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PubMedDate not supplied

Interaction of anti-leprosy drugs with the rat serum complement system.

Dapsone, clofazimine and rifampicin, the three most important constituents of multidrug therapy against leprosy, were studied with respect to their effects on the rat serum complement system, in vitro as well as in vivo. Of the three drugs only dapsone and clofazimine exhibited significant in vitro anti-complement activity and only at a very high, non-therapeutic dose of 0.24 mg/ml. On the contrary, rifampicin could not induce significant in vitro complement consumption. Furthermore, dapsone and clofazimine could reduce rat-serum-mediated rabbit erythrocyte haemolysis in the presence of Mg2+-EGTA, indicating that they could also affect the alternative pathway of complement activation. However, the latter pathway of complement consumption by these drugs seems to be insignificant because the factor-B-mediated complement-consumption system is minimal in rat sera. Immunoelectrophoretic study of mixtures of fresh rat sera and anti-leprosy drugs against specific anti-rat-C3 antisera demonstrated that dapsone and clofazimine could not cleave the C3 complement component. In a separate experiment we attempted to reconstitute the haemolytic complement activity consumed by dapsone and clofazimine by adding Crat-EDTA sera (a source of C3, C5, C6, C7, C8 and C9), but at most only 12% reconstitution of haemolytic activity could be achieved. We thus conclude that both dapsone and clofazimine could affect the complement system, predominantly through the earlier complement components and at very high, non-therapeutic doses. On the contrary, in-vivo experiments in rats showed that a combination of these three drugs, when given at a therapeutic dose or at 10 times the therapeutic dose for three months, did not affect the complement system.

Animals↗
PubMed2002

Pseudorabies virus (PRV) is protected from complement attack by cellular factors and glycoprotein C (gC).

Swine kidney derived CPK cells were resistant to swine complement attack in vitro while rabbit kidney derived RK13 cells were destroyed by swine complement. To rabbit complement, RK13 cells were resistant but CPK cells were sensitive. This phenomenon was known as homologous restriction (Proc. Natl. Acad. Sci. USA 78 (1981) 5118). The gC deletion mutant of pseudorabies virus (PRVdlgC) grown in CPK cells was resistant to swine complement while the same virus grown in RK13 cells was neutralized by swine complement. PRVdlgC grown in RK13 cells was more resistant to rabbit complement than the virus grown in CPK cells. Hence, the sensitivity of PRVdlgC to swine or rabbit complement was similar to that of the cells in which the virus was grown. It would appear that cell derived factors were present on the virion and they were protective against homologous complement but not against heterologous complement. The expression of gC rendered PRV more resistant to swine or rabbit complement, but the protective effect of gC was much less than that of cell derived factors. The best protection against complement was obtained when gC and cell derived factors were coexistent on the virion.

Animals↗
PubMed2004

Activation of microglial cells and complement following traumatic injury in rat entorhinal-hippocampal slice cultures.

The complement cascade has been suggested to be involved in development of secondary brain damage following traumatic brain injury (TBI). Previous studies have shown that reactive microglia are involved in activation of the complement cascade following various injuries to the nervous system. Macrophages seem to have a significant role in this process, but it is still unclear whether these cells, as well as the complement components, are derived from reactive microglia or if these biological events only can occur as a result from the influx of plasma and monocytes via a disrupted blood-brain barrier (BBB). The aim of this study was to investigate the response of microglial cells and the complement system in the absence of plasma/blood components following a standardized crush injury in an entorhinal-hippocampal slice culture. There was a clear increase in complement component C1q and C5b-9-IR (Membrane Attack Complex, MAC) in the area near the crush injury. MAC-IR appeared as numerous dots in clusters which co-localized with anti-NeuN labelled neurons in the injury border zone. Complement C1q-IR co-localized with reactive microglia, co-labelled with OX42 antisera. These findings show activation of the complement cascade near the injury zone and in particular, formation of MAC at the surface of neurons in this area. There was a distinct activation of microglial cells (OX42-IR) near the site of injury, as well as an increase in ED-1 expressing macrophages. In the absence of blood and plasma components it is likely that ED-1-labelled cells represent reactive microglia transformed into macrophages. In addition, Neurons (Neun-IR) near the injury were found to co-localize with clusterin-IR indicating upregulation of a defense system to the endogenous complement attack. The present study provides evidence that microglia and complement is activated in the injury border zone of the tissue slice in a similar fashion as in vivo following TBI, despite the absence of plasma/blood products and cells. These findings support the hypothesis that reactive microglia have a key role in complement activation following TBI by local synthesis of complement with a potential impact on development of secondary neuronal insults.

