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PubMed1987

Plasma levels of main granulocyte components in patients dialyzed with polycarbonate and cuprophan membranes.

Plasma levels of granulocyte lactoferrin, granulocyte myeloperoxidase and granulocyte elastase in complex with alpha 1-proteinase inhibitor (E-alpha 1PI) were investigated in regular hemodialysis patients dialyzed with hollow-fiber dialyzers made from polycarbonate (FD 100) or cuprophan (GFS 120 H). Plasma levels of all these main granulocyte components increased significantly during hemodialysis. E-alpha 1PI levels were significantly higher in patients dialyzed with the polycarbonate compared with the cuprophan membrane, whereas the increases of myeloperoxidase and lactoferrin were not different for the two dialyzers. On the other hand, plasma C3a levels were higher in patients dialyzed with the cuprophan compared with the polycarbonate dialyzer. Therefore, granulocyte activation during hemodialysis does not necessarily need complement activation.

Blood Proteins↗

PubMedDate not supplied

Prekallikrein activation in the adult respiratory distress syndrome.

Prekallikrein is the zymogen form of plasma kallikrein, a proteolytic enzyme of the contact system of blood coagulation, fibrinolysis and kinin formation. To assess whether prekallikrein was activated in the adult respiratory distress syndrome (ARDS), we examined plasma samples from 12 critically ill patients including five individuals with ARDS. Using the ratio between functional prekallikrein and prekallikrein-kallikrein antigen as an index for prekallikrein activation, we found that prekallikrein was extensively activated in patients with ARDS, while this was significantly less in the case of critically ill patients without ARDS. Following activation of prekallikrein in plasma, kallikrein reacts with its substrates and with protease inhibitors, among which the alpha 2-glycoprotein C1-inhibitor. Thus, we examined whether C1-inhibitor of critically ill individuals was modified in a way suggesting that it had reacted with kallikrein. Such a modification was found in the five patients with ARDS, while it was not detectable in the seven patients without ARDS. This observation further confirmed the activation of prekallikrein in patients with ARDS. We suggest that plasma kallikrein-mediated reactions, which include bradykinin release and neutrophil activation, may contribute to the pathogenesis of ARDS.

Adolescent↗

PubMed1998

Transforming growth factor-beta2 regulates C3 secretion in monocytes through a protein kinase C-dependent pathway.

Previously, we reported that TGF-beta2 regulates the C3 gene expression in a dose- and time-dependent manner in monocytes. To extend these studies, we examined the role of PKC in the TGF-beta2-mediated induction of C3 expression by the human monocyte cell line, U937. Treatment of U937 cells with the PKC inhibitors, H7 and calphostin C, suppressed TGF-beta2-mediated induction of C3 protein levels, but not mRNA levels, in a dose-dependent manner. At the highest concentrations of H7 and calphostin C, C3 protein levels were inhibited 50% and 93%, respectively, compared to control levels. Treatment of U937 cells with HA1004, a weak PKC inhibitor used as a control for H7, did not inhibit induction of C3 protein levels. Down-modulating PKC with a prolonged exposure of U937 cells to PMA also suppressed TGF-beta2-mediated C3 protein induction by as much as 82%. Incubating cell extracts isolated from TGF-beta2-treated U937 cells with the PKC substrate, MIBP(4-14), resulted in increased substrate phosphorylation compared to cell extracts isolated from untreated cells. Addition of calphostin C suppressed the increased substrate phosphorylation by TGF-beta2. Furthermore, biosynthetic labeling of U937 cells treated with TGF-beta2 and calphostin C demonstrated an accumulation of C3 protein within cell lysates compared to controls. Collectively, these studies suggest a role for PKC in the secretion of C3 protein during TGF-beta2-mediated regulation of C3 expression in U937 cells.

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

PubMed1982

Anaphylatoxin-mediated regulation of the immune response. I. C3a-mediated suppression of human and murine humoral immune responses.

