilitate Pseudomonas colonization and the subsequent established infections in the respiratory tracts of CF subjects.

Antibodies, Bacterial↗
PubMed1990

Neutrophil elastase cleaves C3bi on opsonized pseudomonas as well as CR1 on neutrophils to create a functionally important opsonin receptor mismatch.

Neutrophil elastase has been implicated as a factor that impairs local host defenses in chronic Pseudomonas aeruginosa (Pa) lung infection in cystic fibrosis (CF). We recently showed that this enzyme cleaves the C3b receptor, CR1, from neutrophils (PMN) in the lungs of infected CF patients. The C3bi receptor on these cells, CR3, is resistant to elastase. We now show that purified neutrophil elastase markedly impairs complement-mediated PMN-Pa interactions including phagocytosis of opsonized Pa, stimulation by opsonized Pa of PMN superoxide production, and killing of opsonized Pa by PMN. When PMN and opsonized Pa were treated separately with elastase, additive levels of inhibition were observed in each of the above assays. The effects on the bacteria were due to cleavage of the bound C3bi from the surface of opsonized Pa by neutrophil elastase. C3bi was also cleaved by pseudomonas elastase, or bronchoalveolar lavage fluid from CF patients with chronic Pa lung infection. Inhibitors of neutrophil elastase eliminated C3bi cleavage by BAL fluid, while inhibitors of pseudomonas elastase had no effect. Blocking CR1 and CR3 on PMN with specific monoclonal antibodies reduced phagocytosis of opsonized Pa to an extent similar to that caused by elastase cleavage of CR1 on PMN and C3bi on Pa. We conclude that neutrophil elastase in the lungs of chronically infected CF patients cleaves C3bi from opsonized Pa as well as CR1 from PMN, creating an "opsonin-receptor mismatch" that severely impairs complement-mediated phagocytic host defenses against these bacteria.

Bacterial Adhesion↗
PubMed1993

Human mannose-binding protein functions as an opsonin for influenza A viruses.

Influenza A viruses (IAVs) cause substantial morbidity and mortality in yearly epidemics, which result from the ability of the virus to alter the antigenicity of its envelope proteins. Despite the rapid replication of this virus and its ability to infect a wide variety of cell types, viremia is rare and the infection is generally limited to the upper respiratory tract. The preimmune host defense response against IAV is generally, therefore, successful. We have previously provided (and summarized) evidence that neutrophils contribute to defense against IAV, although neutrophil dysfunction and local tissue damage may be less salutory byproducts of this response. Here we provide evidence that the serum lectin mannose-binding protein directly inhibits hemagglutinin activity and infectivity of several strains of IAV. In addition mannose-binding protein acts as an opsonin, enhancing neutrophil reactivity against IAV. Opsonization of IAV by mannose-binding protein also protects the neutrophil from IAV-induced dysfunction. These effects are observed with physiologically relevant concentrations of mannose-binding protein. Two different allelic forms of recombinant mannose-binding protein are found to have similar effects. We believe, on the basis of these data, that mannose-binding protein alone and in conjunction with phagocytic cells is an important constituent of natural immunity (i.e., preimmune defense) against IAV.

Acute-Phase Proteins↗
PubMed1998

Acute phase and opsonin response in cardiac surgery patients: influence of underlying cardiac disease.

Cardiopulmonary bypass (CPB) leads to an activation of plasma cascade systems, complement activation, and an acute phase response. To evaluate the influence of the underlying cardiac disease on the activation pattern of these systems, we compared inflammatory changes in coronary artery bypass grafting (CABG) patients with patients undergoing aortic valve replacement. We investigated changes of the acute phase proteins alpha 1-proteinase inhibitor and fibrinogen, the unspecific opsonin fibronectin, and the complement components C3c and C4 induced by extracorporeal circulation in 12 patients undergoing aortic valve replacement and in 12 patients undergoing CABG. Concentrations of C3c and C4 decreased in both groups after the onset of CPB and C4 concentration remained below post-induction levels up to 24 h after onset of CPB (p = 0.04). Fibronectin levels dropped immediately before the onset of CPB (p = 0.01), reaching the lowest values after 20 min of extracorporeal circulation. Fibrinogen and alpha 1-proteinase inhibitor levels after induction of anaesthesia were significantly higher in the CABG group and remained higher throughout the entire study period (p < 0.001). As an indicator of a postoperative acute phase response, concentrations of both proteins rose in the postoperative period above post-induction levels (p < 0.02).

Acute-Phase Reaction↗
PubMed2006

Critical role for serum opsonins and complement receptors CR3 (CD11b/CD18) and CR4 (CD11c/CD18) in phagocytosis of Francisella tularensis by human dendritic cells (DC): uptake of Francisella leads to activation of immature DC and intracellular survival of the bacteria.

