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PubMed1998

Anemia-inducing factor expressed in gastric cancer is homologous with complement regulatory factor CD59?

Anemia-inducing factor (AIF) was isolated from gastric cancer tissue; however, the human placenta used as the volume of AIF for further analysis did not prove sufficient. This substance was named placental anemia-inducing factor (PAIF). PAIF directly reduces the number of erythrocytes in vitro and reduces the RBC count in rabbits to 80% when i.v. administration of 27 microg/kg of body weight is given. The aim of this study is to better define PAIF and to examine whether the identifical substance expresses on either the surface or in the cytoplasm of established gastric cancer cell lines. PAIF is a glycoprotein with about 20 KD, whose 17 amino acid residues of N terminus were sequenced after Edman treatment. The N-terminus of PAIF were determined as Lqcyncpnptadcktav. This is homologous with that of CD59, which is thought as a regulator of membrane attack complex of complement system. Expression of PAF or CD59 in four established gastric cancer cell lines were examined by indirect immunofluorescence method and by Northern blot hybridization. The cells (1 x 106) were seeded into plastic plates for three days and reacted overnight at 4 degrees C in 0.5 ml of PBS with anti-PAIF polyclonal antibody or with anti CD59 rat monoclonal antibody. Both PAIF and CD59 were stained positively on the surface and/or in the cyroplasm. The total RNAs were prepared from the four kinds of cell lines and normal human lymphocytes. CD59 mRNA was probed in all cell lines by BamH1-EcoR1 fragment of PSRa CD59. The signal levels of MKN-28, MKN-45 and KATO-III were stronger than that of MKN-74, whereas the signal of normal lymphocytes was the lowest. Although there is no decisive evidence that PAIF is exactly the same substance as CD59, and although the biological functions of these two substances are conflictive, and still to be further investigated, the 17 amino acid residues of N-terminus of PAIF expressed in gastric cancer cells were homologous with those of CD59. A derivative of CD59 may exist in gastric cancer.

Amino Acid Sequence↗
PubMed2001

The earliest pathologic alterations in dysferlinopathy.

BACKGROUND: Dysferlinopathies are associated with proximal or distal muscular dystrophy. Dysferlin immunolocalizes to the muscle fiber periphery but does not associate with the dystrophin--glycoprotein complex; its function in humans, and the mechanism by which it causes muscle fiber injury, are not known. The authors therefore searched for pathogenetic clues by examining early abnormalities in nonnecrotic muscle fibers in dysferlinopathy. Five dysferlin-deficient patients were investigated. Weakness was distal in two, proximal in one, and both proximal and distal in two. Patient 5 was only mildly affected. METHODS: Immunoblot analysis, membrane attack complex (MAC) immunolocalization, and quantitative electron microscopy. RESULTS: In Patients 1 through 4, but not in 5, part or the entire surface of isolated nonnecrotic muscle fibers immunostained for MAC. Quantitative electron microscopy of 175 nonnecrotic muscle fibers revealed one or more of the following: 1) small (0.11 to 1.8 microm) plasmalemmal defects in 64% of fibers; 2) thickened basal lamina over some defects; 3) replacement of the plasma membrane by one to multiple layers of small vesicles in 57% of fibers; 4) papillary projections, frequently disintegrating, in 24 to 36% of fibers in Patients 1 through 4 but absent in fibers of Patient 5; 5) small subsarcolemmal vacuoles, some undergoing exocytosis, in 57% of fibers; and 6) infrequent subsarcolemmal regions containing rough endoplasmic reticulum and abundant free ribosomes. CONCLUSIONS: Dysferlin is likely required for maintaining the structural integrity of the muscle fiber plasma membrane, and plasma membrane injury is an early event in the pathogenesis of dysferlinopathy. MAC activation can participate in but is not an initial or primary event causing muscle fiber injury.