Animals↗
PubMed1996

Activation of the complement system by synthetic DNA complexes: a potential barrier for intravenous gene delivery.

We have examined the complement-activating properties of synthetic cationic molecules and their complexes with DNA. Commonly used gene delivery vehicles include complexes of DNA with polylysine of various chain lengths, transferrin-polylysine, a fifth-generation poly(amidoamine) (PAMAM) dendrimer, poly(ethyleneimine), and several cationic lipids (DOTAP, DC-Chol/DOPE, DOGS/DOPE, and DOTMA/DOPE). These agents activate the complement system to varying extents. Strong complement activation is seen with long-chain polylysines, the dendrimer, poly(ethyleneimine), and DOGS (half-maximal at about 3 microM amine content in the assay used). Compared to these compounds, the other cationic lipids (in liposome formulations) are weak activators of the complement system (half-maximal approximately 50-100 microM positive charge in assay). Complement activation by polylysine is strongly dependent on the chain length. Short-chain oligolysines are comparable to cationic lipids in their activation of complement. Incubation of these compounds with DNA to form complexes reduces complement activation in virtually all cases. The degree of complement activation by DNA complexes is strongly dependent on the ratio of polycation and DNA (expressed as the charge ratio) for polylysine, dendrimer, poly(ethyleneimine), and DOGS. To a lesser degree, charge ratio also influences complement activation by monovalent cationic lipid-DNA complexes. For polylysine-DNA complexes, complement activation can be considerably reduced by modifying the surface of preformed DNA complexes with polyethyleneglycol (half-maximal approximately 20 microM amine content). The data suggests that, by appropriate formulation of DNA complexes, complement activation can be minimized or even avoided. These findings should facilitate the search for DNA complex formulations appropriate for reproducible intravenous gene delivery.

Animals↗
PubMed1985

Interactions of Plasmodium berghei-infected erythrocytes with complement.

Incubation of radioactively labeled parasitized (Plasmodium berghei) erythrocytes (PE) with adherent peritoneal exudate cells in the presence of 10% (v/v) fresh mouse serum (NMS) resulted in the uptake of a proportion of radioactive material (PE). Inactivation of the added serum by heat or zymosan treatment resulted in diminished uptake of radioactivity. These results suggest that PE activated complement. Incubation of fresh NMS with PE reduced the hemolytic complement level of the serum as shown by its subsequent decreased ability to lyse antibody-coated rabbit red blood cells. No such effect was found when uninfected erythrocytes from either infected or uninfected blood were preincubated with fresh NMS. Thus, PE or PE-derived material activated complement. Addition of EGTA during incubation of fresh NMS with PE did not inhibit the decrease in complement level. This indicated that complement was activated by the alternative pathway. Complement levels decreased even when fresh NMS and PE were incubated in the presence of EDTA (which inhibits both classical and alternative pathway activation), suggesting that a complement activating factor (or a complement inhibitor) was released from the PE. However, lysis of PE after incubation with either fresh rabbit or guinea pig serum did not occur unless anti-mouse erythrocyte antibody was added. The production of a complement-activating factor by PE might explain part of the decreasing complement levels during infection and might enable the parasite to escape from a complement-mediated defense mechanism of the host.

Animals↗
PubMed1991

Infectious diseases associated with complement deficiencies.

