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PubMed1978

Leukocyte complement: neoantigens of the membrane attack complex on the surface of human leukocytes prepared from defibrinated blood.

The neoantigenic determinants (neoAg) which have been identified in the human C5b-9 membranolytic C complex were detected here by the direct fluorescent antibody technique on the surface of 27 +/- 11% of viable peripheral blood leukocytes (PBL). The cells were prepared from defibrinated blood by sedimentation on Ficoll-Hypaque. Specificity of the antisera was established by quantitative inhibition of the fluorescent staining reaction, and of agglutination of EAC1-7, by highly purified C5b-9 complex. No inhibition was observed with fresh normal human serum. The majority of the PBL with surface neoAg was found in the B lymphocyte subpopulation that failed to form rosettes with sheep erythrocytes. NeoAg on B lymphocytes was removed to differing degrees by trypsin, papain, or pepsin treatment, and by maintaining the cells at 4 degree C for 20 hr in serum-free medium. The individual components, C5, C6, C7, C8, and C9, were also detected on the surface of PBL. With differential fluorescent stains, C5 and neoAg as well as C8 and neoAg could be detected on the same cells. The results indicate that viable B lymphocytes prepared from defibrinated blood, have the components of the membrane attack complex of C on their surface. The concomitant occurrence of the neoAg indicates that these proteins are present at least in part in the form of the assembled terminal complex.

Antigens↗
PubMed1989

Multimeric C9 within C5b-9 deposits in unique locations in the cell wall of Salmonella typhimurium.

We have shown previously that multimeric C9 within C5b-9 (C9:C5b-8 greater than 3:1) is needed for killing of a rough strain of Escherichia coli. We now extend these studies using serum sensitive, rough (R) and serum resistant, wild type (WT) strains of Salmonella typhimurium as well as a mutant S. typhimurium strain (TS) with a temperature sensitive mutation in synthesis of keto-deoxy-octulosonate, a constituent within the deep core structure of Salmonella LPS. Both R and TS required multimeric C9 within C5b-9 to be killed. Addition at 37 degrees C of increasing inputs of C9 to TS or R bearing C5b-9 led to a dose-related increase in C9 binding and killing. In contrast, addition of high inputs of C9 to the same strains at 4 degrees C, a procedure that limits the C9:C5b-8 ratio to 1:1, resulted in low C9 binding and minimal killing. Bactericidal C5b-9 formed at 37 degrees C on R and TS with high inputs of C9 co-sedimented with the bacterial outer membrane on sucrose density gradient analysis. Non-bactericidal C5b-9 on R, WT, and TS co-sedimented near the inner membrane, despite the presumed lack of association between these constituents. Whereas 125I C9 within the non-bactericidal pools immunoprecipitate with anti-C5, 125I C9 within bactericidal pools did not immunoprecipitate with anti-C5, anti-C7, or anti-C9. These findings suggest that bactericidal C5b-9 may be deposited in a unique location or configuration within the bacterial cell wall.

Cell Wall↗
PubMed1997

Serum amyloid P component forms a stable complex with human C5b6.

A 30,000 m.w. protein bound tightly to C5b6, which was formed by activating C7-depleted human serum with zymosan. The protein remained bound to the C5b6 complex during the isolation procedure for C5b6, including chromatography on lysine-Sepharose and an anion exchange resin. Following electrophoresis and electroblotting of the C5b6 complex to a polyvinylidene difluoride transfer membrane, the 30,000 m.w. protein was microsequenced. The 24 N-terminal amino acid sequence was determined and showed identity of the 30,000 m.w. protein with the serum amyloid P (SAP) component. The C5b6-SAP complex did not dissociate in the presence of 10 mM EDTA, which distinguishes SAP-C5b6 binding from SAP's usual Ca2+-dependent binding to other molecules. SAP, which was isolated from serum by chromatography, was able to bind to preformed C5b6, which had been assembled and isolated from purified components. Functionally, the C5b6-SAP could bind C7, and the resulting C5b67-SAP complex had only moderately lower specific hemolytic activity than that of C5b67. In addition, hemolytically inactive C5b67-SAP, such as hemolytically inactive C5b67, was chemotactically active for neutrophils, while isolated SAP had no effect on cell mobility. Because SAP reacts with other serum proteins and with cells, it is likely that the addition of SAP to terminal complement complexes may affect the fate of these complexes.

