Determination of immunoglobulin E (IgE) and complement III (C3) in children with giardiasis.
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Child↗
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Maternal transfer of complement components C3-1, C3-3, C3-4, C4, C5, C7, Bf, and Df to offspring in rainbow trout (Oncorhynchus mykiss).
Defense mechanisms in developing fish are poorly known but before maturation of lymphoid organs and immunocompetence, innate mechanisms are essential. The complement system represents a major part of innate immunity. Our main objective was to map the presence of complement components early in fish development. Rainbow trout eggs, embryos, and hatchlings were assayed for the onset and duration of C3-1, C3-3, C3-4, C4, C5, C7, factor B, and factor D transcription using real-time reverse transcription-polymerase chain reaction. In general, complement transcript levels increased steadily from day 28 postfertilization to hatch, followed by a decrease during yolk-sac resorption. All the complement proteins studied were found in unfertilized eggs. There was no correlation between the transcript and protein levels throughout the study period. Complement proteins appeared in the liver, kidney, and intestine between day 7 and 35 but not until day 77 in the heart. This study is the first to address the ontogeny of several complement components and represents the first evidence that maternal transfer of complement components, other than C3, occurs in teleost fish.
Animals↗
The binding of complement component C3 to antibody-antigen aggregates after activation of the alternative pathway in human serum.
Preformed immune aggregates, containing antigen and either IgG (immunoglobulin G) or F(ab')2 rabbit antibody, were incubated with normal human serum under conditions allowing activation of only the alternative pathway of complement. Both the IgG and F(ab')2 immune aggregates bound C3b, the activated form of the complement component C3, in a similar manner, 2-3% of the C3 available in the serum being bound to the aggregates as C3b, and the rest remaining in the fluid phase as inactive C3b or uncleaved C3. It was found that the C3b was probably covalently bound to the IgG in the aggregates, since C3b-IgG complexes could be demonstrated on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, after repeated washing with buffers containing high salt or boiling under denaturing conditions. Incubation of the C3b-antibody-antigen aggregates in buffers known to destroy ester linkages had little effect on the C3b-IgG complexes, which suggested that C3b and IgG might be linked by an amide bond. Two main types of C3b-IgG complexes were found that had apparent mol.wts. of 360000 and 580000, corresponding to either one to two C3b molecules respectively bound to one molecule of antibody. On reduction of the C3b-IgG complexes it was found that the beta-chain, but not the alpha'-chain, of C3b was released along with all the light chain of IgG but only about half or less of the heavy chain of IgG. These results indicate that, during activation of the alternative pathway of complement by immune aggregates containing IgG antibody, the alpha'-chain of C3b may become covalently bound at one or two sites in the Fd portion of the heavy chain of IgG.
Antigen-Antibody Complex↗
Genomic organization of human complement component C3.
Six overlapping clones, spanning the entire C3 gene and the 5' flanking region, were isolated from two genomic lambda libraries. Thirty exons, covering the complete beta chain and part of the alpha chain as far as the C3d region, were analyzed. The full exon-intron organization of the gene was deduced by combining our data with the reported organization of the alpha' chain (Barnum et al., 1989, J. Biol. Chem. 264: 8471-8474). The complete gene is 41 kb and consists of 41 exons. The C3 beta chain spans 13 kb from exon 1 to exon 16. Exon 16 encodes both alpha and beta chains. The alpha chain is 28 kb and contains 26 exons, including exon 16. The 5' flanking region was sequenced up to 514 bases upstream from the ATG start site. The major transcription initiation site was mapped to an adenine residue 61 bases upstream from the signal peptide by primer extension analysis of poly(A)+ mRNA from hepatocytes and U937 cells. The TATA box motif was assigned at position -85. Several putative binding sites for transcription factors were found in the 5' flanking region, suggesting possible pathways for the regulation of the C3 gene.
Base Sequence↗
Human complement activation via the alternative pathway on porcine endothelium initiated by IgA antibodies.