The complement system consists of both plasma and membrane proteins. The former influence the inflammatory response, immune modulation, and host defense. The latter are complement receptors, which mediate the cellular effects of complement activation, and regulatory proteins, which protect host cells from complement-mediated injury. Complement activation occurs via either the classical or the alternative pathway, which converge at the level of C3 and share a sequence of terminal components. Four aspects of the complement cascade are critical to its function and regulation: (i) activation of the classical pathway, (ii) activation of the alternative pathway, (iii) C3 convertase formation and C3 deposition, and (iv) membrane attack complex assembly and insertion. In general, mechanisms evolved by pathogenic microbes to resist the effects of complement are targeted to these four steps. Because individual complement proteins subserve unique functional activities and are activated in a sequential manner, complement deficiency states are associated with predictable defects in complement-dependent functions. These deficiency states can be grouped by which of the above four mechanisms they disrupt. They are distinguished by unique epidemiologic, clinical, and microbiologic features and are most prevalent in patients with certain rheumatologic and infectious diseases. Ethnic background and the incidence of infection are important cofactors determining this prevalence. Although complement undoubtedly plays a role in host defense against many microbial pathogens, it appears most important in protection against encapsulated bacteria, especially Neisseria meningitidis but also Streptococcus pneumoniae, Haemophilus influenzae, and, to a lesser extent, Neisseria gonorrhoeae. The availability of effective polysaccharide vaccines and antibiotics provides an immunologic and chemotherapeutic rationale for preventing and treating infection in patients with these deficiencies.

Animals↗
PubMed1979

Inactivation or elimination of potentially trypanolytic, complement-activating immune complexes by pathogenic trypanosomes.

Trypanosoma brucei subsp. brucei and T. congolense incubated in homologous antibody at 0 degrees C for 30 min were lysed by subsequent addition of guinea pig complement. Trypanosomes incubated in antibody at 37 degrees C before complement treatment remained intact. Parasites bearing adsorbed antibody also remained intact when incubated at 37 degrees C before complement treatment. The proportion of cells which survived complement treatment decreased with increasing antibody concentration. Parasites which survived complement treatment continued to express antigens which could bind complement-activating antibody, but did not bear complement-activating immune complexes. Virtually all cells in T. brucei populations exposed to antibody at 37 degrees C, but only 10(-3) to 10(-5) of the cells in populations exposed to antibody at 0 degrees C before complement treatment, remained infective for X-irradiated mice. Only 10(-6) to 10(-7) of T. brucei populations exposed to antibody at 0 or 37 degrees C before complement treatment infected mice immunized with homologous antigens. Serotype analysis of substrains and of T. brucei populations isolated from mice infected with antibody and complement-treated parasites suggested that variant-specific antigens participated in trypanolysis and that T. brucei which survived complement treatment could undergo antigenic variation. Mechanisms by which trypanosomes may inactivate or eliminate surface immune complexes and the possible significance of this phenomenon in trypanosomiasis are discussed.

Animals↗
PubMed2002

Complementation analysis of the flavivirus Kunjin NS3 and NS5 proteins defines the minimal regions essential for formation of a replication complex and shows a requirement of NS3 in cis for virus assembly.

We have previously reported successful trans-complementation of defective Kunjin virus genomic RNAs with a range of large lethal deletions in the nonstructural genes NS1, NS3, and NS5 (A. A. Khromykh et al., J. Virol. 74:3253-3263, 2000). In this study we have mapped further the minimal region in the NS5 gene essential for efficient trans-complementation of genome-length RNAs in repBHK cells to the first 316 of the 905 codons. To allow amplification and easy detection of complemented defective RNAs with deletions apparently affecting virus assembly, we have developed a dual replicon complementation system. In this system defective replicon RNAs with a deletion(s) in the nonstructural genes also encoded the puromycin resistance gene (PAC gene) and the reporter gene for beta-galactosidase (beta-Gal). Complementation of these defective replicon RNAs in repBHK cells resulted in expression of PAC and beta-Gal which allowed establishment of cell lines stably producing replicating defective RNAs by selection with puromycin and comparison of replication efficiencies of complemented defective RNAs by beta-Gal assay. Using this system we demonstrated that deletions in the C-terminal 434 codons of NS3 (codons 178 to 611) were complemented for RNA replication, while any deletions in the first 178 codons were not. None of the genome-length RNAs containing deletions in NS3 shown to be complementable for RNA replication produced secreted defective viruses during complementation in repBHK cells. In contrast, structural proteins produced from these complemented defective RNAs were able to package helper replicon RNA. The results define minimal regions in the NS3 and NS5 genes essential for the formation of complementable replication complex and show a requirement of NS3 in cis for virus assembly.

