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PubMed1981

A fluorescent assay for complement activation.

We report here a rapid assay for the complement enzymes CVFBb, C4b2a and Cls. This assay involves the use of a peptide substrate that releases a fluorescent coumarin derivative (AMC) upon cleavage by the convertase. The substrate, BocLeuGlyArgAMC, was chosen because its sequence is similar to the carboxyl terminus of C3a, and identical to that of C5a. The Km of this substrate are about 125 microM for the C3/5 convertase CVFBb, 169 microM for C4b2a, and 140 microM for C1s.

Complement Activation↗
PubMed1987

Induction of human complement activation without cytolysis by mouse monoclonal antibodies to human leukocyte antigens.

Ten monoclonal antibodies to human leukocyte subsets that had previously been shown to lyse their respective target cells in the presence of rabbit serum as complement source were evaluated for their cytolytic capacity with human complement. Four of the ten were lytic with human complement. All were of IgM type. Antibodies were also evaluated for their capacity to induce C3 binding to target cells. With this method we could demonstrate that, indeed, 3 of the 6 noncytolytic antibodies had the capacity to initiate the human complement activation process and to induce C3 binding. Two of these 3 antibodies were of IgM class (VIT3 and VIM13), one of IgG3 (562). From the practical point of view the most interesting of these 3 antibodies is the nonmitogenic anti-CD3 pan-T cell antibody VIT3. Therefore, this antibody was analyzed in more detail. VIT3 antibody concentrations needed to induce detectable C3 binding to human T cells are very low (down to 1 ng VIT3/ml). Human serum as complement source can also be considerably (100X) diluted before C3 binding becomes undetectable. Activation of C3 is a prerequesite for VIT3-induced C3 binding, and bound C3 seems to lack the C3a fragment. Bound C3, in contrast to the quickly occuring antigenic modulation of the CD3 complex and the simultaneous disappearance of the antibody coat, remains expressed also after prolonged incubation at 37 degrees C. C3 fragments bound to T cells after activation with VIT3 are also recognized by cells bearing C3 receptors of types CR1 and CR2.

Antibodies, Monoclonal↗
PubMedDate not supplied

Report of studies on monoclonal antibodies (MABS) to complement components.

Twenty-five monoclonal antibodies (MABS) to complement components were evaluated according to the ISBT/ICSH protocol by twelve laboratories. Seven detected some form of C3c, but one of them, 174, did not react with EiC3b, although it was positive with 'EC3b' (Fruitstone). 174 may detect some form of enzyme sensitive C3b antigen, but C3a was not evaluated (present on 'EC3b' Fruitstone). Twelve of the antibodies were anti-C3d, one was an anti-C3g and five were anti-C4c.

Antibodies, Monoclonal↗
PubMed2007

Leukocyte effects of C5a-receptor blockade during simulated extracorporeal circulation.

BACKGROUND: Distinct pathways of leukocyte activation during simulated cardiopulmonary bypass are mediated by the complement C5a anaphylatoxin. We hypothesized that a human C5a receptor antagonist would specifically inhibit the inflammatory response of neutrophils to simulated extracorporeal circulation, while preserving the C5b-9 pathway for innate immunity. METHODS: An in vitro extracorporeal circuit recirculated fresh heparinized whole blood through a membrane oxygenator with and without addition of a small molecule human C5a receptor antagonist. Samples were periodically drawn over 90 minutes for complement and leukocyte activation studies. RESULTS: Addition of the C5a receptor antagonist to simulated extracorporeal circulation abrogated both neutrophil CD11b upregulation and interleukin 8 release (p < 0.01 for both), despite full generation of C3a and C5b-9; however, elastase release from neutrophils was unaffected. Although C5a receptor blockade only trended toward inhibiting monocyte CD11b upregulation (p = 0.09), circuit clearance of both monocytes (p = 0.04) and neutrophils (p = 0.01) was significantly decreased. In addition, the C5a receptor antagonist completely blocked both neutrophil-platelet and monocyte-platelet conjugate formation (p < 0.001 for both), without affecting platelet P-selectin expression. CONCLUSIONS: C5a receptor blockade during simulated extracorporeal circulation completely blocked neutrophil beta2 integrin upregulation and induction of plasma interleukin 8, suggesting an acute downregulatory effect on neutrophil chemotaxis-related pathways, while preserving terminal complement generation and neutrophil elastase release. Inhibition of leukocyte-platelet conjugate formation suggests a novel function for leukocyte adhesive receptors, possibly related to preservation of elastase generation.

