Genetic aspects of deficiency of the ninth component of complement in man.
Explore the source record for details and available documents.
Aged↗
SEARCH · PubMed Health
Results for “Complement C9”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Serine esterase in cytolytic T lymphocytes.
The mechanisms that enable cytotoxic T lymphocytes (Tc cells) to destroy target cells are only vaguely understood. However, recent studies have identified in Tc cells and natural killer cells cytoplasmic granules that contain perforin, a cytolytic protein that resembles the ninth component of complement (C9). Antigen-specific lysis of target cells, traditionally ascribed solely to Tc cells, has now also been demonstrated in some T-helper cell (Th cell) lines, referred to here as T helper-killer or Th/c cells. We recently found a novel serine esterase that is present at greatly elevated levels in cloned murine Tc cell lines and one Th/c cell line, but not in two non-cytolytic Th cell lines. These findings suggest that the serine esterase is involved in cytolytic activity and that a variety of effector cells share a common cytolytic mechanism. To explore the role of the serine esterase in this process, we have been studying additional properties of the enzyme in murine T cells. We show here that it is a membrane-associated, disulphide-linked dimer, it has trypsin-like properties but is not a general protease, in density gradient centrifugation it sediments with perforin, it is secreted by Tc cells during their cytolytic attack on target cells, and antiserum to Tc-cell serine esterase reacts with the enzyme in Th/c cells.
Animals↗
Perforin. A family of killer proteins.
Explore the source record for details and available documents.
Amino Acid Sequence↗
Direct measurement of the increase in intracellular free calcium ion concentration in response to the action of complement.
1. The effect of rabbit anti-(pigeon erythrocyte) antibodies plus human complement on the concentration of intracellular free Ca2+ in sealed pigeon erythrocyte 'ghosts' was investigated with the photoprotein obelin. 2. The addition of human serum, as a source of complement, to 'ghosts' coated with antibody caused a rapid increase in intracellular free Ca2+ after a lag of 20-40 s, as detected by an increase in obelin luminescence. 3. The increase in obelin luminescence could not be explained by release of obelin into the medium. It was also Ca2+-dependent in that extracellular EGTA abolished the effect and intracellular EGTA inhibited it and required the complete terminal complex (C56789). No effect was seen with C5678. 4. The concentration of intracellular free Ca2+ before addition of complement was approx. 0.3 microM. This increased to a maximum of 5-30 microM after complement addition and then remained constant for at least 1-2 min. 5. Antibody plus complement induced a rapid increase in 42K+ efflux and an inhibition of cyclic AMP formation. 6. When partially purified complement components (C5b-9) were used in 'reactive lysis' it was possible to inhibit the release of macromolecules from pigeon erythrocyte 'ghosts' by extracellular EGTA. 7. It was concluded that the increase in intracellular free Ca2+ concentration caused by anti-cell antibody plus complement occurred before cell lysis and may be involved in the mechanism of complement-induced cell injury.
Animals↗
Isolation and characterization of a membrane-attack-complex-inhibiting protein present in human serum and other biological fluids.
We have previously reported the isolation of a membrane-attack-complex-inhibiting protein (MIP) from human erythrocyte membranes [Watts, Patel & Morgan (1987) Complement 4, 236] and the production of polyclonal antibodies to this protein. Here we report the identification in plasma, urine, saliva and cerebrospinal fluid of a protein immunochemically identical with the membrane-derived MIP. The protein has been isolated from plasma by immunoaffinity chromatography on an anti-(erythrocyte MIP)-Sepharose column and shown by SDS/polyacrylamide-gel electrophoresis to be of similar molecular mass to the erythrocyte protein (55 kDa non-reduced and 65 kDa under reducing conditions). Monoclonal antibodies have been raised against plasma MIP and used to establish a two-site enzyme-linked immunoadsorbent assay, enabling quantification of MIP in plasma, urine and cerebrospinal fluid. Plasma MIP, though not able to incorporate spontaneously into membranes, was deposited on heterologous and homologous erythrocyte membranes during complement activation in a C8-dependent manner. Depletion of MIP from plasma resulted in enhancement of the lytic capacity of the plasma on heterologous erythrocytes.
Animals↗
Steady-state analysis of tracer exchange across the C5b-9 complement lesion in a biological membrane.
Resealed erythrocyte ghosts have been used to define the kinetics of tracer exchange across the membrane-bound terminal complex of the complement cascade (C5b-9). Under steady-state conditions and at net chemical equilibrium, C5b-9 ghosts showed no significant lysis above control levels as measured by hemoglobin efflux. In 1 mM sucrose at 37 degrees C, [14C]sucrose isotopic exchange diffusion into C5b-9 ghosts occurred at 4.8 (+/- 0.5, SEM) X 10(-20) mol sec-1 per functional lesion, equivalent to an apparent permeability coefficient of 4.8 X 10(-14) cm3 sec-1 for the single C5b-9 lesion. No significant uptake of [14C]sucrose above control levels was observed in C5b67 ghosts. The apparent rate of tracer permeation through the complement lesion is one to two orders of magnitude slower than predicted by a model of a transmembrane channel of dimensions permitting free diffusion of sucrose. The data support earlier assertions from this laboratory that diffusion of small molecules across the complement lesion in biological membranes is significantly restricted.