The C3a fragment of the third component of complement was found to have immunosuppressive properties. C3a is capable of suppressing both specific and polyclonal antibody responses. In contrast, C3a had no effect on antigen- or mitogen-induced B or T cell proliferative responses. The carboxy-terminal arginine is essential for C3a to exhibit its immunosuppressive properties. The serum carboxypeptidase inhibitor 2-mercaptomethyl-5-guanodinopentanoic acid, which prevents cleavage of the terminal arginine that would produce C3ades Arg-77, allowed us to assay the effects of C3a on in vitro immune response systems where serum is required. When the terminal arginine is removed from C3a, the resulting C3ades Arg-77 molecule is nonsuppressive. Helper T lymphocytes are the target of C3a-mediated suppression of the immune response. Substitution of T cells by soluble T cell factors was found to abrogate the C3a suppressive activity.

Anaphylatoxins↗

PubMed1981

Demonstration of IgG-Fc and C3 receptors on adult Schistosoma mansoni.

Previous studies have indicated that adult schistosomes have an affinity for both IgG and C; however, thorough investigations on the possible presence of receptors for these serum proteins on the adult schistosome tegument have not been attempted. The present study presents evidence for both IgG-Fc and C3 receptors on adult schistosomes. An indirect assay utilizing fluoresceinated Staphylococcus aureus was developed to detect antigen-antibody (Ag-Ab) and antigen-antibody-C (Ag-Ab-C) binding to adult parasites. Detection of Ag-Ab and Ag-Ab-C complex binding was dependent on the presence of a metabolic inhibitor in the incubation mixture presumably to prevent shedding of bound complexes. Ag-Ab complex binding required the presence of an intact Fc on the IgG of the complex and could be partially inhibited by preincubation of parasites in heat-aggregated IgG or an isolated Fc preparation. Binding of Ag-Ab-C complexes was dependent on active C3 in the C source but not on an intact Fc on the IgG of the complex. Ag-Ab-C binding could be blocked by prior incubation of parasites in heat-aggregated IgG-C but not by C alone. Binding of host serum proteins to IgG-Fc and C3 receptors on adult schistosomes may aid parasite survival by helping to prevent immune detection.

Animals↗

PubMed1991

Monitoring the response to injury.

Tissue trauma leads to a severity-dependent activation of plasma and cellular systems. This response can be recorded by determining parameters which represent the activation state of these systems. In severely injured patients with multiple trauma three out of 14 parameters measured at the time of admission proved to be indicators of subsequent septic complications with a high degree of accuracy: Fibrinopeptide A (FPA--the first split product of fibrinogen), the C3 split product C3a, and the elastase-alpha 1 proteinase inhibitor-complex (E alpha 1 PI). In a second series of multiple-injured patients with femoral fractures who did not develop clinical sepsis (N = 25) these parameters were measured continuously to evaluate the influence of injury severity and of therapeutic strategy on the further course. We found a strong correlation between injury severity (ISS) and the degree of activation. The signs of activation decreased rapidly following immediate operative fixation, and remained elevated or even increased after primary femoral traction and secondary stabilization. The operative procedure did not cause any additional activation. Complications such as infection or the formation of haematomas were reflected by raised parameter levels.

Adolescent↗

PubMed2003

Inhibition of complement activation by recombinant Sh-CRIT-ed1 analogues.

Sh-CRIT-ed1 is a potent anti-complement peptide that inhibits the classical complement-activation pathway by interfering with the formation of the C3-convertase complex, C4b2a. C2 is an essential serum glycoprotein that provides the catalytic subunit of the C3 and C5 convertases of the classical pathways of complement activation. Because only in its C4-bound state is C2a capable of cleaving its physiological protein substrates C3 and C5, the interaction of Sh-CRIT-ed1 with C2 plays a decisive role of inhibition in the classical complement-activation process. However, the role of individual Sh-CRIT-ed1 amino acid residues in C2 binding is not fully understood. We constructed nine recombinant Sh-CRIT-ed1 (rSh1) analogues, substituted at conserved residues, and evaluated their anti-complement and C2-binding activities. Results from glutathione S-transferase (GST) pull-down and haemolytic assays suggested that residues 10K, 17E, 19K and 26Y are critical for the interaction of rSh1 with C2. We then constructed an improved anti-complement peptide by duplicating Sh-CRIT-ed1 C-terminal motifs (17H-26Y). This linear homodimer (rH17d) was more potent than rSh1 with respect to binding to C2 and anti-complement activity (the 50% inhibitory concentration value was approximately equal 1.2 micro m versus approximately equal 6.02 micro m for rSh1). Furthermore, rH17d showed higher anti-complement activity in vivo, providing additional evidence that this duplication is a more effective inhibitor of complement activation than rSh1. Taken together, these results identify four key residues in rSh1 and strongly suggest that rH17d is a potent inhibitor of complement activation that may have therapeutic applications.

