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Biomedical subjects

M Mannik

Publications and source records attributed to M Mannik.

At least 91 records · Page 5Linked to original sources
PubMed1982

Effect of cationized antibodies in performed immune complexes on deposition and persistence in renal glomeruli.

To study the interaction of positively charged antibodies in immune complexes with the fixed negative charge on the glomerular capillary wall, chemical cationization of antibody was accomplished with the maintenance of antigen-binding activity. These cationized antibodies bound rapidly to glomeruli but did not persist. Large-latticed immune complexes formed with these cationic antibodies showed rapid deposition and persistence in renal glomeruli, even when administered in small doses. Electron-dense deposits were present at the anionic sites in the glomerular basement membrane at 1 min and 1 h, with extensive subendothelial deposits present from 12 to 72 h. By 14 d, the deposits were seen in the subepithelial region and the glomerular mesangium. The administration of small-latticed immune complexes prepared with cationized antibody revealed initial deposition without persistence in glomeruli in a manner similar to cationized antibodies alone. Thus, the positive charges on antibodies in immune complexes contribute to the deposition and persistence of the complexes in glomeruli, particularly in the subendothelial area.

Animals↗
PubMed1982

Clearance of circulating DNA-anti-DNA immune complexes in mice.

DNA-anti-DNA immune complexes, produced from single-stranded DNA and IgG from a patient with systemic lupus erythematosus were cleared from the circulation of normal mice extremely rapidly, at a rate similar to the clearance of DNA alone. The initial clearance of these complexes was more rapid than the clearance of aggregated IgG, a surrogate immune complex containing a comparable number of IgG molecules, suggesting that the antigen (DNA) in the complexes significantly altered the clearance kinetics of the complexes. Analysis of the late clearance component of these complexes showed that anti-DNA is released back into the circulation after initial removal, and is then cleared at a rate similar to monomeric IgG. Whether this anti-DNA represents free antibody, or antibody bound to small nuclease digested DNA fragments, awaits further study.

Animals↗
PubMed1982

Human complement activation by self-associated IgG rheumatoid factors.

IgG rheumatoid factors (IgG-RFs) undergo concentration-dependent self-association into dimers and higher polymers, as previously reported. The interactions of purified IgG-RF from the plasma of 3 patients with rheumatoid arthritis, with guinea pig and human complement were studied. Self-associating IgG-RFs were isolated by affinity columns and gel filtration. These preparations contained no detectable IgM and were composed only of IgG subclasses known to fix complement. Complement utilization of IgG-RF was compared with that of monomeric IgG, heat-aggregated IgG, and soluble rabbit IgG immune complexes. Although incubation of IgG-RF or monomeric IgG with 3 units of guinea pig or human complement resulted in decreased hemolysis of sheep erythrocytes sensitized with IgM hemolysin, these substances were less than 100 times as effective as heat-aggregated IgG or soluble immune complexes. The ability of human or guinea pig complement that had been incubated with IgG-RF to restore hemolytic activity to C4-deficient guinea pig serum served to distinguish Clq binding from complement cascade activation. IgG-RFs and monomeric IgG did not activate guinea pig complement cascade in contrast to aggregated IgG. IgG-RFs, however, activated human complement cascade; monomeric IgG only bound human Clq. These results indicate that self-associated IgG-RFs can activate human complement in fluid phase, but less effectively than aggregated IgG or large-latticed immune complexes.

Arthritis, Rheumatoid↗
PubMed1982

Evaluation of aggregated IgG in mice as an Fc receptor specific probe of the hepatic mononuclear phagocyte system.

In experimental models of immune complex diseases the hepatic mononuclear phagocyte system removes circulating immune complexes (CIC) by interaction with Fc receptors, and the spleen has a relatively insignificant role in this function. We have used heat-aggregated human IgG (AHGG) to detect altered hepatic mononuclear phagocyte system activity in an acute immune complex model in mice in order to evaluate its suitability for possible use in humans. Immune complexes inhibited the clearance of AHGG, as a function of the dose and of the time after injection of complexes. The delayed clearance resulted from decreased hepatic uptake of the AHGG. Alterations in the comparatively small splenic uptake of AHGG did not correlate with changes in the clearance or the hepatic uptake that were produced by the complexes. Studies with Rose Bengal showed that the complexes caused a small but definite decrease in hepatic blood flow. Immune complexes also inhibited the clearance and hepatic uptake of aggregated mouse albumin and aggregated ovalbumin. The aggregated albumins, however, were cleared very rapidly, indicating high extraction ratios, so their clearance was more affected by the decreased blood flow than the clearance of AHGG. We conclude that a small dose of AHGG is a sensitive probe for hepatic Fc receptor function and has potential for human use.

