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PubMed2006

Modulation of the SDF-1-CXCR4 axis by the third complement component (C3)--implications for trafficking of CXCR4+ stem cells.

Several organs including hematopoietic ones may regenerate by attracting stem cells that are mobilized from their niches in response to stress related to tissue/organ damage and after mobilization circulate in the peripheral blood. The trafficking of these cells is regulated by alpha-chemokine stromal derived factor-1 (SDF-1) that is upregulated in damaged organs and binds to seven-transmembrane-span G-protein-coupled CXCR4 receptor that is expressed on circulating stem cells. In parallel, evidence has accumulated that the complement (C) system, which is part of innate immunity, may also orchestrate regeneration. C becomes activated with the release of the third complement component (C3) cleavage fragments (e.g., C3a, desArgC3a, and iC3b) during tissue/organ injury. Our recent work demonstrated that these fragments modulate responsiveness of CXCR4+ stem cells to an SDF-1 gradient. Thus the high concentration of both SDF-1 and C3 cleavage fragments in damaged organs results in the formation of an optimal gradient for chemoattracting circulating CXCR4+ stem cells. In this review we will focus on interactions between the SDF-1-CXCR4 axis and the C3 cleavage fragments in a model of mobilization, trafficking, and homing of hematopoietic stem/progenitor cells (HSPC).

Animals↗
PubMed1976

Effects of activated complement components on enzyme secretion by macrophages.

Purified cleavage products of the guinea-pig complement component C3, namely C3b and C3a, interact with guinea-pig and mouse macrophages in culture to induce a dose- and time dependent release of lysosmal enzymes into the medium. In the case of C3b the selectivity of the release of hydrolases, which occurs without cell killing, is shown by morphological observations and the failure of lactate dehydrogenase to appear in the medium. However, lysosomal enzyme release in the presence of C3a is accompanied by loss of cellular lactate dehydrogenase. Preincubation of C3b with anti-C3 Fab inhibits its attachment to macrophages, after which there is hardly detectable enzyme release into the medium. We have found that stimulated macrophages release enzyme(s) which can cleave C3, generating more C3b either directly or via the alternative pathway; the C3b so formed would induce further enzyme release. This amplification system may provide an explanation for the ability of macrophages to generate mediators of inflammation and cause tissue damage and degradation at sites of chronic inflammation while retaining their ability for long periods of time.

Acetylglucosaminidase↗
PubMedDate not supplied

Platelet glycoprotein IIb/IIIa inhibitor attenuates complement activation during in vitro ventricular assist circulation.

Complement activity and platelet glycoprotein (GP) IIb/IIIa dysfunction have been demonstrated during in vitro ventricular assist device circulation. Platelets contain C1 serine protease inhibitor (C1 INH) in secretory granules, which normally regulates complement. Complement activity may result from a loss of platelet regulation on complement during ventricular assist device circulation as platelets lose viability. The purpose of this study was to assess the ability of a platelet GP IIb/IIIa receptor inhibitor to attenuate ventricular assist device associated complement activation during in vitro ventricular assisted circulation. Eight in vitro nonpulsatile centrifugal ventricular assist device circuits were simulated for 4 days using 450 ml fresh human whole blood. Cardiac index, temperature, pH, PO2, PCO2, Ca, glucose, and activated clotting time were maintained at physiologic levels. Levels of C1 INH and C3a were measured with and without a reversible glycoprotein IIb/IIIa inhibitor (MK-383). Concentrations of C1 INH increase on exposure to ventricular assist device, and decrease to a plateau within 12 hr. The decrease in circulating unbound C1 INH was attenuated with pre treatment with MK-383. Concentrations of C3a increase 34 fold within 4 hr of exposure to a ventricular assist device with and 22 fold without pre treatment with MK-383. These findings suggest that protection of the platelet GP IIb/IIIa complex delays complement activation during in vitro ventricular assist device circulation.

Complement Activation↗
PubMed1994

Immunologic assessment of host defense impairment in patients with septic multiple organ failure: relationship between complement activation and changes in neutrophil function.

