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C W Vogel

Publications and source records attributed to C W Vogel.

At least 55 records · Page 3Linked to original sources
PubMed1987

Doxorubicin enhances complement susceptibility of human melanoma cells by extracellular oxygen radical formation.

In two recent publications we showed that rapid inactivation of cell-bound C3b is a protective mechanism of human melanoma cells against killing by the R24 monoclonal antibody and human complement (Panneerselvam, M., Welt, S., Old, L.J., and Vogel, C.-W. (1986) J. Immunol. 136, 2534-2541) and that this protective mechanism can be inhibited by both the free and immobilized anthracycline glycoside doxorubicin (adriamycin) resulting in an enhanced complement susceptibility (Panneerselvam, M., Bredehorst, R., and Vogel, C.-W. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 9144-9148). In this paper we show that the complement enhancing effect of both free and immobilized doxorubicin is caused by the generation of reactive oxygen species including superoxide anion radical, hydrogen peroxide, and hydroxyl radical. The complement-enhancing effect of the anthracyclines can be completely inhibited by the reactive oxygen scavengers superoxide dismutase, catalase, and dimethyl sulfoxide. Consistent with this observation, 5-iminodaunorubicin, an anthracycline glycoside with an imine-substituted quinone moiety and, therefore, with a significantly reduced ability to form oxygen radicals, did not cause an enhanced-complement susceptibility. The complement-enhancing effect of the anthracycline glycosides could also be inhibited by bivalent metal chelators but was unaffected by sulfhydryl-blocking reagents or glutathione. Our results suggest that the anthracycline glycosides generate in a metal- (most probably iron) dependent reaction superoxide anion radicals with subsequent formation of hydrogen peroxide and hydroxyl radicals. These reactive oxygen species then cause alterations in the melanoma cells resulting in the enhanced complement susceptibility. While the target molecule(s) of the reactive oxygen species responsible for the enhanced complement susceptibility is not known, the data obtained with immobilized doxorubicin suggest that the target molecule(s) is located in the cell membrane.

Catalase↗
PubMed1987

A homogeneous immunoassay for the mycotoxin T-2 utilizing liposomes, monoclonal antibodies, and complement.

The trichothecene mycotoxin T-2 is a fungal metabolite known to contaminate agricultural products and cause intoxication of humans and animals. We have developed a homogeneous competition inhibition assay for T-2 mycotoxin based on complement-mediated lysis of liposomes. The T-2 mycotoxin was converted to an acid chloride derivative, subsequently coupled to the amino group of phosphatidylethanolamine, and incorporated with the phospholipid into unilamellar liposomes. Carboxyfluorescein, which is self-quenched at high concentrations, was entrapped in the liposomes as a release marker. We used a monoclonal IgG1 antibody specific for T-2 mycotoxin and a polyclonal anti-mouse Ig as a secondary antibody since the anti-T-2 IgG1 does not activate complement. In the absence of free T-2, the liposomes were lysed within 30 min after the addition of complement, releasing carboxyfluorescein into the surrounding buffer. In the presence of free T-2 toxin, the binding of antibodies to the liposomes was reduced, causing a corresponding decrease in lysis. This assay proved to be sensitive to T-2 toxin levels as low as 2 ng, which is 10-fold more sensitive than the present enzyme immunoassay using the same antibodies.

Antibodies, Monoclonal↗
PubMed1987

Immune and nonimmune effector functions of IgG3 mouse monoclonal antibody R24 detecting the disialoganglioside GD3 on the surface of melanoma cells.

R24, an IgG3 mouse monoclonal antibody reactive with the disialoganglioside GD3, was found to be a potent mediator of human complement cytotoxicity and human effector cell cytotoxicity. Cytotoxicity correlated with the degree of antibody binding (GD3 cell surface expression) for each of the melanoma cell lines and melanocyte cell cultures tested. Melanoma cell lines binding low amounts of R24 (low GD3 cell surface expressors) were not lysed in R24-directed immune reactions, suggesting that a threshold number of R24 molecules bound per cell is necessary to initiate these cytotoxic mechanisms. Since both complement- and cell-mediated reactions lysed the same subpopulations of cells in each cell line, both mechanisms appeared to depend on similar threshold quantities of bound R24 molecules. However, due to the heterogeneity of R24 binding in each cell line, the numerical value for this threshold could not be determined. Only in cell lines binding greater than 10(7) R24 molecules per cell were greater than 90% of the cells lysed. Normal melanocytes in culture were not lysed by R24-directed immune mechanisms, due to their low GD3 expression, indicating that monoclonal antibodies such as R24 may show tumor specificity with regard to effector functions even though normal cells express the relevant antigen. In contrast to the potent in vitro activity of R24, treatment of nu/nu mice bearing human melanoma grafts resulted in tumor inhibition only when started within 3 days of tumor cell inoculation. No effect was seen on established tumors. Thus, this in vivo mouse model failed to predict the clinical and pathological findings observed in treatment trials of R24 in human melanoma patients--urticaria involving skin metastases, cellular infiltration of tumor tissue, and tumor regression. In addition to activating immunologic effector functions, R24 had direct effects on melanoma cells, blocking their ability to attach to surfaces and causing tumor cell aggregation. These effects were again related to the number of R24 molecules bound to the cell surface; no aggregation was seen with cell lines binding less than 4 X 10(5) molecules per cell. Both immune and nonimmune effector functions may be involved in the tumor inhibitory activity of R24 in humans.