Animals↗
PubMed1982

The disappearance kinetics and glomerular deposition of small-latticed soluble immune complexes.

The disappearance from circulation and the glomerular localization of human serum albumin (HSA) anti-HSA complexes made at fifty-fold antigen excess were examined in mice and compared with the same features of complexes made at five-fold antigen excess. Complexes prepared at fifty-fold antigen excess consisted principally of small-latticed complexes (Ag2Ab2 and Ag1Ab1) that persisted in the circulation after the initial rapid disappearance attributed to extravasation. The presence of small-latticed complexes in the circulation did not lead to glomerular localization of complexes during a 96 hr period. In contrast, when large-latticed soluble complexes, prepared at five-fold antigen excess, were injected, abundant glomerular deposits developed. These observations indicate that the lattice of circulating immune complexes must exceed the Ag2Ab2 structure in order for glomerular deposition to occur.

Animals↗
PubMed1981

Studies on the antigenic determinants in the self-association of IgG rheumatoid factor.

The number, location, and other characteristics of the antigenic determinants for self-association of IgG-rheumatoid factors (IgG-RF) were examined using the IgG-RF isolated from the plasma of one patient as a model system. Affinity chromatography was employed for isolation of the IgG-RF. Sedimentation equilibrium ultracentrifugation was used to study the various interactions. The antigenic valence of IgG-RF Fc, normal human Fc, and rabbit Fc fragments was two for the interaction with Fab fragments from IgG-RF, as might be expected from the molecular symmetry of IgG. The antigenic valence of intact normal IgG, however, was only one, indicating that when one of the available antigenic determinants interacted with the Fab fragment of IgG-RF, the other determinant becomes sterically inaccessible. Reduction and alkylation, known to increase the flexibility of the hinge region, did not alter the antigenic valence of IgG for Fab fragments of IgG-RF. The antigenic valence of IgG-RF in self-association could not be experimentally determined but must be two to permit the observed concentration-dependent further polymer formation of IgG-RF dimers. Unique antigenic determinants on the Fc fragments of IgG-RF were sought and not found, thus reaffirming the formation of two antigen-antibody bonds as the basis for dimerization of IgG-RF molecules. The pFc' and Fc' fragments, representing Cgamma3 domains of IgG, failed to show significant interaction with Fab fragments of IgG-RF, indicating that the antigenic determinants were not expressed by the Cgamma3 regions but are located either on Cgamma2 region or require intact Cgamma2 and Cgamma3 regions for expression. These conclusions were corroborated by the antigenic valence of one for the Fc(i) fragment, a new papain-generated intermediate fragment of Fc, composed of two intact Cgamma3 domains and one intact Cgamma2 domain. Normal IgG, because of its valence of one for interaction with IgG-RF, would effectively terminate further polymerization of IgG-RF dimers. This may well in part explain the finding of smaller IgG-RF complexes in the serum than in synovial fluid of patients with rheumatoid arthritis.

Alkylation↗
PubMed1981

Preparation and characterization of 4-azido-2-nitrophenyl human serum albumin as an antigen for covalent cross-linking of immune complexes.

Human serum albumin (HSA) was conjugated with 4-fluoro-3-nitrophenyl azide to yield varying density of the 4-azido-2-nitrophenyl haptenic group, useful for covalent cross-linking in the antibody-combining site. The epitope density of the antigen influenced several examined biologic properties. Precipitation in gel diffusion occurred when the average epitope density was 13 or above. Complement (C) activation was not found by incubation with guinea pig C, by binding to human Clq, or by conversion of the electrophoretic mobility of human C3 with epitope densities up to 13. Upon i.v. injection, rapid removal of the conjugated HSA occurred when more than seven 4-azido-2-nitrophenyl groups were present. This rapid removal was in part due to hepatic uptake. These studies point out the epitope density-dependent alterations of biologic properties of an antigen useful for preparation of immune complexes covalently cross-linked in the antibody-combining site.