Amino Acid Sequence↗

PubMed1993

Levels of complement regulatory molecules in lung cancer: disappearance of the D17 epitope of CD55 in small-cell carcinoma.

The levels of complement-regulatory molecules (complement receptor type one [CR1], decay-accelerating factor [DAF], membrane cofactor protein [MCP], and an inhibitor of membrane attack complex [CD59]) in lung cancer cells were analyzed to investigate the relation between their expression and histological subtypes, and the possibility of homologous complement deposition on cancer cells. In 25 cell lines (10 adenocarcinoma, 3 large-cell carcinoma, 7 small-cell lung cancer [SCLC], and 5 squamous cell carcinoma), flow cytometric analysis revealed that MCP was expressed in all cell lines, whereas none of the cell lines was CR1-positive. CD59 was detected in all cells. The DAF epitope defined by IA10 was expressed in all cells except one large cell carcinoma cell line. However, another epitope for anti-DAF monoclonal antibody, D17, was not detected in 5 (71.4%) SCLC and in 4 (22.2%) non-small-cell lung cancer. This disparity was seen in most cell lines, irrespective of histological subtypes. The loss of D17 reactivity seemed to be pertinent to malignant phenotype, because most of the normal pulmonary cells possessed the D17 epitope. Furthermore, a cell line lacking DAF (IA10-/D17-) allowed alternative pathway-mediated homologous complement (C3) deposition after pretreatment with anti-MCP antibody. This raises a new possibility for immunotargeting of cancer. These cell lines should be useful in studying the biology of lung cancer.

Antigens, CD↗

PubMed1985

Complement profile in a C1 inhibitor deficient family.

Complement components and anaphylatoxins in a C1 inhibitor (C1INH) deficient family were studied. C4a was increased when C1INH was decreased, and C3a was increased in subjects with systemic lupus erythematosus (SLE)-like symptoms and with angioedema attacks. Danazol was effective in controlling the clinical as well as complement abnormalities including low CH50, C1INH and C4, which increased within 10 days after danazol treatment was started. Two-dimensional immunoelectrophoresis of C1INH showed that there was no functionally or electrophoretically abnormal C1INH present before or after danazol treatment. C3a and C4a were considered to play important roles in the pathogenesis of angioedema and associated SLE-like symptoms.

Anaphylatoxins↗

PubMed2003

Effect of various forms of the C1 esterase inhibitor (C1-INH) and DAF on complement mediated xenogeneic cell lysis.

The purpose of the present study was to assess the effect of various forms of the surface-bound form of the C1 esterase inhibitor (C1-INH-PI) and decay accelerating factor (DAF) on xenogenic cells. cDNAs of various deletion mutants of the C1-INH-PI, such as delta-1-99 amino acid (AA), delta-108-183AA loop, delta-whole loop, delta-exon5, delta-exon6 + 7, and delta-exon5 + 6 + 7, and that of DAF, the delta-short consensus repeat (SCR) 1-DAF were established. While all deletion mutants of C1-INH-PI except the delta-1-99AA were expressed in the cytoplasm but not on the cell surface, the delta-1-99AA was clearly expressed on the xenogeneic cell surface. Amelioration of complement-mediated xenogeneic cell lysis by delta-1-99AA was next tested, and compared with delta-SCR1 DAF. Both molecules blocked human complement-mediated cell lysis by approximately 57 to 90 and 93 to 98%, respectively, in Chinese hamster ovarian tumor (CHO) cells and pig endothelial cells (PECs). The CHO cell transfectants were incubated with 20% normal human serum, and the amounts of C4 and C3 deposition on the cell surface were analysed by flow cytometry. The DAF transfectant showed a large amount of C4-deposition and much less C3-deposition than the controls (approximately 85% suppression), whereas the delta-1-99AA showed approximately a 40% suppression in both C4- and C3-deposition. Consequently, both the delta-1-99AA C1-INH-PI and delta-SCR1 DAF molecules are quite effective in down-regulating the xenogeneic cell lysis, but accomplished this in different manners.

