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Results for “Complement C3”

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PubMed1993

Immunoglobulin (IgG and IgA) and complement (C3) concentrations in uterine secretion following an intrauterine challenge of Streptococcus zooepidemicus in mares susceptible to versus resistant to chronic uterine infection.

The validity of measuring concentrations of immunoglobulins in undiluted uterine secretions was established. The concentrations of IgG, IgA, and cleavage factor C3 of the complement system in uterine secretions were compared in mares with different resistance to chronic uterine infection (CUI). The uteri of mares susceptible (n = 6) and resistant to CUI (n = 5) were inoculated with 5 x 10(6) Streptococcus zooepidemicus when the mares were in estrus. Uterine secretions were sampled, and sampling was immediately followed by a uterine lavage at 5 and 24 h after bacterial inoculation. During a subsequent estrus, bacterial inoculation of the uterus was repeated, and samples were taken from the mares 12 and 36 h later. The fraction of uterine secretion in each uterine washing was determined by dividing the protein concentration of the undiluted uterine secretion by the protein concentration of the corresponding uterine washing. There was a significant correlation between measured concentrations of immunoglobulins in uterine secretions and calculated concentrations in the uterine washings (p < 0.05). Concentrations of IgG and C3 in uterine secretions declined similarly in both susceptible and resistant mares during the first 24 h after bacterial inoculation (p < 0.04). In contrast to the susceptible group, which showed a continuous decline at 36 h, resistant mares demonstrated an increased concentration of both IgG and C3 at this time. Concentrations of IgA did not differ between susceptible and resistant mares. It was concluded that the described method of sampling uterine secretions was useful for analyzing IgG and IgA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Separation of active and inactive forms of the third component of human complement, C3, by fast protein liquid chromatography (FPLC).

C3(H2O), an inactive form of C3 present to a variable extent in most C3 preparations, has been isolated in 40 min from previously purified C3 using FPLC ion exchange chromatography on a Mono Q column. As many as six peaks were obtained from some C3 preparations, corresponding to different molecular forms of the protein. One of these peaks consisted of a molecular form of C3 with intact alpha and beta chains, a free sulfhydryl group but no hemolytic activity and was identified as C3(H2O). C3(H2O) eluted as a homogeneous peak well resolved from native C3, C3b, high molecular weight aggregates and small degradation fragments. The same C3(H2O) peak was generated from native C3 by repeated freeze-thaw cycles or NH2OH treatment. C3(H2O) alpha chain appeared as a doublet about 2 kDa heavier than native C3 alpha chain in low cross-linked gels. Two forms of C3b could be separated on the Mono S column, both able to form the C3 convertase. The present report describes a very fast method to resolve and isolate to homogeneity C3(H2O) and native C3 from C3 preparations. Both molecular forms of C3 are very suitable for studies of the initial and amplification C3 convertases of the alternative pathway of complement.

Chromatography, High Pressure Liquid↗

PubMed1989

Complement C3 proteins in psoriasis.

A new polymorphism of the complement factor C3 in human plasma was demonstrated by isotachophoresis in agarose gels followed by immunodetection with rabbit anti-human C3c and C3d immunoglobulins. Four bands were detected in the immunoprint of freshly drawn EDTA-plasma, which were C3s1, C3s2, C3f1 and C3f2. At least four additional C3 components in Mg2+ -zymosan activated plasma were present, which were C3b1 to C3b4. The different forms of C3 in frozen and thawed heparin-plasma from 20 patients with psoriasis and 20 healthy individuals were studied from the immunoprint. The total content of C3 components was 29% greater in the patients with psoriasis than controls. The major difference was in the C3b components which were increased by 46%. In psoriatic patients, the two slow C3 components C3s1 and C3s2 were increased by 24 and 56% respectively, when compared with controls. The two fast C3 components C3f1 and C3f2 were decreased to 29 and 37%. The results suggest a direct involvement of the complement factor C3 in psoriasis.

Adult↗

PubMed1977

Platelet-bound complement (C3) in immune thrombocytopenia.