Animals↗
PubMed1981

Clearance and tissue uptake of immune complexes in complement-depleted and control mice.

The clearance kinetics, specific hepatic uptake and specific splenic uptake of immune complexes were examined in control mice and in mice treated with large doses of purified cobra venom factor (CoF) to deplete serum C3. At least 90% depletion of C3 was achieved as tested by double diffusion with antiserum specific to antigenic determinants on C3. A saturating dose of preformed immune complexes, consisting of HSA and rabbit antibodies to HSA, was used in these experiments. No differences in clearance kinetics and organ uptake of the immune complexes containing IgG as antibodies were observed between the two groups of mice. Within the limits of the experimental system no evidence was obtained for the participation of serum C3 and C3b receptors on Kupffer cells in the hepatic uptake of circulating immune complexes. The apparent discrepancies on the role of C3 and C3b receptors between these experiments and the in vitro studies on the uptake of immune complexes by macrophages is most likely related to the differences in the lattice of immune complexes employed by investigators.

Animals↗
PubMed1981

Covalently cross-linked immune complexes prepared with multivalent cross-linking antigens.

Covalently cross-linked immune complexes were prepared with multivalent antigens, obtained by coupling varying numbers of 4-azido-4-nitrophenyl groups (NAP) on human serum albumin as the carrier molecule (NAPn . HSA). In this system the haptenic group served to bind the antigen to the antibody (antibodies to NAP) and to form covalent bonds upon photoactivation. The covalently cross-linked immune complexes contained around 30% of antibodies that were dissociable from complexes by SDS polyacrylamide gel electrophoresis. A comparable portion of antibody-combining sites were accessible to the free hapten (NAP . lysine) in molar excess by equilibrium dialysis. The stable, covalently cross-linked complexes with NAP7.0 . HSA and NAP12.9 . HSA were prepared and separated into complexes with varying degrees of lattice by sequential steps of gel filtration. Ag1Ab1 complexes were obtained with reasonable homogeneity. Other preparations contained successively higher lattices but were not homogeneous. When these complexes were injected into mice, the increasing lattice of complexes resulted in increasingly rapid removal of the complexes from the circulation. The antigen, independent of lattice, also contributed to removal of complexes from circulation. NAP12.9 . HSA alone was removed from circulation faster than NAP7.0 . HSA, and Ag1Ab1 complexes with NAP12.9 . HSA were removed faster than Ag1Ab1 complexes with NAP7.0 . HSA. The studied system adds covalently cross-linked immune complexes with multivalent antigens to the armamentarium of covalently cross-linked complexes that previously were obtained only with bivalent affinity labels.

Antigen-Antibody Complex↗
PubMed1980

Physicochemical and functional relationships of immune complexes.

The biological properties of immune complexes depend on the nature of antigens and antibodies comprising these complexes. The lattice of immune complexes influences their tissue deposition, complement activation, and interaction with Fc receptors. The lattice of immune complexes depends on the valence of antigens, the antigen-antibody ratio, the association constant of these reactants and the concentration of antigen and antibody. Kupffer cells effectively remove large-latticed immune complexes from the circulation due to their Fc receptors. This system is saturable, leading to prolonged circulation of the complexes and enhanced deposition in tissues. Small-latticed immune complexes are slowly removed from the circulation by yet unidentified mechanisms. The renal glomerulus serves as an example of immune complex deposition from the circulation. Only large-latticed complexes are deposited in the glomerular capillary wall in the subendothelial area and the mesangial matrix. An influx of bone marrow-derived monocytes participates in the disposal of immune complexes deposited in these areas of the glomerulus, the resident mesangial cells do not phagocytize these substances. The subepithelial deposits of immune complexes appear to be locally formed and not deposited from the circulation.

Animals↗
PubMed1980

Effect of preformed immune complexes on the clearance and tissue localization of single-stranded DNA in mice.

