Biomedical subjects

Seppo Meri

Publications and source records attributed to Seppo Meri.

At least 19 recordsLinked to original sources

PubMed2025

Antibiotic-resistant Acinetobacter baumannii can be killed by a combination of bacteriophages and complement.

Infections caused by multidrug-resistant Acinetobacter baumannii are an emerging global health threat. Although phages have shown promising results in treating bacterial infections, the mechanisms of the combined effect of phages and innate immunity on clearing A. baumannii remain unclear. Here, we report a synergistic effect of the complement system and phages on clearing multidrug-resistant A. baumannii. We show that A. baumannii rapidly adapts and becomes resistant to phage or serum complement by modifying the expression of capsule and lipooligosaccharides, which can be regulated through reversible transposon mutagenesis in the K locus. Compared to the encapsulated phenotype, the non-encapsulated, phage-resistant A. baumannii showed a higher level of membrane attack complex deposition and were susceptible to killing by complement. In contrast, the encapsulated phenotype escaped the complement system by shedding the membrane attack complex to the environment. Thus, while the complement system targets the non-encapsulated phenotype, the phage infects and eliminates the encapsulated subpopulation. These results suggest means of combatting antibiotic-resistant A. baumannii by a simultaneous treatment with phages and complement, a combination which can be supplemented further with antibacterial antibodies.

Acinetobacter baumannii↗

PubMed2006

Differential gene expression in non-malignant tumour microenvironment is associated with outcome in follicular lymphoma patients treated with rituximab and CHOP.

Rituximab in combination with chemotherapy (immunochemotherapy) is one of the most effective treatments available for follicular lymphoma (FL). This study aimed to determine whether differences in gene expression in FL tissue correlate with outcome in response to rituximab and CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone) chemotherapy (R-CHOP). We divided 24 patients into long- [time to treatment failure (TTF) >35 months] and short-term (TTF <23 months) responders, and analysed the gene expression profiles of lymphoma tissue using oligonucleotide microarrays. We used a supervised learning technique to identify genes correlating with outcome, and confirmed the expression of selected genes with quantitative polymerase chain reaction (qPCR) and immunohistochemistry. Among the transcripts with a high correlation between microarray and qPCR analyses, we identified EPHA1, a tyrosine kinase involved in transepithelial migration, SMAD1, a transcription factor and a mediator of bone morphogenetic protein and transforming growth factor-beta signalling, and MARCO, a scavenger receptor on macrophages. According to Kaplan-Meier estimates, high EPHA1, and low SMAD1 and MARCO expression were associated with better progression-free survival (PFS). Immunohistochemistry showed that EphA1 was primarily localised in granulocytes. In addition, both EphA1 and Smad1 were expressed in vascular endothelia. However, no difference in vasculature was detected between long- and short-term responders. In a validation set of 40 patients, a trend towards a better PFS was observed among patients with high EphA1 expression. We conclude that gene expression in non-malignant cells contributes to clinical outcome in R-CHOP-treated FL patients.

Adult↗

PubMed2006

Subtly impaired humoral immunity predisposes to frequently recurring genital herpes simplex virus type 2 infection and herpetic neuralgia.

BACKGROUND: Immunogenetic factors predisposing to recurrent genital herpes remain poorly characterized. METHODS: In a prospective case-control study, 52 consecutive patients with frequently recurring outbreaks of genital herpes were compared with 80 herpes simplex virus (HSV)-seropositive (types 1 and 2) and 70 HSV-seronegative control subjects. Immunoglobulins (Igs), type-specific anti-HSV-2 IgG and IgG subclass antibodies against glycoprotein G, levels of C3 and C4, and classical pathway hemolytic complement activity were measured, and IgG1 and IgG3 allotyping; C4 immunophenotyping; C4* real-time polymerase chain reaction (PCR) genotyping; and HLA-A*, B*, and DR* typing were performed. RESULTS: The G3m(g),G1m(a/a(x)) haplotype was more frequent in patients than in HSV-seronegative control subjects (P=.047). Compared with all control subjects, low levels of total IgG1 (odds ratio [OR], 4.9 [95% confidence interval {CI}, 2.0-12.5]; P=.001) and IgG3 (OR 3.6 [95% CI 1.7-7.8]; P=.001), but not of anti-HSV-2 antibodies, were associated with recurrences. Levels of complement were lowest in patients. The C4* null type was negatively associated with neuralgia (OR, 0.2 [95% CI, 0.06-0.81]; P=.022). CONCLUSIONS: Low levels of antibody-dependent cellular cytotoxicity-mediating IgG1 and IgG3 antibodies, partly dependent of allotype, may predispose to recurrent genital herpes. Antibodies produced by T helper type 1 responses, potentially against an unknown epitope, appear to be relevant in recurrences. In patients, C4* deficiencies are associated with protection from herpetic neuralgias, possibly through reduced inflammation.