Animals↗
PubMed1986

Effect of covalent attachment of immunoglobulin fragments on liposomal integrity.

Liposome stability during and after covalent coupling of Fab' antibody fragments was investigated. Large unilamellar vesicles containing entrapped 5(6)-carboxyfluorescein (CF) as a marker for liposomal integrity were prepared by extrusion through polycarbonate membranes. N-[4-(p-Maleimidophenyl)-butyryl]phosphatidylethanolamine (MPB-PE) was employed as a liposomal anchor for the covalent coupling of Fab' fragments. We observed that coupling of Fab' fragments to liposomes containing 5 mol % MPB-PE caused a concentration-dependent increase in size and polydispersity of the liposomes. Dependent on the concentration of the MPB-PE anchor in the membrane and the concentration of Fab' added, coupling was associated with the release of up to 95% of the entrapped CF. Rupture of the liposomes was identified as the primary mechanism of CF release during Fab' coupling. Reduction of the MPB-PE concentration to 1 mol % resulted in liposomes that were stable during and after Fab' coupling. The increased stability of these liposomes was due to the lower MPB-PE concentration and not to the lower number of attached Fab' fragments. By proper adjustment of the experimental conditions for coupling, the number of Fab' fragments attached to the 1 mol % MPB-PE liposomes could be increased without affecting the stability of the resulting liposomes. These stable liposomes, made by an extrusion method that avoids the use of organic solvents, detergents, or sonication, are therefore suitable for entrapment of labile compounds and can be used for immunotargeting or immunoassays.

Animals↗
PubMed1986

The effects of metal ions and temperature on the interaction of cobra venom factor and human complement factor B.

An alternative pathway C3 convertase is formed by the equilibrium association of Factor B with cobra venom factor (CVF) followed by the activation step catalyzed by Factor D. However, the association of Factor B with CVF has only occasionally been demonstrated and has not been quantitatively analyzed. Here we show that in the absence of metals the two proteins have significant affinity for each other and reversibly associate in a one-to-one stoichiometry with a dissociation constant of 11.6 microM. Upon the addition of metal ions, the complex is stabilized only 2- to 30-fold in the order Ni2+(Kd = 6.6 microM) less than Mg2+(Kd = 1.1 microM) less than Mn2+(Kd = 0.4 microM). These results suggest that metal ions may be less important in stabilizing the CVF.B complex and more important in promoting the subsequent equilibrium association of CVF.B with Factor D. The stability of the CVF.B complex is variously dependent on temperature in the range studied (14-21 degrees C) depending on the metal ion that is present. The complex formation was demonstrated in the analytical ultracentrifuge at sedimentation equilibrium employing a combination of single- and multiple-independent variable nonlinear least squares analytical techniques. Two different numerical approaches gave very similar results.

Complement Factor B↗
PubMed1986

A molecular mechanism of complement resistance of human melanoma cells.

The susceptibility of human melanoma cells to lysis by human complement after sensitization with the R24 murine IgG3 monoclonal antibody to the GD3 ganglioside antigen was investigated. It was found that the melanoma cell lines were either susceptible (greater than or equal to 70% cytotoxicity) or resistant (less than or equal to 30% cytotoxicity) to complement-mediated killing. We determined the kinetics of binding of C3 to and its subsequent fate on the melanoma cells. We found that on susceptible cell lines, maximal binding of C3 occurred within 10 min of incubation. At that time, approximately 90% of the bound C3 was in the form of C3b. During the subsequent incubation, the C3b was slowly inactivated, apparently generating the physiologic degradation products iC3b, C3dg, and C3d. However, this degradation of C3b could be inhibited without affecting the final degree of cytotoxicity, indicating that it is of no apparent consequence for the killing of susceptible melanoma cells. Very different results were obtained with resistant melanoma cells. Bound C3b was rapidly inactivated, and C3d was the predominant form of C3 on resistant cells throughout the incubation. Therefore, rapid inactivation of C3b was identified as a protective mechanism of human melanoma cells against complement attack. In addition, we found that resistance to complement is not an inherent property of the cells but depends on the antibody used for sensitization, because the resistant cell lines could be lysed after sensitization with polyclonal antiserum.