BACKGROUND: The pathogenesis of gram-negative sepsis-induced multiple organ failure (MOF) remains to be elucidated. METHODS: Blood samples were obtained from eleven patients with septic MOF, three patients with sepsis, three patients who underwent operation, and three healthy volunteers. In these patients the relationship between changes in polymorphonuclear neutrophil (PMN) function and complement activation was investigated. RESULTS: PMNs from patients with sepsis exhibited enhanced endothelial cell adhesion, enhanced chemotaxis, increased oxygen radical generation, and increased lysosomal enzyme release. Although PMNs from patients with septic MOF also exhibited enhanced adhesion and chemical mediator production, chemotaxis was markedly depressed. Complement activation in septic MOF was indicated by decreases in total complement activity and complement component 4 (C4) and increases in C3a and C4a des-Arginine. Increases in plasma concentrations of circulating immunoglobulin G immune complexes and decreases in PMN Fc gamma R expression suggest that the classic pathway is the main pathway of complement activation. On the other hand, we could not detect decreases in C4 or increases in C4a des-Arginine in patients with sepsis, suggesting that the alternate pathway is the main pathway of complement activation. Increases in serum concentrations of the membrane attack (SC5b-9) complex also suggested that activated complement itself may participate in organ injury in patients with septic MOF. Moreover, PMN up-regulation of surface inhibitory factors of complement activation likely allows these neutrophils to survive and function. CONCLUSIONS: The combination of changes in PMN function and complement activation appears to be intimately associated with the pathogenesis of septic MOF.

Adult↗
PubMed1988

Surface expression of Gp 165/95, the complement receptor CR3, as a marker of disease activity in systemic Lupus erythematosus.

Complement-derived peptides capable of activating neutrophils appear in plasma during flares of systemic lupus erythematosus (SLE). One possible consequence of such activation is an increased expression of the surface adhesion promoting heterodimer gp165/95 (the complement receptor CR3). The quantity of gp165/95 was measured by indirect immunofluorescence using a monoclonal antibody of the CD11b group. Mol, directed to the alpha chain. Eighty-three percent of 26 patients with SLE expressed gp165/95 on their neutrophil surface to a greater extent than normals. The highest levels of surface gp165/95 were found in patients with the most severe disease, who also had the highest levels of the circulating anaphylatoxin C3a (mean = 560 ng/ml versus 147 ng/ml in controls). There was a negative correlation between expression of gp165/95 and absolute neutrophil count. Five individuals followed serially demonstrated an increase in surface gp165/95 during disease flares which returned to normal with clinical improvement. These data support the hypothesis that the neutrophils of patients with active SLE recruit increased numbers of gp165/95 molecules to their surface in respose to complement activation; these activated neutrophils bearing increased numbers of adhesion promoting gp165/95 may contribute to endothelial injury in SLE.

Antibodies, Monoclonal↗
PubMed1988

Complement activation during cardiopulmonary bypass in children.

Complement activation was evaluated prospectively in serial serum and plasma samples from 30 children, who underwent cardiopulmonary bypass operations. Each patient showed a decrease in total hemolytic C levels and increase in C3 activation product (C3a desArg and C3bi/c) levels. In 11 of the 30 patients surgery was associated with a complication: death (2), respiratory failure (RF, 9), septicaemia (4), postpericardiotomy syndrome (PPS, 1) and pancreatitis (1). Patients suffering from RF were younger, underwent longer perfusions and had somewhat more extensive changes in the C system, although no direct correlation between high C3a desArg levels and RF existed. Instead, the increase in C3a desArg was in linear correlation with the perfusion time. Most complications during the latter postoperative period were associated with distinct episodes of lower grade C activation.

Cardiopulmonary Bypass↗
PubMed1989

Modulation of immunity in patients with autoimmune disease and cancer treated by extracorporeal immunoadsorption with PROSORBA columns.

