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PubMed1985

Characterization of tryptic fragments of human complement factor C3.

C3c and C3d fragments were prepared in pure form from trypsin-digested human C3, and the individual chains of tryptic C3c were isolated by gel filtration on Sepharose 4B in 6M guanidinium hydrochloride. No low mol. wt (Mr) fragments were identified. The polypeptide chains were characterized with regard to Mr, amino acid composition and N-terminal amino acid sequence. Tryptic C3c consisted of one fragment from the beta-chain (Mr 64,000) and two from the alpha'-chain (Mr 40,000 and 23,000). The beta-chain fragment was derived from the C-terminal part of the chain, and the 23,000-Mr component constituted the amino terminal end of the alpha-chain. The 40,000-Mr fragment emanated from the C-terminal end of the alpha-chain. Tryptic C3d displayed microheterogeneity on polyacrylamide gel electrophoresis in sodium dodecyl sulfate, but possessed a homogeneous N-terminal, identical to that described by Tack et al. (1980) (Proc. natn. Acad. Sci. U.S.A. 77, 5764-5768). By utilization of antisera against subunits of C3 and C3c in immunoblotting a degradation scheme for C3 by trypsin was proposed and the positions of the fragments in the intact molecule indicated.

Amino Acid Sequence↗

PubMed1979

[Serum complement and protein metabolism in chronic dialysis patients].

1. When a so-called free diet is granted there is the danger of a protein deficit, which can be proved in a significant decrease of the serum transferrin and of the complement factor E3c, in patients in the chronic haemodialysis programme. 2. Within the group undergoing dialysis a correlation analysis did not result in a statistically ascertained connection between the complement factor C3c and the total haemolytic activity and the transferrin, respectively. 3. On the basis of a diet analysis a connection between the protein supply and the serum transferrin level could be established, which was not to be proved for the complement factor C3c and the total haemolytic activity, respectively. 4. Low transferrin values in the serum seem to be followed by a deterioration of the anaemia situation of the patient undergoing haemodialysis. 5. Compared with the total haemolytic activity and the complement factor C3c the determination of the serum transferrin allows an essentially exacter information about the protein metabolism of the patient undergoing a chronic haemodialysis.

Blood Proteins↗

PubMed1988

Immune reactive C3d on the surface of myelin sheaths in neuropathy.

Immunofluorescence studies of sural nerve demonstrated immune reactive C3d and IgM on the surface of myelin sheaths in seven patients with neuropathy and an anti-myelin-associated glycoprotein (MAG) IgM M-protein. Similar deposits of C3d and sometimes IgM were found in four of six patients with acute or chronic inflammatory demyelinating polyneuropathy and in three of six patients with vasculitic neuropathy (including one with acquired immunodeficiency syndrome (AIDS)). C3d was not found in 80 patients with other peripheral nerve disorders except for two with metachromatic leukodystrophy. None of the C3d deposits contained immune reactive C3c implying substantial degradation of C3b. C3d is a sensitive index of complement activation in nerve and may be useful in classification of neuropathies.

Antibodies, Monoclonal↗

PubMed1990

Glomerular CR1 express in situ cofactor activity for degradation of C3b.

Adherence of sheep erythrocytes (E) sensitized with IgM antibodies (A) and C3b (EAC3b) to C3b/C4b receptors (CR1) in cryostat sections of human renal glomeruli was studied using the closed chamber technique. The adsorption was stable for at least 3 h at 37 degrees C. In the presence of purified factor I, the indicator cells, however, detached from the sections after 30 min at 37 degrees C. Factor H was not required. The release was not due to loss of CR1 activity in the tissue. The detached indicator cells were negative in the immune adherence test and were agglutinated by antibody to C3d, but not by antibody to C3c. Western blot of the detached indicator cells revealed the presence of C3d and C3c was found in the chamber fluid. Accordingly, detachment of the indicator cells was due to degradation of C3b to C3d with the release of C3c into the chamber fluid. Protease inhibitors did not prevent the detachment of the indicator cells. EAC3b incubated with sections of renal glomeruli preincubated with anti-CR1 antibody were not degraded. The results therefore indicate that CR1 in situ in renal glomeruli can provide the necessary cofactor activity for factor I-mediated degradation of C3b to C3d and C3c.

Complement C3b↗

PubMed1983

Hypercatabolism of complement in Crohn's disease--assessment of circulating C3c.

