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PubMed2006

A dominant complement fixation pathway for pneumococcal polysaccharides initiated by SIGN-R1 interacting with C1q.

The intricate system of serum complement proteins provides resistance to infection. A pivotal step in the complement pathway is the assembly of a C3 convertase, which digests the C3 complement component to form microbial binding C3 fragments recognized by leukocytes. The spleen and C3 provide resistance against blood-borne S. pneumoniae infection. To better understand the mechanisms involved, we studied SIGN-R1, a lectin that captures microbial polysaccharides in spleen. Surprisingly, conditional SIGN-R1 knockout mice developed deficits in C3 catabolism when given S. pneumoniae or its capsular polysaccharide intravenously. There were marked reductions in proteolysis of serum C3, deposition of C3 on organisms within SIGN-R1(+) spleen macrophages, and formation of C3 ligands. We found that SIGN-R1 directly bound the complement C1 subcomponent, C1q, and assembled a C3 convertase, but without the traditional requirement for either antibody or factor B. The transmembrane lectin SIGN-R1 therefore contributes to innate resistance by an unusual C3 activation pathway.

Animals↗
PubMed1983

Changes of complement values in calves during the first month of life.

Hemolytic complement activity and the 3rd component of complement (C3) concentrations were measured in the blood sera of 8 dams before, at, and after parturition, and in the sera of their calves before and after feeding colostrum and at fixed intervals up to 1 month of life. The mean hemolytic titer in the dams, as measured by incubating guinea pig RBC sensitized with bovine natural antibodies in serially diluted serum, was slightly less than 200 and was not influenced by parturition and onset of lactation. The titers in the sera of the calves immediately after birth ranged from 63 to 149 with a mean of 99. One day later, values in all calves had dropped markedly to a mean of 39. During the following month, the titers increased and reached the precolostral levels after about 4 weeks; however, these titers were still far below the titers measured in adult cows. A similar pattern was seen in the C3 concentration. The mean value at birth was 28% of the values measured in adult cows. Values decreased to 18% one day later and increased during the following month to 43% of the adult C3 concentration.

Aging↗
PubMed2004

Uterine effects of the phytoestrogen 6-(1,1-dimethylallyl)naringenin in rats.

Phytoestrogens are discussed as candidate substances to treat symptoms related to estrogen deficiency. In in vitro experiments, the naturally occurring flavonoid 6-(1,1-dimethylallyl)naringenin (6-DMAN) emerged as one of the most potent phytoestrogenic substances. 6-DMAN is not as well characterized as other flavonoids (8-prenylnaringenin) or isoflavones (genistein). We tested 6-DMAN for the first time in vivo, in a dose-dependent three-day uterotropic assay in ovariectomized Wistar rats, using 6-DMAN at three different concentrations (1.5 mg/kg; 7.5 mg/kg and 15 mg/kg BW/d). Estradiol (E2; 10 microg/kg BW/d) and the carrier castor oil were used as positive and negative controls. 6-DMAN did not have any effect on uterine wet weight, while the positive control E2 did. In contrast, 6-DMAN stimulated uterine mRNA expression of estrogen responsive genes in ovariectomized rats. Estrogen receptor alpha and beta mRNA were expressed in the uterus. They mediate the expression of genes with an estrogen responsive element in the promoter, e. g., complement C3 and the progesterone receptor. Therefore, we analyzed the expression of the above-mentioned genes in three different concentrations. 6-DMAN up-regulated progesterone receptor and particularly complement C3 mRNA expression however, less pronounced than E2. In conclusion, we demonstrated for the first time estrogenic activities of 6-DMAN in vivo. Surprisingly, although 6-DMAN regulated estrogen responsive gene expression, there was no uterine wet weight gain. These findings make 6-DMAN a very interesting candidate substance for further characterization, as it potentially represents a naturally occurring selective estrogen receptor modulator.

Animals↗
PubMed1976

Changes in C3 metabolism during protozoan infection (Babesia rodhaini) in rats.

