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PubMed2000

The application of human complement factor H-related protein (BTA TRAK) in monitoring patients with bladder cancer.

The BTA TRAK assay is a quantitative sandwich format enzyme immunoassay performed in a reference laboratory. It measures levels of human complement factor H-related protein (hCFHrp) which is similar to human complement factor H. Test characteristics reveal an overall sensitivity of 68% to 77.5% and a specificity of 50%-75%. Retrospective analysis of urine specimens employing hazard analysis suggests that BTA TRAK may have a role as a quantitative diagnostic marker in monitoring bladder cancer patients. Prospective studies are required to validate this application and other uses of the BTA TRAK assay in the management of bladder cancer patients.

Antigens, Neoplasm↗
PubMed1983

[B, C2 and C4 complement factors, the HLA system and diseases. Genetic relation].

Close linkage of the complement factor loci C2, C4 and Bf to HLA loci has been firmly documented. A review of the literature was made about genetic defects of these components associated with a variety of disorders, especially immunologic diseases. Some allotypes of these factors are also closely linked to several diseases. Relationship between these diseases and the genes controlling the synthesis of C2, C4 and Bf and their allelic variants is not yet known but this association suggested several pathogenic hypotheses.

Complement C2↗
PubMed1995

Crystal structure of a complement factor D mutant expressing enhanced catalytic activity.

Complement factor D is a serine protease regulated by a novel mechanism that depends on conformational changes rather than cleavage of a zymogen for expression of proteolytic activity. The conformational changes are presumed to be induced by the single natural substrate, C3bB, and to result in reversible reorientation of the catalytic center and of the substrate binding site of factor D, both of which have atypical conformations. Here we report that replacement of Ser94, Thr214, and Ser215 of factor D (chymotrypsinogen numbering has been used for comparison purposes) with the corresponding residues of trypsin, Tyr, Ser, and Trp, is sufficient to induce substantially higher catalytic activity associated with a typical serine protease alignment of the catalytic triad residues His57, Asp102, and Ser195. These results provide a partial structural explanation for the low reactivity of "resting-state" factor D toward synthetic substrates.

Amino Acid Sequence↗
PubMed2006

Complement factor H: spatial and temporal expression and localization in the eye.

PURPOSE: Complement factor H (CFH) is a component of the mammalian complement system, which regulates the alternative pathway of complement activation and protects the host cell from inappropriate complement activation. CFH is a key regulator of innate immunity, and CFH deficiency leads to membranoproliferative glomerulonephritis type II. A variation in human CFH, Y402H, has been shown to be associated with an increased risk for age-related macular degeneration. The authors describe studies on the spatial and temporal expression of the CFH gene and localization of this protein in ocular tissues to gain insight into its role in the eye. METHODS: CFH expression in human and mouse tissues was studied by quantitative RT-PCR and Western blot analysis, and localization of CFH was studied by immunohistochemical analysis followed by fluorescence microscopy. RESULTS: In human and mouse, CFH expression was found to be similar to the highest level of expression in the liver. In ocular tissue, CFH was detected in the distalmost optic nerve (3 mm) cut from the scleral surface of the eyeball, sclera, RPE-choroid, retina, lens, and ciliary body. In mouse, Cfh expression was observed from early embryonic stages, and in the eye its expression increased with age. CONCLUSIONS: A significant level of CFH expression is maintained in different ocular tissues during development and aging. Sustained high levels of CFH expression in eye tissues suggest that this protein may play a role in protecting these tissues from indiscriminate complement activation and inflammatory insult.

Aged↗
PubMed1992

Two additional human serum proteins structurally related to complement factor H. Evidence for a family of factor H-related genes.