Animals↗
PubMed1986

The effect of complement depletion on immunologically mediated middle ear effusion and inflammation.

Immunologic injury during immune response to antigen in the middle ear cavity has been suggested to be a contributing factor in otitis media with effusion (OME). One of the mechanisms proposed involves the generation of immune complexes, with subsequent injury mediated by complement fixation. To evaluate the potential role of complement in OME, an animal model of immune-mediated middle ear effusion and inflammation was used. Antigenic challenge of the middle ear of normal, sensitized guinea pigs results in OME. This response was compared with that observed in guinea pigs whose sera were decomplemented by treatment with cobra venom factor. As compared to controls, decomplemented animals exhibited less effusion [130 (+/- 35) vs 83 (+/- 60) microliter, P less than 0.05] and inflammation in the middle ear following antigenic challenge. These results suggest that complement could play a role in the pathogenesis of OME. However, the fact that animals with severely depleted serum complement still displayed a moderate amount of effusion and inflammation indicates that other mechanisms are also involved in our model of immune-mediated OME.

Animals↗
PubMed1986

Immobilized doxorubicin increases the complement susceptibility of human melanoma cells by protecting complement component C3b against inactivation.

Human melanoma cells resistant to killing by monoclonal antibody R24 plus human complement became susceptible after treatment with doxorubicin (adriamycin). Treatment with doxorubicin prevented the rapid degradation of surface-bound complement component C3b that has been identified as a protective mechanism of complement-resistant melanoma cells. Doxorubicin caused the increased complement susceptibility as free drug and after immobilization onto glass beads to prevent cellular uptake. Immobilized doxorubicin was more effective than free drug, causing enhanced complement susceptibility at concentrations where the free drug was no longer active. In contrast to free doxorubicin, which exhibited a direct cytotoxic effect leading to cell death within 4 days, immobilized doxorubicin did not affect cell viability. These findings suggest that combination therapy of the complement-activating monoclonal antibody R24 with the complement-enhancing drug doxorubicin may be a promising approach for the treatment of melanoma.

Antibodies, Monoclonal↗
PubMed1985

The cobra complement system: I. The alternative pathway of activation.

The complement system of the cobra snake is of particular interest because cobra venom contains cobra venom factor (CVF), a protein that is related to C3 and forms a stable C3 convertase with mammalian Factor B. We investigated the alternative pathway of cobra complement. Cobra plasma lysed erythrocytes in presence of Mg-EGTA of some mammalian species, but not cobra erythrocytes. The hemolytic activity was inhibited by EDTA and destroyed by heating. Preincubation of cobra plasma with alternative pathway activators (zymosan, inulin, lipopolysaccharide), with small nucleophiles (methylamine, hydrazine), or with chaotropes (KSCN) abrogated the hemolytic activity. The activity of cobra plasma was not affected by CVF. Cobra plasma also lysed EAC1423 cells in presence of EDTA but not EAC142 cells (prepared with sheep erythrocytes, rabbit antibody, and human complement proteins) indicating the presence of C5 in cobra plasma that is susceptible to activation by the human C5 convertase. These results indicate that the cobra has a complement system with an alternative pathway very similar to mammalian complement.

Animals↗
PubMed1985

The cobra complement system: II. The membrane attack complex.

Rabbit erythrocytes are lysed by cobra plasma. The membranes of the lysed rabbit erythrocytes exhibited typical ultrastructural complement lesions with an inner diameter of 72 A. Structures similar to human C5b-8 complexes were also visualized. The proteins found in membranes lysed by cobra plasma resembled closely the proteins of the human membrane attack complex in number and molecular weight. Cobra poly C9 that is resistant to reduction and boiling in SDS could also be demonstrated. These results indicate that the membrane attack complex of cobra complement is very similar to its mammalian counterpart.

Animals↗
PubMed1984

Cobra venom factor: improved method for purification and biochemical characterization.

A method to purify cobra venom factor (CVF) from cobra venom by sequential column chromatography is described which yields a product virtually free of phospholipase A2, a common contaminant of CVF preparations. The separation of phospholipase A2 from CVF was achieved by chromatography on Cibacron blue-agarose, a resin that tightly binds cobra venom phospholipase A2. A rapid and simple hemolytic assay for the qualitative and quantitative determination of CVF based on its ability to induce bystander lysis of erythrocytes has been devised. CVF was isolated from the venom of the Naja naja kaouthia subspecies and some of its biochemical properties and physicochemical parameters were delineated.

Amino Acids↗
PubMed1984

Molecular architecture of human properdin, a positive regulator of the alternative pathway of complement.