Blood Platelets↗
PubMed1992

Dissociation of primary antigen-antibody bonds is essential for complement mediated solubilization of immune precipitates.

The role of dissociation of primary antigen-antibody bonds in the solubilization of immune complexes (IC) has been investigated using photo-affinity crosslinked IC comprising NAP15-BSA and murine monoclonal anti-DNP antibodies. Non-covalently linked IC were solubilized rapidly when incubated with normal human serum (NHS), whereas covalently-linked IC were solubilized poorly or not at all. The rate and extent of complement activation produced by incubating covalently-linked and non-covalently linked IC with NHS was similar as assessed by the production of the C1s:C1-inhibitor, C3:properdin and C5b-9 complexes and the anaphylatoxins C4a and C3a. Thus, the inability of serum to solubilize photo-affinity crosslinked IC must be due to failure of dissociation of primary antigen-antibody bonds.

Animals↗
PubMed1989

[Anaphylatoxin in the aqueous humor of rabbit with endotoxin induced endophthalmitis].

Anaphylatoxin-activated complement fragment is an important mediator of inflammation. In this study, trends of anaphylatoxin in clinical and experimental endophthalmitis was evaluated. The level of anaphylatoxin (C3a, C4a and C5a) and protein of human aqueous humor aspirated from patients with senile cataracts before surgery was measured. As a model of acute endophthalmitis, endotoxin-Lipopolysaccharide from E. coli (LPS) was used intravitreously in albino rabbits. The level of anaphylatoxin of aqueous humor was measured by radioimmunoassay. The level of C3a was 44.0 +/- 13.4 ng/ml in aqueous humor of cataract patients. An increase of cell count and protein was demonstrated in the aqueous humor of rabbits 24 hrs after endotoxin injection. The level of C3a increased remarkably with time. It was suggested that C3a in aqueous humor of the rabbit eye with endotoxin-induced endophthalmitis plays an important role in chemotaxis and in mediating the inflammatory process.

Aged↗
PubMed1987

Activation of complement in human serum by some synthetic polymers used for intraocular lenses.

Determination of the potential to activate complement can be used as one criterion in testing the biocompatibility of various synthetic polymers that are utilized in the medical field. Intraocular lenses (IOLs) made of poly(methyl methacrylate) (PMMA) with PMMA loops, poly(hydroxyethyl methacrylate) (PHEMA) lenses, silicone lenses, and PMMA lenses with polypropylene loops were examined in this study. The concentrations of the activation peptides C3a, C4a and C5a were measured by radioimmunoassay (r.i.a.) in human serum after incubation with and without IOLs for up to 12 h. The presence of silicone lenses caused an increase in C3a levels. In the presence of polypropylene loops, the concentrations of both C3a and C5a were significantly higher than in serum incubated alone. There was no statistically significant increase in the concentration of C4a caused by any of the materials tested. The results suggest that IOLs made from silicone or lenses with polypropylene loops activate the complement system via the alternative pathway.

Biocompatible Materials↗
PubMed1989

Complement levels in septic primates treated with anti-C5a antibodies.

During gram-negative sepsis it is known that endotoxin activates complement by the alternate pathway. The complement anaphylatoxin C5a, a result of this activation, is thought to play a key role in attracting and activating neutrophils in the lungs, leading to the adult respiratory distress syndrome. Complement levels were measured in primates made septic by Escherichia coli infusions. Anti-human C5a antibodies were administered to study their effect on neutrophil-mediated lung injury. Control (I), septic (II) and septic + anti-C5a antibody (III) groups (n = 4) were studied. The antibody-treated group (III) demonstrated a significant attenuation of septic shock and pulmonary edema as has been previously reported. All complement profiles were corrected for varying hemoglobin concentrations. C3, C4, and C5 levels were measured by radial immunodiffusion and were depleted in both septic groups. Once the levels were depleted from the plasma, they did not recover. The depletion of C4 indicates that classical pathway activation also occurred. C3a, C4a, and C5a levels were measured by radioimmunoassay. Significantly increased peak levels were reached in the septic groups 15 min after initiation of the E. coli infusion. There were no significant differences in early peak C3a and C4a levels between groups II and III. However, the mean peak C5a level in group III (anti-C5a antibodies) was 42% lower than that in group II, and after this early peak, C5a levels were not elevated above control levels in group III. The antibody to human C5a was thus shown to be cross-reactive with primate C5a and was specific since C3a and C4a levels were not decreased in group III.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Establishing the relationship between complement activation and stimulation of phagocyte oxidative metabolism in hemodialyzed patients: a randomized prospective study.