The fixation of complement to the circulating platelet in immune thrombocytopenia was detected by measurement of one of the complement components, C3, on the surface of platelets from patients with idiopathic thrombocytopenic purpura (ITP) and systemic lupus erythematosus (SLE) using the anti-C3 consumption assay. The surface IgG was determined simultaneously using the previously described anti-IgG consumption assay. Washed platelets from normal controls had 3.5 fg (10(-15) g) of C3, or about 11,000 molecules, per platelet, an amount comparable to the IgG (4.1 FG, or 15,000 molecules, per platelet). For most patients with ITP both C3 and IgG were increased on the platelet surface, although for 5 of 16 patients only IgG was increased. Two patients with SLE and thrombocytopenia had an increase in both C3 and Ig, six patients with SLE who were not thrombocytopenic had normal amounts of membrane-bound C3 and IgG. In 5 patients, 3 with ITP and 2 with collagen vascular disease, both surface immunoproteins decreased with successful treatment of the thrombocytopenia.

Blood Platelets↗

PubMed1983

Complement (C3)-receptor-mediated phagocytosis of agarose beads by mouse macrophages. II. Extracellular activation of macrophage-derived complement on agarose via the alternative pathway.

Phagocytosis of agarose beads by macrophages cultured under serum-free conditions was studied. 48 h was needed before a plateau in the uptake was reached. The ingested agarose beads were coated extracellularly with macrophage-derived protein before attachment and ingestion of the beads. Intracellularly, the agarose-linked protein was removed from the agarose. If the ingested agarose beads were extracted from the macrophages within 24 h after the plateau in the uptake was reached, a fraction of the beads could attach to new macrophages, demonstrating modification of the agarose beads by opsonin(s). Because of binding of anti-human C3c antibodies to beads extracted from the macrophages after 24 h of phagocytosis and the trypsin sensitivity of the protein on the agarose, we conclude that the main opsonin on the agarose beads is C3bi. Requirements for the stimulatory effect of agarose on macrophages are summarized.

Animals↗

PubMed1985

Limited proteolysis of a chemically modified third component of human complement, C3, by cathepsin G of human leukocytes.

We have investigated the limited proteolysis of the third component of complement, C3, by a human leukocyte protease, cathepsin G, by using a chemically modified C3, which was prepared by treatment of C3 with methylamine and a fluorescent thiol reagent, N-(dimethylamino-4-methylcoumarinyl)-maleimide (DACM) and was thus named DACM-C3me. Although native C3 was hardly cleaved by cathepsin G, DACM-C3me was cleaved by cathepsin G into three major fragments, which were termed C3c-G (150,000 daltons, 150 kd), C3d-G (25 kd), and C3a-G (10 kd). C3c-G was composed of four disulfide-linked polypeptide chains of 75 kd, 35 kd, and two 25 kd. C3d-G and C3a-G were single-chain fragments derived from the alpha chain. The N-terminal sequence of C3d-G was determined as Thr-Glu-Asp-Ala-Val-, suggesting that cathepsin G released C3d-G by cleaving a Met-Thr peptide bond which is located at 19 residues toward the N-terminal from the cysteinyl residue forming an internal thiolester linkage in native C3. C3d-G, like C3d-K (a C3d fragment produced by the action of plasma kallikrein), was found to have bioactivities such as leukocytosis-inducing and immunosuppressive activities.

Amino Acid Sequence↗

PubMed1994

[Regulation of the complement C3 gene expression: regulatory elements required for cytokine-induced expression].

I isolated murine and human genomic cosmid clones of complement C3 gene and sequenced 5'-flanking region of their transcriptional initiation sites to determine cis-elements that participate in regulation of C3 gene expression. The murine and human 5'-flanking regions are 51% identical overall, with positions -36 to -1 and -146 to -68 showing 80% identity. Four TATA boxes were identified upstream of the murine transcriptional initiation site, but only the TATA element at position -30 is essential for expression of murine C3 in hepatocytes. Deletion and transfection analysis indicated that sequences -395 to -111 are essential for constitutive expression of C3 gene and suggested that sequences between -1457 and -800 contain regulatory elements that are involved in suppressing basal expression. Mutation analyses showed that sequences between -88 and -83 are essential for IL-6 responsiveness and both sequences between -88 and -83 and -77 to -72 are necessary for enhancer activity and responsiveness to IL-1. These sequences are highly homologous to binding sites of DNA binding proteins, C/EBP and NF-kappa B, respectively. Collectively, these results localize cis-acting elements involved in constitutive and IL-1/IL-6-regulated murine C3 gene expression, and provide implication for specific trans-acting factors.