Adult↗

PubMed2006

Analysis of variants in the complement factor H, the elongation of very long chain fatty acids-like 4 and the hemicentin 1 genes of age-related macular degeneration in the Finnish population.

PURPOSE: A strong association of a Tyr402His polymorphism in the complement factor H (CFH) gene and a Met299Val polymorphism in the elongation of very long chain fatty acids-like 4 (ELOVL4) gene with age-related macular degeneration (AMD) has been identified in Caucasian populations in the United States. Earlier a Gln5345Arg variant in the hemicentin 1 (HMCN1) gene was reported in a large AMD family in the United States. We wanted to investigate whether the polymorphisms of the CFH and the ELOVL4 genes or the mutation of the HMCN1 gene are associated with AMD in patients originating from the Finnish population with characteristics of a genetic isolate. METHODS: The material consisted of familial (n=181) and sporadic cases (n=154) with AMD, a control group with no AMD (non-AMD controls, n=105), and a control group of anonymous blood donors (blood donor controls, n =350). The DNA of the subjects was sequenced to analyze the variants of the three genes. RESULTS: We detected a strong association between the C/C-genotype compared to the T/T-genotype of Tyr402His polymorphism (first base of the Tyr-codon changes) of the CFH gene and AMD in the AMD cases compared to the non-AMD (p=8.86x10(-12)) or to blood donor controls (p=2.02x10(-13)). The frequency of the C/C genotype was significantly increased in both familial cases compared to non-AMD controls with non-adjusted odds ratio (OR) 10.1 (confidence intervals [CI] 95% 4.64-22.2) or compared to blood donor controls with non-adjusted OR 5.50 (CI 95% 3.17-9.55) and in sporadic cases with non-adjusted OR 9.33 (CI 95% 4.10-21.3; non-AMD-controls), OR 5.06 (CI 95% 2.75-9.28; blood donor controls). Frequency of C allele differed significantly between cases and controls (p=1.32x10(-11); non-AMD-controls and p=3.94x10(-14); blood donor controls). No association with AMD was detected with Met299Val polymorphism in the ELOVL4 gene in the familial or sporadic cases compared to non-AMD or blood donor controls. None of our subjects (258 AMD cases, 72 non-AMD controls) had the Gln5345Arg variant in the HMCN1 gene. CONCLUSIONS: The CFH gene polymorphism seems to be an important etiologic factor for AMD also in the isolated Finnish population.

Aged↗

PubMed2006

Complement regulation in human atherosclerotic coronary lesions. Immunohistochemical evidence that C4b-binding protein negatively regulates the classical complement pathway, and that C5b-9 is formed via the alternative complement pathway.

OBJECTIVE: The complement system is activated in human atherosclerotic lesions and may hence aggravate local inflammation. We studied the presence and localization of C4b-binding protein (C4bp), the major inhibitor of the classical complement pathway, in human atherosclerotic lesions in relation to complement activation products and protein S, which circulates in complex with C4bp. METHODS AND RESULTS: Immunohistochemistry of human coronary arteries showed C4bp to be virtually absent in normal arteries but present in early and advanced atherosclerotic lesions. In the lesions, C4bp is associated with proteoglycans, and affinity chromatography showed that C4bp interacts with human arterial proteoglycans. Areas containing C4bp also contained IgM and C4 suggesting that C4bp is involved in the regulation of the classical complement pathway. However, C5b-9 was virtually absent in these areas but, instead, colocalized with properdin deeper in the intima, suggesting that C5b-9 is formed by the alternative complement pathway. A fraction of C4bp was associated with protein S and apoptotic cells. CONCLUSIONS: The results indicate that C4bp regulates the classical complement pathway in human atherosclerotic lesions. Thus, unlike the alternative pathway, the classical complement pathway does not generate C5b-9, but is likely to be involved in the clean-up of apoptotic cells and cell debris in the arterial intima.

Apoptosis↗

PubMed2006

Structure of complement factor H carboxyl-terminus reveals molecular basis of atypical haemolytic uremic syndrome.

Factor H (FH) is the key regulator of the alternative pathway of complement. The carboxyl-terminal domains 19-20 of FH interact with the major opsonin C3b, glycosaminoglycans, and endothelial cells. Mutations within this area are associated with atypical haemolytic uremic syndrome (aHUS), a disease characterized by damage to endothelial cells, erythrocytes, and kidney glomeruli. The structure of recombinant FH19-20, solved at 1.8 A by X-ray crystallography, reveals that the short consensus repeat domain 20 contains, unusually, a short alpha-helix, and a patch of basic residues at its base. Most aHUS-associated mutations either destabilize the structure or cluster in a unique region on the surface of FH20. This region is close to, but distinct from, the primary heparin-binding patch of basic residues. By mutating five residues in this region, we show that it is involved, not in heparin, but in C3b binding. Therefore, the majority of the aHUS-associated mutations on the surface of FH19-20 interfere with the interaction between FH and C3b. This obviously leads to impaired control of complement attack on plasma-exposed cell surfaces in aHUS.