Amino Acids↗
PubMed1984

Complement potentiation of phagocyte-mediated ADCC of HSV-infected corneal cells.

The authors have shown previously that rabbit alveolar macrophages, peritoneal exudate macrophages, and polymorphonuclear leukocytes are highly effective mediators of antibody-dependent cellular cytotoxicity (ADCC) against herpes simplex virus (HSV)-infected rabbit stromal keratocytes. Using a completely homologous system of nonimmune rabbit phagocytes, anti-HSV serum, complement, and HSV-infected stromal keratocyte targets, the authors have found significant potentiation of ADCC by complement. Lymphocyte-mediated ADCC, on the other hand, was not potentiated by complement. Using a 1:100 dilution of complement (noncytolytic in antibody-mediated lysis) and a 1:10 dilution of antiserum obtained from rabbits undergoing stromal keratitis, ADCC mediated by the three phagocytic cell types was augmented by approximately 22%. For example, using alveolar macrophages as effector cells, the addition of complement increased the level of ADCC From 40% to 60%, a 20% increase. Percent ADCC was augmented less by complement at higher antiserum dilutions. However, the percent of the total ADCC attributable to complement potentiation increased at these higher antiserum dilutions. In some cases, ADCC was not detectable at these high antiserum dilutions without the added complement. The potentiating effect was observed at complement dilutions as high as 1:400. Further dilution or heat-inactivation resulted in ADCC values comparable to those obtained without complement. Target cells exposed to complement alone were not killed by phagocytes.

Animals↗
PubMed1996

Complement resistance of Leishmania amazonensis promastigotes is independent of parasite proteases and lysis of sensitive forms is not due to natural antibodies in normal human serum.

Leishmania amazonensis promastigotes cultivated in vitro differentiate from complement-sensitive to complement-resistant forms. In order to determine the possible involvement of parasite proteases in this process, L. amazonensis promastigotes were collected daily and their proteolytic enzyme patterns analyzed using polacrylamide gels copolymerized with gelatin. Although promastigotes at different growth stages showed differences in protease patterns, these changes did not correlate with their susceptibility to complement. The major protease of promastigotes, gp63, was expressed at the same level throughout culture, regardless of the complement resistance of the promastigotes. Furthermore, inhibitors specific for the classes of proteases found in L. amazonensis promastigotes did not interfere with the complement-mediated killing of promastigotes. We also investigated the binding of natural antibodies to promastigotes. at different stages of growth using ELISA. Although complement-sensitive promastigotes bound significantly more antibodies from fresh normal human serum than complement-resistant promastigotes, equivalent amounts of C3 were detected on their surfaces following complement activation. Moreover, serum depleted of anti-Leishmania antibodies was an efficient in killing promastigotes and the intact serum. These data suggest that the resistance of L. amazonensis to complement killing involves strategies other than that of the regulated expression of endogenous proteases capable of inactivating complement components, or the differential ability to bind natural antibodies that might interfere with complement deposition on the parasite surface.

Animals↗
PubMed2000

The role of complement in B cell activation and tolerance.