Francisella tularensis is one of the most infectious human pathogens known. Although much has been learned about the immune response of mice using an attenuated live vaccine strain (LVS) derived from F. tularensis subspecies holarctica (Type B), little is known about the responses of human monocyte-derived immature dendritic cells (DC). Here, we show that optimal phagocytosis of LVS by DC is dependent on serum opsonization. We demonstrate that complement factor C3-derived opsonins and the major complement receptors expressed by DC, the integrins CR3 (CD11b/CD18) and CR4 (CD11c/CD18), play a critical role in this adhesion-mediated phagocytosis. LVS induced proinflammatory cytokine production and up-regulation of costimulatory surface proteins (CD40, CD86, and MHC Class II) on DC but resisted killing. Once taken up, LVS grew intracellularly, resulting in DC death. DC maturation and cytokine production were induced by direct contact/phagocytosis of LVS or interaction with soluble products of the bacteria, and enhanced activation was seen when LVS was pretreated with serum. Sonicated LVS and supernatants from LVS cultures were potent activators of DC, but LVS LPS failed to activate DC maturation or cytokine production. Serum-treated LVS rapidly induced (within 6 h) a number of cytokines including IL-10, a potent suppressor of macrophage functions and down-regulator of Th1-like responses and the Th1 response inducer IL-12. These results suggest that the simultaneous production of an activating (IL-12, IL-1beta, and TNF-alpha) and a suppressing (IL-10) cytokine profile could contribute to the immunopathogenesis of tularemia.

Bacterial Vaccines↗
PubMed1987

Relationships of serum opsonins and complement in human experimental gingivitis.

This study assessed the phagocytosis of polymorphonuclear neutrophils and the opsonic capacity of serum in experimental human gingivitis. Relationships were sought among these two measurements, clinical indices of gingivitis and complement-related opsonins. Measurements of chemiluminescence provided an index of phagocytosis and of opsonic capacity. Test group Plaque Index scores were higher than the control group on Days 7, 14, and 21, while the Gingival Index of the test group was elevated only on Day 21. Phagocytosis of test subjects' PMNs and opsonic capacity of their sera were no different from that of the controls'. Levels of C3 in both nonactivated and activated sera of the test group were significantly lower than that of the control group only on Day 14. In the test group, differences of per cent C3 conversion occurred between Days 14 and 21, and Plaque Index scores were inversely correlated with the order of per cent C3 data on these same days. Our results also indicate that complement contributes significantly to the serum opsonic capacity. The levels of developing plaque and subsequent gingival inflammation are apparently related to the degree of complement activation.

Adult↗
PubMed1989

Serum opsonins to serogroup B meningococci in meningococcal disease.

The opsonic activity to serogroup B meningococci (B:15:P1.16) was measured in sera from 101 patients with meningococcal disease using a chemiluminescence method. On admission to hospital the opsonic activity was lower in 12 patients who died than in survivors (p = 0.0007). A close association was observed between the opsonic activity and the duration of symptoms before admission, the severity of the disease, and the levels of IgG antibodies to the outer membrane complex (15:P1.16). The opsonic activity was low in 2 premorbid sera compared to healthy controls. The mean opsonic activity peaked 2 weeks after admission and was still high 3-5 years later. Meningococcal strains of different serogroups, serotypes and subtypes induced a similar increase in opsonic activity to B:15:P1.16 meningococci. No increase in activity was observed in sera from patients with meningitis and septicemia caused by other bacteria. Serum opsonins seem to be of significant importance in the host defence against serogroup B meningococci.

Adolescent↗
PubMed1983

Novel immunofluorescent technique for identification of ovine immunoglobulins and other potential opsonins binding to live Staphylococcus aureus.

A qualitative in vitro technique has been developed for identification of potential opsonins (immunoglobulins G1, G2, A, M; the third component of ovine complement C3, and fibronectin) of sheep origin, binding to cell walls of viable Staphylococcus aureus. The technique uses monospecific antisera to these ovine proteins. The antisera are conjugated to FITC-protein A such that the protein A-binding sites in the Fc region of the immunoglobulin molecules are occupied with FITC-protein A complexes and are prevented, therefore, from binding to protein A in the staphylococcal cell wall. The technique is highly specific and sensitive, and once conjugated monospecific antisera are prepared, many tests can be done in a short time. Staphylococcus aureus incubated in samples of milk whey showed variable binding of immunoglobulins G1, G2, and M; immunoglobulin A was bound from only one sample of milk whey, and the third component of ovine complement C3- and fibronectin binding were not detected. Most samples of blood serum and colostral whey produced binding of immunoglobulins G1, G2, A, and M, and the third component of ovine complement C3 to the Staphylococcus aureus cell surface; fibronectin binding was found in serum but not in colostral whey. Washings from involuted mammary glands invariably produced binding of all immunoglobulins but not of the third component of ovine complement C3 or fibronectin.