Biological Transport↗
Evasion of alternative complement pathway by Trypanosoma cruzi results from inefficient binding of factor B.
During its differentiation in the insect vector to a stage infective for the mammalian host, Trypanosoma cruzi becomes resistant to lysis by the alternative pathway of complement. To elucidate the mechanism of complement evasion, we studied control of complement activation on the surface of the noninfective epimastigote and the infective culture-derived metacyclic trypomastigote stages (CMT) of T. cruzi. It was found that the predominant form of complement component C3 on epimastigotes is C3b, whereas the majority of C3 on CMT is in the form of the hemolytically inactive fragment iC3b, which cannot participate in C5 convertase formation or lead to deposition of the lytic C5b-9 complex. Our results also showed that C3 binds by a covalent ester linkage to surface molecules of different molecular weight in the epimastigote stage and CMT. Binding studies with purified complement components indicated that CMT do not support efficient formation of an alternative pathway C3 convertase. C3b on the parasite surface fails to bind the amplification component, factor B, rather than showing enhanced binding of the control component, factor H. These results identify the biochemical basis for evasion of complement-mediated killing in T. cruzi and reveal a mechanism for developmental regulation of complement activation.
Animals↗
Chemistry and function of the complement system.
Explore the source record for details and available documents.
Chemical Phenomena↗
Lysis of oncornaviruses by human serum. Isolation of the viral complement (C1) receptor and identification as p15E.
Moloney leukemia virus activated both the classical and alternative pathways of human complement. About 500,000 virions were required to detect activation of the classical pathway whereas 5,000 times as many virions were necessary to initiate the alternative pathway, indicating that in this system only the former is of biological significance. Disruption of the virus with Triton X-100 destroyed its ability to initiate the alternative pathway without affecting its ability to activate the classical pathway. After ultracentrifugation of disrupted virus the active component could be recovered in the supernate and was isolated by isoelectric focusing in granulated gels. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic and analysis and cyanogen bromide digestion studies revealed that the activity resided in a methionine-containing protein having a pI of 7.5 and a molecular weight of approximately equal to 15,000 daltons. The purified protein interacts strongly with Clq and efficiently activates Cl. RNase and lipolytic enzymes had no effect on the isolated protein but incubation with trypsin resulted in loss of activity. Enzymatic digestion studies of surface-labeled virus indicate that the active protein is a viral membrane protein. On the basis of these results it is concluded that the complement receptor of Moloney leukemia virus is the surface protein p15E.
Binding Sites↗
Serine esterase and hemolytic activity in human cloned cytotoxic T lymphocytes.
Target cell lysis by most murine cytotoxic T lymphocytes appears to be mediated by a complement (C9)-like protein called perforin, contained in high-density cytoplasmic granules. These granules also contain high levels of serine esterase activity, which may also play a role in cytolysis. Analysis of 17 cloned human cytotoxic T lymphocytes revealed the presence of serine esterase that is very similar to its murine counterpart in substrate and inhibitor specificities, pH optimum, and molecular mass; dot blot hybridization with synthetic oligonucleotides corresponding to the active sites of two known murine CTL esterases suggests homology to the murine enzyme HF. However, serine esterase was present at only approximately 10% of the level found in murine CTLs, and was not secreted during CTL-target cell interaction; moreover, hemolytic activity could not be detected in any of the seven cell lines tested. The results suggest that the human CTLs examined here kill their target cells by a mechanism different from that used by most cloned murine CTLs.
Cell Line↗
Clinical applications of complement measurements in rheumatic diseases.
There is now convincing evidence that the complement system is involved in the pathogenesis of at least some of the manifestations of human rheumatic diseases. Complement measurements in serum and/or pathologic fluids from patients with these disorders not only reflect this involvement but also may provide important clues regarding the activity and extent of the disease processes. Future studies should provide additional information concerning the usefulness of such measurements for predicting the outcome of specific therapeutic regimens, and perhaps also be the basis for the evolution of new and more rational forms of therapy.
Antigen-Antibody Reactions↗
Functionally active complement proteins C6 and C7 detected in C6- and C7-deficient individuals.