Adult↗
PubMed1993

Two-site ELISA for quantification of the terminal C5b-9 complement complex in plasma. Use of monoclonal and polyclonal antibodies against a neoantigen of the complex.

A quantitative ELISA procedure using monoclonal and polyclonal antibodies against neoantigens of the terminal C5b-9 complement complex has been developed. The ELISA was demonstrated to be both sensitive and reproducible. The normal range for C5b-9 determinations, defined as 2.5-97.5% interval of the values obtained in 76 healthy blood donors, was 3.12-10.3 AU/ml. The presence of rheumatoid factor did not affect the determination of C5b-9 as demonstrated by immunoabsorption studies.

Antibodies, Monoclonal↗
PubMed1989

Mechanisms of lymphocyte-mediated lysis.

Cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells use multiple mechanisms to destroy their target cells. Pore formation resulting in osmotic lysis of the target is one mechanism; the pore-forming protein (perforin) responsible for this activity has been purified. Antigenically and functionally it resembles proteins of the membrane attack complex of complement. The other known mediators of cytotoxicity appear to be closely interrelated. Tumor necrosis factor (TNF), lymphotoxin (LT), and leukalexin are the three members of this group that have been purified, although their mechanisms of action are still unknown. CTLs fragment the DNA of target cells, as do TNF, LT, and leukalexin; this may be one of the mechanisms of action of these mediators. CTLs and NK cells do not self lyse. The basis of this phenomenon is unclear, although recent advances have shed some light on the problem.

DNA↗
PubMed2005

C5b-9 complement complex in autoimmune demyelination and multiple sclerosis: dual role in neuroinflammation and neuroprotection.

Complement system activation plays an important role in innate and acquired immunity. Activation of complement leads to the formation of C5b-9 terminal complex. While C5b-9 can promote cell lysis, sublytic assembly of C5b-9 on plasma membranes induces cell cycle activation and survival. Multiple sclerosis (MS) and its animal model experimental allergic encephalomyelitis (EAE) are inflammatory demyelinating diseases of the central nervous system (CNS) mediated by activated lymphocytes, macrophages/microglia and the complement system. Complement activation may contribute to the pathogenesis of these diseases through its dual role: the ability of activated terminal complex C5b-9 to promote demyelination and the capacity of sublytic C5b-9 to protect oligodendrocytes (OLG) from apoptosis. By inducing EAE in C5-deficient mice, we showed that complement C5 promotes remyelination and protects oligodendrocytes from apoptotic cell death. These findings indicate that activation of complement C5b-9 plays a pro-inflammatory role in the acute phase of the disease, but may also be neuroprotective during the chronic phase of the disease.

Animals↗
PubMed1994

Reduced complement and granulocyte activation with heparin-coated cardiopulmonary bypass.

Plasma concentrations of the complement activation products C3b, iC3b, and C3c; the terminal C5b-9 complement complex; and the granulocyte proteins calprotectin, myeloperoxidase, and lactoferrin were assessed in two groups of patients undergoing aortocoronary bypass procedures. In 10 patients operated on, the bypass circuits were coated by the Carmeda Bio-Active Surface and systemic heparinization was reduced to 1.5 mg/kg; in another 10, the systems were uncoated and the dosage of systemic heparinization was 4 mg/kg. In both groups, significant complement activation was observed after the onset of cardiopulmonary bypass, but the maximum levels of C3b, iC3b, and C3c and the terminal C5b-9 complement complex were significantly lower in the heparin-coated group. In both groups, a significant increase in calprotectin, myeloperoxidase, and lactoferrin release was observed by the end of operation. The maximum myeloperoxidase levels were significantly lower in the heparin-coated group than those in the uncoated group (p = 0.03). There was a correlation of borderline significance between the formation of terminal C5b-9 complement complex and lactoferrin release, as well as between the formation of terminal C5b-9 complement complex and myeloperoxidase release (p = 0.05). The postoperative blood loss did not differ significantly between the two groups. We conclude that coating by end point-attached and functionally active heparin allows a significant reduction in the amount of systemic heparinization, and significantly reduces complement and granulocyte activation.