Metabolism of the third component of complement (C3) and IgG was measured in rats before and during infection with the hemosporidium agent Babesia rodhaina. In the course of infection, hypocomplementemia and immune complex nephritis developed. During babesial infection, in most animals the half-life of C3 fell sharply, as did serum levels of C3; the catabolic rate for C3 sharply increased, whereas the synthetic rate sharply decreased. In contrast, the catabolic rate for IgG remained unchanged. The alteration in the metabolism of C3 in the face of nonparallel changes in IgG metabolism suggests that abnormal glomerular filtration and increased vasopermeability cannot explain the findings. Babesial infection in the rat provides a useful model for the study of acquired C3 metabolic defects that have been observed in humans with immune complex diseases.

Animals↗
PubMed1984

Measurement of fragments of the third component of human complement on erythrocytes by a new immunochemical method.

This paper describes a new antiglobulin consumption method to quantitate the fragments of the third component of human complement (C3) on red blood cell (RBC) membranes. Zymosan-bound C3, which can be stored frozen at -80 degrees C for years, was used as a standard in these tests. Using anti-C3c antibody, zymosan-bound C3 could be calibrated against soluble converted C3 (beta 1A), but not against soluble, native C3 (beta 1C). Calibration with several commercial serum standards yielded virtually identical values. Approximately 79.8 +/- 28.2 C3d molecules (mean +/- 1 SD, n = 50) were detected on normal, freshly collected RBC by this method, whereas no C3c fragments were noted. EC43, prepared by dilution of blood samples with low ionic strength solution, had between 650 and 3,100 C3 molecules/RBC when measured with anti-C3c and between 1,140 and 6,500 C3 molecules when measured with anti-C3d. These data indicated that part of the C3b molecules on EC43 had cleaved to C3d. EC43 are reported to have up to 200,000 C3 molecules when measured by other techniques. To resolve this discrepancy, EC43 were prepared by dialysis of blood samples against low ionic strength solution. About 97.5% of C3 remained in plasma after dialysis supporting the results of our tests. The new assay is an accurate and sensitive method of quantitating C3 fragments bound to RBC in vivo and in vitro.

Binding Sites, Antibody↗
PubMed2004

Investigation of the activation of a human serum complement protein, C3, by orthopedic prosthetic particulates.

Myriad molecular, cellular, and physiological processes underlie the inflammatory and osteolytic processes induced by particles of biomaterials resulting from the wear of implants such as total joint replacement prostheses. The objective this study was to investigate the role that the complement system may be playing in these phenomena. The aim was to evaluate the degree to which particles of selected orthopaedic materials--high density and ultrahigh molecular weight polyethylene, polymethylmethacrylate, and commercially pure titanium--cause the elevation of a key complement molecule, C3a, in an in vitro assay that directly measured the concentration of C3a. The results demonstrated that HDPE particles, at high concentration, are capable of causing the elevation of C3a in the in vitro assay. This finding is discussed in the context of other work and the mechanics of the complement system as it may affect the osteolytic process.

Biocompatible Materials↗
PubMed1994

Predicting renal outcomes in severe lupus nephritis: contributions of clinical and histologic data.

Despite several years of intense investigation, there continues to be controversy about the value of clinical, demographic and histologic features in prediction of outcomes of lupus nephritis. In addition, contemporary treatments have reduced the risk of progressive renal injury and thus may have altered the prognostic significance of some of these factors. We have therefore re-examined the predictive value of variables previously associated with an increased risk of renal insufficiency by studying 65 patients with severe lupus nephritis treated with intensive regimens of intravenous pulse cyclophosphamide or methylprednisolone. Five clinical features at study entry were each associated with an increased probability of doubling the serum creatinine: age greater than 30 years, Black race, hematocrit less than 26%, serum creatinine greater than 2.4 mg/dl, and C3 complement less than 76 mg/dl. By multivariate survival analysis, serum creatinine, hematocrit and race emerged as the strongest set of independent clinical predictors; the other clinical and demographic factors, including age and C3 complement did not contribute significantly to outcome predictions in the context of these three variables. Renal biopsy evaluation offered additional prognostic information and showed that patients with severe active and chronic histologic changes were at increased risk for developing renal insufficiency. The combination of cellular crescents and interstitial fibrosis was particularly ominous. Outcome predictions based on the strongest clinical model (serum creatinine, hematocrit and race) were significantly enhanced by the addition of renal pathology data. Consideration of these prognostic factors may contribute to decisions regarding the type and intensity of immunosuppressive therapy for patients with lupus nephritis.

