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PubMed1999

The influence of complement receptor type 1 (CD35) and decay-accelerating factor (CD55) on complement receptor type 2- (CD21) mediated alternative pathway activation by B cells.

The influence of complement receptor type 1 (CR1; CD35) and decay-accelerating factor (DAF; CD55), both down-regulators of complement activation, on the complement receptor type 2- (CR2) mediated alternative pathway (AP) activation of complement on normal B cells, was assessed. The data indicate that, while neither DAF nor CR1 hinder the function of the AP convertase formed on CR2, CR1 plays a significant role in the remodelling of C3b fragments, generated by the convertase and deposited at secondary acceptor sites on the B-cell surface, such that they become suitable ligands for CR2. The significance of this finding is briefly discussed.

B-Lymphocytes↗
PubMed1982

Antibody-independent complement activation by myelin via the classical complement pathway.

Murine or rabbit whole brain homogenates were shown to activate human complement via the classical pathway by an antibody-independent reaction. This activity required Ca++ ions. Anticomplementary activity in fractionated murine brain was found to reside in the myelin fraction and in purified myelin. It was absent, however, both from highly purified myelin basic protein (MBP) and from the MBP-free residue. Because purified MBP is a monomer and this protein exists in brain tissue largely as a dimer, the ability of the cross-linked form of MBP to activate complement was investigated. MBP, dimerized with difluorodinitrobenzene, was highly anticomplementary. The murine brain, inactive when taken from the newborn mouse, was shown to first acquire the capacity to activate complement at 7 d after birth. This finding is consistent with the report that the synthesis of myelin protein has been shown to be initiated in murine brain 8 d after birth. Complement activation by MBP could play an important role in the pathological changes observed in neurological disorders.

Animals↗
PubMed1980

A newly described control mechanism of complement activation in patients with mixed cryoglobulinemia (cryoglobulins and complement).

Levels in serum of components of complement were studied in a group of 10 patients with mixed cryoglobulinemia. The profiles found in most patients showed decreased levels of the early complement components C1, C4, and C2, with normal levels of C3. Experiments performed to define the mechanism(s) responsible for this unusual complement profile showed that activation of the early complement components in serum was due to the activation of the classical pathway by mixed cryoglobulins. They also showed that the characteristic lack of effect on C3 was due to the action of a previously unrecognized regulatory mechanism upon C3 convertase of the classical pathway mediated by 2 normal serum proteins, namely, the C4 binding protein (C4-bp) and the C3b inactivator (C3bINA).

Complement Activating Enzymes↗
PubMed1986

Suppression of complement-mediated vascular injury at Arthus reaction sites by complement inhibitors.

Certain complement inhibitors, namely chlorpromazine, suramin, 2-hydroxystilbamidine and chlorophenothiazine sulphonate were tested for their ability to suppress complement deposition and vascular injury at the site of an Arthus reaction. Deposition of complement was suppressed in the order 2-hydroxystilbamidine greater than suramin greater than chlorpromazine. All the above mentioned four compounds strongly protected vascular injury as observed by electron microscopic studies. At Arthus reaction sites prepared without drug treatment venules ranged from normal to severely altered and damaged. Discontinuities in endothelial linings varied from small to longer stretches. In the latter situation remaining endothelial cells were degenerated and endothelial remnants did not have an intact basal lamina. After treatment with the above complement inhibitors, at arthus reaction sites some venules appeared normal, whereas others were altered but in all cases the endothelium and its basal lamina remained intact.

Animals↗
PubMed1999

Protection of baculovirus-vectors against complement-mediated inactivation by recombinant soluble complement receptor type 1.

Baculovirus-based vectors are efficient means for gene transfer into hepatocytes in vitro. However, gene transfer in vivo is hampered by inactivation of baculovirus by the complement system. In this study, we demonstrate protection of baculovirus vectors against complement-mediated inactivation through recombinant soluble complement receptor type 1 (sCR1). Blocking of only the alternative complement pathway by a mutant of sCR1 did not result in baculovirus survival in human serum. The data suggest the use of sCR1 as a potent drug to facilitate baculovirus-mediated gene transfer into hepatocytes in vivo.