Calcium↗
PubMed1990

C5b-8 and C5b-9 modulate the collagen release of human glomerular epithelial cells.

Aside from their lytic function the late complement components C5b-9 stimulate release of prostanoids, interleukin 1 and oxygen radicals from a number of cells. Since C5b-9 has also been connected to the development of sclerosis in animal models of glomerulonephritis, we addressed the question whether C5b-9 would affect the collagen synthesis. We used human glomerular epithelial cells (GEC) obtained as primary outgrowth cultures. The cells were cultivated in the presence of 14C-proline. Collagen synthesis was quantitated by counting the radioactivity associated with collagenase digestible material. Furthermore, collagen was analyzed by SDS-PAGE. GEC in culture produce spontaneously some collagen type IV. Addition of sublytic doses of highly purified C5b-9 increased the collagen synthesis considerably within 12 to 24 hours. In the absence of C9, C5b-8 stimulated collagen synthesis to a similar extent, whereas in the absence of C7 or C8, the collagen synthesis was not enhanced. Furthermore, fluid-phase-formed C5b-9 complexes did not stimulate the collagen synthesis, indicating that assembly of the complex on the target membrane was required. Since C5b-9 deposits are found in sclerotic areas, our data support the hypothesis that C5b-9, by stimulating collagen synthesis as well as release, might contribute to the development of chronic nephritis.

Animals↗
PubMed2000

The delayed induction of c-jun in apoptotic human leukemic lymphoblasts is primarily transcriptional.

Because of their ability to induce lymphoid cell apoptosis, glucocorticoids have been used for decades to treat certain human leukemias and lymphomas. Studies presented in this paper complement our previous work demonstrating that sustained induction of the proto-oncogene c-jun plays a crucial role in the glucocorticoid-induced apoptotic pathway in CEM cells, human leukemic lymphoblasts. Results from measurements of c-jun mRNA half-life with RNase protection assays and of transcription by nuclear run-on assays indicate that, in the dexamethasone-sensitive cloned CEM-C7 cells, c-jun is induced at the transcriptional level. Consideration of time-course, however, suggested that this might be a secondary or possibly a delayed primary response. Use of cycloheximide to block protein synthesis strongly induced c-jun mRNA, suggesting that there had been relief from a labile protein repressor of transcription. Comparing the level of induction by cycloheximide with that of dexamethasone indicated that the two did not induce by an identical mechanism. The high induction by cycloheximide obscured simple interpretation of elevated c-jun mRNA levels after concomitant administration of cycloheximide and dexamethasone. This was resolved by nuclear run-on experiments, which showed that the dexamethasone induction of c-jun mRNA in this system does require protein synthesis.

Apoptosis↗
PubMed1975

Studies on the inhibition of C56-induced lysis (reactive lysis). VI. Modulation of C56-induced lysis polyanions and polycations.

Multiple polyanions and polycations were tested for their ability to influence formation of EC567 from C56, C7, and sheep erythrocytes. Six of 11 polyanions tested, including polyanethol sulfonate, heparin, and dextran sulfate, inhibited this reaction. By contrast, polycations (five or seven tested), including polybrene, protamine, and polyornithine, potentiated formation of EC567. The inhibition was similar to that previously described for anionic serum factors termed C567-INH, while the potentiation seemed to involve neutralization of serum C567-INH. Thus, this step of the complement attack mechanisms seems amenable to modulation by certain polyelectrolytes, and may thereby be susceptible to pharmacologic manipulation.

Animals↗
PubMed1981

Regulation of toxinogenesis in Corynebacterium diphtheriae. I. Mutations in bacteriophage beta that alter the effects of iron on toxin production.