Aged↗
PubMedDate not supplied

Induction of matrix protein synthesis in human glomerular mesangial cells by the terminal complement complex.

Exposure of human glomerular mesangial cells (GMC) in culture to sublytic doses of the terminal complement proteins C5b-8 and C5b-9 caused a transient increase in abundance of mRNA specific for collagen type IV and fibronectin; mRNA of laminin was not affected. Since C5b-9 is found deposited in inflamed or sclerotic areas we propose that stimulation of matrix protein synthesis by C5b-9 might contribute to the development of glomerular sclerosis.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1994

Bioincompatibility--perspectives in 1993.

Bioincompatibility reactions related to the non-physiology of the procedure have plagued dialysis from its early days. Although the problem is certainly multifactorial, the present overview selectively focuses on some aspects of activation of late complement (C) components, the importance of which may have been underappreciated in the past. Dialysis patients are poised for intense C activation because of cumulation of the low molecular weight factor D, an intrinsically active serine esterase which is not inhibited by any known endogenous inhibitor and catalyzes an early step in the alternative pathway. C activation reflects the net balance between activation and inhibition, the latter particularly via factor H binding. Dialyzer membrane characteristics that are related to factor H binding and regulation of initial activation steps include not only membrane surface chemistry but also its microdomain structure. Kinetic studies of the generation of the terminal complement complex (TCC) suggest ongoing generation throughout the duration of a dialysis session (in contrast to the transient release of C-derived anaphylatoxins). Potential consequences of TCC generation include amplification of the non-C-dependent cell activation signals through L-fucose-dependent steps. Efforts to reduce TCC generation by membrane engineering, for example, end group derivatization and optimization of microdomain structure, open perspectives for the development of more biocompatible membranes.

Biocompatible Materials↗
PubMed1996

Influence of the terminal complement-complex on reperfusion injury, no-reflow and arrhythmias: a comparison between C6-competent and C6-deficient rabbits.

OBJECTIVE: The complement system has been suggested to play a role in reperfusion injury which may result from an enhanced destruction of myocardial tissue or from an impairment of reflow. We investigated the influence of the C5b-9 complement complex on infarct size, reflow and arrhythmogenesis. METHODS: Twenty-eight C6-competent rabbits and 18 rabbits with congenital C6 deficiency were subjected to either 30 min or 2 h of coronary artery occlusion followed by reperfusion. C6 deficiency was confirmed by the complement titration test and immunohistology. The triphenyl tetrazolium chloride method was used to delineate infarct size. Reflow into infarcted areas was evaluated histologically after an in vivo injection of propidium iodide which served as an early fluorescence microscopic marker of damaged myocardium subjected to reflow. Continuous ECG monitoring allowed the recording of arrhythmias. RESULTS: After 30 min of coronary artery occlusion infarct size was significantly smaller in C6-deficient rabbits (5.0 +/- 2% of the risk region) as compared to C6-competent rabbits (28.4 +/- 8.5%, P = 0.0371). The extent of reflow into damaged myocardium was nearly the same in both animal groups at this time (38 +/- 9 vs. 39 +/- 7% of the risk region). After 2 h of coronary artery occlusion, infarct size was not different between both animal groups, but the extent of reflow into damaged myocardium was significantly smaller in C6-competent rabbits than in C6-deficient rabbits (25 +/- 4 vs. 40 +/- 4%; P = 0.0185). Two of the 18 C6-deficient rabbits had ventricular arrhythmias (Lown II-IV), none of which was fatal. Eleven of the 28 C6-competent animals had major ventricular arrhythmias which were fatal in 6 rabbits. CONCLUSIONS: These results suggest that the lytic C5b-9 complement complex leads to reperfusion injury in the early phase (30 min) of ischaemia, resulting in a larger infarct. After 2 h of ischaemia, complement activation enhances the no-reflow phenomenon but does not affect infarct size. Finally, the C6 status seems to influence the susceptibility to ventricular arrhythmias after coronary artery occlusion, independent of reperfusion.