Animals↗
PubMed1988

Effect of time, temperature and anticoagulants on in vitro complement activation: consequences for collection and preservation of samples to be examined for complement activation.

The effects of time, temperature, ethylene-diamine-tetra-acetic acid (EDTA), citrate and heparin on in vitro complement activation were examined in enzyme immuno assays (EIA) for detection of C3 activation products and the terminal complement complex (TCC). In vitro complement activation occurred during coagulation since baseline concentrations of activation products were considerably higher in serum than in plasma. EDTA was more efficient than citrate and heparin in inhibiting in vitro activation. Minimal activation was observed in all preparations when samples were kept at 4 degrees C for up to ten days, whereas a very rapid increase in activation products occurred even in EDTA plasma when the temperature was elevated. Based on the data obtained, guidelines for the collection and preservation of samples to be examined for complement activation are given.

Blood Preservation↗
PubMed1977

Pleural fluid complement, complement conversion, and immune complexes in immunologic and nonimmunologic diseases.

Forty-four pleural fluids and 41 blood specimens from patients with various diseases were examined for concentration of whole complement, C4, C3, conversion products of C3 and C3PA, and immune complexes. C3 conversion was found in all eight pleural fluids from patients with rheumatoid arthritis, five of seven with lupus erythematosus, two of six with congestive heart failure, and nine of 23 with malignant diseases. Conversion of C3PA correlated closely with C3 conversion and both were significantly inversely related to whole complement, C4, and C3. Concentration of immune complexes was highest in patients with rheumatoid arthritis. Pleural fluid immune complex concentrations correlated positively with conversion of C3 and C3PA. These findings suggest that the reduced levels of pleural fluid complement in rheumatoid arthritis and lupus erythematosus may be secondary to complement conversion by immune complexes.

Antigen-Antibody Complex↗
PubMed1998

Peroxisome biogenesis disorders: identification of a new complementation group distinct from peroxisome-deficient CHO mutants and not complemented by human PEX 13.

Ten complementation groups of generalized peroxisome biogenesis disorders (PBD), (excluding rhizomelic chondrodysplasia punctata) have been identified using complementation analysis. Four of the genes involved have been identified using two different methods of (1) genetic functional complementation of peroxisome deficient CHO cell mutants and (2) homology searches for human dbEST, based on yeast genes involved in peroxisome biogenesis (PEX genes). We report here the first identification of a new complementation group which is genetically different from peroxisome deficient CHO mutants. There were no complementations by the human PEX 13 gene. The nature of the related gene is being investigated.

Animals↗
PubMed1993

Human chromosome 11 complements ataxia-telangiectasia cells but does not complement the defect in AT-like Chinese hamster cell mutants.

It has been shown that the X-ray-sensitive Chinese hamster V79 mutants (V-E5, V-C4 and V-G8) are similar to ataxia-telangiectasia (A-T) cells. To determine whether the AT-like rodent cell mutants are defective in the gene homologous to A-T (group A, C or D), human chromosome 11 was introduced to the V-E5 and V-G8 mutant cells by microcell-mediated chromosome transfer. Forty independent hybrid clones were obtained in which the presence of chromosome 11 was determined by in situ hybridization. The presence of the region of chromosome 11q22-23 was shown by molecular analysis using polymorphic DNA markers specific for the ATA, ATC and ATD loci. Seventeen of the obtained monochromosomal Chinese hamster hybrids contained a cytogenetically normal human chromosome 11, but only twelve hybrid cell lines were shown to contain an intact 11q22-23 region. Despite the complementation of the X-ray sensitivity by a normal chromosome 11 introduced to A-T cells (complementation group D), these twelve Chinese hamster hybrid clones showed lack of complementation of X-ray and streptonigrin hypersensitivity. The observed lack of complementation does not seem to be attributable to hypermethylation of the human chromosome 11 in the rodent cell background, since 5-azacytidine treatment had no effect on the streptonigrin hypersensitivity of the hybrid cell lines. These results indicate that the gene defective in the AT-like rodent cell mutants is not homologous to the ATA, ATC or ATD genes and that the human gene complementing the defect in the AT-like mutants seems not to be located on human chromosome 11.