Two sensitive sandwich ELISAs based on monoclonal antibodies directed to native C6 and C7 allowed the detection and quantitation of these complement proteins in 20 out of 37 serum samples from individuals who had previously been classified as deficient in these proteins as assessed by immunochemical and/or functional assays. Furthermore, serum from four C6-deficient and one combined C6-/C7-deficient individual showed an increase in the terminal complement complex (TCC) and a decrease in native C6 and C7 after complement activation as assayed by specific ELISAs. Despite their (incomplete) deficiencies, these individuals therefore possess functionally active terminal complement proteins with respect to their ability to generate the TCC. As these individuals have no history of a susceptibility to neisserial infections, even low concentrations of functionally active C6 and C7 may provide sufficient protection against those micro-organisms whose destruction requires TCC formation.
Antibodies, Monoclonal↗
Coronavirus induced primary demyelination: indications for the involvement of a humoral immune response.
Coronavirus MHV-JHM infection of rodents can result in demyelinating encephalomyelitis. We analysed histological changes induced by coronavirus MHV-JHM infection in Lewis rats. Besides an acute disease (AE), chronic panencephalitis (CPE) and subacute demyelinating encephalomyelitis (SDE) were induced. These disease types were differentiated by the incubation period, the localization of lesions, the type of tissue damage and distribution of virus antigen. In AE and CPE, virus antigen was detected in neurons, astrocytes and oligodendrocytes, whereas in SDE neurons lacked virus antigen. Viral nucleocapsid protein (N) was present in the cytoplasm and the spike protein (S) was displayed on the surface of infected neural cells. However, expression of S protein relative to N protein was severely impaired in SDE lesions. Quantitative analysis of infiltrating inflammatory cells revealed that the number of macrophages and T cells were similar in lesions of AE, CPE and SDE. In contrast to that, SDE lesions contained a significantly higher number of IgG + B cells and plasma cells. In addition active demyelinating SDE lesions displayed an enhanced IgG content and deposits of complement C9. These results indicate that virus induced primary demyelination could be a consequence of antibody mediated cytotoxicity. Furthermore, a reduction in the number of cells producing spike protein in the chronic forms of the disease indicates down-regulation of this protein, possibly mediated by anti-S antibodies.
Animals↗
Complement lysis: the ultrastructure and orientation of the C5b-9 complex on target sheep erythrocyte membranes.
The C5b-9 complex derived from human serum and assembled on target sheep erythrocyte membranes is a thin-walled cylinder rimmed by an annulus at one end. The total height of the cylinder is 150 A, towards which the annulus contributes 30 A. The cylinder has an apparently uniform internal diameter of 100 A. The external diameter of the annulus is 200 A. The classical complement 'rings' visualized on membranes after complement lysis represent such C5b-9 cylinders perpendicularly oriented on the membranes. The thin-walled cylinder is anchored in the membrane matrix and the annulus located in the exterior membrane glycocalyx. At the sites of attachment of the C5b-9 complexes, the continuity of the membrane bilayer is disturbed and the presence of trans-membrane pores is indicated. The data essentially support the 'doughnut' theory of complement lysis.
Animals↗
The terminal complement complex in sera deficient in the eighth component of complement (C8).
The terminal complement complex (TCC) was quantified in sera from patients with a genetic deficiency of C8 alpha-gamma or C8 beta. The individual sera contained only trace amounts of TCC compared with a normal serum pool. The content of TCC increased after mixing the two sera, which was consistent with reconstitution of C8 activity. Only a moderate increase in TCC was obtained after zymosan activation of the individual sera, whereas activation of the mixture resulted in high amounts of TCC. C8 was demonstrated in the TCC of both deficient sera. These results may indicate that functional C8 is present in trace amounts despite the genetic deficiency, and that the terminal pathway may function to some extent although not enough to be detectable in less sensitive assays.
Antibodies, Monoclonal↗
Terminal complement complexes (SC5b-9) in cerebrospinal fluid in autoimmune nervous system diseases.
Explore the source record for details and available documents.
Autoimmune Diseases↗
Effect of the late complement components C5b-9 and of platelet-derived growth factor on the prostaglandin release of human synovial fibroblast-like cells.
We examined the prostaglandin E (PGE) synthesis of cultured adherent synovial fibroblast-like cells (SFC) from patients with osteoarthritis (OA) in the noninflammatory state as well as with rheumatoid arthritis (RA). In cells from RA patients the spontaneous PGE release was generally higher compared to that of OA patients, but decreased fast with time in culture. After cell passage, similar PGE baseline levels were seen in cells of the two patient groups. The cells could then be stimulated by the terminal complement components C5b-9 or C5b-8. PGE synthesis was also stimulated by the platelet-derived growth factor (PDGF), interleukin-1 (IL-1), or lipopolysaccharide (LPS). The amount of PGE synthesis after incubation with PDGF, LPS and IL-1 was comparable to that released after C5b-9. Thus, like other inflammatory mediators C5b-9 and PDGF trigger the increased PGE production by SFC and thus may participate in the development of synovial inflammation and contribute to the pathogenesis of RA.
Arthritis, Rheumatoid↗