The role of the classical pathway (CP) and the alternative pathway (AP) of complement activation in hyperacute xenograft rejection remains a matter of considerable debate. In addition, it is unknown whether IgG and IgA antibodies activate complement, although these antibodies have been found in hyperacutely rejected xenografts. This study was initiated to assess a possible role of the AP of complement activation in a pig-to-human transplantation model using fresh human sera and isolated antibodies with cultured porcine endothelial cells (PEC) as targets. IgM, IgG, monomeric IgA, and dimeric IgA (dIgA) antibodies with reactivity toward PEC as determined by ELISA were isolated from pooled normal human sera. Serum from patients with agammaglobulinemia was used as a source of human complement. C3 and C4 deposition on nonfixed PEC during CP (1% serum) or AP activation (10% serum with MgEGTA) was analyzed using an ELISA. Complement-mediated PEC lysis was tested in a 51Cr release assay. Using normal human sera as the source of antibodies and complement, C3 and C4 deposition was already found after 10 min of incubation in the CP, whereas an increasing amount of C3 was found in the AP. During AP activation, no C4 deposition was observed, indicating that CP activation did not contribute to the observed AP-mediated C3 deposition. Moreover, dIgA antibodies caused deposition of C3 and not C4. Purified IgM and dIgA antibodies (1 mg/ml) in the presence of 10% agammaglobulinemic serum showed a mean specific PEC lysis of 31% and 28%, respectively. Agammaglobulinemic serum alone or with IgG or monomeric IgA antibodies had no detectable lytic activity. In conclusion, dIgA antibodies might play an additional role in pig-to-human xenograft rejection by activating human complement via the AP.
Acute Disease↗
Serum amyloid A, properdin, complement 3, and toll-like receptors are expressed locally in human sinonasal tissue.
BACKGROUND: There is a growing appreciation of the role that nasal mucosa plays in innate immunity. In this study, the expression of pattern recognition receptors known as toll-like receptors (TLRs) and the effector molecules complement factor 3 (C3), properdin, and serum amyloid A (SAA) were examined in human sinonasal mucosa obtained from control subjects and patients with chronic rhinosinusitis (CRS). METHODS: Sinonasal mucosal specimens were obtained from 20 patients with CRS and 5 control subjects. Messenger RNA (mRNA) was isolated and tested using Taqman real-time polymerase chain reaction with primer and probe sets for C3, complement factor P, and SAA. Standard polymerase chain reaction was performed for the 10 known TLRs. Immunohistochemistry was performed on the microscopic sections using antibodies against C3. RESULTS: Analysis of the sinonasal sample mRNA revealed expression of all 10 TLRs in both CRS samples and in control specimens. Expression of the three effector proteins was detected also, with the levels of mRNA for C3 generally greater than SAA and properdin in CRS patients. No significant differences were found in TLR or innate immune protein expression in normal controls. Immunohistochemical analysis of sinonasal mucosal specimens established C3 staining ranging from 20 to 85% of the epithelium present. CONCLUSION: These studies indicate that sinonasal mucosa expresses genes involved in innate immunity including the TLRs and proteins involved in complement activation. We hypothesize that local production of complement and acute phase proteins by airway epithelium on stimulation of innate immune receptors may play an important role in host defense in the airway and, potentially, in the pathogenesis of CRS.
Base Sequence↗
Insulin decreases hepatic acute phase protein levels in severely burned children.
BACKGROUND: Severe burn induces the hepatic acute phase response. In this study, we wondered whether continuous insulin treatment decreases acute phase protein levels in the severely burned. METHODS: Eighteen children aged 2 to 17 years with burns >40% of total body surface area were randomized to receive either insulin (n=9) or no treatment (n=9) within 72 hours after injury until the wounds were 95% healed. Insulin was given at a continuous rate of > or =1.5 microU/kg/min to maintain euglycemia (serum glucose 100-140 microg/dL). Plasma was examined at days 7, 14, 21, and 28 for acute phase protein levels including C-reactive protein, C3 complement, alpha1-acid glycoprotein, haptoglobin, alpha2-macroglobulin, prealbumin, transferrin, and retinol-binding protein. Statistical analysis was by ANOVA and t test. RESULTS: With insulin treatment, alpha1-acid glycoprotein, C3 complement, alpha2-macroglobulin, and haptoglobin levels decreased (P<.05) after a severe burn compared with control, especially at days 21 and 28. Additionally, the hepatic constitutive proteins (prealbumin, transferrin, and retinol-binding protein) were lower in the insulin-treatment group than those of the control group at day 21 (P<.05). CONCLUSIONS: Continuous insulin treatment decreases acute phase protein levels after a severe burn. The results suggest insulin downregulation of the hepatic acute phase response to injury.
Acute-Phase Proteins↗
Immunohistologic findings in otosclerosis.
The cause of otosclerosis is still unclear. Between 1981 and 1988 we obtained 186 biopsy specimens of otosclerotic bone during the course of stapedectomies. Serial sections of the specimens were examined histologically (H & E) and immunohistologically (peroxidase-antiperoxidase technique) for immunoglobulin G, immunoglobulin M, and C1q and C3 complements. Active otosclerotic foci were found in 61 cases, 43 of which had IgG deposits. IgM antibodies were absent. In specimens with inactive otosclerosis, IgG and IgM were not evident, C1q and C3 complements were demonstrated together with IgG, but sometimes also in the mucosa independent of the phase of the otosclerosis. Our findings suggest that an immunologic process may be important in the pathogenesis of otosclerosis.