Recent studies have shown that DNA is cleared from the circulation extremely rapidly by the liver, and that normal individuals have low or immeasurable levels of circulating DNA. In some patients with SLE and in NZB/W mice, however, significant amounts of free DNA as well as DNA-anti-DNA immune complexes have been found in the circulation, suggesting a possible defect in DNA clearance in these conditions. To delineate factors which might contribute to the persistence of DNA in the circulation, we have assessed the effects of immune complexes on the clearance of single stranded DNA in normal C57Bl/6J mice. HSA-anti-HSA immune complexes at five-fold antigen excess were injected intravenously and after a variable, the clearance of single-stranded DNA was determined. Clearance of all doses of DNA was markedly suppressed 6 to 12 hr after the administration of immune complexes and returned to normal by 24 hr. Immune complexes decreased DNA clearance by blocking the hepatic uptake of DNA without altering the distribution of DNA to other organs. Histology and studies on the effect of immune complexes on the clearance of bromosulphophthalein (BSP) and sulphur colloid suggest that immune complexes affect DNA clearance by altering hepatic blood flow. The results obtained in this study suggest that circulating immune complexes in patients with SLE or in other conditions may suppress normal DNA clearance, and thereby contribute to the persistence of DNA in the circulation.

Animals↗
PubMed1979

Role of marrow-derived monocytes and mesangial cells in removal of immune complexes from renal glomeruli.

Phagocytosis of intravenously administered immune complexes by cells in the mesangium was investigated. The model used was that of exchange marrow transplantation between Chediak-Higashi (CH) mice and syngeneic partners after X-irradiation. This model was chosen since marrow-derived macrophages could be differentiated from resident mesangial cells by the presence of the characteristic giant lysosomes in phagocytic cells of the CH mice. Injected immune complexes were cleared normally and localized in the glomerular mesangium in CH or C57BL/6J mice receiving either C57BL/6J or CH marrow. C57BL/6J mice with CH marrow injected with immune complexes prepared with reduced and alkylated antibodies accumulated many cells within the mesangium that contained both giant lysosomes and electron dense deposits. Deposits were not found in cells with subplasmalemmal microfilaments and perpheral dense bodies. Conversely, the cells in the mesangium of CH mice with C57BL/6J marrow that contained electron dense deposits were devoid of giant lysosomes. Based on these observations, we concluded that (a) marrow-derived monocytes contribute to mesangial hypercellularity after deposition of immune complexes and (b) phagocytosis of immune complexes localized in the glomerular mesangium was by marrow-derived monocytes rather than by mesangial cells.

Animals↗
PubMed1979

Detection of intermediate complexes by evaluation of the difference between gamma-globulin and IgG concentrations.

A simple analysis based on techniques readily available in the routine clinical laboratory has been presented for identification of patients with moderate and high levels of intermediate complexes. If the gamma-globulin concentration determined by serum protein electrophoresis minus the IgG concentration determined by radial immunodiffusion exceeds 1.0 gm/dl, intermediate complexes of IgG should be present in concentrations greater than 0.5 gm/dl. In principle, any disease association with sufficient polymerization of IgG might cause an abnormal result with this analysis. Furthermore, sera from patients with liver disease and marked beta-gamma-bridging on electrophoresis may also give abnormal values.

Arthritis, Rheumatoid↗
PubMed1978

Kinetics and mechanisms for removal of circulating single-stranded DNA in mice.

Clearance of exogenous ssDNA from circulation was rapid and occurred primarily through the liver. With higher doses of single-stranded DNA (ssDNA), both liver uptake and whole blood clearance approached a maximum, enabling larger amounts of ssDNA to persist in the circulation. The large molecular weight material (precipitable ssDNA) which remained in circulation was rapidly cleaved to 20,000-30,000 mol wt fragments by endonucleases, at least some of which could be demonstrated in plasma in vitro. Mononucleotide breakdown products appeared rapidly in circulation with no lag phase, suggesting that exonuclease activity was not dependent upon prior phagocytosis. Since no exonuclease activity could be demonstrated in plasma in vitro, it was postulated that breakdown of ssDNA by exonucleases occurs on the surface of hepatocytes of Kupffer cells.

Animals↗
PubMed1978

Synthesis by an established lymphocyte cell line from a rheumatoid synovium.

Lymphocytes derived from the synovium of a patient with rheumatoid arthritis were shown to synthesize predominantly IgG as measured by an equilibrium binding assay. Chromatographic separation of the radiolabeled lymphocyte culture supernatant revealed rheumatoid factor activity associated with IgG and IgM. In addition, immunofluorescence studies on fixed lymphocytes demonstrated that the majority of cells stained positive for both IgG and rheumatoid factor.

Arthritis, Rheumatoid↗