Animals↗

PubMed1979

Immunoelectron-microscopical localization of in vivo-bound complement C3 in bullous pemphigoid with the use of the peroxidase-antiperoxidase multistep technique.

In vivo-bound complement C3 in bullous pemphigoid was precisely localized by means of the peroxidase-antiperoxidase multistep technique. In the nonbullous lesions peroxidase deposits filled the lamina lucida completely, i.e., the space between lamina densa and the cell membranes of the basal cells. In developed bullae, the reaction product was located both on the lamina densa and on the surface of separated keratinocytes. These findings may indicate that antigen components in bullous pemphigoid are localized almost exclusively within the ground substance which fills the lamina lucida and covers the surface of the basal cells.

Aged↗

PubMed1984

Acute local inflammation alters synthesis, distribution, and catabolism of third component of complement (C3) in rabbits.

In order to evaluate the basis for changes in plasma concentrations of the third component of complement (C3) during inflammation, we injected purified radiolabeled C3 into normal New Zealand White rabbits and into rabbits with turpentine-induced pleurisy. In the normal animals, C3 was distributed between the intravascular compartment (75%) and the extravascular space (25%), with an exchange rate of 1.8 +/- 0.1% of the plasma pool per hour. The fractional catabolic rate (FCR) was 2.7 +/- 0.3% of the C3 plasma pool per hour, the synthesis rate was 1.0 +/- 0.2 mg C3/kg per h, and the plasma concentration was 1.23 +/- 0.3 mg C3/ml. Rabbits with turpentine-induced inflammation showed a shift of the volume of C3 distribution in favor of the extravascular compartment. In addition, the rate by which 125I-C3 was cleared from the circulation increased by 29% and was related to the appearance of 20% of the C3-bound circulating radioactivity in the affected pleural cavity at the zenith of inflammation. The FCR, calculated by measuring urinary excretion of radiolabel, increased by only 9% and was probably related to the C3 degradation that was observed in the pleural fluid during the early stages of inflammation. The plasma C3 concentration reached a peak at 230% of the baseline concentration, owing to an increase in the rate of synthesis by as much as 480%. The latter increase could be blocked by cycloheximide, an inhibitor of protein synthesis. We conclude that the increase of plasma C3 in the acute phase is due to stimulated synthesis, which is partially offset by a rise in FCR and by a shift of protein to the site of inflammation.

Acute Disease↗

PubMed1988

Survival of albumin, IgG, IgM, and complement (C3) in human blood after ingestion by Aedes albopictus and Phlebotomus papatasi.

The levels of albumin, IgG, IgM, and complement (C3) were determined by enzyme-linked immunosorbent assay in Aedes albopictus and Phlebotomus papatasi at regular intervals after feeding on human blood. Albumin disappeared most rapidly; by 48 hr, detectable levels of albumin had decreased 100-fold. In contrast, IgG and IgM survived longer and were still detectable at low levels several days after ingestion. C3 was intermediate in its rate of degradation. In general, serum protein disappearance occurred more rapidly in Ae. albopictus than in Ph. papatasi, despite a larger volume of blood ingested by the former.

Aedes↗

PubMed1985

Blood level of C3 complement component as an aid in the management of acute phase glomerulonephritis.

Ninety-five patients with acute glomerulonephritis, based upon clearly defined pathological criteria, were studied and scored. The scoring was correlated to their levels of blood complement components. Patients with low C3 serum levels had a severe course during the acute phase of their disease, as compared with those with normal C3 serum levels. No such correlation was established with regard to C4 serum levels. It is suggested that C3 serum level may serve as an indicator of the expected severity of the inflammatory process and thus as an aid in the management of patients with acute glomerulonephritis in the initial phase of the disease.