Acute Disease↗
Proceedings: Cleavage of the third complement component (C3) and release of a spasmogenic, C3-derived peptide (C3a) by epsilon-aminocaproic acid (EACA) in serum: a process involving the complement activating properdin system.
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Aminocaproates↗
Localisation of a group of antigenic sites in complement component C3, and identification of a new fragmentation pattern.
Immunisation of rabbits or goats with denaturated human C3 reproducibly gives rise to an antiserum of restricted specificity which precipitates native C3, C3b and iC3b, but not C3c or C3d isolated from 'aged' serum. The antigenic sites recognised by the antiserum appear to be localised in a small segment of the polypeptide chain located close to the N-terminus of the C3b alpha' chain. Affinity chromatography using antibodies developed by this procedure reveals an unusual pattern of degradation of C3 which occurs on conventional 'ageing' of serum at 37 degrees C.
Amino Acids↗
The difference between human C3F and C3S results from a single amino acid change from an asparagine to an aspartate residue at position 1216 on the alpha-chain of the complement component, C3.
The third component of the human C system, C3, exhibits two common genetic variants. These variants have been characterized by high voltage agarose electrophoresis and are designated C3 fast (C3F) and C3 slow (C3S). C3F occurs at appreciable frequencies only in Caucasian populations and has been shown to be associated with an increased incidence of certain diseases, such as partial lipodystrophy, IgA nephropathy, and Indian childhood cirrhosis. It has been shown that C3F differs from C3S with regard to isoelectric point as well as its ability to bind macrophages. The availability of a full-length cDNA probe for human C3 has made it possible to study the polymorphism at the genomic level. We have used RNA/RNA hybridization to demonstrate that the difference between C3F and C3S occurs in the C3d region. We subsequently used oligonucleotide-primed DNA amplification to show that C3F arises from a point mutation at codon 1216 converting a deoxyadenosine for a deoxyguanosine. The result of this point mutation at the translational level is the substitution of an asparagine residue in C3S for an aspartic acid residue in C3F. It is known that C3d contains the binding site for CR2 as well as the internal thioester site and multiple protease cleavage sites. The identification of the structural basis of the differences between C3F and C3S will assist our continuing studies of the mechanism of the functional differences between the two alleles and the disease associations of C3F. It also allows us to use DNA based techniques to allotype C3 in subjects with little or no C3 in their serum.
Amino Acid Sequence↗
The role of certain immunologic parameters in silicosis.
The paper presents some possibilities of estimating the immunologic aggression in silicosis in a group of 68 patients divided into three subgroups according to the evolutive stage of disease. The results were compared with the data obtained in a control group of 35 clinically healthy subjects not subjected to respiratory noxae. Parameters such as the immunogram (IgG, IgA IgM, IgD), the C3 complement, the circulating immune complexes (CIC) and the C reactive protein (CRP) were investigated using classical immunochemical methods. It was observed that the immunoglobulin titer presented a polyclonal increase. The mean values of C3 complement decreased in stages I and II of disease. The CIC level presented high mean values unrelated to the stage of the disease. The incidence of CRP was found high in stage III. It was demonstrated that there is no significant correlation between the humoral immunologic abnormalities and the radiologic changes or the depression of the pulmonary functional test. These changes suggest that the humoral immunologic abnormalities are not directly responsible for the lung changes in silicosis and cannot be used as a predictive indicator of the severity of the disease or of its progress. The data obtained showed a hyperreactivity of the humoral mediated immunity over the whole course of the disease thus supporting the assumption of an immunopathogenic mechanism in this disease.
Adult↗
Peripheral clearance of amyloid beta peptide by complement C3-dependent adherence to erythrocytes.
Brain deposits of amyloid beta peptide (Abeta) have been a diagnostic hallmark of Alzheimer's disease (AD) for nearly a century. Recent studies have demonstrated that Abeta is also present in peripheral blood. Here, we present evidence that circulating Abeta42 is subject to complement C3b-dependent adherence to complement receptor 1 (CR1) on erythrocytes, a classical set of mechanisms by which pathogens and proteins recognized as foreign are cleared from the bloodstream. Levels of Abeta42 targeted by this pathway differ significantly in AD compared to mild cognitive impairment and nondemented elderly controls.
Alzheimer Disease↗
Metabolic indicators of oxidative stress correlate with haemichrome attachment to membrane, band 3 aggregation and erythrophagocytosis in beta-thalassaemia intermedia.