Animals↗
PubMed1979

The presence of complement in human cervical mucus and its possible relevance to infertility in women with complement-dependent sperm-immobilizing antibodies.

Full-complement component lytic activity was measured in human midcycle cervical mucus, using a sensitive 51Cr release hemolytic assay. The level measured was 11.5% of the activity of complement in an equal volume of undiluted human serum. The relevance of this level of complement to complement-dependent sperm-immobilizing antibody activity was studied. After 1 hour's incubation with mucus levels of complement, immobilization of about 50% of spermatozoa occurred and after 3 hours' incubation, immobilization of about 70% of spermatozoa occurred.

Antibodies↗
PubMed1980

The role of complement in viral infections. II. the clearance of Sindbis virus from the bloodstream and central nervous system of mice depleted of complement.

The following studies were performed to investigate the mechanism(s) by which the complement system limits Sindbis virus infection in the central nervous system of mice. After the intracerebral inoculation of Sindbis virus, no differences in mortality or viral growth in the central nervous system were observed between normal mice and mice depleted of complement by treatment with cobra venom factor. In addition, animals that had been inoculated subcutaneously with Sindbis virus and depleted of complement after the viremic phase had ended did not show any differences in mortality or viral growth in the central nervous system. In contrast, it was found that after the intracardiac inoculation of virus, complement-depleted mice demonstrated a defect in the clearance of infectious virus from the blood. These studies suggest that the increased growth of virus in the brains of complement-depleted mice after the subcutaneous inoculation of Sindbis virus is due to a defect in clearance of infectious virus from the bloodstream rather than to a primary defect within the central nervous system.

Animals↗
PubMed1995

Complementation of Xanthobacter Py2 mutants defective in epoxyalkane degradation, and expression and nucleotide sequence of the complementing DNA fragment.

Three Xanthobacter Py2 mutants (M3, M8 and M10) lacking epoxyalkane-degrading activity were isolated and characterized. All mutants were able to grow on acetone, the degradation product of 1,2-epoxypropane conversions. Furthermore, they contained the unidentified 'low molecular mass fraction' (LMF) necessary for epoxyalkane-degrading activity. Three cosmids from a gene bank complemented the mutation in M10 and M8 but not in mutant M3. Epoxyalkane-degrading activity in crude extracts of 1,2-epoxypropane-grown complemented mutants was similar to the wild-type activity. Surprisingly, M10 transformed with complementing cosmid pEP9 showed a constitutively expressed epoxyalkane-degrading activity, which was not observed in the wild-type strain. The cosmid pEP9 was conjugated into Xanthobacter autotrophicus GJ10, which is not able to degrade 1,2-epoxypropane. In crude extracts of X. autotrophicus GJ10(pEP9), epoxyalkane-degrading activity was demonstrated, but only after the addition of the LMF from Xanthobacter Py2. Hybridization experiments demonstrated an overlap on complementing cosmids pEP1, pEP3 and pEP9. Subcloning revealed a 4.8 kb EcoRI-HindIII fragment to be necessary for complementing the mutant M10. In the sequence of this fragment four different ORFs were found.

Alkanes↗
PubMed1996

Quantification of the CD55 and CD59, membrane inhibitors of complement on HIV-1 particles as a function of complement-mediated virolysis.