We identify and characterize two human serum proteins with an apparent molecular mass of 24 and 29 kDa, which are antigenically related to complement factor H. These proteins represent differently glycosylated forms and are encoded by the same mRNA. The corresponding cDNA clone is 1051 bp in size and hybridized to a 1.4-kb mRNA derived from human liver. The predicted translation product represents a protein of 270 amino acids, which displays a hydrophobic leader sequence, indicative of a secreted protein. The secreted part is organized in four short consensus repeats (SCR) and has a single putative N-linked glycosylation site. This predicted sequence is closely related to that of the previously described factor H-related proteins h37 and h42, which are also derived from a 1.4-kb mRNA. Amino acid comparison of these factor H-related proteins showed identical leader sequences, an exchange of three amino acids in SCR1, identical sequences of SCR2, and a lower degree of homology between SCR3-4 (h24 and h29) and SCR4-5 (h37 and h42). In addition, SCR3-4 of h24 and h29 display homology to SCR19-20 of human complement factor H. The relatedness of structural elements of the factor H-related proteins h24, h29, h37, and h42 and of factor H, suggests a function common to these proteins and indicates the existence of a gene family consisting of factor H and at least two factor H-related genes.

Amino Acid Sequence↗
PubMed1994

Molecular cloning of a lamprey homologue of the mammalian MHC class III gene, complement factor B.

To elucidate the origin and evolution of the complement system and the MHC, we isolated cDNA clones for the MHC class III complement factor B (Bf) gene from lamprey, one of the most primitive extant vertebrates. A part of the serine protease domain of the lamprey Bf was amplified by reverse transcriptase-PCR using the degenerated primers corresponding to the conserved amino acid stretches between the mouse Bf and C2 sequences. A full-length lamprey Bf cDNA clone was isolated from the lamprey liver cDNA library using a PCR-amplified DNA clone as a probe. The deduced amino acid sequence of 763 residues showed essentially the same domain structure as mammalian Bf or C2, consisting of three short consensus repeat domains, a von Willebrand domain, and a serine protease domain. Lamprey Bf showed 33 and 29% overall amino acid similarity to mouse Bf and mouse C2, respectively, whereas amino acid similarity between mouse Bf and mouse C2 was 36%, suggesting that the gene duplication of Bf/C2 occurred in the main line of vertebrate evolution after the divergence of cyclostomes. This is the first report of the molecular cloning from cyclostomes of a component of the mammalian MHC that offers the possibility of genetic analysis of the presumably primitive MHC of cyclostomes.

Amino Acid Sequence↗
PubMed1999

Familial relapsing haemolytic uraemic syndrome and complement factor H deficiency.

BACKGROUND: In a recent study of three families we have found that inherited haemolytic uraemic syndrome (HUS) maps to a region of chromosome 1q containing the gene for complement factor H. In one of these families and also in a case of sporadic D-HUS, we have identified mutations in the factor H gene. A further family with inherited HUS has therefore been investigated. METHODS: DNA extracted from the family members and DNA extracted from archival post-mortem material from a deceased family member, was studied. Review of renal biopsies and study of complement components was also undertaken. RESULTS: This family demonstrates an inherited deficiency of complement factor H. Non-diarrhoeal HUS has affected at least two family members with half normal levels of factor H. CONCLUSION: These findings represent further evidence of the association between factor H dysfunction and HUS.

Adolescent↗
PubMed2006

Individuals homozygous for the age-related macular degeneration risk-conferring variant of complement factor H have elevated levels of CRP in the choroid.

Polymorphisms in the complement factor H gene (CFH) are associated with a significantly increased risk for, or protection against, the development of age-related macular degeneration (AMD). The most documented risk-conferring single-nucleotide polymorphism results in a tyrosine-to-histidine substitution at position 402 (Y402H) of the CFH protein. In this work, we examined the ocular distributions and relative abundance of CFH, several CFH-binding proteins, and abundant serum proteins in the retinal pigmented epithelium (RPE), Bruch's membrane, and choroid (RPE-choroid) in CFH homozygotes possessing either the "at-risk" 402HH or "normal" 402YY variants. Although CFH immunoreactivity is high in the choroid and in drusen, no differences in CFH-labeling patterns between genotypes are apparent. In contrast, at-risk individuals have significantly higher levels of the CFH-binding protein, C-reactive protein (CRP), in the choroidal stroma. Immunoblots confirm that at-risk individuals have approximately 2.5-fold higher levels of CRP in the RPE-choroid; no significant differences in the levels of CFH or other serum proteins are detected. Similarly, we find no differences in CFH transcription levels in the RPE-choroid nor evidence for local ocular CRP transcription. Increased levels of CRP in the choroid may reflect a state of chronic inflammation that is a by-product of attenuated CFH complement-inhibitory activity in those who possess the CFH at-risk allele. Because the CRP-binding site in CFH lies within the domain containing the Y402H polymorphism, it is also possible that the AMD risk-conferring allele alters the binding properties of CFH, thereby leading to choroidal CRP deposition, contributing to AMD pathogenesis.