The present prospective study was conducted in order to establish the relationship between complement activation and stimulation of phagocyte oxidative metabolism observed in long-term hemodialysis (HD) patients during the early phase of dialysis with cellulosic membranes. Two groups of 10 randomized (HD) patients treated with cellulosic (Cuprophan, CUP) or synthetic polyacrilonitrile (PAN AN-69) membranes were studied. Leukocyte counts, C3a antigen plasma concentration and whole blood basal and stimulated chemiluminescence (CL) production were determined in blood samples drawn from the fistula before dialysis (T0) and from both the afferent and efferent lines of the dialyser at 15 min (T15) and at the end (Tend) of the dialysis session. This study confirms that, coincident with the nadir of leukopenia observed at T15, dialysis with CUP but not PAN membranes induces a marked rise in C3a antigen levels and profound alterations in whole blood CL production consisting of a dramatic increase in basal CL and a significant loss in CL response capacity to stimulating agents. It further demonstrates that a direct relationship exists between the variations in C3a antigen plasma levels and whole blood CL production observed in the CUP group of patients from T0 to T15 (delta 15) of dialysis. This relationship is characterized by a positive correlation between delta 15 C3a and delta 15 basal CL levels in afferent and efferent lines, and a negative correlation between delta 15 C3a and delta 15 CL response capacity values in the efferent but not afferent line. In contrast, no significant correlation with the type of dialysis membrane could be demonstrated between the variations in polymorphonuclear neutrophil counts and C3a antigen levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylic Resins↗
PubMed1995

Complement components and fibrinogen: correlations and association with previous myocardial infarction.

Serum complement levels have been found to be predictive of myocardial infarction up to 4 years before the acute event. To assess whether they are a marker of a hypercoagulable state, the serum or plasma levels of C3, C4, C3a, C4a, C1 inactivator, antithrombin III, protein S, protein C, fibrinogen and tissue plasminogen activator were measured in 31 patients with previous myocardial infarction and 33 controls (all males, 40-60 years old). C3, C4 and fibrinogen (which share the common characteristic of being acute phase proteins) were correlated and were associated with previous myocardial infarction, although this association persisted only for C4 in multivariate analysis. None of the coagulative variables directly involved in the complement system differed significantly in the two groups.

Adult↗
PubMed2006

Distribution of complement anaphylatoxin receptors and membrane-bound regulators in normal human retina.

To characterize the distribution of membrane-bound components of the complement system in normal human retina, eyes from eight human donors with no history of ocular disease, ranging in age from 47 to 85 years were examined using immunohistochemistry to localize the C3a receptor (C3aR), C5a receptor (C5aR), CD46, CD55, and CD59 in cryosections prepared from donor posterior segments. The C3aR was identified in the nerve fiber layer in a sawtooth-patterned band. Vimentin, used as a Müller cell marker, produced a similar staining pattern. The C5aR was detected on specific rounded structures in the inner plexiform layer and occasionally in the nerve fiber layer. CD46 produced markedly specific staining of the basolateral surface of the retinal pigment epithelium. CD55 was localized to the nerve fiber layer. Staining for these proteins was consistent across all eyes studied. CD59 was expressed throughout the nerve fiber layer and labeled vessels that extended through the ganglion cell, inner plexiform, and inner nuclear layers, but this pattern was only confirmable in a single subject. Complement anaphylatoxin receptors and regulatory proteins are localized in different but internally consistent patterns in normal adult human retina, independent of the age of the donor. C3aR and C5aR localization only in the inner retina contrasts with previously reported findings in the central nervous system of wide spread diffuse staining. The complement regulators CD55 and CD59 were found primarily on the inner retina, while CD46 was present exclusively in a polarized fashion on the RPE.