Extensive animal studies and clinical observations support an immunosuppressive role for certain antibodies and circulating immune complexes (CIC) in malignant and autoimmune diseases. Investigators have attempted to correct or modulate dysfunction by removal of antibodies or CIC from plasma. Extra-corporeal immunoadsorption of plasma over columns containing a silica matrix and covalently attached highly purified staphylococcal protein A (PROSORBA column) is a procedure that specifically removes those plasma components by the interaction of protein A with the Fc region of IgG. The interaction of CIC with the Fc receptor on protein A has three specific results. First, there is direct removal of immunosuppressive CIC from the circulation. Studies of CIC-mediated immunosuppression in experimental systems have shown dose-response relationships over wide ranges of CIC concentrations. Thus, removal of CIC relative to the IgG antibody may be expected to exert some stimulation of the immune system. Second, the complement system is activated. Elevated levels of C3a, C4a, and C5a are observed in patients' circulating plasma after PROSORBA treatment. These levels peak one to three hours post-perfusion and are near normal levels by six hours post-perfusion. These complement components are stimulators of growth and activity of immune cells. In addition, by binding to CIC they stimulate clearance of CIC by the reticuloendothelial system. Thus, treatments may induce removal of more CIC than could be anticipated by the binding capacity of treatment columns. Third, antibody is released from CIC. Interaction of CIC with bound protein A with or without the aid of activated complement components leads to liberation of free antibody. Depending upon other factors, eg, amount of circulating antigen and/or unbound IgG, either free antibody or CIC containing more antibody relative to antigen (or both) may be infused into patients with the posttreatment plasma. Such CIC function as immune stimulators rather than suppressors of immune cell activity. The consequences of the treatments are summarized as follows. Stimulation of immune cellular activity is seen one to three hours posttreatment. During the first one to three treatments, cells of the granulocyte/macrophage series show the greatest increase. During and after treatments 2 to 4, lymphocytes show the greatest increase. At this point, increased blastogenic response to mitogens is observed along with an increase in the T helper/suppressor cell ratio.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenocarcinoma↗
PubMed1997

Functional bioactive recombinant acylation stimulating protein is distinct from C3a anaphylatoxin.

Acylation stimulating protein (ASP) acts upon adipose tissue to stimulate triglyceride synthesis and glucose transport. The aim of the present study was to produce recombinant ASP and to measure its bioactivity. The cDNA region of the parent complement C3 sequence coding for ASP (C3adesArg) was cloned and expressed in E. coli. Bioactivity of the purified recombinant material was tested by determining its effect on triglyceride synthesis, glucose transport, and competition binding assays. In standard assays, concentrations of 5.5 microM recombinant ASP (rASP) stimulated triglyceride synthesis comparably to plasma ASP (pASP): 228% versus 237%, respectively, in 3T3 preadipocytes and 568% versus 440% in human differentiated adipocytes. rASP also increased glucose transport in L6 myocytes (163% at 10 microm rASP) and in human differentiated adipocytes (334% rASP vs. 329% pASP at 5 microM). rASP competitively displaced radiolabeled plasma ASP from high affinity association with the cell surface in both human differentiated adipocytes and 3T3 preadipocyte fibroblasts. Furthermore, immunoprecipitation of rASP and pASP with a specific monoclonal antibody abolished stimulation of cellular triglyceride synthesis. Lastly, we contrasted the structure:function activities of the arginated (C3a) and desarginated (ASP) proteins. The lipogenic activity and the anaphylatoxic activity result from distinct structural domains of the polypeptides. Thus rASP retains full biologic ASP activity and may provide a tool to study structure-function relationships in this physiologic system.

Adipocytes↗
PubMed1985

Generation of anaphylatoxin activity related to C3a, by treatment of human serum with the nitrogen nucleophile N2H4 or the chaotrope KSCN.

The present study is concerned with the proteolytic processing of complement component C3 in normal human serum treated with N2H4 or KSCN in the presence of EDTA. Upon incubation with these agents, C3 is first converted to the thiolester-cleaved form (C3i) and thereafter fragmented by factor I. In consecutive, relatively slow steps, spasmogenic and platelet-aggregating activity is released. The active principle shows characteristics of C3a. First, the pretreated sera deactivate guinea pig ileum and platelets towards the action of C3ahog, but not C5a-desArghog. Second, the activity is only stable under conditions causing inhibition of serum carboxypeptidase N, such as in the presence of EDTA or of MERGETPA (DL-2-mercaptomethyl-3-guanidinoethylthiopropanoic acid). Third, the molecular weight determined by gel filtration is in agreement with that of C3a. The release of C3a activity requires conversion of C3 to C3i, as well as the complement-independent generation of proteolytic activity in the pretreated sera. The enzyme releasing C3a activity is a serine esterase probably identical with Hageman factor, kallikrein, or another protease related to the contact system.