Acute Disease↗

PubMed1988

Biochemical characterization of a factor produced by trypomastigotes of Trypanosoma cruzi that accelerates the decay of complement C3 convertases.

Infective- and vertebrate-stage trypomastigotes of Trypanosoma cruzi resist serum killing by the alternative complement pathway, whereas noninfective vector-stage epimastigotes, from which trypomastigotes derive, are serum-sensitive. This form of developmental preadaption is commonly observed in protozoan parasites, but its mechanisms are poorly understood. We have demonstrated previously that trypomastigotes spontaneously shed molecules which interfere with formation and accelerate the intrinsic decay of complement C3 convertases, a finding which may explain the evasion of complement lysis by trypomastigotes. We now describe the partial purification and characterization of the T. cruzi C3 convertase inhibitor from the supernatant of culture metacyclic and tissue culture trypomastigotes. Decay-accelerating activity for both classical and alternative pathway C3 convertases copurifies on anion-exchange fast protein liquid chromatography and chromatofocusing with 35S-labeled molecules of 87-93 kDa, pI 5.6-5.8. The labeled components are destroyed by papain and retained on concanavalin A-Sepharose, procedures which remove functional decay-accelerating activity from the supernatant. The 87-93-kDa components are immunoprecipitated by sera from patients chronically infected with T. cruzi, but not by antisera to any known regulatory proteins of the human complement cascade. Lytic activity for tissue culture trypomastigotes in chagasic sera is associated with antibody reactivity against the 87-93-kDa 35S-labeled components and with inhibition of decay-accelerating activity. The T. cruzi factor is the first developmentally regulated microbial complement inhibitor to be biochemically characterized.

Animals↗

PubMed1989

Effects of serotonin (5HT) and complement C3 on the synthesis of the surface membrane precursors of adult Schistosoma mansoni.

The syncytial surface epithelium of Schistosoma mansoni plays an important role in immune evasion. This syncytium is covered by an unusual double-membrane complex consisting of an apical plasma membrane (APM) and an overlying envelope (En) that have been shown to have different rates of synthesis and turnover. It has been suggested that discoid bodies (DBs) and multilamellar bodies (MLBs), the major syncytial inclusion bodies of schistosomes, may be the precursors of the APM and En, respectively. In this ultrastructural study, we examined the effects of serotonin (5HT) and complement C3, which have been shown to stimulate synthesis and turnover of the APM and En, respectively, on the synthesis of DBs and MLBs in vitro. With short-time incubations (20 or 40 min), 5HT stimulated the synthesis of the DBs by 2-fold, whereas C3 accelerated synthesis of the MLBs by 2-fold. Furthermore, when microtubules within the cytoplasmic connections between the syncytium and the underlying cell bodies (the site of membrane synthesis) were disrupted with colchicine, the DBs and MLBs synthesized in response to 5HT or C3 accumulated in the cell bodies. This suggests that the transport of the organelles to the syncytium is dependent upon the microtubules but not the signaling mechanism in response to 5HT or C3. These observations also support the suggestion that the DBs and MLBs are synthesized in subsyncytial cell bodies and serve as precursors of the APM and En, respectively. The rapid synthetic response to 5HT and C3 is also consistent with rapid synthesis and turnover of the APM/En, as suggested by previous studies.

Animals↗

PubMed1987

Brefeldin A arrests the intracellular transport of a precursor of complement C3 before its conversion site in rat hepatocytes.

The effects of brefeldin A on intracellular transport and posttranslational modification of complement C3 (C3) were studied in primary culture of rat hepatocytes. In the control culture C3 was synthesized as a precursor (pro-C3), which was processed to the mature form with alpha- and beta-subunits before its discharge into the medium. In the presence of brefeldin A the secretion of C3 was strongly blocked, resulting in accumulation of pro-C3. However, after a prolonged interval the mature form of C3 was finally secreted. The results indicate that brefeldin A impedes translocation of pro-C3 to the Golgi complex where pro-C3 is converted to the mature form, but not its proteolytic processing, in contrast to the effects of monensin and weakly basic amines.