It is becoming well accepted that innate immunity serves as a natural adjuvant in enhancing and directing the adaptive immune response. In this review, I have discussed how the complement system, a major mediator of innate immunity, links the two systems. The recent availability of knockout mice bearing selective deficiencies in the critical complement proteins and receptors has allowed formal demonstration of the importance of complement in enhancement of humoral immunity. Characterization of the mice has also uncovered mechanisms for maintaining survival of activated B cells within the lymphoid compartment. For example, co-ligation of the CD21/CD19/Tapa-1 receptor with the BCR not only reduces the threshold for B cell follicular survival but provides a unique signal for survival in the germinal centers. In addition complement receptors are critical for localization of antigen and C3d ligand to FDCs for maintenance of long-term B cell memory. A surprise that has come from analysis of the deficient mice is that complement is also important in negative selection of B lymphocytes. This observation provides new insight to a long-standing enigma that the major predisposing factor in lupus is deficiency in complement C1q or C4. The seeming contradiction of dual role for complement in both B cell activation and tolerance is reconciled by the hypothesis that natural IgM provides a mechanism to selectively identify self-antigens that are highly conserved and cross-react with microbial ones such as DNA and nuclear proteins. Thus, the importance of complement in tolerance to self-antigens is restricted to those self-antigens that are evolutionary conserved, and they are identified by natural antibody. The future should hold further surprises as to the intricate interactions between the complement system and acquired immunity.

Adjuvants, Immunologic↗
PubMed1997

Neutralization of cytomegalovirus virions: the role of complement.

Complement provides a key immunologic defense against invading pathogens; thus, a clear understanding of the interactions between cytomegalovirus (CMV) and complement may permit the development of strategies to enhance CMV neutralization. In the presence of specific anti-CMV antibodies, complement enhanced the neutralizing ability of serum by 2- to 3-fold. However, in the absence of specific anti-CMV antibodies, complement was ineffective in neutralizing CMV virions by plaque assay. Although complement alone did not mediate any neutralizing effect, CMV consumed complement activity from seronegative serum, resulting in the deposition of C3 on the virion. However, only in the presence of specific anti-CMV antibody did complement activation continue to the deposition of C9 on the virions. These results strongly suggest complement regulation by CMV virions that is modulated by anti-CMV antibody; this regulation may be attributed to three host complement regulators on the virions: CD55, CD46, and CD59.

Antibodies, Viral↗
PubMedDate not supplied

Complement receptors and regulatory proteins in human atherosclerotic lesions.

Complement activation in human atherosclerotic lesions is indicated by the presence of C5b-9 terminal complexes. By using monoclonal antibodies to the complement C3b receptor (CR1) and the iC3b receptor (CR3), it was observed that approximately 20% of the cells in complicated human carotid lesions express CR1 and CR3 antigens. One to five percent of complement receptor-positive cells stained for smooth muscle cell-specific myosin, and the remainder were determined to be predominantly macrophages, based on their reactivity to anti-LeuM3 (CD14) monoclonal antibody. No C3dg receptor (CR2)-positive cells were observed in any of the eight lesions examined. The complement regulatory glycoprotein decay accelerating factor (DAF) was widely distributed extracellularly, in addition to being present on 20% to 60% of the total cell population. Factor H, a plasma protein that regulates alternative pathway C3 convertase formation, was observed extracellularly in 70% of the lesions examined. C1 inhibitor was present in a few plaque specimens, was relatively sparse, and appeared largely cell associated. Terminal C5b-9 complement complexes were pervasive in all lesions. Both the complement regulatory proteins and the activation products were limited to the area of lesion involvement and were absent from normal arterial wall. The results demonstrate that molecules involved in complement regulation and complement ligand binding are present in atherosclerotic lesions, where they may function to modulate the activities of complement.

Arteriosclerosis↗
PubMed1988

The ability of Sephadex to activate human complement is suppressed in specifically substituted functional Sephadex derivatives.

The capacity of Sephadex and of chemically substituted Sephadex derivatives to activate human complement was examined by incubating polymer particles in normal human serum (NHS) under conditions that allow classical and/or alternative pathway activation, and by determining complement consumption or generation of C3a antigen in serum. Sephadex was found to activate complement in NHS, mainly through the alternative pathway. The complement-activating capacity of Sephadex was directly related to the surface area of polymer that could interact with serum. Substitution of hydroxyl groups of Sephadex with carboxymethyl (CM) groups suppressed the complement-activating capacity of the polymer in a dose-dependent fashion so that Sephadex bearing an average of one or more CM groups per saccharidic unit exhibited no complement-activating ability. Blocking of CM groups on CM sephadex with amide bonds did not restore a complement-activating capacity to the polymer, indicating that intact hydroxyl groups of the sugar units are required for complement activation by Sephadex. CM Sephadex was also found to adsorb C3adesArg which bound to the polymer with a calculated affinity of 1 x 10(6) l x M-1. Substitution of Sephadex with carboxymethyl and benzylamide sulphonate groups which confers to the polymer the capacity to catalyse thrombin inactivation on its surface also suppressed the complement-activating capacity of Sephadex. Sephadex derivatives that lack complement-activating properties and adsorb anaphylatoxins may provide useful models for the design of cellulosic membranes and biomaterials with blood compatible properties.