Animals↗
PubMed2001

Assessment of in vivo complement activation on the Echinococcus granulosus hydatid cyst wall.

The larval stage of the parasite Echinococcus granulosus causes hydatid disease. The hydatid cyst is potentially capable of activating host complement, since it is a large, persistent, carbohydrate-rich structure, coated with host immunoglobulins, and localized in the host's internal organs. Nonetheless, in vitro studies have suggested that the cyst surface, the hydatid cyst wall (HCW), is a poor complement activator. In this study, we assessed the occurrence of in vivo complement activation on the hydatid cyst by measuring the levels of two complement activation products, C3d and complexes bearing a C9 activation neoepitope (TCC/MAC), in extracts from HCW of human origin. Low amounts of C3d and TCC/MAC were found in HCW in comparison with their levels in normal human plasma and activated human sera, suggesting that in vivo complement activation on HCW is efficiently down-regulated. This regulation may contribute to limit host inflammation which has been observed to correlate with parasite degeneration and death.

Animals↗
PubMed1994

Homologous restriction factor: effect on complement C8 and C9 uptake and lysis.

Homologous restriction factor (HRF) is a complementary regulatory protein found on the surface of human erythrocytes and other cell types. It has the function of blocking the lytic action of the membrane attack complex (MAC) of complement when incorporated into a membrane. HRF was found to inhibit not only the MAC composed of the proteins C5b-9, but also the C5b-8 complex. When 125I-labelled HRF was allowed to insert into an erythrocyte target, lysis by C5b-8 was reduced by about 80%. When human erythrocytes were treated with antibody to HRF, which bound to and presumably blocked the action of HRF, lysis by C5b-8 increased. This increase was not caused by additional binding of C8 on the cell membrane. When HRF was inserted into a target cell membrane, it had the effect of reducing the amount of C9 that could bind to very low levels, in one experiment from 6000 molecules per cell to about 500 molecules per cell. When this value was compared to the number of C7 molecules that bound, it was found that HRF reduced the amount of C9 bound to the level of C7 that was bound. HRF seemed to reduce the number of molecules of C9 that could bind to the C5b-8 complex so that only one C9 bound per complex.

Animals↗
PubMedDate not supplied

Removal of anaphylatoxins C3a and C5a and chemokines interleukin 8 and RANTES by polyester white cell-reduction and plasma filters.

BACKGROUND: A few bedside polyester white cell (WBC)-reduction filters have been shown to scavenge C3a anaphylatoxin from stored blood components. One has been shown to remove the chemokines interleukin (IL)-8 and RANTES, but not the proinflammatory cytokines IL-1, IL-6, and tumor necrosis factor alpha. Removal by any filter of the anaphylatoxin C5a or the soluble membrane attack complex (SC5b-9) has not been studied. Further, the ability of other filters to scavenge these biologic response modifiers (BRM) is not known. Four WBC-reduction filters and one plasma filter were studied for their ability to remove IL-8, RANTES, IL-1 beta, C3a, C5a, and SC5b-9. STUDY DESIGN AND METHODS: Plasma was obtained either as freshly thawed fresh-frozen plasma, fresh-frozen plasma thawed and stored for 5 days, or platelet-poor supernatant. Cell-poor plasma was obtained and samples were taken before and after filtration through the various filters Levels of IL-1 beta, IL-8, RANTES, C3a, and SC5b9 were quantitated by enzyme immunoassay. To evaluate filter scavenging of C5a, an in vitro model was developed to generate high levels of C5a in plasma by activating plasma with zymosan. RESULTS: Levels of C3a, C5a, IL-8, and RANTES were reduced by filtration through two bedside platelet WBC-reduction filters, a plasma filter, and a prestorage red cell WBC-reduction filter, but not following filtration through a prestorage platelet WBC-reduction filter. For some BRMs and filters, however, evidence of filter saturation was seen. IL-1 beta was not removed by any of the filters tested. CONCLUSION: Some, but not all, bedside polyester filters and prestorage polyester filters can remove IL-8, RANTES, C3a, and C5a from units of plasma or platelets. Improved biomaterial engineering of these and other filters could maximize scavenging of BRMs and potentially diminish the adverse reactions associated with their infusion during transfusion.