Animals↗

PubMed1981

Instability of immunoglobulins and complement (C3) as predictor of renal allograft rejection.

Ten renal allograft recipients were studied for a period of three months with weekly measurements of serum complement C3 including a baseline value before transplantation. Immunoglobulins (IgG, IgM, IgA) were studied in nine of these patients. Fifteen rejection episodes occurred, three patients losing their graft because of irreversible rejections. The patients were followed for 2.5 years. The degree of of change in serial C3 and immunoglobulin levels from baseline was determined by variability index s. Fourteen out of 15 rejections were preceded by si (C3) greater than .1, one to several weeks in advance. The si (Ig) was useful in week 1 and predicted the rejection missed by si (C3). We conclude that instability of immunoglobulins and complement as measured by s is not only associated with rejections but appears to be a precursor to rejection events. We suggest the following prognostic two-step procedure: (1) Week 1: If either si (C3) or si (Ig) greater than .1, predict rejection. (2) Cases that pass step 1 are monitored by C3 at weekly intervals. As soon as si (C3) greater than .1, predict rejection.

Complement C3↗

PubMed1998

Targeted disruption of the murine gene coding for the third complement component (C3).

Complement is a system of more than 30 proteins found both in plasma and on cell membranes. The complement system has several important functions in the immune response including initiation of inflammation, neutralization and elimination of pathogens, regulation of antibody responses, clearance of immune complexes and disruption of cell membranes. Under certain conditions complement may, however, act as a mediator of deleterious inflammatory reactions and complement activation has been implicated in the pathogenesis of autoimmune disorders, atherosclerosis, neurodegenerative diseases, bioincompatibility reactions and decompression sickness. Using gene targeting, we have generated mice deficient for the third complement component (C3). These mice represent an animal model in which complement activation by any pathway is prevented at an early stage. The C3-deficient mice should be valuable for the study of the roles of the complement system in vivo in a variety of physiological and pathological situations.

Animals↗

PubMed1993

Synthetic Alzheimer amyloid beta/A4 peptides enhance production of complement C3 component by cultured microglial cells.

Primary microglial cultures prepared from newborn mice showed the production and release of the third component of complement (C3). Newly synthesized [35S]methionine-labelled C3 was purified by immunoprecipitation using anti-C3-antibody. C3 was detected by SDS-PAGE and fluoroaraphy of the immunoprecipitated protein from cell lysates as a 195 kDa band, and from the supernatants of cultures as two major bands corresponding to the C3 alpha-chain (125 kDa) and beta-chain (75 kDa), consistent with known C3 characteristics. Increased biosynthesis of C3 was elicited by endotoxin lipopolysaccharide (LPS). Further, the synthesis of C3 was increased 5-10-fold in response to various synthetic peptides corresponding to the amyloid beta/A4 protein, which is the main constituent of extracellular amyloid deposits in Alzheimer's disease (AD). The increased synthesis of C3 was shown to be dose dependent at concentrations of beta/A4 peptide ranging from 10 micrograms/ml to 50 micrograms/ml. These results suggest that complement components found previously in amyloid deposits may be partly derived from reactive microglia preferentially associated with senile plaques in AD brain.

Amyloid beta-Peptides↗

PubMedDate not supplied

Interactions of the third component of human complement (C3) with tumour cells: evidence for presence of C3b acceptor sites and direct activation of C3 by tumour cells.

The interaction of C3 with different tumour cell lines was investigated. Our results indicated that nearly all the cell lines had C3b acceptors on their membranes. The binding of C3b was visualized by the detection of this protein on the cell surface with fluoresceinated anti-C3c serum. The involvement of proteases in the activation of C3 was demonstrated: complement-membrane fluorescence occurred in the presence of EDTA but was completely abolished with epsilon-aminocaproic acid. Experiments performed with purified C3 led to the conclusion that the protease activity might be the initial event for the activation of the alternative pathway by tumour cells.

Burkitt Lymphoma↗