Anaphylatoxins↗
PubMed1996

Specific complement inhibition with heparin-coated extracorporeal circuits.

BACKGROUND: Although it is well established that heparin-coated extracorporeal circuits reduce complement activation during cardiac operations, little in vivo information is available on the reduction in alternative and classic pathway activation. METHODS: In a prospective, randomized study involving patients undergoing coronary artery bypass grafting with standard full heparinization, we compared heparin-coated circuits (Duraflo II) (10 patients) with uncoated circuits (10 patients) and assessed the extent of initiation of complement activation by detecting iC3 (C3b-like C3) concentrations, classic pathway activation by C4b/c (C4b, iC4b, C4c) concentrations, terminal pathway activation by soluble C5b-9 concentrations, and C3 activation by C3a (C3a desArg) and C3b/c (C3b, iC3b, C3c) concentrations. RESULTS: Heparin-coated extracorporeal circuits significantly reduced circulating complement activation product C3b/c and soluble C5b-9 concentrations at the end of cardiopulmonary bypass and after protamine sulfate administration compared with the uncoated circuits, but not iC3, C4b/c, or C3a concentrations. CONCLUSIONS: Heparin-coated extracorporeal circuits reduce complement activation through the alternative complement pathway, probably at the C3 convertase level, and, consequently, the terminal pathway. C3b/c seems to be a more sensitive marker than C3a to assess complement activation during cardiac operations.

Aged↗
PubMed2003

[Acute adverse effects of dialysis].

Adverse reactions to dialyzers are a not very frequent, but because of the serious, sometimes fatal course, a dreaded complication of haemodialysis treatment. Most important among these reactions are hypersensitive reactions (anaphylactoid, reaction type A to dialyzer), which develop as a rule within the 10th minute of the procedure, and the reaction caused by the action of perfluorohydrocarbon which develop hours after onset or even completion of haemodialysis. Explanation of the development of hypersensitive reactions (HSR) by complement activation and formation of anaphylatoxins C3a and C5a during contact of blood with the bioincompatible dialysis membrane has been abandoned. Evidence of the etiological role of ethylene oxide (ETO) in the development of HSR influenced the selection of materials for the production of dialyzers and sterilization during manufacture, it emphasized the importance of rinsing of the dialyzer in the dialysis centre and led to the wide application of alternative methods of sterilization by gamma radiation and steam. HSR may be also caused by overproduction of bradykinin and inhibition of its degradation or degradation of its metabolites. Excessive bradykinin production caused by dialysis membranes with a negative charge is potentiated e.g. by a lower pH and increased plasma dilution in the initial stage of haemodialysis. Inhibition of bradykinin degradation develops during treatment with angiotensin converting enzyme inhibitors (ACEI). In prevention of HSR associated with bradykinin in addition to elimination of a combination of a negatively charged dialysis membrane and ACEI treatment a part is played also by rinsing of the dialyzer before haemodialysis with a bicarbonate solution and the modification of the membrane surface (implemented by the manufacturer) which reduces its negative charge. The first reaction to the dialyzer in conjunction with perfluorohydrocarbon (PF-5070), used in production of some dialyzers for testing the integrity of their capillaries were first described in 2001 and have caused since then at least 50 deaths. Reactions associated with PF-5070 are still the subject of research and forensic investigations. Despite this they draw already now attention to the failure in manufacture of dialyzers, to the inadequacy of hitherto accepted testing procedures of dialyzers and the constant necessity of careful clinical, laboratory and post-mortem examination of dialyzed patients.

Complement Activation↗
PubMed1996

Hageman factor and kallikrein in pathogenesis of senile cataracts and the pseudoexfoliation syndrome.