Animals↗

PubMed2005

Comparative tissue factor pathway inhibitor release potential of heparins.

Tissue factor pathway inhibitor (TFPI) is released following the administration of unfractionated heparin, low-molecular-weight heparins, defibrotide and PI-88. In this study, the comparative effects of heparin, a low-molecular-weight heparin-gammaparin and a heparin-derived oligosaccharide mixture-subeparin (C3) were studied on functional and immunologic tissue factor pathway inhibitor activity levels in a non-human primate (Macaca mulatta) model. The dose-dependent effect was studied following intravenous and subcutaneous administration. Following the administration of 1 mg/kg of heparin, gammaparin, and C3, the functional levels of TFPI at 5 minutes were 2.40, 2.56, and 1.08 U/mL and the corresponding TFPI immunologic levels were 4.3-, 4.0-, and 2.1-fold, increased, respectively, over the baseline value. From these results, it can be concluded that heparin and gammaparin produced similar levels of TFPI release. Hence, gammaparin and heparin have similar TFPI release potential despite their differences in molecular weight. The influence of molecular weight, charge density, and interactions with heparin cofactor II on TFPI release are also discussed.

Animals↗

PubMed1980

Control of complement activation in membranous and membranoproliferative glomerulonephritis.

Renal biopsy specimens from 22 membranous (MGN) and 19 membranoproliferative glomerulonephritis (MPGN) patients were examined for the presence of the three regulators of the complement system; C1- inhibitor (C1--INH), C3b inactivator (C3b-INA), and beta 1H. The serum concentrations of these proteins, at the time of biopsy, were also measured. To study the modulation of complement activation by these three control proteins in MGN and MPGN, we examined the relationship between each control protein and the protein whose activity it regulates, in four ways; (a) the concordance between the presence of the control proteins and the components regulated was studied, (b) the correlations in intensity of deposition of the control and complement proteins were measured, (c) the patterns of distribution of the proteins within the glomeruli were compared, and (d) the serum levels of control proteins and components, regulated were examined. C1--INH (23 of 35 biopsies) and beta 1H (34 of 36 biopsies) were frequently deposited in both disease groups. C3b-INA was found only rarely in MPGN (4 of 19 biopsies). This is probably because the former two proteins modulate complement activation stoichiometrically, whereas C3b-INA acts enzymatically. A relationship was demonstrated between C1--INH and C1s and between beta 1H and C3 in both groups, but no such relationship was found between C3bINA and C3. Conclusion. There is no generalized deficiency in modulation of complement activation in MGN or MPGN.

Complement C1 Inactivator Proteins↗

PubMed1999

Development of adenovirus vectors encoding rat complement regulators for use in therapy in rodent models of inflammatory diseases.

C activation has been implicated in the pathogenesis of numerous inflammatory human diseases and disease models. A therapy based on C inhibition might therefore be of benefit to reduce inflammation and ameliorate disease. C inhibition in vivo can be accomplished by the delivery of soluble recombinant C regulators either systemically or directly to a target site, but effects are transitory. We have developed a strategy for the efficient delivery of the membrane-bound rat C inhibitors, CD59, Crry, and decay-accelerating factor (DAF), using replication-deficient adenovirus vectors with the intention of treating rat models of disease in which C is implicated. The adenovirus recombinants(RAd), RAdCD59, RAdCrry, and RAdDAF, respectively, have been tested for expression and function of the transgene in vitro. Infection of human fetal foreskin fibroblasts resulted in high levels of expression of each of the rat inhibitors. The constructs were also tested for inhibition of rat C-mediated cell lysis and C3b deposition. In a cell lysis assay, each inhibited to varying degrees of efficiency in the order RAdCD59 = RAdDAF > RAdCrry. In a C3b deposition assay, RAdDAF caused a greater reduction in C3b deposition than RAdCrry and RAdCD59 was ineffective. These agents, individually or in combination, provide the tools for testing the effects of prolonged inhibition of C at a target site on the progress of experimental models of disease.