Adult↗
PubMed1990

The complements and immunoglobulins in different media of healthy pregnant women and in pregnant women with increased blood pressure.

We have determined the levels of complement C3, C4 and immunoglobulin G, M, A in mothers' and cord blood serum. Parallelly properdin factor B and immunoglobulin G tests were done in urine samples. All estimations were performed on Immunochemistry Analyzer "Beckman". The investigations were made on 30 healthy pregnant women and 30 with arterial hypertension at the end of third trimester. In the mothers' serum C3 was not significantly changed. In the cord blood of healthy pregnant women it was 0.69 g/L. (SD 0.12) and in those with hypertension 0.38 g/L. (SD 0.15), which means significantly decreased. Complements C4 was not significantly increased in mothers' and cord blood serum. Properdin factor B was significantly increased in mothers' and cord blood serum (healthy pregnant women in serum 0.38 g/L., SD 0.07; with hypertension 0.48 g/L., SD 0.15; while in the cord blood serum of healthy women it was 0.14 g/L., SD 0.06; and hypertensive it was 0.22 g/L., SD 0.10). The same parameter was significantly decreased in the urine of healthy subjects 3.94 mg/L., SD 1.91; and in the hypertensive too, 2.42 mg/L., SD 0.90. The IgG level was significantly increased in the urine of healthy pregnant women 4.42 mg/L., SD 2.24; with hypertension 6.64 mg/L., SD 3.61. IgM was not significantly changed in mothers' and cord blood serum. IgA was significantly increased in the cord blood serum of healthy mothers', 0.02 g/L., SD 0.01, with hypertension 0.12 g/L., SD 0.05.

Complement C3↗
PubMed1975

A study of complement components C3, C5, C6, C7, C8 and C9 in chronic membranoproliferative glomerulonephritis, systemic lupus erythematosus, poststreptococcal nephritis, idiopathic nephrotic syndrome and anaphylactoid purpura.

In a comparative study the hemolytic activity of C3, C5, C6, C7, C8, C9 and the C3 proactivator (C3PA) were measured in sera of 22 patients with chronic membrano-proliferative glomerulonephritis (CMPGN), 15 patients with idiopathic nephrotic syndrome, 10 patients with systemic lupus erythematosus, 7 patients with anaphylactoid purpura and 10 patients with acute poststreptococcal nephritis. In CMPGN, C3, C5, C6, C7 and C8 were low in the majority of the patients, whereas C9 and C3PA were depressed only in 21% and 11% of the patients, respectively. By contrast, C3PA and C8 showed striking depressions in the idiopathic nephrotic syndrome. In lupus erythematosus, all the C factors, including C3PA were found to be low with the exception of C9, which was normal in 80% of the patients studied. C3, C5, C6 and C7 were found to be depressed in acute glomerulonephritis; C8 and C9 titers were normal. In all patients studied with anaphylactoid purpura, CH50 and C3 titers were elevated markedly.

Adolescent↗
PubMed1977

Cellular reaction to group A beta-haemolytic streptococcal membrane antigen and its relation to complement levels in patients with rheumatic heart disease.

Cell-mediated immunity and blood complement activities were studied in 35 patients with chronic rheumatic heart disease (RHD) and 17 normal subjects. The T-cell population in patients with RHD was reduced, as were the CH50 and C3 complement levels. The response to phytohaemagglutinin stimulation was deficient, but the lymphocytes of patients with RHD showed increased avidity for 3H-thymidine when stimulated with specific streptococcal membrane antigen. No differences were found between patients with acute rheumatic activity and those without such activity. The susceptibility of individual patients may be related to the specific sensitisation of lymphocytes, while the fact that this persisted even when T-cell numbers had returned to normal may account for the well-known recrudescenses after streptococcal infections in these patients.

Antigens, Bacterial↗
PubMed1988

[Early and late results of heterotopic spleen autotransplantation in pediatric splenic trauma].

In this study, early and late results of heterotopic splenic autotransplantation in 18 children with type IV splenic injuries (Upadhyaya-Simpson classification) are presented. Splenic scintigrams, quantitative analysis of Howell-Jolly inclusion bodies, immunoglobulin (IgG, IgM, IgA) and complement C3 levels and T and B lymphocyte counts were analysed in the postoperative evaluation of the autotransplantation group. The total follow-up period was 7 years. According to our results, splenic implants increased complement C3 levels and improved filtration function of the splenectomized children. This autotransplantation group has two important characteristics: a) it is one of the largest series of the literature (pediatric age group), with b) longest follow-up period.