Split products from the main complement component 3 (C3) were investigated in untreated outpatients, 20 with Crohn's disease and 20 with ulcerative colitis. The median plasma concentration of c split product of C3 (C3c) in normals was 2 mg X 1(-1), in patients with Crohn's disease 20 mg X 1(-1) and in patients with ulcerative colitis 3 mg X 1(-1). This tenfold increase in C3c was significant at the 0.005-level. Plasma C3c exceeded the reference interval in two patients with ulcerative colitis. C3c levels did not correlate to the activity of the disease or to the occurrence of the C3 phenotypes S, FS and F. Substantially elevated plasma C3c in Crohn's disease suggests hypercatabolism of C3, that is, involvement of complement reactions. Further studies are needed to reveal the site of cascade activation and to define the role of complement for the pathogenesis of the disease.

Colitis, Ulcerative↗

PubMed1985

The quantitation of C3d by routine methods after the direct absorption of human plasma with anti-C3c.

The immunological methods for quantitating C3d in plasma require first the removal of less fragmented intermediates as well as the intact C3. We describe an alternative method for the quantitation of C3d in human plasma. The components which should be removed are absorbed (precipitated) directly in the plasma by a specific anti-C3c antiserum. It is then possible to determine the concentration of C3d by routine immunological methods.

Antibodies↗

PubMed1983

Quantitative quality control of antiglobulin reagents.

Double antibody radioimmunoassays have been developed for the quantification of anti-IgG, anti-C3, anti-C3c, anti-C3d and anti-C4 antibodies and for the determination of their binding constants. Assays were undertaken on 53 polyspecific antiglobulin reagents obtained from a variety of commercial and public sources. Concentrations of anti-IgG varied from 1.2 to 12.8 micrograms/ml in commercial products and from 0.4 to 6.0 micrograms/ml in public products. Concentrations of anti-C3 and anti-C3c varied from 0.1 to 1.0 micrograms/ml in most commercial products but in public products concentrations varied by more than 100-fold from 0.02 to 6.5 micrograms/ml. Concentrations of anti-C3d varied from 0.05 to 0.7 micrograms/ml in most commercial products and from less than 0.01 to 1.3 micrograms/ml in public products. Concentrations of anti-C4 varied from less than 0.01 to 0.18 micrograms/ml in commercial products and from less than 0.01 to 0.08 micrograms/ml in public products. Mean binding constants for commercial products were: anti-IgG 6.6 x 10(9) l/mol, anti-C3 4.6 x 10(9) l/mol, anti-C3c 5.3 x 10(9) l/mol, anti-C3d 0.4 x 10(9) l/mol and anti-C4 4.9 x 10(9) l/mol. Relationships were found between results obtained in quantitative assays of specific antibodies and independently performed serological assessments of potency. Anti-IgG was present in suboptimal concentrations for agglutination in several public products and anti-C3 and anti-C3c were in suboptimal concentrations for agglutination in many public and commercial products.

Antibodies, Anti-Idiotypic↗

PubMed1982

C3c and C3d fragments of human C3 bind myeloma IgG1 and IgG3 proteins.

Eight human myeloma proteins, two of each IgG subclass, were studied for binding to solid-phase C3c and C3d by the ELISA technique. Myeloma IgG1 kappa, IgG1 lambda, IgG3 kappa and IgG3 lambda proteins bound to C3c and C3d, while two IgG2 kappa, and two IgG4 kappa proteins failed to show significant binding affinity. The results suggest that like C1q, the stable binding sites of C3, located on the C3c and C3d parts of the molecule, have affinity for IgG subclasses 1 and 3.

Animals↗

PubMed1991

Computer imaging analysis of the correlation between intensities of glomerular immune-deposits and histopathology in patients with IgA nephropathy.

The relationship between the intensities of IgA, C3c, and C9 deposition in renal glomeruli and the severity of histopathologic injuries in patients with IgA nephropathy was examined using Microscope-Photometer 01K and a computer. Percentages of glomerular adhesion to Bowman's capsules, crescent formation, and glomerular sclerosis were calculated in the renal specimens. There was a significant correlation between the intensity of each C3c and C9 deposition in glomeruli and the degree of glomerular adhesion to Bowman's capsules and crescent formation in patients with IgA nephropathy. There was no significant correlation between the intensity of C3c or C9 deposition in glomeruli and the degree of glomerular sclerosis. No relationship was found between the intensity of IgA deposition in glomeruli and the degree of histopathologic injuries. The patients with negative or trace amounts of glomerular C3c deposits showed less severe glomerular injuries. Thus, the intensity of C3c and C9 deposition in glomeruli appears to be one of the critical factors responsible for the active progression of glomerular inflammatory process in patients with IgA nephropathy.

Complement C3c↗

PubMed1984

[Normal values of IgA, IgM, IgG, C3c, C4, alpha 1-acid glycoprotein in blood from the umbilical cord of healthy newborn infants using laser-nephelometry. III: C3c, C4, alpha 1-acid glycoprotein].