Adenoviridae↗

PubMed2002

Transgenic expression of a soluble complement inhibitor protects against renal disease and promotes survival in MRL/lpr mice.

To investigate the role of complement in lupus nephritis, we used MRL/lpr mice and a transgene overexpressing a soluble complement regulator, soluble CR1-related gene/protein y (sCrry), both systemically and in kidney. Production of sCrry in sera led to significant complement inhibition in Crry-transgenic mice relative to littermate transgene negative controls. This complement inhibition with sCrry conferred a survival advantage to MRL/lpr mice. In a total of 154 animals, 42.5% transgene-negative animals had impaired renal function (blood urea nitrogen > 50 mg/dl) compared with 16.4% mice with the sCrry-producing transgene (p < 0.001). In those animals that died spontaneously, MRL/lpr mice with the sCrry-producing transgene did not die of renal failure, while those without the transgene did (blood urea nitrogen values of 46.6 +/- 9 and 122 +/- 29 mg/dl in transgene-positive and transgene-negative animals, respectively; p < 0.001). Albuminuria was reduced in those transgenic animals in which sCrry expression was maximally stimulated (urinary albumin/creatinine = 12.4 +/- 4.3 and 36.9 +/- 7.7 in transgene-positive and transgene-negative animals, respectively; p < 0.001). As expected in the setting of chronic complement inhibition, there was less C3 deposition in glomeruli of sCrry-producing transgenic mice compared with transgene-negative animals. In contrast, there was no effect on glomerular IgG deposition, levels of anti-dsDNA Ab and rheumatoid factor, or spleen weights between the two groups. Thus, long-term complement inhibition reduces renal disease in MRL/lpr mice, which translates into improved survival. MRL/lpr mice in which complement is inhibited still have spontaneous mortality, yet this is not from renal disease.

Animals↗

PubMed1976

Membranoproliferative glomerulonephritis in childhood cirrhosis associated with alpha1-antitrypsin deficiency.

Three alpha1-antitrypsin (alpha1AT) deficient, protease inhibitor type ZZ children who died from cirrhosis and its complications had membranoproliferative glomerulonephritis at postmortem examination. During life, all three had clinical and laboratory evidence of renal disease which became apparent when hepatic decompensation developed. Immunofluorescence studies and electron microscopy performed in one patient revealed subendothelial deposits of alpha1AT, complement, and immune globulins along the glomerular basement membrane. The pathogenesis of these renal lesions is speculative. Glomerular lesions were not observed in kidney sections of 16 children who died from cirrhosis but who were not alpha1AT-deficient. The present study suggests that renal involvement may be yet another manifestation of disease associated with alpha1AT deficiency.

Child↗

PubMed1988

In vivo effects of C3a on neutrophils and its contribution to inflammatory lung processes in a guinea-pig model.