Blood↗
PubMed2004

Artificial surface-induced cytokine synthesis: effect of heparin coating and complement inhibition.

BACKGROUND: Contact between blood and artificial surfaces induces an inflammatory response including activation of leukocytes and platelets, as well as complement and other plasma cascade systems. In the present study we investigated the roles of complement and surface modification in polyvinylchloride-induced cytokine production. METHODS: Human whole blood was incubated in rotating loops of polyvinylchloride or heparin-coated polyvinylchloride tubing for 4 hours. Plasma concentrations of the cytokines tumor necrosis factor alpha, interleukin (IL) 1 beta, IL-6, IL-8, IL-10, and monocyte chemoattractant protein 1 (MCP-1) were quantified. RESULTS: Polyvinylchloride induced a substantial increase in IL-8 and MCP-1, which was abolished by cycloheximide, indicating that they were synthesized during incubation. Interleukin 8 synthesis was completely complement-dependent since it was abolished by neutralizing antibodies to factor D and complement factor 5, as well as by a complement factor 5a receptor antagonist. Monocyte chemoattractant protein 1 synthesis was reduced by approximately half the amount by the complement inhibitors. Heparin-coated polyvinylchloride efficiently prevented synthesis of both IL-8 and MCP-1. Addition of recombinant human complement factor 5a to blood incubated in heparin-coated polyvinylchloride restored IL-8 and MCP-1 production completely and partly, respectively. In contrast to IL-8 and MCP-1, tumor necrosis factor alpha, IL-1 beta, interleukin 6 and IL-10 increased only marginally. A minor but significant increase in IL-1 beta was complement-dependent, whereas a similar increase in IL-10 was completely prevented by heparin-coated polyvinylchloride. No significant changes were observed for tumor necrosis factor alpha and IL-6. CONCLUSIONS: Polyvinylchloride induced a marked increase in IL-8 and MCP-1, in contrast to a marginal increase in tumor necrosis factor alpha, IL-1 beta, IL-6, and IL-10. The increase in IL-8 and MCP-1 was prevented by heparin-coated polyvinylchloride. Interleukin 8 production was totally complement-dependent and mediated by complement factor 5a.

Anticoagulants↗
PubMed2006

Candidate inhibitors of porcine complement.

Therapeutic complement inhibition is a promising strategy for treatment of a number of diseases as judged from rodent studies. The species distance from rodents to humans may limit the clinical relevance of these studies. The pig is an alternative animal for studies of human diseases like sepsis and ischemia/reperfusion injury. However, available complement inhibitors for use in pigs are scarce. The aim of the present study was to investigate and compare the efficacy of selected candidate inhibitors of porcine complement in vitro for possible future application in vivo. Sera from three different pigs were each incubated with three different activators of the complement system (zymosan, heat-aggregated immunoglobulin G (HAIGG) and Escherichia coli). Three groups of complement inhibitor candidates were tested: serine protease inhibitors (FUT-175 and C1-inhibitor), monoclonal antibodies (anti-factor B (fB) and anti-factor D (fD)) and a recombinant regulatory protein (vaccinia virus complement control protein (VCP)). Read-out was the terminal C5b-9 complement complex (TCC). The serine protease inhibitors FUT-175 and C1-inhibitor dose-dependently inhibited TCC formation in zymosan-, HAIGG- and E. coli-activated porcine sera, but with different efficacy. Complete inhibition of TCC was obtained using 0.2 mg/mL FUT-175, but required 16 mg/mL of C1-inhibitor. The monoclonal anti-fB and -fD antibodies both inhibited TCC formation dose-dependently, but in different ways. Anti-fB at high dose (1 mg/mL) completely inhibited TCC formation in sera activated with zymosan and virtually completely in sera activated with HAIGG, but not in sera activated with E. coli. Anti-fD inhibited all three activators at low dose (0.05 mg/mL), and approximately 50% TCC reduction was obtained. The recombinant complement regulatory protein VCP efficiently and dose-dependently inhibited TCC formation with a complete inhibition found at 0.05 mg/mL for all three activators. All candidates tested inhibited porcine complement activation, but in different ways and to different degrees. Of the complement-specific candidates, VCP inhibited all activators completely at low doses.