It is thought that dystrophic changes in the human aging anterior eye are due to lipid peroxidation in both the cortical and nuclear structures of the lens under the conditions of ischemia. These changes are often accompanied by only lens opacification (senile cataract-SC) or by formation of amorphous or fibrillar deposits in anterior eye, disturbances of eye hydrodynamics and lens opacification (pseudoexfoliation syndrome-PES). Our results suggest that the main reason of dystrophic changes in the tissues of the aging anterior eye is the disturbance of the haemato-ophthalmic barrier and that the plasma kallikrein-kinin system takes part in this disturbance. Penetration of plasma proteins, such as C-reactive protein, complement components, immunoglobulins and coagulation factors, from plasma into the aqueous humor is responsible for damaging epithelial structures of anterior eye and formation of pseudoexfoliative material. Using ELISA, the C-reactive protein, IgG and IgM antigens have been shown to localize on the surface of the opaque lenses. Presence of these complement binding proteins in the superficial lens structures as well as the high C3a concentration in the aqueous humor substantiates the pathogenic role of complement activation in the lenticular epithelium upon cataract and PES formation.

Age Factors↗
PubMed1985

Determination of C3b receptors on normal and patient polymorphonuclear neutrophils with C3b-coated fluorescent microspheres.

A method, devised in the authors' laboratories, for the determination of C3b receptors on normal and patient neutrophils using C3b-coated fluorescent microspheres, was applied to the quantitation of C3b receptors on the neutrophils of several patients suffering from burns and trauma and a patient with pancreatitis. From three to 11 days in the clinical course the relative number of C3b receptors was, or rose to, two to ten times the number of receptors present at later times in the clinical course and, in most of the cases studied, the increase in C3b receptor number coincided with enhanced neutrophil bactericidal function. The rise in C3b receptor number was ascribed to up-regulation by C3a and C5a des Arg from complement activation and also, in the cases where sepsis occurred, to the presence of bacterial chemotactic peptides. Preliminary experiments with zymosan-activated serum and the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine confirmed this explanation.

Blood Bactericidal Activity↗
PubMed1986

Cardiac mast cells: partial purification of guinea-pig atrial mast cells and release from them of histamine and leukotriene C4 by immune and non-immune stimuli.

The response of cardiac mast cells in enzymically dispersed guinea-pig atrial tissue to various immune and non-immune stimuli was studied. These cells were also partially purified by density-gradient centrifugation. The release of histamine, and in some experiments leukotriene C4, was measured. The cells responded strongly and consistently to the calcium ionophore A23187 but their response to other non-immune stimuli such as neuromuscular blockers and morphine (which are known to cause anaphylactoid reactions in human and other species) was relatively weak and inconsistent. Relatively weak responses were also obtained by immune stimuli in the following decreasing order: anti-IgG, antigen, histamine-releasing lymphokine and then the complement fragments C5a-desArg and C3a.

Animals↗
PubMed1990

Humoral immune response following extracorporeal immunoadsorption therapy of patients with hypercholesterolemia.

Low-density lipoprotein apheresis (LDL-apheresis) is an extracorporeal procedure that preferentially removes LDL cholesterol from the blood. One of the primary techniques for performing this procedure uses immunoadsorption columns containing monospecific polyclonal sheep antibodies to human LDL covalently coupled to a gel filtration medium. LDL-apheresis has generally been well-tolerated, with chills, fever, or flushing occurring rarely. The possibility of an immune reaction was investigated as a basis for these reactions observed in 12 of the 1312 procedures performed. Antibodies to sheep IgG developed in 12 of the 15 patients treated with LDL-apheresis as a result of the shedding of small quantities of the sheep immunoglobulin from the columns. A column acid-washing procedure minimized the quantity of shed antibody but did not prevent immunization of the patient. The clinical reactions were probably unrelated to shedding and immunization, as the reactions occurred even in patients who were not immunized to the sheep IgG. Immunization to ethylene oxide was not the cause, as determined by a radioallergosorbent test. The reactions were more likely related to the activation of complement, as indicated by the generation of C3a des Arg by the columns and an increase in C3a des Arg levels systemically.

Antibody Formation↗
PubMed1990

Molecular epitope identification by limited proteolysis of an immobilized antigen-antibody complex and mass spectrometric peptide mapping.