Age Distribution↗
PubMed2004

HIV-1 induces complement factor C3 synthesis in astrocytes and neurons by modulation of promoter activity.

Virus-induced complement expression and activation in the brain is hypothesized to contribute to the process of neurodegeneration in AIDS-associated neurological disorders. Previous experiments have shown that the human immunodeficiency virus (HIV) upregulates the low basal production of complement factor C3 in astrocytes and neurons. Since inhibition of complement synthesis and activation in the brain may represent a putative therapeutic goal to prevent virus-induced damage, we analysed the mechanism of the HIV-induced modulation of C3 expression. Detailed studies using different C3 promoter constructs revealed that HIV activates the synthesis of C3 by stimulation of the promoter. This HIV-induced promoter activation could be measured both in different astrocytic cell lines and in neurons. Deletion constructs of the C3 promoter defined the IL-6/IL-1beta responsive element within the promoter region as a central element for the responsiveness of the C3 promoter towards the influence of HIV. A binding site for the transcription factor C/EBPdelta was identified as important regulatory domain within the IL-6/IL-1beta responsive element, since a point mutation which eliminates the binding capacity of C/EBPdelta to this site also abolishes the induction by HIV-1. Similarly, the viral proteins Nef and gp41 which had also been shown to stimulate the synthesis of C3, exert their effect via the IL-6/IL-1beta responsive element with binding of the transcription factor C/EBPdelta representing the critical step. Our experiments clearly define the mechanism for the induction of complement factors in the HIV-infected brain and reveal a decisive role of the regulator protein C/EBPdelta for the HIV-induced increase in C3 expression.

Astrocytes↗
PubMed1995

Inhibition of degranulation of human polymorphonuclear leukocytes by complement factor D.

A degranulation inhibiting protein could be isolated from human plasma ultrafiltrate by a three-step purification method including ion-exchange chromatography, gelfiltration and affinity-chromatography. The protein was identified as complement factor D by means of sequence analysis. Its degranulation inhibiting activity was determined with regard to its effect on the FNLPNTL-induced lactoferrin secretion of human polymorphonuclear leukocytes. Complement factor D caused a dose-dependent decrease of the FNLPNTL-stimulated lactoferrin degranulation down to 34% of stimulated controls.

Amino Acid Sequence↗
PubMed2001

Human immunodeficiency virus type 1 induces expression of complement factors in human astrocytes.

Since the brain is separated from the blood immune system by a tight barrier, the brain-resident complement system may represent a central player in the immune defense of this compartment against human immunodeficiency virus (HIV). Chronic complement activation, however, may participate in HIV-associated neurodegeneration. Since the level of complement factors in the cerebrospinal fluid is known to be elevated in AIDS-associated neurological disorders, we evaluated the effect of HIV type 1 (HIV-1) on the complement synthesis of brain astrocytes. Incubation of different astrocytic cell lines and primary astrocytes with HIV-1 induced a marked upregulation of the expression of the complement factors C2 and C3. The synthesis of other secreted or membrane-bound complement proteins was not found to be altered. The enhancement of C3 production was measured both on the mRNA level and as secreted protein in the culture supernatants. HIV-1 laboratory strains as well as primary isolates were capable of inducing C3 production with varied effectiveness. The usage of viral coreceptors by HIV-1 was proved to be a prerequisite for the upregulation of C3 synthesis, which was modulated by the simultaneous addition of cytokines. The C3 protein which is secreted after incubation of the cells with HIV was shown to be biologically active as it can participate in the complement cascade.

Antibodies↗
PubMed1991

Human complement factor H: two factor H proteins are derived from alternatively spliced transcripts.