Diphtherial toxin is produced in maximal yields by Corynebacterium diphtheriae (C7(beta tox+) only when iron is present in growth-limiting amounts. Toxin production is markedly decreased under high-iron conditions. We studied the role of the bacteriophage beta genome in this apparent regulation of toxin production by iron. Using a passive immune hemolysis assay to detect toxin antigen production in individual plaques, we identified rare phage mutants that were toxinogenic in high-iron medium. Lysogenic derivatives of C. diphtheriae C7 harboring such phage mutants were constructed. The lysogens were compared with wild-type strain C7(beta) for their ability to produce toxin in deferrated liquid medium containing varying amounts of added iron. Quantitative tests for extracellular toxin were performed by competitive-binding radioimmunoassays. We identified phenotypically distinct mutant strains that produced slightly, moderately, or greatly increased yields of toxin antigen under high-iron conditions. The toxin produced by the mutant lysogens was biologically active and immunochemically indistinguishable from wild-type toxin. Complementation experiments demonstrated that the phage mutation designated tox-201 had a cis-dominant effect on the expression of the toxin structural gene of phage beta. The characteristics of the tox-201 mutation suggest that it defines a regulatory locus of phage beta that is involved in control of toxinogenesis by iron in C. diphtheriae.

Bacteriophages↗
PubMed1984

Ultrastructure of the membrane attack complex of complement. Heterogeneity of the complex caused by different degree of C9 polymerization.

The membrane attack complex (MAC) of complement and its precursors, i.e. C5b-7 and C5b-8, were examined by electron microscopy. C5b-7 bound to lipid vesicles exhibits an extended structure of 25 nm connected to the lipid membrane via a 10-nm long, 3-nm wide stalk. Binding of C8 to vesicle-bound C5b-7 results in the disappearance of this stalk, whereas the overall length remains unchanged. Addition of 12 C9 molecules per C5b-8 induces C9 polymerization which is accompanied by the formation of C9 tubules and membrane lesions. By using biotinyl precursors and streptavidin -coated colloidal gold particles, C5b-6, C7, and C8 was found to be in the club-like part of the MAC; C9 was identified in the tubular moiety. Only one C5b-8 moiety was detected in an individual MAC complex thus excluding the proposed "dimeric" structure of the MAC. A membrane channel of 10 nm was formed by the MAC at a C9 to C5b-8 ratio equal or larger than 12 to 1, as suggested by the penetration of negative stain into the vesicle. In contrast, binding of an average of three C9 per C5b-8 caused formation of incomplete C9 tubules with apparent membrane channels of less than 10 nm diameter. The MAC isolated from red blood cells was ultrastructurally heterogenous . Although an excess of serum was used for the formation of the complexes, mostly incomplete poly C9 tubules were formed. It is proposed that the MAC is an ultrastructurally heterogenous complex that induces the formation of membrane channels of different sizes.

Animals↗
PubMed1982

Activation of complement by serum-resistant Neisseria gonorrhoeae. Assembly of the membrane attack complex without subsequent cell death.

Interaction of the human complement system in normal human serum (NHS) with serum-resistant and -sensitive Neisseria gonorrhoeae was evaluated to better understand the mechanism of serum-resistance. Complement activity (CH50) was depleted from NHS in a dose-dependent fashion by both serum-resistant and -sensitive N. gonorrhoeae. No detectable CH50 remained in NHS incubated with 10(9) colony-forming units (CFU)/ml serum of either resistant or sensitive strains. When smaller numbers of bacteria were incubated with NHS, lesser, yet comparable, amounts of CH50 were depleted by both resistant and sensitive strains. Hemolytic C2 activity was diminished by 33% in the case of resistant N. gonorrhoeae (10(8) CFU/ml serum) and by 48% in the case of a sensitive strain. No detectable decreases in hemolytic C4 or C7 activities were found with either sensitive or resistant strains at this concentration. Both resistant and sensitive strains activated C1s in NHS. Resistant strains specifically activated 19-21% of radiolabeled C1s in NHS, whereas sensitive strains activated 18-32%. Both resistant and sensitive strains also activated C5 in NHS. In binding assays using radiolabeled C5 and C9 in NHS, resistant and sensitive strains bound comparable amounts of C5 and C9. The number of bound C5 and C9 molecules varied according to the number of bacteria or amount of serum used in the assay. The ratio of C9/C5 bound to a sensitive strain was 6.8, and to a resistant strain was 8.2, suggesting that C5 and C9 were incorporated into membrane attack complexes (MAC). Electron microscopic examination of resistant and sensitive strains incubated with NHS revealed that MAC is bound to the surfaces of the resistant strain as well as the sensitive strain.

Blood Bactericidal Activity↗
PubMed1989

Isolation and characterization of a membrane protein from normal human erythrocytes that inhibits reactive lysis of the erythrocytes of paroxysmal nocturnal hemoglobinuria.