Sequences of antigenic determinants were identified by limited proteolysis of peptide antigens bound to an immobilized monoclonal antibody and direct molecular weight determination of the monoclonal antibody-bound peptide fragments by 252Cf plasma desorption mass spectrometry. The epitope peptides to the monoclonal antibody h453 [Burger, R., Zilow, G., Bader, A., Friedlein, A. & Naser, W. (1988) J. Immunol. 141, 553-558] were isolated from immobilized antigen-antibody complexes by partial trypsin digestion. A synthetic eicosapeptide comprised of the C-terminal sequence of the human complement component polypeptide des-Arg77-C3a as well as guinea pig des-Arg78-C3a was used as an antigen. Conditions were developed under which trypsin specifically degraded the antigens without inactivation of the immobilized antibody. After proteolysis, epitope peptides were dissociated from the antibody with 4 M MgCl2. The antigenic peptides were purified by HPLC and identified by 252Cf plasma desorption mass spectrometry. The epitope recognized by h453 resides on the C-terminal tryptic peptides of human (residues 70-76) and guinea pig (residues 70-77) C3a. As an estimation of accuracy this method is able to provide, trypsin digestion of immune complexes caused cleavage of the antigen within a distance of two amino acid residues upstream from the epitope.

Amino Acid Sequence↗
PubMed1993

Complement activation in newborn infants with early onset infection.

The complement system is an important element in host defense. Quantitative deficiencies of total hemolytic complement activity and decreased C3 levels were reported in sera from normal neonates. However, little is known about complement activation products in the newborn. In a prospective study, complement activation products were determined in 32 healthy term neonates, in 41 neonates with colonization of their mothers, in 15 colonized neonates, and in 10 neonates with early onset infection. In all newborns, EDTA plasma was obtained within the first 6 h of life. The anaphylatoxin C3a-desArg was determined with a novel ELISA using an MAb reacting with a neoepitope of C3a-desArg. C3bBbP (alternative pathway convertase) and C1rsC1-inactivator (activation product of classical pathway) were measured with double-sandwich ELISA. C3 was determined by radial immunodiffusion. Plasma concentrations of C3a-desArg were similar in healthy term neonates and healthy adults, whereas diminished C3 levels were observed in the newborn infants. There were no significant differences between healthy neonates, neonates with colonized mothers, and colonized neonates. In neonates with infection, a significant elevation of C3a-desArg was found at the onset of the disease, resulting from alternative pathway activation. In contrast, the C1rsC1-inactivator complex showed no significant differences among healthy, colonized, and infected neonates. The anaphylatoxin C3a mediates inflammatory reactions such as vasodilatation and an increase in microvascular permeability and might therefore play an important role in severe neonatal infection.

Complement Activation↗
PubMed1993

The influence of dialyzer geometry on blood coagulation and biocompatibility.

The influence of dialyzer geometry on blood coagulation, heparin requirement and complement activation was studied in fourteen chronic hemodialysis patients. Each patient was dialyzed with two different cuprophan dialyzers, hollow fiber GF 120M and parallel plate Lundia IC5N. Both dialyzers had a wall thickness of 11 microns, surface area of 1.2 m2 and both were sterilized with ethylene oxide. Heparin doses were individually titrated. The mean heparin dose was 6089 +/- 988 U. Platelet count decreased from 218 x 10(9)/l to 193 x 10(9)/l and from 235 x 10(9)/l to 197 x 10(9)/l respectively (hollow fiber/plate dialyzer, ns). The number of leucocytes decreased at 15 min after start of dialysis by 56% and 61% (hollow fiber/plate dialyzer, ns). The heparin requirement, measured as prolongation of whole blood activated coagulation time after identical doses of heparin, were the same in hollow fiber and plate dialysis sessions. The arterial fibrinopeptide A concentrations increased during dialysis from 5.4 to 7.1 nmol/l and 8.5 to 9.6 nmol/l respectively (hollow fiber/plate dialyzer, ns). The residual blood volume in the hollow fiber dialyzers was 1.3 +/- 1.1 ml and in the plate dialyzers 1.5 +/- 0.9 ml (ns). C3a activation, indicated by a marked arterio-venous difference, was observed at 15 min after start of dialysis with hollow fiber as well as plate dialyzers. The arterio-venous difference was less pronounced at the end of dialysis. There were no differences in C3a activation between hollow fiber and plate dialyzers at any timepoint. It is concluded that dialyzer geometry does not significantly influence platelet count, blood coagulation, heparin requirement or complement activation.

Aged↗