The human complement factor H is an important component in the control of the alternative pathway of complement activation. We have previously shown that a least three factor H homologous mRNA species of 4.3 kb, 1.8 kb and 1.4 kb in length are constitutively expressed in human liver. In addition, several factor H-related proteins have been detected in human sera using antibodies directed against the classical human factor H glycoprotein of 150 kDa. The structure of the additional polypeptides has not been shown so far. Circumstantial evidence suggests that the 1.8-kb mRNA might encode the 43-kDa factor H-like polypeptide. Here we report the isolation, characterization and eukaryotic expression of the first full-length cDNA representing the major 4.3-kb mRNA and the 1.8-kb mRNA of human factor H. We show that the 4.3-kb transcript encodes the 150-kDa-factor H glycoprotein and the 1.8-kb mRNA the 43-kDa factor H polypeptide. The identity of the two cDNA in a region of 1400 nucleotides suggests that the two factor H-related transcripts are derived from one gene by a process of alternative splicing.

Amino Acid Sequence↗
PubMed2005

Complement factor H Y402H gene polymorphism, C-reactive protein, and risk of incident myocardial infarction, ischaemic stroke, and venous thromboembolism: a nested case-control study.

OBJECTIVES: An exonic polymorphism (Y402H) in the complement factor H (CFH) gene, which locates within the binding sites for heparin and C-reactive protein, has recently been described and hypothesized to play an important role in atherothrombosis. METHODS: We, therefore, evaluated the CFH genetic variant Y402H amongst 685 Caucasian individuals who subsequently developed arterial or venous thrombotic event (incident myocardial infarction (MI), ischaemic stroke, or venous thromboembolism) and amongst 685 age- and smoking-matched Caucasian individuals who remained free of reported vascular disease during follow-up (controls) within the Physicians' Health Study cohort. RESULTS: Genotype distribution for the polymorphism tested was in Hardy-Weinberg equilibrium in the control group. In contrast to expected results, we found no association of Y402H polymorphism with risk of atherothrombosis (adjusted: myocardial infarction, OR=1.09, 95%CI 0.88-1.36, p=0.43; ischaemic stroke, OR=1.11, 95%CI 0.81-1.54, p=0.52; venous thromboembolism, OR=1.41, 95%CI 0.88-2.24, p=0.15), nor with baseline plasma C-reactive protein levels [median (interquartile range) mg/L: YY, 1.39 (0.70-2.60); YH, 1.10 (0.57-2.16); HH, 1.00 (0.48-1.79); p=0.14]. CONCLUSIONS: In this large, prospective cohort of apparently healthy Caucasian men, we found no association of the complement factor H Y402H gene polymorphism with risk of incident thromboembolic events, nor with baseline levels of C-reactive protein.

Adult↗
PubMed1999

Genetic polymorphism of human complement factor I (C3b inactivator) in the Chinese Han population.

The human complement factor I (IF) polymorphism has been analysed by polyacrylamide gel isoelectric focusing electrophoresis of neuraminidase-treated EDTA plasma samples followed by immunoblotting and enzymatic detection. In a population study among 121 random individuals from Chengdu, PR China, three different common phenotypes were observed. The results show that IF is polymorphic in the Chinese population. The allele frequencies were as follows: FI*A = 0.153, FI*B = 0.847. The distribution of observed phenotypes was in accordance with the Hardy-Weinberg equilibrium. In comparison to other Asian population studies, the frequency of the IF*A allele was the highest in the Chinese population studied here.

Alleles↗
PubMed1988

Molecular basis for the microheterogeneity of human complement factor B.

The involvement of sialic acids in the microheterogeneity of human complement factor B was investigated. Desialylation kinetics revealed all the charge intermediates from a complex native to a homogeneous form. The relation between this heterogeneity and posttranslational events was explored in cultured hepatoma cells. Intracellular factor B exhibited the same isoelectric focusing pattern as the desialylated purified protein, whereas a highly heterogeneous form was secreted. In contrast, when N-glycosylation was prevented by tunicamycin, both intracellular and secreted forms focused like intracellular factor B from control cultures. These data lead to the conclusion that the microheterogeneity of human factor B results from different degrees of sialylation of its N-glycans.

Carcinoma, Hepatocellular↗
PubMed2005

Hypothetical LOC387715 is a second major susceptibility gene for age-related macular degeneration, contributing independently of complement factor H to disease risk.