Haematological data, genotype, transfusion requirements, metabolic indicators of oxidative stress (flux via hexose-monophosphate shunt (HMPS); steady state level of GSH and GSSG, NADPH and NADP; activity of anti-oxidant enzymes), parameters of membrane damage (aggregated band 3; membrane-bound haemichromes, autologous immunoglobulins (Igs) and C3 complement fragments) and erythrophagocytosis were measured in erythrocytes (RBC) of 15 beta-thalassaemia intermedia patients (nine splenectomized) with low, if any, transfusion requirements. Patients presented increased aggregated band 3, bound haemichromes, Igs and C3 complement fragments, and increased erythrophagocytosis. Bound haemichromes strongly correlated with aggregated band 3. Anti-band 3 Igs were predominantly associated with aggregated band 3. Erythrophagocytosis positively correlated with aggregated band 3, haemichromes and Igs, suggesting the involvement of haemichrome-induced band 3 aggregation in phagocytic removal of beta-thalassaemic RBC. Splenectomized patients showed higher degrees of membrane damage and phagocytosis, significantly higher numbers of circulating RBC precursors, and tendentially higher numbers of reticulocytes. Basal flux via HMPS was increased twofold, but HMPS stimulation by methylene blue was decreased, as was the glucose flux via HMPS. GSH was remarkably decreased, whereas NADPH was increased. Except for unchanged catalase and glutathione reductase, anti-oxidant enzymes had increased activity. Negative correlation between HMPS stimulation by methylene blue and bound haemichromes indicated that the ability to enhance HMPS may counteract haemichrome precipitation and limit consequent membrane damage leading to erythrophagocytosis.
Adult↗
[Factors of nonspecific resistance in hepatitis B and acute hepatic insufficiency].
Studies of nonspecific resistance factors in grave forms of viral hepatitis B (VHB) have revealed their significance in the prediction of acute hepatic insufficiency (AHI) development and its unfavorable outcome. IgM and IgA levels were found the most informative as far as the prognosis is concerned; these levels were the highest in the patients with precoma eventuating in hepatic coma. C3 complement concentration was reduced in all the patients whatever the disease severity, but more so in those developing AHI, which fact may serve the criterion predicting AHI development in VHB; to add to this, C3 complement level reflects the degree of hepatocyte destruction whereas the degree of transferrin level reduction is explained by its impaired synthesis by the liver as well. Transferrin levels were reduced in all the patients with AHI.
Acute Disease↗
The role of third complement component (C3) in homing of hematopoietic stem/progenitor cells into bone marrow.
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Animals↗
Analysis of specific proteins in prostatic fluid for detecting prostatic malignancy.
In an attempt to identify an indicator(s) specifically associated with prostatic cancer prostatic fluid was collected by rectal massage from patients with prostatic cancer, prostatitis, benign prostatic hyperplasia and from those without recognized prostatic lesions in order to measure various immunoproteins. The proteins examined were IgG, IgA, IgM, complements C3 and C4, and transferrin. Prostatic fluid samples were subjected first to immunoelectrophoresis. Distinct differences in C3, C4 and transferrin concentrations were noted between patients with prostatic cancer and other patients. These proteins were stained heavily in the electrophoresis gels of fluid from cancer patients but were either missing or lightly stained in all other groups. These qualitative determinations were replaced subsequently by a quantitative measurement using the radial immunodiffusion technique. Results of the latter study confirmed the aforementioned observations and indicated that the levels of C3, C4 and transferrin in the prostatic fluid of cancer patients were elevated significantly when compared to all other patient groups. These observations indicate that the measurement of complements C3 and C4, and transferrin in the prostatic fluid may assist in the identification of patients with a high risk of prostatic cancer.
Body Fluids↗
Structure of murine complement component C3. II. Nucleotide sequence of cloned complementary DNA coding for the alpha chain.
From the inserts of two recombinant plasmids isolated from a murine liver cDNA library, the nucleotide sequence coding for the C3 alpha chain was obtained and the corresponding amino acid sequence was derived. The alpha chain portion of the mRNA is 2979 nucleotides long, specifying a polypeptide of 993 amino acids. The molecular weight of the alpha chain, in the absence of carbohydrate, was calculated from the sequence data to be 112,933. Two possible carbohydrate attachment sites were predicted at residues 269 (Asn) and 947 (Asn). In addition, the positions for two putative factor I cleavage sites were predicted from a comparison with the cleavage sites in the human C3 alpha chain. The C3 alpha chain contains 24 cysteine residues, 10 of these clustered in the C-terminal 175 amino acids of the alpha chain. Together with the accompanying report (Lundwall, A, Wetsel, R.A., Domdey, H., Tack, B.F., and Fey, G.H. (1984) J. Biol. Chem. 259, 13851-13856), this study completes the nucleotide and amino acid structure of the murine precursor prepro-C3 molecule.
Amino Acid Sequence↗