C3a, when injected intravenously in guinea-pigs, caused a rapid drop of circulating neutrophils and platelets. The neutropenia was reversible and followed by a neutrophilia, which reached about 200% of baseline values. Upon challenge with octa- and hexapeptide, mimicking the C-terminal sequence of C3a, neutrophils and platelets reacted in the same manner. The hexapeptide-desArg (pentapeptide without the C-terminal arginine of hexapeptide) induced no neutropenia but a significant neutrophilia. Likewise, when injected in animals with a genetic deficiency or dysfunction of the C3a-receptor, the hexapeptide caused no drop of the neutrophils, but a neutrophilia, indicating that both neutrophil reactions are mediated by different mechanisms. With the octapeptide in vivo dose-response studies were performed. Despite maximal doses of octapeptide about 40% of the neutrophils remained in circulation, indicating that some but not all PMNs are susceptible to C3a. By pretreating the animals with an inhibitor of the serum carboxypeptidase N (SCPN-Inh) the C3a-induced neutropenia could be significantly augmented. But intravenous application of the inhibitor itself caused a 20-40% reduction of neutrophils during the first hour after injection, followed by a neutrophilia. In histological studies the timecourse of neutrophil sequestration in the lung was established, showing that the initial high neutrophil content of the lung lasted for at least 1 h and declined thereafter. Structural derangements could not be detected. These observations stress the importance of C3a besides C5a as an important mediator of inflammatory processes in species, where the C3a-receptor is present on inflammatory cells such as granulocytes.

3-Mercaptopropionic Acid↗

PubMed1988

Detection of the terminal complement complex in patient plasma following acute myocardial infarction.

The mechanisms of inflammation responsible for the myocardial tissue damage seen after an acute myocardial infarction (AMI) have not been clearly identified. Recent lines of evidence, demonstrating depressed sera levels of individual complement components in patients after myocardial infarction, have suggested involvement of the complement (C) system in micro- and macrovascular injury subsequent to AMI. The present study assessed the role of complement as a mediator of myocardial inflammation by quantifying products of complement activation including, the terminal complement complex (TCC) the cytolytic component of the complement system, C1rC1s-C1 inhibitor complex and C3bBbP complex, formed following activation of the classical and alternative pathway, respectively, and anaphylatoxins C3a and C5a in 41 patients following AMI. Plasma TCC and C1rC1s-C1 inhibitor complex concentrations increased up to 32-fold (P less than 0.001) and 8-fold (P less than 0.001), respectively, while the C3bBbP complex, C3a des-Arg and C5a des-Arg each increased over 2-fold (P less than 0.001) 16 h after AMI, and were only minimally detectable during non-inflammatory myocardial conditions. Furthermore, TCC concentrations increased over 150% (P less than 0.001) one day after patients reinfarcted, subsequent to hospitalization for a primary AMI. These results demonstrate activation of complement after AMI and suggest that inflammatory mediators of the complement system may contribute to myocardial tissue damage during the infarction process.

Adult↗

PubMed2000

Exceptional resistance of human H2 glioblastoma cells to complement-mediated killing by expression and utilization of factor H and factor H-like protein 1.

Of over 20 nucleated cell lines we have examined to date, human H2 glioblastoma cells have turned out to be the most resistant to complement-mediated cytolysis in vitro. H2 cells expressed strongly the membrane attack complex inhibitor protectin (CD59), moderately CD46 (membrane cofactor protein) and CD55 (decay-accelerating factor), but no CD35 (complement receptor 1). When treated with a polyclonal anti-H2 Ab, anti-CD59 mAb, and normal human serum, only 5% of H2 cells became killed. Under the same conditions, 70% of endothelial-like EA.hy 926 cells and 40% of U251 control glioma cells were killed. A combined neutralization of CD46, CD55, and CD59 increased H2 lysis only minimally, demonstrating that these complement regulators are not enough to account for the resistance of H2 cells. After treatment with Abs and serum, less C5b-9 was deposited on H2 than on U251 and EA.hy 926 cell lines. A reason for the exceptional resistance of H2 cells was revealed when RT-PCR and protein biochemical methods showed that the H2 cells, unlike the other cell lines tested, actively produced the soluble complement inhibitors factor H and factor H-like protein 1. H2 cells were also capable of binding human factor H from the fluid phase to their cell surface and promoted the cleavage of C3b to its inactive form iC3b more efficiently than U251 and EA.hy 926 cells. In accordance, anti-factor H mAbs enhanced killing of H2 glioblastoma cells. Taken together, our results show that production and binding of factor H and factor H-like protein 1 is a novel mechanism that these malignant cells utilize to escape complement-mediated killing.

Antibodies, Monoclonal↗