Previous studies have demonstrated that the murine monoclonal antibody (MoAb) NM-01 activates the human complement classical pathway resulting in lysis of human immunodeficiency virus (HIV). The present study was performed to determine the availability of the V3-loop of gp120 relative to the complement regulatory proteins, CD55 (DAF) and CD59 (HRF20) molecules on HIV. The results demonstrate that CD55 and CD59 exist on HIV virions, along with gp120 molecules. These findings suggest that activation of human complement on free viral particles is induced by MoAb NM-01 and that this occurs regardless of the presence of CD55 and CD59 molecules. The destruction of viral particles was demonstrated by a decrease in infectivity. The involvement of human complement in this process was confirmed with an immunoelectron microscopy technique by the presence of a human C9 to prove membrane attack complex (MAC). The results indicate that NM-01 can induce complement activation because of the ratios of CD55 and CD59 to gp120 molecules on HIV virions. The availability of the gp120 V3 domain on the virion is sufficient for binding of NM-01 and thereby the formation of MAC that results in virolysis.

Antibodies, Monoclonal↗
PubMed1980

A complement-fixation test for enzootic pneumonia of pigs using a complement dilution method.

Complement-fixing antibody to Mycoplasma hyopneumoniae in the serums of pigs experimentally infected with enzootic pneumonia was demonstrated by comparing the haemolytic titre of guinea-pig complement titrated in the presence of heated test serum, M. hyopneumoniae antigen and unheated normal pig serum with the titre obtained when the antigen was omitted. The haemolytic titres against sensitised sheep erythrocytes were determined after a fixation period of 16 to 18 hours at 5 degrees C. When serums, collected at intervals of 3 to 7 days, from 43 pigs exposed to pigs experimentally infected with enzootic pneumonia were tested, 4.6 or more complement units were first fixed 14 to 44 (mean 23.4) days after contact began. Serums collected subsequently fixed from 4.6 to more than 31 complement units. This positive reaction usually persisted until the pigs were killed 4 to 35 weeks after contact began. Thirty-three had gross enzootic pneumonia lesions and 9 had lung lesions detected microscopically. Serum antibody was not detected in 73 weaned pigs aged 7 weeks in a pneumonia-free herd but serums from 9 of 15 unweaned piglets aged 9 to 14 days in the same herd, fixed between 3 and 7 complement units.

Animals↗
PubMed1992

Markers of complement-dependent and complement-independent glomerular visceral epithelial cell injury in vivo. Expression of antiadhesive proteins and cytoskeletal changes.

BACKGROUND: Visceral glomerular epithelial cells (GEC) are an important component of the glomerular filtration barrier to proteins. While ultrastructural GEC changes have frequently been observed in proteinuric states, no suitable light microscopic markers of GEC injury have yet been identified. EXPERIMENTAL DESIGN: We have analyzed in vivo the GEC expression of proteins known to be involved in cell shape changes. SPARC (osteonectin, BM-40) and tenascin (cytotactin, J1, hexabrachion) belong to a group of anti-adhesive glycoproteins, that modulate cell-matrix interactions. We also studied cytoskeletal intermediate filament proteins, including desmin and vimentin. The GEC expression of SPARC, tenascin, desmin, and vimentin was analyzed in various types of GEC injury in the rat, including complement-mediated injury (passive Heymann nephritis, autologous immune complex nephritis, conA anti-conA nephritis), complement-independent injury (nephrotoxic nephritis), toxic injury (aminonucleoside nephrosis) and hypertensive injury (5/6 nephrectomy, angiotensin-II infusion). A complement-mediated model of mesangial cell injury (anti-Thy 1.1 mesangial proliferative nephritis) served as a control. RESULTS: SPARC mRNA and protein were constitutively expressed in normal rat glomeruli. Immunostaining and immunoelectron microscopy primarily localized SPARC to the cytoplasm of GEC. Markedly increased glomerular SPARC synthesis and GEC immunostaining was observed in all instances of complement-mediated GEC injury but in none of the other conditions. In contrast, glomerular immunostaining for tenascin, that also stained in a GEC pattern, either remained unchanged or increased to a minor degree (complement-mediated models). GEC immunostaining for desmin in normal rats was low and variable, and increased significantly in any form of GEC injury but not in anti-Thy 1.1 nephritis. No concomitant increase of GEC immunostaining for vimentin was detectable, which could have been due to the constitutively high expression of vimentin in GEC. CONCLUSIONS: SPARC and desmin, but not tenascin or vimentin, are suitable light microscopic markers of GEC injury. The combined staining for these proteins may be useful in differentiating the mechanisms of GEC injury.