Aged↗
PubMed1994

Clinical comparison of high-flux cellulose acetate and synthetic membranes.

Solute transport and alterations in complement and clotting induced by a new high-flux cellulose acetate membrane (CA-HF800-E, Diaphan) were compared with those for cellulose triacetate (CTA) and polysulphone in a cross-over clinical study. The membranes are similar in their small-molecule removal. Serum beta 2-microglobulin decreased with all membranes but the decrease was independent of membrane type. Associated with beta 2-microglobulin removal was a protein loss which averaged 2636 mg for Diaphan, 4937 mg for CTA, and 2500 mg for polysulphone. Albumin presence in the dialysate was less than the limit of detection (5 mg/l) but for each of the membranes, occasional readings above the limit of detection were noted. C3a generation for Diaphan is comparable with that for CTA and polysulphone, but differed for C5a and neutropenia. A highly significant correlation of the area under the concentration time curve of the two complement components was noted for the cellulose based membranes (r = 0.875, P = 0.0002 for Diaphan, r = 0.823, P = 0.006 for CTA) this relationship was less marked for polysulphone (r = 0.396, P = 0.29). Induction of clotting characterized by the thrombin-antithrombin III (TAT) complex were similar for the three membranes, as were changes in platelet counts. Our findings indicate that while it is possible to modify cellulose to produce a membrane whose solute transport and biocompatibility is similar to synthetic membranes such as polysulphone, the structural modifications induce considerable differences in the amount of protein lost.

Adult↗
PubMed2006

Treatment with an inhibitory monoclonal antibody to mouse factor B protects mice from induction of apoptosis and renal ischemia/reperfusion injury.

Complement activation in the kidney after ischemia/reperfusion (I/R) seems to occur primarily via the alternative complement pathway. The ability of an inhibitory mAb to mouse factor B, a necessary component of the alternative pathway, to protect mice from ischemic acute renal failure was tested. Treatment with the mAb prevented the deposition of C3b on the tubular epithelium and the generation of systemic C3a after renal I/R. Treated mice had significantly lower increases in serum urea nitrogen and developed significantly less morphologic injury of the kidney after I/R. For gaining insight into potential mechanisms of protection, the activity of caspases within the kidney also was measured, and it was found that caspases-2, -3, and -9 increased in a complement-dependent manner after renal I/R. Apoptotic cells were detected by terminal deoxynucleotidyl transferase catalyzed labeling of DNA fragments, and mice in which the alternative pathway was inhibited demonstrated significantly less apoptosis than control mice. Thus, use of an inhibitory mAb to mouse factor B effectively prevented activation of complement in the kidney after I/R and protected the mice from necrotic and apoptotic injury of the tubules.

Analysis of Variance↗
PubMed2003

Hyperacute lung rejection in the pig-to-human model. 2. Synergy between soluble and membrane complement inhibition.

BACKGROUND: The role of complement in hyperacute lung xenograft rejection has not been elucidated. The present study evaluates the effect of complement (C) C3/C5 convertase inhibition on hyperacute rejection of pig lung by human blood. METHODS: In an established ex-vivo model, lungs from pigs heterozygous for human decay accelerating factor (hDAF), non-transgenic littermate control pigs, or farm-bred pigs were perfused with fresh human blood that was either unmodified or treated with soluble complement receptor type 1 (sCR1: TP10, 100 microg/ml). RESULTS: Non-transgenic lungs from littermate controls had a median survival time of 35 min (range 5 to 210; P = 0.25 vs. farm-bred piglets: median 5 min, range 5 to 10). Lungs expressing hDAF survived for a median of 90 min (range 10 to 161; P = 0.5 and 0.01 vs. littermate and farm-bred controls, respectively), with sCR1, whereas hDAF (-) lungs failed by 35 min (range 6 to 307), hDAF (+) lungs survived for 330 min (range 39 to 577) [P = 0.002 vs. farm-bred; P = 0.08 vs. hDAF (-); P = 0.17 vs. sCR1/hDAF (-)]. The rise in pulmonary vascular resistance (PVR) at 5 min was blunted only by hDAF (+) with sCR1 (0.26 +/- 0.2 vs. 0.5 to 0.7 mmHg/ml/min for other groups). Plasma C3a and sC5b-9 and tissue deposition of C5b-9 were dramatically diminished using sCR1, and further decreased in association with hDAF. Histamine and thromboxane were produced rapidly in all groups. CONCLUSION: Complement plays an important role in lung HAR. However, even potent inhibition of C3/C5 convertase, both membrane bound in lung and by a soluble-phase inhibitor in the blood, does not prevent activation of inflammatory responses known to be particularly injurious to the lung. Our findings implicate a role for innate immune pathways resistant to efficient complement regulation. The role of anti-species antibody, coagulation pathway dysregulation, and additional environmental or genetic influences remain to be defined.