The observation that type III erythrocytes of paroxysmal nocturnal hemoglobinuria (PNH) are susceptible to hemolysis initiated by activated cobra venom factor complexes (CoFBb), whereas normal erythrocytes are resistant, implies that the PNH III cells are deficient in a membrane constituent that regulates this process. To isolate the inhibitory factor from normal erythrocytes, membrane proteins were first extracted with butanol and then subjected to sequential anion exchange, hydroxylapatite, and hydrophobic chromatography. Analysis by SDS-PAGE and silver stain of the inhibitory fractions showed a single band corresponding to a protein with an apparent Mr of 18 kD. PNH erythrocytes were incubated with incremental concentrations of the radiolabeled protein and then washed. In a dose-dependent fashion, the protein incorporated into the cell membrane and inhibited CoFBb-initiated lysis. This protein inhibitor functioned by restricting the assembly of the membrane attack complex at the level of C7 and C8 incorporation. By using a monospecific antibody to block the function of the inhibitor, it was shown that normal erythrocytes are rendered susceptible to CoFBb-initiated hemolysis. Analysis by Western blot of membrane proteins revealed that PNH III erythrocytes are deficient in the 18-kD protein. By virtue of its molecular weight and inhibitory activity, the 18-kD protein appears to be discrete from other previously described erythrocyte membrane proteins that regulate complement. These studies also indicate that the susceptibility of PNH III erythrocytes to reactive lysis is causally related to a deficiency of the 18-kD membrane inhibitor.

Autoradiography↗
PubMed1988

Analysis of human C8 with monoclonal antibodies. Characterization of a monoclonal antibody that recognizes free C8 alpha-gamma subunit.

The eighth component of human C is essential for the formation of the membranolytic C attack complex. C8 has a unique structure in that two covalently linked chains, C8 alpha and C8 gamma, are associated non-covalently with the third chain, C8 beta. In order to study the structure and assembly of the C8 molecule, a panel of mAb has been produced against the C component C8. Eight of these mAb had reactivity to the C8 alpha-gamma subunit, whereas four reacted with C8 beta. One of the C8 alpha-gamma mAb, C8A2, had specificity for an epitope on the C8 alpha-chain and exhibited no cross-reactivity to any of the other terminal C components, including C8 beta. C8A2 inhibited the hemolytic activity of the C8 alpha-gamma subunit but had no effect on the activity of fluid phase whole C8 or C8 within membrane-bound C5b-8. Functional experiments suggest that C8A2 inhibits C8 alpha-gamma activity by interfering with its interaction with the C8 beta-chain. In an enzyme immunoassay using the C8A2 mAb, free C8 alpha-gamma subunit could be detected in both homozygous and heterozygous C8 beta-deficient serum. However, only low level binding was observed when homozygous C5- and C7-deficient sera were tested. Thus the mAb, C8A2, recognizes an epitope expressed on the C8 alpha-gamma subunit but not on intact C8 and can detect free C8 alpha-gamma in the presence of native C8.

Antibodies, Monoclonal↗
PubMed2000

Inhibition of complement-mediated haemolysis in paroxysmal nocturnal haemoglobinuria by heparin or low-molecular weight heparin.

Complement (C')-mediated haemolysis in paroxysmal nocturnal haemoglobinuria (PNH) is mainly due to the deficiency of glycosyl phosphatidylinositol-anchored membrane proteins with C'-regulatory activities CD55 and CD59 in PNH-affected red blood cells (RBCs). Hydrophobic insertion of C5b-7 to RBC membranes, initiating the formation of a membrane attack complex, readily results in lysis of PNH RBCs due to the deficiency of CD59. We studied the significance of the electrostatic interactions between C5b-6 and RBC membranes preceding the insertion of C5b-7. In vitro, C'-mediated lysis of PNH RBCs (assessed by sucrose haemolytic assay) was inhibited by heparin, low-molecular weight heparin (LMWH) or protamine, indicating the significance of the electrostatic interactions between C' components and RBC membranes in the process of C'-mediated haemolysis. Neuraminidase-treated PNH RBCs became resistant to C' activation, suggesting that the sialic acid moieties on RBC membranes are involved in the interactions of RBC with C' components. By using biotin-labelled C7, we demonstrated that LMWH as well as heparin inhibited the insertion of C5b-7 to RBCs, although they did not inhibit the incorporation of C7 into membrane-associated C5b-6. Neither heparin nor LMWH could inhibit the procoagulant alteration of PNH RBC membranes induced by C' activation even at concentrations which inhibited the haemolysis completely. Because LMWH inhibited the C'-mediated lysis of PNH RBCs in vitro at the range which induced a limited prolongation of activated partial thromboplastin time of normal plasma, we consider that LMWH may be useful for both the inhibition of haemolysis and the prevention of thrombosis, which often follow a haemolytic attack in PNH.