Animals↗
PubMed1999

Mechanism of complement-dependent haemolysis via the lectin pathway: role of the complement regulatory proteins.

Mannan-binding lectin (MBL) is an acute phase protein which activates the classical complement pathway at the level of C4 and C2 via two novel serine proteases homologous to C1r and C1s. We recently reported that haemolysis via this lectin pathway requires alternative pathway amplification. The present experiments sought to establish the basis for this requirement, and hence focused on the activity and regulation of the C3 convertases. Complement activation was normalized between the lectin and classical pathways such that identical amounts of bound C4 and of haemolytically active C4,2 sites were present on the indicator cells. Under these conditions, there was markedly less haemolysis, associated with markedly less C3 and C5 deposited, via the lectin pathway than via the classical pathway, particularly when alternative pathway recruitment was blocked by depletion of factor D. Lectin pathway activation was associated with enhanced binding in the presence of MBL of complement control proteins C4bp and factor H to C4b and C3b, respectively, with decreased stability of the C3-converting enzyme C4b,2a attributable to C4bp. Immunodepletion of C4bp and/or factor H increased lectin pathway haemolysis and allowed lysis to occur in absence of the alternative pathway. Thus, the lectin pathway of humans is particularly susceptible to the regulatory effects of C4bp and factor H, due at least in part to MBL enhancement of C4bp binding to C4b and factor H binding to C3b.

Animals↗
PubMed1987

Interactions of the platelets in paroxysmal nocturnal hemoglobinuria with complement. Relationship to defects in the regulation of complement and to platelet survival in vivo.

The blood cells of patients with paroxysmal nocturnal hemoglobinuria (PNH) have abnormal interactions with complement. The activity of the alternative pathway C3 convertase on the platelets of 9 out of 19 patients with PNH was elevated. 10 patients had C3 convertase activity within the normal range even though 80-95% of their platelets lacked the complement regulatory protein decay accelerating factor (DAF) that is absent from the affected blood cells in PNH. PNH and normal platelets released factor H when C3 was bound to their surfaces. This may account for the apparent regulation of C3 convertase activity on platelets that lack DAF. The abnormal uptake of the membrane attack complex of complement by PNH III erythrocytes was not seen in PNH platelets. 111Indium-labeled platelet survival times were normal in five of eight patients, which suggests that the lack of the membrane attack complex defect results in normal platelet survival in PNH.

Blood Coagulation Factors↗
PubMed1990

Anaphylatoxins and terminal complement complexes in pancreatitis. Evidence of complement activation in plasma and ascites fluid of patients with acute pancreatitis.

Complement activation has been proposed as a mediator of remote complications of acute pancreatitis. Thirty-seven patients with acute pancreatitis were studied with respect to the formation of anaphylatoxins (C3a/C3adesArg, C5a/C5adesArg) and terminal complement complexes (TCC) in plasma and ascites fluid. The patients were classified according to Ranson's criteria. Eighteen patients with moderate or severe pancreatitis had higher maximum plasma C3a/C3adesArg and TCC concentrations than 19 patients with mild pancreatitis. During convalescence, the concentrations had returned to normal. High concentrations of C5a/C5adesArg and TCC were also found in ascites and pancreatic cyst fluid, drawn from patients with moderate or severe pancreatitis. As the terminal complement pathway activation is involved in reactive lysis and anaphylatoxins increase vascular permeability, anemia and impaired respiration in these patients may be influenced by complement activation.

Acute Disease↗