The structure of the human properdin molecule was investigated by hydrodynamic, spectroscopic, and transmission electron microscope studies. Sucrose density gradient ultracentrifugation of purified, functionally active properdin showed a single component sedimenting at 5.5 S. Electron microscopic examination by two different methods, however, revealed polydispersity of the protein which consisted of cyclic dimers, trimers, tetramers, pentamers, and higher cyclic oligomers. Approximately 80% of the oligomers were dimers, trimers, and tetramers. Monomers could not be detected. These polymers could be partially separated by gel filtration on Sephacryl S-300 and all fractions were active in terms of binding to C3b. The specific activity increased with oligomer size. When reexamined after incubation at 37 degrees C for 4 h or at 4 degrees C for 2 weeks, the chromatographic behavior of the oligomers and their electron microscopic appearance were unchanged, suggesting that in vitro no rapid equilibration occurred. The protomer is clearly visualized within polymers as a flexible, rod-like structure 26.0 nm in length and 2.5 nm in diameter, with pronounced thickening at each end. The monomer is bivalent with respect to binding to other properdin monomers and the binding sites are localized to the ends of the structure. A model could be devised which is consistent with the distinct geometry of the intersubunit contacts observed in micrographs. The circular dichroism spectrum of properdin suggests the presence of little alpha helix or beta structure and shows positive ellipticity at 231 nm. In contrast to previous investigators, we conclude that isolated human properdin is polydisperse and consists of a set of cyclic polymers constructed from a single highly asymmetric and flexible protomer.

Binding Sites↗
PubMed1984

MHC Class III products: an electron microscopic study of the C3 convertases of human complement.

We have reported a transmission electron microscopic study of the two C3 convertases of human complement and their precursors. The corresponding proteins and complexes of the classical and alternative pathway appear very similar. Cofactors C3b and C4b are nearly indistinguishable and display a characteristic but highly irregular substructure. C2 and Factor B are globular with diameters of 85 +/- 8 A and 80 +/- 8 A and both consist of three discrete globular domains each approximately 40 A in diameter. Bb and C2a each contain two domains connected by a short linker segment. Both domains of Bb and one domain of C2a are 42 A in diameter (28 kd), while the second domain of C2 is 47 A in diameter (39 kd). Attachment of the enzymatic subunits to cofactors occurs through one domain only.

Complement Activating Enzymes↗
PubMed1984

Cobra venom factor: structural homology with the third component of human complement.

The functional analogy between cobra venom factor (CVF), the complement-activating protein in cobra venom, and C3b, the activated form of the third complement component, prompted us to conduct a comparative analysis of structural properties of the two proteins derived from two phylogenetically distant species. We subjected CVF and human C3 and its physiologic cleavage products, C3b and C3c, to a variety of biochemical analyses. We report here structural similarities of these proteins, which include similarities in amino acid composition, far and near UV circular dichroism spectra, secondary structure, band patterns and pI values from isoelectric focusing, immunochemical cross-reactivity, ultrastructural morphology, and amino-terminal amino acid sequences. Analysis of these data reveals that, structurally, CVF resembles C3c more than C3b. We conclude that CVF is not the product of a convergent evolution, but is, in all likelihood, derived from a common C3 ancestor protein.

Amino Acid Sequence↗
PubMed1983

The membrane attack complex of complement and its precursor proteins lack phospholipase activity.

The membrane attack complex of human complement and its highly purified precursor proteins have been analyzed for phospholipase activity. Using three different sensitive assays, phospholipase A1, A2, C or D activity could not be detected. Based on the sensitivity of the assays employed, these results indicate the complement-mediated membrane damage is not enhanced by covalent breakdown of membrane phospholipids, but is entirely caused by physical action of the membrane attack complex. The results also imply that the putative serine esterase sites of C6 and C7 are not acting on phospholipids.

Chromatography, Thin Layer↗
PubMed1982

Ultrastructure of cobra venom factor-dependent C3/C5 convertase and its zymogen, factor B of human complement.

The molecular architecture of the cobra venom factor (CVF)-dependent C3/C5 convertase (EC 3.4.21.47) of human complement was deduced from electron microscopy of the purified bimolecular complex (CVF,Bb) and its isolated subunits, CVF and Bb. Negatively stained CVF imaged as an irregularly shaped cylindrical structure, with approximate dimensions of 137 A x 82 A (length x diameter). The zymogen Factor B appeared globular with a diameter of about 80 A and its image suggested a bipartite structure of two compact, closely associated regions, one about twice as large as the other. Bb, the larger, catalytic site-bearing cleavage fragment of Factor B, revealed two globular domains, each 40 A in diameter, connected by a short linker region about 10 A long and thick. CVF and Bb could be distinguished in micrographs of the CVF,Bb complex: Bb attached to one end of the CVF molecule through only one of its two domains, and in an orientation making the long axes of both molecules approximately orthogonal. It is suggested the naturally occurring C3 convertases (C3b,Bb and C4b,2a) have a similar morphology.

Complement Activating Enzymes↗