Anticoagulants↗
PubMed1987

First cysteine-rich repeat in ligand-binding domain of low density lipoprotein receptor binds Ca2+ and monoclonal antibodies, but not lipoproteins.

The ligand binding domain of the low density lipoprotein receptor consists of seven cysteine-rich repeats of approximately 40 amino acids each. These repeats, which are located at the NH2 terminus of the protein, are homologous to sequences in complement components C8 and C9. To determine the role of the first repeat (amino acids 2-42), we prepared two plasmids containing expressible low density lipoprotein receptor cDNAs. The first plasmid, p delta R1, lacks only the nucleotides encoding the first repeat. It produced a receptor that bound and internalized lipoproteins and recycled to the cell surface with the same efficiency as the normal receptor. This deleted receptor failed to bind two monoclonal antibodies, IgG-C7 and IgG-15C8, which were shown previously to react with the ligand-binding domain. The second plasmid, pR1, encodes a markedly truncated protein whose extracellular domain consists of the first repeat joined to the transmembrane and cytoplasmic domains. This protein bound the two monoclonal antibodies with the same affinity as the normal receptor, but failed to bind lipoproteins. Binding of IgG-15C8 to the normal receptor and the pR1-encoded protein was Ca2+-dependent, indicating that the first repeat binds Ca2+. We conclude that repeats 2-6 in the ligand-binding domain are sufficient for binding lipoproteins and that the first repeat is highly immunogenic, but is not required for lipoprotein binding.

Antibodies, Monoclonal↗
PubMed1999

The genetic basis for the association of the 8.1 ancestral haplotype (A1, B8, DR3) with multiple immunopathological diseases.

An individual's major histocompatibility complex (MHC) ancestral haplotype (AH) is the clearest single determinant of susceptibility to MHC associated immunopathological disease, as it defines the alleles carried at all loci in the MHC. However, the direct effects of any of the 150-200 genes that constitute the MHC are difficult to determine since recombination only occurs at defined hotspots. This review concerns the 8.1 AH (HLA-A1, C7, B8, C4AQ0, C4B1, DR3, DQ2), which is carried by most Caucasians with HLA-B8. It is associated with accelerated human immunodeficiency virus (HIV) disease, and susceptibility to insulin-dependent diabetes mellitus (IDDM), systemic lupus erythematosus, dermatitis herpetiformis, common variable immunodeficiency and IgA deficiency, myasthenia gravis and several other conditions. We have mapped susceptibility genes for HIV, IDDM and myasthenia gravis to the central MHC between HLA-B and the tumour necrosis factor or complement genes. Here we consider which of the remaining 8.1-associated diseases are more closely associated with HLA-DR3 and/or DQ2. Several candidate genes in the central MHC have the potential to modulate immune or inflammatory responses in an antigen-independent manner, as is seen in studies of cultured cells from healthy carriers of the 8.1 AH. Hence these genes may act as a common co-factor in the diverse immunopathological conditions associated with the 8.1 AH.

Animals↗
PubMed1994

Antibody-mediated complement activation on nucleated cells. A quantitative analysis of the individual reaction steps.