Animals↗
PubMed1975

The role of C3 as an opsonin in the early stages of infection.

In order to investigate the role of C3 in host defense in vivo, normal AKR/J mice, genetically deficient in C5, were depleted of serum C3 by the injection of purified cobra venom factor (CoVF). Concurrent with their C3 depletion, their serum opsonizing activity decreased to a level less than 20% of normal. When these mice were challenged with an intraperitoneal injection of pneumococci 2 hr after the CoVF treatment, the LD50 was from 30 to 80 times lower than the LD50 in saline-treated control animals. When the CoVF was given only 6 hr after the pneumococcal challenge, the LD50 was the same as in the control mice. If the pneumococci were first preopsonized in vitro and then injected into CoVF-treated animals, the LD50 was the same as that in control animals. These experiments demonstrate that C3 plays a significant role in vivo in the host's defense against infection and that a major part of that role is through its action as an opsonin. Furthermore, these experiments demonstrate that the role of C3 is most significant during the early stages of bacterial invasion.

Animals↗
PubMed1992

Serum opsonins and liposomes: their interaction and opsonophagocytosis.

Removal of intravenously injected liposomes from the circulation is achieved by cells of the mononuclear phagocyte system, also known as the reticuloendothelial system. On exposure to blood, liposomes become coated with plasma proteins; some of these proteins (opsonins) are thought to determine their recognition by mononuclear phagocytes. This review provides a critical discussion of factors that control opsonization of liposomes and their phagocytosis in vivo and in vitro.

Animals↗
PubMed1990

[Preoperative autologous blood donation, effect of hydroxyethyl starch on the reticuloendothelial system and opsonins].

The effect of 6% low molecular weight (LMW) HES (MW 270,000) on reticuloendothelial function was studied in 9 male patients, median of age 50 years, who were scheduled for vascular surgery. An erythrocyte clearance test (Anti Rh) labeled with 99 mTc, evaluating primarily the splenic section of the RES, showed a considerable variation (37-87%) prior to hemodilution. 24 hours after replacement of 15 ml/kg body weight of blood, there was no significant change of the clearance rate, a follow up weeks later approached the base line values. Plasma opsonins like fibronectin, complement fraction 3, complement fraction 4 and immunoglobulin G showed a proportional decrease following hemodilution, and after 24 hours approached control levels. Changes at this time seemed to be independent from the course of the hematocrit. It is concluded that LMW HES does not adversely influence the spleen dependent phagocytic capacity of the RES system.

Blood Transfusion, Autologous↗
PubMed1991

[The relationship between opsonin, endotoxin and chemical mediators in postoperative complications after surgery].

The role of various chemical mediators in the development of complications after major surgery was investigated. Phospholipase A2 activity (PLA2), and the levels of pancreatic secretory trypsin inhibitor (PSTI), polymorphonuclear leukocyte elastase (PMNE), thromboxane B2 (TxB2), 6-keto-PGF1 alpha (6-KF), leukotriene (LT) B4, C4, D4, interleukin-beta (IL-1 beta), tumor necrosis factor (TNF), and endotoxin (Et) in the serum were measured in 134 surgical patients of whom 36 developed postoperative complications. PLA2, arterial TxB2 and 6-KF showed significant changes in the patients with post-operative complications, associated with elevated Et levels. The majority of these patients had a significantly higher ratio of TxB2/6-KF. These results suggest TxB2 and 6-KF, and the TxB2/6-KF ratio are useful indices of outcome in critically ill patients with hepatic failure. Our findings revealed marked production of prostanoids in sepsis and indicate a severity of the complication in balance of the thromboxane/prostacyclin axis. It was also suggested that the opsonin and eicosanoid levels are closely related to the serum endotoxin level. LTB4, C4 and D4 were increased in the patients with postoperative sepsis or DIC, especially at the initial onsets. The increased levels of IL-1 beta or TNF were observed in some patients with postoperative complications, especially those with severe postoperative complications.

Bacterial Infections↗
PubMed1989

Ovine opsonins for Staphylococcus aureus cell wall and pseudocapsule.

Blood serum, milk whey and purified IgG1 and IgG2 antibody preparations from sheep immunised with live or killed Staphylococcus aureus vaccines were assayed for opsonising activity against S aureus using ovine mammary neutrophils as effector cells. Serum had much higher levels of opsonins than whey; whey did not inhibit the potent opsonising activity of hyperimmune serum. IgG1 antibodies against cell wall antigens of in vitro-grown S aureus and pseudocapsular antigens of in vivo-grown S aureus had low opsonising activity. IgG2 antibody against in vitro-grown S aureus surface antigens had significantly greater opsonising activity than IgG1 of this specificity. The most powerful opsonising activity was associated with IgG2 antibody against the pseudo-capsular antigens produced by S aureus grown under in vivo, or simulated in vivo cultural conditions.

Animals↗