Blood Component Removal↗
PubMed2001

Induction of complement C9 messenger RNAs in human neuronal cells by inflammatory stimuli: relevance to neurodegenerative disorders.

Neurons express proteins of the classical complement pathway, including C9. Both the mRNA and protein levels for C9 are sharply upregulated in brain areas affected by Alzheimer's disease (AD). Since little is known about the signals that are responsible for this upregulation, we evaluated in human SH-SY5Y neuroblastoma cells the factors which stimulate C9 production. Interferon-gamma, phorbol myristate acetate and interleukin-6 all stimulated C9 mRNA expression but the inflammatory cytokines tumor necrosis factor-alpha, interleukin-1 beta, as well as the anaphylatoxin C5a and the bacterial lipopolysaccharide, were ineffective. Immunohistochemical analysis of postmortem human brains for C9 protein demonstrated its presence in many cortical pyramidal neurons in AD, Down's syndrome, the parkinsonism dementia complex of Guam and pallido-ponto-nigral degeneration, as well as in thalamic neurons of progressive supranuclear palsy and ballooned neurons of Pick's disease. Since C9 is required for the membrane attack complex of complement to become functional, interfering with signaling pathways that stimulate its production could offer new therapeutic strategies for treating various neurodegenerative disorders.

Aged↗
PubMed1998

Ragweed allergy: correlation between skin reactivity and in vitro complement activation.

Recently we have reported on several observations which indicate that allergen-induced complement activation contributes to the development of the symptoms of ragweed allergy. In the present paper a new finding that supports this assumption is summarized. In 48 ragweed-allergic patients individual skin reactivity to ragweed allergen extract (RWA) was assessed using dilution skin prick testing. Sera of these patients were incubated with 20, 100, and 400 U/ml RWA and generation of two complement activation products, alternative pathway C3-convertase (C3bBbP) and terminal pathway activation complex (C5b-9) was measured by ELISA methods. A strong positive correlation (Spearman correlation coefficient r = 0.495, P = 0.0004, and r = 0.454, P = 0.0012, respectively) was found between individual skin reactivity to RWA and C3bBbP generation induced by 20 and 100 A allergological units/ml (U/ml) RWA. This finding further supports the role of complement activation products in the aggravation of the basic IgE-mediated immunopathology of ragweed allergy.

Complement Activation↗
PubMed1990

Epithelial deposition of immunoglobulin G1 and activated complement (C3b and terminal complement complex) in ulcerative colitis.

The epithelial destruction seen in ulcerative colitis remains unexplained. Complement activation has been proposed to be involved, but no definite evidence has been available to this end. In the present study, we examined immunohistochemically ulcerative colitis lesions with monoclonal antibodies to activation neoepitopes in the complement component C3b and in the cytolytically active terminal complement complex. Colonic tissue specimens from 23 patients with ulcerative colitis were examined by indirect two-color immunofluorescence staining with monoclonal antibodies to the four human immunoglobulin G subclasses and to activated complement C3b or terminal complement complex. All except two patients had activated C3b deposited apically on the surface epithelium of involved mucosa. Immunoglobulin G1 was found on the epithelium in extensively prewashed specimens from 7 of 11 patients, and a striking colocalization of immunoglobulin G1, C3b, and terminal complement complex was observed in 4. Immune deposits were not observed in 31 noninflamed specimens from the same ulcerative colitis patients. Only 1 of 44 histologically normal mucosae from 17 controls and 1 of 10 colonic adenomas contained some epithelial complement deposits. It is concluded that activated complement is often deposited along the brush border of the surface epithelium in active ulcerative colitis lesions and may be associated with immunoglobulin G1 autoantibody.