The authors have determined, using the laser-nephelometric technique, the concentration of C3c, C4 and alpha 1-acid glycoprotein in the umbilical cord blood of normal newborns. The results obtained are sufficiently in agreement with literature data, even if there are some differences derived by methods and environmental factors.

Complement C3↗

PubMed1984

[Effects of the use of FRIGEN (AG-Ffm-HOECST) on the determination of blood levels of some proteins (IgA, IgM, IgG, C3c, C4) in cord blood of healthy newborn infants at term by laser nephelometry].

The purpose of this paper is to establishes the FRIGEN effects on the determination of IgA, IgM, IgG, C3c, C4 cord-blood levels, by means of laser-nephelometry. The results show substantial interferences only in the IgA levels, whereas the other on almost all proteins are not affected, the found interference can be due to the amount of IgA bound to B-lipoprotein, that are precipitated by FRIGEN.

Chlorofluorocarbons, Methane↗

PubMed1987

Immunoelectron microscopic study of glomerular lesions using a postembedding method with a protein A-gold complex.

Renal biopsy tissue from 33 children with various glomerular diseases has been investigated by electron microscopy using a postembedding immunostaining technique with a protein A-gold complex in order to establish more precise correlations between immunopathologic and morphologic findings in glomeruli. This technique could detect immunoglobulins (IgG, IgA, and IgM), complement factor (C3c), and fibrinogen-related antigen. The immunoreactivity of these antigens was essentially confined to the mesangial, paramesangial, subendothelial, and subepithelial 'electron-dense deposits' in the glomeruli. Except for IgM and C3c in the case of glomerular sclerosis, the distribution of the mentioned factors was even in the electron-dense deposits, as could be shown by 'double-immunolabeling'. From the above-mentioned findings one can conclude that several of the localized factors are associated with the formation of electron-dense deposits, the ultrastructural hallmarks of glomerular disease.

Antigens↗

PubMed1982

Influence of time, temperature and coagulation on the measurement of C3, C3 split products and C4.

Quantitative and qualitative immunoelectrophoretic analyses of circulating C3, C3 split products and C4 were performed in matched EDTA plasma and serum obtained from 5 normal subjects and stored for up to 48 h at room temperature (18 degrees C-22 degrees C) and 4 degrees C. Fluctuations in apparent levels of C3 were greater in serum than plasma stored at room temperature, a fall in levels seen by 24 h being followed by a significant increase. By contrast, levels of C3 did not alter if stored at 4 degrees C. C4 levels in both EDTA plasma and serum remained unchanged for 24 h, a slight decrease being seen at 48 h. Levels of C4 remained constant if samples were stored at 4 degrees C. Crossed immunoelectrophoresis revealed a significant progressive decrease in C3 levels and a simultaneous increase in C3c occurring after 4 h in serum and 8 h in EDTA plasma, stored at room temperature. In studies conducted at 4 degrees C, similar but delayed fluctuations were seen. A progressive and significant increase in C3d levels was seen in both plasma and serum samples stored at room temperature, levels rising to 276% (plasma) and 308% (serum) of levels seen at zero time. At 4 degrees C marginal increases in C3d levels only were observed. These results suggest that in vitro degradation of C3 and C4 are readily facilitated by temperature, time and coagulation, and that conditions of collection and storage of samples must be optimized for the accurate definition of activation of the complement cascade.

Adult↗

PubMed1987

Host serum protein levels in cysts of human hydatidosis.

8 proteins (albumin, IgG, IgM, IgA, C3c, C4, orosomucoid and alpha 1 antitrypsin) were determined by laser immunonephelometry in hydatid cyst fluid from cysts and sera from 16 patients. The cystic level of albumin was 34.5 +/- SD 59.1 micrograms/ml (range 3.6-85); of IgG 12.9 +/- 18.7 micrograms/ml (1.9-75); of IgM 10.5 +/- 10.4 micrograms/ml (3-37); and of IgA 7.2 +/- 3.5 micrograms/ml (4-19.7). The 4 other proteins represented a smaller fraction: C3c, 0.9 +/- 0.6 micrograms/ml (0.5-2.5); C4, 1.3 +/- 0.9 micrograms/ml (0.5-3.5); orosomucoid, 2.8 +/- 2.3 micrograms/ml (1.4-9.2); and alpha 1-antitrypsin, 5 +/- 4.5 micrograms/ml (2-19). These 8 host proteins constituted 24.6 +/- 24.5% (2.4-76) of the total hydatid cyst fluid proteins (343.7 +/- 172.1 micrograms/ml, range 180-900). The albumin/IgG ration of 3 +/- 2.8 (0.4-10.8) in hydatid cyst fluid was more variable than that in sera, 2 +/- 0.5 (1.2-2.7).

Blood Proteins↗

PubMed1983

Rapid turbidimetric determination of serum C3c and C4 by end point centrifugal analysis.