Animals↗
PubMed2004

Effect of complement inhibition and heparin coating on artificial surface-induced leukocyte and platelet activation.

BACKGROUND: Exposure of blood to artificial surfaces, as in cardiopulmonary bypass, induces an inflammatory response involving complement, leukocyte and platelet activation. To elucidate the specific role of complement in this process, studies were performed on blood circulated in polyvinyl chloride tubing in the absence and presence of complement inhibitors. Parallel experiments were performed with heparin-coated polyvinyl chloride tubing, which is known to prevent complement and cell activation. METHODS: A novel experimental model was used, based on human whole blood anticoagulated with lepirudin. Complement activation products, myeloperoxidase, lactoferrin, and thrombospondin were quantified in enzyme immunoassays. Leukocyte CD11b expression and leukocyte-platelet conjugates were detected by flow cytometry. RESULTS: Increased levels of C3 activation products, alternative pathway convertase, and the terminal SC5b-9 complex, combined with unchanged levels of C1rs-C1-inhibitor complexes and marginal changes in C4 activation demonstrated that complement was activated through the alternative pathway. Granulocyte and monocyte CD11b expression and granulocyte-platelet conjugate formation were efficiently attenuated by blocking either factor D, C3, C5, or C5a receptor. In contrast, monocyte-platelet conjugate formation and release of myeloperoxidase, lactoferrin, and thrombospondin were not reduced by complement inhibition. Heparin-coated polyvinyl chloride tubing efficiently reduced all inflammatory markers studied, except for C1rs-C1-inhibitor complexes, which increased, consistent with the enhancing effect of heparin on C1-inhibitor function. This effect did not, however, reduce fluid-phase classic pathway activation induced by heat-aggregated immunoglobulin G. CONCLUSIONS: Leukocyte and platelet activation in response to artificial materials occur by mechanisms that vary in their dependence on complement. Heparin coating precludes both the complement-dependent and complement-independent reactions.

CD11 Antigens↗
PubMed1984

Complement (C3, C4) consumption in cardiopulmonary bypass, cardioplegia, and protamine administration.

Anaphylatoxins produced by complement activation have been postulated to be responsible for postperfusion syndrome and protamine hypotension in patients undergoing cardiac surgical procedures. The consumption of serum complement components C3 and C4, which reflects the classic and alternate pathway activations of the complement system, was studied in 22 patients undergoing cardiac operations. Prior to the onset of cardiopulmonary bypass, the complement levels were within normal range. Rapid reduction in both C3 and C4 within minutes of cardiopulmonary bypass indicated rapid complement activation. Such a reduction in complement levels could not be accounted for by either hemodilution or transfusion of complement-poor blood. Aortic cross-clamping and cold potassium cardioplegia followed by myocardial reperfusion did not lead to further consumption of C3 and C4. Slow intravenous infusion of protamine sulfate after cardiopulmonary bypass did not change C3 and C4 levels significantly in our patients, although protamine and heparin-protamine complex have been shown to activate complement components in vitro. In another group of 9 similar cardiac surgical patients, C3 and C4 were found to return to normal levels within 24 hours after operation. This study thus confirms the rapid activation of the complement system by cardiopulmonary bypass but fails to demonstrate further activation of the complement system by cardioplegia or protamine administration.

Adult↗