Adolescent↗
PubMed1998

Randomized controlled trial of pulse/synchronization cyclophosphamide/apheresis for proliferative lupus nephritis.

OBJECTIVE: To assess the efficacy of pulse/synchronization cyclophosphamide/apheresis in patients with proliferative lupus nephritis. METHODS: Eighteen patients with Class III or IV renal biopsies and chronicity indices <6 were prospectively randomized to receive 6 courses of parenteral cyclophosphamide over 8 months along with prednisone. Nine of these patients also received 3 daily plasmaphereses prior to each of the 6 courses of cyclophosphamide. Assessments compiled at 6 and 24 months included serum creatinine, albumin, anti DNA, 24-hour urine protein, and C3 complement along with SLAM scores. RESULTS: Two out of nine patients in each group evolved end stage renal disease and 3/9 patients in each group went into a renal remission at 24 months. Serum albumin, C3 complement, and SLAM scores improved in both groups, and anti-DNA improved in the pulse/synchronization patients (P < 0.025). No intergroup comparisons were significant. CONCLUSION: The addition of pulse/synchronization apheresis to cyclophosphamide therapy does not improve the course of patients with proliferative lupus nephritis.

Adult↗
PubMed1992

Acute and subacute toxicity of 7.5% hypertonic saline/6% dextran-70 (HSD) in dogs. 1. Serum immunoglobulin and complement responses.

Clinical use of modern dextran solutions has been limited by concerns of anaphylactoid reactions. To assess the short-term antigenic response to 7.5% hypertonic saline in 6% Dextran-70 (HSD), sera were obtained from dogs involved in the acute and subacute toxicology testing of HSD and its individual components, and analyzed for IgG, IgM and C3 complement. In separate studies, beagles were infused i.v. with a single dose of HSD or its components at 20 ml kg-1 (the maximum tolerated dose; MTD), or the MTD daily for 14 days, and serum was obtained prior to and at various times after infusion up to 14 days. In both studies, despite serum dextran concentrations exceeding 2000 mg dl-1, no induction of IgG, IgM or C3 complement concentrations were observed. In addition, serum IgG immunoelectrophoretic patterns were of normal curvature, position and intensity; the immunoprecipitin bands were not displaced, bowed, inhibited or thicker than the normal preinfusion immunoelectrophoretograms. The data suggest that single or multiple HSD i.v. injections, as much as five times the proposed therapeutic level for the treatment of hypovolemia, evoked no increase in antibody titers in dogs. Therefore, therapeutic use of HSD in the treatment of hemorrhagic shock should not be associated with widespread concomitant allergic complications.

Animals↗
PubMed1990

Complement activation in systemic sclerosis.

The use of a synthetic protease inhibitor, nafamstat mesilate, has enabled reliable estimations of in vivo complement activation to be made in patients with systemic sclerosis. Elevations of C3a and C4a anaphylatoxins were found in 2 and 24 out of 30 patients respectively, indicating that complement activation, predominantly by the classical pathway, is a common occurrence in the disease, even though complement C3 and C4 levels were within the reference range.

Adult↗
PubMed1976

Surface markers on human B and T-lymphocytes. IX. Two-color immunofluorescence studies on the association between ebv receptors and complement receptors on the surface of lymphoid cell lines.

Receptors for the third component of complement (C3) were demonstrated on the surface of established human lymphoid cell lines by a membrane fluorescence test with FITC- or TRITC-conjugated antibodies against human C3. Two-color fluorescence staining of EBV receptors and C3 receptors showed complete overlapping of green and red fluorescence. Capping of the EBV receptor induced co-capping of the C3 receptor and vice versa. There was neither overlapping nor co-capping when EBV or C3 receptors were examined in relation to Fc receptors, surface IgM or beta2 microglobulin. The kinetic pattern of EBV receptor capping was identical with the pattern of C3 receptor capping but differed from the pattern of IgM capping. These results suggest a close association between EBV and C3 receptors on the human B-lymphocyte.

B-Lymphocytes↗