Adolescent↗
PubMed1991

Local complement activation in inflammatory bowel disease.

To trace sites for local complement activation in inflammatory bowel disease, an indirect two-colour immunofluorescence method was applied on prewashed and directly ethanol-fixed mucosal specimens from patients with ulcerative colitis, Crohn's colitis, or terminal ileitis. Monoclonal antibodies to the IgG subclasses and to neoepitopes of activated complement C3b and the terminal complement complex (TCC) were used in combination with rabbit antiserum to immunoglobulins and various complement components. Deposits of activated C3b were found on the luminal face of the surface epithelium in the most affected ulcerative colitis specimens from 91% of 23 studied patients, together with cytolytic TCC in 81%. Furthermore, there was a selective deposition of the immunoglobulin G subclass 1 (IgG1) within the epithelial immune complexes in 63% of 11 studied patients. These results suggested that IgG1 autoantibodies to brush-border antigen(s) induce a complement-mediated attack on the epithelium in ulcerative colitis. The epithelial complement deposition seen in Crohn's disease tended to be more granular and was observed in 5 of 10 patients with colitis and in 4 of 10 with ileitis. No co-localization of IgG was observed, suggesting that complement activation had been induced by the alternative pathway. Type III immune reaction may, in addition, take place in both diseases since there was evidence of continuous vascular complement activation in submucosal blood vessels.

Blood Vessels↗
PubMed2006

The complement system in central nervous system diseases.

The activation of complement system is important factor in inflammatory, neurodegenerative and cerebrovascular diseases. CNS cells are able to synthesize complement components, and myelin and oligodendrocytes (OLG) are known to activate the classical pathway of complement in vitro in the absence of antibodies. Although activation of the complement system is known to promote tissue injury, recent evidence has also indicated that this process can have neuroprotective effects. In particular, terminal C5b-9 complexes enhance OLG survival both in vitro and in vivo. Complement activation may also reduce the accumulation of amyloid and degenerating neurons by promoting their clearance and suggest that certain inflammatory defense mechanisms in the brain may be beneficial in neurodegenerative disease. Complement system activation plays also an important role in brain damage after ischemic injury or head trauma. These findings strongly suggest that complement activation and membrane assembly of C5b-9 can play a role in injury but can also provide neuroprotection depending on the pathophysiological context.

Animals↗
PubMed2002

Complement activation in postpartum thyroiditis.

BACKGROUND: Postpartum thyroid dysfunction (PPTD) develops in 50% of pregnant women who have raised levels of circulating thyroid peroxidase autoantibodies (TPOAb) at booking. Although these antibodies are able to activate the complement cascade in vitro, it is not known whether complement activation plays any role in the pathogenesis of this disease. AIM: To investigate potential and actual activation of the complement system in women with postpartum thyroiditis. DESIGN: Complement activation was monitored on a weekly basis in 24 postpartum women who had raised TPOAb at 16 weeks gestation, attending an antenatal clinic in Mid-Glamorgan, Wales. METHODS: ELISA procedures were used to measure both in-vitro complement C3 activation by TPOAb and circulating terminal complement complexes (TCC) in serum. RESULTS: Higher levels of bioactive TPOAb activity were seen in women who developed PPTD when compared to those who did not. However, TCC remained undetectable in serum throughout the period of study. CONCLUSIONS: In PPTD, despite the presence of circulating bioactive TPOAbs, the extent of complement activation is inadequate to cause detectable increases in peripheral blood TCC, suggesting that the complement system may not play a major role in PPTD pathogenesis.

Autoantibodies↗