The sequential molecular events of the initiation, amplification, and membrane attack phases of classical C pathway activation on nucleated cells were investigated. As a model system, C-susceptible human melanoma cells (SK-MEL-93-2) expressing the disialoganglioside Ag GD3 were studied. Activation of the classical C pathway was initiated by the anti-GD3 mAb R24 (murine IgG3). The initiation phase is characterized by a very inefficient molar ratio of deposited C1q per Ab molecule. At an Ab density of 5.86 x 10(6) molecules/cell, only 3% of cell-bound R24 molecules form suitable pairs for C1q binding. During the amplification phase maximally 2.44 x 10(6) molecules of C4 and 0.67 x 10(6) molecules of C2/cell are being bound to form the C3 convertase. Despite the rather inefficient binding of C2, the C3 convertase is highly active in depositing high numbers of C3b molecules on the cell surface. Maximum binding of C3b occurred within 5 min of incubation with a total number of 2.1 x 10(7) molecules/cell. This indicates amplification factors at the level of C4 and C3 of 28 (C4/C1q) and 241 (C3/C1q), respectively. C3b was found to be rapidly cleaved into iC3b. As a result of this rapid C3b degradation, the membrane attack phase is initiated with a relatively inefficient C5 activation. The maximal number of 9.5 x 10(5) molecules C5b/cell corresponds to a molar ratio of C5:C3 of only 1:22. The deposition of C5b led to the subsequent maximum binding of the following numbers of molecules of terminal C components per cell: C6, 0.8 x 10(6); C7, 0.89 x 10(6); C8, 0.82 x 10(6); C9, 1.8 x 10(6). These numbers correspond to average molar ratios (calculated per C5b molecule) of C5b/C6/C7/C8/C9 of 1/0.85/0.94/0.86/1.88. In addition to the monomeric C9, dimeric and polymeric (12- to 16-mer) forms of the molecule could be demonstrated. Collectively, our data represent a first comprehensive quantitative analysis of classical pathway activation on a nucleated cell.

Antibodies, Monoclonal↗
PubMed1995

A clinical method for measuring the distribution of segmental flexion mobility in the cervico-thoracic spine.

The aim of this study was to evaluate the validity and the repeatability of a new technique to assess segmental flexion mobility in the cervico-thoracic spine between segments C7 and T5. The new technique is referred to as the Cervico-Thoracic-Ratio (the CTR-technique). The radiological evaluation of skin distraction measurements showed that validity was high for the CTR-technique. A high correlation between vertebral flexion mobility and skin distraction was recognized individually and for the whole group. The evaluation of repeatability was found to be high for intratester and fair for intertester repeatability. The CTR-technique may become a valuable complement to other methods for assessing segmental flexion mobility in patients suffering from neck-shoulder pain in clinical practice.

Adult↗
PubMed1986

H deficiency in two brothers with atypical dense intramembranous deposit disease.

We report an H deficiency in two Algerian brothers who had early-onset glomerulonephritis. In addition, one suffered from serious lung infections. The H deficiency was defined by undetectable CH50 and AP50, and low levels of H, C3 and B (less than 10% of normal levels). I and classical pathway components, including C4-bp were normal. CR1 was present on both patients' erythrocytes. No nephritic factor or other circulating alternative pathway activator was detected. The parents, who are first cousins, and a healthy brother and sister had half-normal levels of H. These findings favor an autosomal recessive transmission of the H defect. Although by electron microscopy renal biopsies from both patients were typical for dense intramembranous deposit disease, immunofluorescence microscopy showed an atypical pattern with abundant granular C3 deposits within the mesangium and along the capillary walls. Alternative pathway activators, possibly related to dense deposits, may allow the formation of membrane-associated C3/C5 convertases, unusually stable in the absence of H, since C5, C6, C7, C8 and C9 levels were decreased in both patients. This observation may represent an interesting clue to the relationship between nephritic factor, alternative pathway activation, and dense intramembranous deposit disease.

Adolescent↗
PubMed1988

Studies on the formation of a unique cellular intermediate (EAC14256) from EAC142 and C56.

The binding reaction of C56 to EAC142 was studied. The following was observed: (1) C56 can bind to EAC142, without participation of C3 or C7, to form EAC14256; (2) the efficiency of EAC14256 formation from EAC142 and C56 depends highly on the ionic strength of the buffer; (3) EAC14256, generated from EAC142 and C56, decays spontaneously by elution of C56 into the medium and thus the reaction between C56 and EAC142 is reversible; (4) the receptor on EAC142 for C56 is C2 or C42 on the cell surface, and (5) the binding of C56 to C2 or C42 on cells is independent of the usual (C3-dependent) complement cascade activation. These observations, together with the results of our previous report, indicate that the binding of C56, generated from the activation of C5 by C42 (without C3), to EAC142 may be the initial step of membrane attack complex formation in C3-independent immune hemolysis.

Antibodies↗