An end point turbidimetric method for the determination of C3c and C4 in serum using a centrifugal analyzer (Cobas Bio) is described. Several analytical factors were evaluated -pH, temperature, PEG and antibody concentration. Wide variations of temperature and pH did not significantly affect the turbidimetric reaction. A 20 g/L PEG concentration and 25-fold antiserum dilution were found satisfactory for the analysis. Precision of the assay was good and comparison with a RID method yielded an r value of 0.97. The procedure is simple and reliable.

Centrifugation↗

PubMed1991

Activation of rabbit C3: studies of the generation of cleavage products in vitro and of their metabolism in vivo.

The cleavage of purified, functionally active rabbit C3 by cobra venom factor and trypsin was analysed by reducing and non-reducing sodium dodecyl sulphate electrophoresis and autoradiography. The specific aim of the study was to compare these reactions to those that occur with human C3. Analysis showed that the pattern of breakdown was very similar to that for the human protein: while the beta-chain remained intact, there was step-wise degradation of the alpha-chain to form C3a, C3b, iC3b and C3c, all of which could be identified by gel analysis. The metabolic behaviour of three of these cleavage products, C3a, C3b and iC3b, was then examined in vivo using dual isotope techniques. Rabbits were studied simultaneously with 131I-C3 and 125I-labelled C3 breakdown products. Analysis of plasma and urine radioactivity for the subsequent 72 h showed that all three breakdown proteins had rapid rates of catabolism in vivo compared to the native molecule. Specifically, 93 and 98% of C3b and iC3b, respectively, were eliminated from the plasma compartment within 10 h of injection. C3a was completely eliminated within 10 h. By comparison, native C3 showed a half-life of 29 +/- 3 h (mean +/- SD) and a fractional catabolic rate of 4.30 +/- 0.75%/h. The data support the use of this species in studies of complement behaviour in models of human immune disease and further clarify the basis for changes in plasma C3 concentration that accompany active immune complex- and antibody-mediated activity, in vivo.

Animals↗

PubMed1984

Immunopathological correlation between mesangial C3d-deposition and C3d-fixing circulating immune complexes in lupus nephritis.

By a direct immunofluorescent technique, glomerular C3d deposition was examined in a total of 50 renal biopsy specimens from patients with lupus nephritis. C3d deposition was then compared with disease activity, glomerular IgG and C3c deposition, and the levels of circulating immune complexes (CIC) measured by a solid-phase anti-C3d assay. There was a good correlation between disease activity and the positivity of glomerular C3d deposits (P less than 0.001), as well as C3c deposits (P less than 0.001). Even in clinically inactive patients, a relatively high percentage (59%) of C3d deposits were positive compared with C3c deposits (17%). Mesangial C3d deposition correlated with clinical disease activity more significantly (P less than 0.005) than capillary wall C3d deposition (P less than 0.025). C3d deposits were detected in all of the 30 cases with positive C3c deposits, and moreover, in 15 of the 20 (75%) cases with negative C3c deposits. Glomerular IgG deposits were almost always associated with C3d deposits, both in mesangial areas and along capillary walls, with statistical significance (P less than 0.005, P less than 0.001, respectively). The serum levels of C3d-fixing immune complexes (IC) were significantly correlated with the positivity and intensity of mesangial C3d deposits. This study demonstrates glomerular deposition of C3d in patients with lupus nephritis and reveals a significant correlation between mesangial C3d deposition and disease activity.

Antigen-Antibody Complex↗

PubMed1983

Partial characterization of physiologically generated C3 components expressing C3d but not C3c epitopes.

Techniques for the quantification of C3d are shown to estimate the sum of 4 different plasma protein components possessing C3d but not C3c epitopes. All 4 components were C3-derived polypeptides as shown by activating serum containing 125I-labelled C3, isolating the anti-C3d reactive material in 14% PEG supernatant, followed by analysis on SDS-PAGE and autoradiography. Identical results were obtained by radiolabelling 14% PEG plasma supernatants followed by analysis of the anti-C3d reactive material. The components are referred to as d1, d1', d2 and d3 based on their relative electrophoretic mobilities (alpha 1, alpha 1, alpha 2 and alpha 2 respectively) judged by crossed immunoelectrophoresis. Their apparent molecular weights by SDS-PAGE were 129K (d1), 110K (d1'), 46K (d3) and 45K (d2). The possibility that one or more of the C3d containing components represented a complex of a C3 fragment with another plasma protein was investigated. The role of these components in the scheme of the physiological breakdown of C3 and the importance of the individual C3d components as indicators of complement activation in clinical materials is discussed. It is proposed that the 45K d2 component represents a final physiological breakdown product of C3 in human serum.

Antigen-Antibody Reactions↗