Acute Disease↗
PubMedDate not supplied

Anticoagulant and membrane effects on humoral and cellular changes during plasmapheresis.

Heparin (H) and citrate (C) anticoagulation with cellulose acetate (CA) and polyvinyl chloride (PVC) membrane devices were evaluated on three myasthenia gravis patients. Changes of white blood cell (WBC) and platelet (PLT) counts, complement activation, granulocyte elastase, and interleukin-1 beta (IL-1 beta) were studied sequentially. Changes in WBC and PLT counts were more dependent on the membrane material and surface area. Changes of C3a and C5a were more related to the anticoagulant used, whereas changes of C4a were membrane-material dominant phenomenon. Systemic elastase levels did not show significant differences among the groups but module outlet values were elevated for Ca + H. IL-1 beta did not show changes in all schemes. CA + H was the most activating and PVC + C was the least activating combination. Both the membrane materials and anticoagulant must be considered in evaluating humoral and blood cellular changes in plasmapheresis.

Blood Cell Count↗
PubMed1978

Relationships between abnormal IgG index, oligoclonal bands, acute phase reactants and some clinical data in multiple sclerosis.

The IgG-index and acute phase reactants were measured and oligoclonal bands were looked for in 30 patients with clinically definite multiple sclerosis (MS) and were compared with the clinical data. IgG-index was found elevated in 77% against 22% in a comparable material of patients with other neurological diseases. Oligoclonal bands were found in 74 and 17%, respectively. No correlation was found between these parameters and age, duration of illness, disability, coefficient of progression or age of onset. A statistical evaluation defines the specificity, sensitivity and validity of the methods used. CRP could no be demonstrated in 28, the rest had normal values. C3A was normal in all cases, but appeared to be elevated a little with increasing age, and to be positively correlated to the albumin-index, indicative of a defective blood-brain barrier. No correlation was found between CRP, C3A and the clinical data.

Acute Disease↗
PubMed1987

A clinical study on different cellulosic dialysis membranes.

A controlled clinical study was performed over a period of 8 weeks in two dialysis centres (Rostock, GDR, and Munich, FRG). The aim was to compare a dialysis membrane made of modified cellulose (Hemophan) with classical regenerated cellulose (Cuprophan). Dialysers containing these membranes, together with a cellulose acetate dialyser, were therefore incorporated in a cross-over programme and clinical and biochemical investigations undertaken. The efficacy of the modified cellulosic membrane with respect to urea and creatinine clearance was shown to be comparable to that of regenerated cellulose and cellulose acetate. However, modified cellulose showed an increased clearance for inorganic phosphate, significantly different from that demonstrated by both regenerated cellulose and cellulose acetate. Blood compatibility studies, which included the assessment of C3a activation and the reduction of white blood cell (WBC) and platelet count, clearly demonstrated that in comparison to regenerated cellulose, modified cellulose resulted in significantly less complement activation and WBC reduction. Similarly in comparison to cellulose acetate, modified cellulose showed reduced complement-activating and WBC-reducing properties. The reason for the improved blood compatibility of modified cellulose is not, as was originally assumed, related to binding of complement-inhibiting heparin, but appears instead to be due to the substitution of hydroxyl groups of regenerated cellulose.

Biocompatible Materials↗