Age-related macular degeneration (AMD) is a multifactorial disease and a prevalent cause of visual impairment in developed countries. Risk factors include environmental components and genetic determinants. The complement factor H (CFH) has been the first major susceptibility gene for AMD identified within 1q32. Here, we focused on a second region of interest in 10q26 where a recent meta-analysis revealed strongest evidence for linkage to AMD at a genome-wide significance level. Within an interval of 22 Mb, we have analyzed 93 single nucleotide polymorphisms for allelic association with AMD in two independent case-control cohorts of German origin (AMD(combined) n=1166; controls(combined) n=945). Significant association was found across a 60 kb region of high linkage disequilibrium harboring two genes PLEKHA1 and hypothetical LOC387715. The strongest association (P=10(-34)) centered over a frequent coding polymorphism, Ala69Ser, at LOC387715, strongly implicating this gene in the pathogenesis of AMD. Besides abundant expression in placenta, we demonstrate weak expression of LOC387715 in the human retina. At present, however, there is no functional information on this gene, which appears to have evolved recently within the primate lineage. The joint contribution of the common risk allele at LOC387715, Ala69Ser, and at CFH, Tyr402His, was assessed in our case-control population, which suggests an additive model indicating an independent contribution of the two gene loci to disease risk. Our data show a disease odds ratio of 57.6 (95% CI: 37.2, 89.0) conferred by homozygosity for risk alleles at both CFH and LOC387715 when compared with the baseline non-risk genotype.

Base Sequence↗
PubMed2002

Complement factor B and the alternative pathway of complement activation in bovine milk.

The contribution of the alternative pathway of complement activation to the capacity of normal milk to deposit C3 fragments on bacteria was tested by attempting to block C3 deposition with antibodies to the alternative pathway component factor B (fB). Factor B was purified and antibodies of the IgY class, which does not activate mammalian complement, were obtained from the egg yolk of immunized laying hens. These antibodies specifically inhibited the deposition of C3. This inhibition and the absence of deposition of C4 demonstrated that C3 deposition in normal milk resulted from the activation of the alternative pathway. Antibodies raised in rabbit were used to develop an ELISA for measuring fB concentrations in milk. The mean concentration of fB was 2.06 microg/ml (+/- 0.18, SEM), 0.57% of the mean value found in serum (360 microg/ml). This proportion was comparable to that of serum albumin (0.63% of serum value) but less than the proportion of C3 in milk (2.71%). Nevertheless, fB was apparently not a limiting factor for the functioning of the alternative pathway, since addition of purified fB to normal milk did not improve C3 deposition. In serum, mild heat-treatment (56 degrees C for 3 min or 50 degrees C for 45 min) blocked the alternative pathway and destroyed fB, as shown by loss of antigenicity in ELISA. In milk, mild heat-treatment did not abrogate C3 deposition, and fB was protected, retaining its functionality and antigenicity. Heating at 56 degrees C for at least 45 min was necessary to completely inhibit C3 deposition in normal milk.

Animals↗
PubMed2005

Mutations in complement factor I predispose to development of atypical hemolytic uremic syndrome.

Mutations in the plasma complement regulator factor H (CFH) and the transmembrane complement regulator membrane co-factor protein (MCP) have been shown to predispose to atypical hemolytic uremic syndrome (HUS). Both of these proteins act as co-factors for complement factor I (IF). IF is a highly specific serine protease that cleaves the alpha-chains of C3b and C4b and thus downregulates activation of both the classical and the alternative complement pathways. This study looked for IF mutations in a panel of 76 patients with HUS. Mutations were detected in two patients, both of whom had reduced serum IF levels. A heterozygous bp change, c.463 G>A, which results in a premature stop codon (W127X), was found in one, and in the other, a heterozygous single base pair deletion in exon 7 (del 922C) was detected. Both patients had a history of recurrent HUS after transplantation. This is in accordance with the high rate of recurrence in patients with CFH mutations. Patients who are reported to have mutations in MCP, by contrast, do not have recurrence after transplantation. As with CFH- and MCP-associated HUS, there was incomplete penetrance in the family of one of the affected individuals. This study provides further evidence that atypical HUS is a disease of complement dysregulation.

Adult↗