Complement C3b↗

PubMed2006

Complement C3 contributes to ethanol-induced liver steatosis in mice.

BACKGROUND: It is becoming increasingly clear that liver steatosis, a typical early consequence of alcohol exposure, sensitizes the liver to more severe inflammatory and fibrotic changes. On the other hand, activation of the key complement component C3, a central player in causing inflammation and tissue damage, is also known to be involved in the regulation of lipid metabolism. This prompted us to study the development of alcoholic liver steatosis in mice lacking C3 (C3-/-). RESULTS: Both C3-/- and normal C3+/+ mice were fed a steatosis-promoting high-fat diet with or without ethanol for 6 weeks. The diet without ethanol caused moderate liver steatosis in C3-/- but not in C3+/+ mice. As expected, ethanol-containing diet caused marked macrovesicular steatosis and increased the liver triglyceride content in C3+/+ mice. In contrast, ethanol diet tended to reduce steatosis and had no further effect on liver triglycerides in C3-/- mice. Furthermore, while in normal mice ethanol significantly increased the liver/body weight ratio, liver malondialdehyde level and serum alanine aminotransferase (ALT) activity, these effects were absent or small in C3-/- mice. A separate experiment with mice on chow diet confirmed the aberrant steatotic effect of ethanol in C3-/-mice: 4 hours after acute dosing of ethanol the liver triglyceride level had increased by 138% in C3+/+ mice (P<0.001), but only by 64% in C3-/- mice (n.s.). CONCLUSION: In C3-/- mice alcohol-induced liver steatosis is absent or strongly reduced after chronic or acute alcohol exposure. This suggests that the complement system and its component C3 contribute to the development of alcohol-induced fatty liver and its consequences.

Alanine Transaminase↗

PubMed2006

Tumor necrosis factor alpha enhances influenza A virus-induced expression of antiviral cytokines by activating RIG-I gene expression.

Epithelial cells of the lung are the primary targets for respiratory viruses. Virus-carried single-stranded RNA (ssRNA) can activate Toll-like receptors (TLRs) 7 and 8, whereas dsRNA is bound by TLR3 and a cytoplasmic RNA helicase, retinoic acid-inducible protein I (RIG-I). This recognition leads to the activation of host cell cytokine gene expression. Here we have studied the regulation of influenza A and Sendai virus-induced alpha interferon (IFN-alpha), IFN-beta, interleukin-28 (IL-28), and IL-29 gene expression in human lung A549 epithelial cells. Sendai virus infection readily activated the expression of the IFN-alpha, IFN-beta, IL-28, and IL-29 genes, whereas influenza A virus-induced activation of these genes was mainly dependent on pretreatment of A549 cells with IFN-alpha or tumor necrosis factor alpha (TNF-alpha). IFN-alpha and TNF-alpha induced the expression of the RIG-I, TLR3, MyD88, TRIF, and IRF7 genes, whereas no detectable TLR7 and TLR8 was seen in A549 cells. TNF-alpha also strongly enhanced IKK epsilon mRNA and protein expression. Ectopic expression of a constitutively active form of RIG-I (deltaRIG-I) or IKK epsilon, but not that of TLR3, enhanced the expression of the IFN-beta, IL-28, and IL-29 genes. Furthermore, a dominant-negative form of RIG-I inhibited influenza A virus-induced IFN-beta promoter activity in TNF-alpha-pretreated cells. In conclusion, IFN-alpha and TNF-alpha enhanced the expression of the components of TLR and RIG-I signaling pathways, but RIG-I was identified as the central regulator of influenza A virus-induced expression of antiviral cytokines in human lung epithelial cells.

Cell Line, Tumor↗

PubMed2006

Complement activation associates with saccular cerebral artery aneurysm wall degeneration and rupture.

OBJECTIVE: Saccular cerebral artery aneurysm (SCAA) wall degeneration and inflammatory cell infiltrations associate with aneurysm rupture and subarachnoid hemorrhage, resulting in a devastating form of stroke. The complement system is the key mediator of inflammation and household processing of injured tissue. We studied how complement activation associates with SCAA wall degeneration and rupture to better understand the pathobiology of SCAA wall rupture. METHODS: Unruptured (n = 26) and ruptured (n = 32) SCAA fundi resected after microsurgical clipping were studied by immunostaining for complement activation (membrane attack complex [MAC]) and by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling reaction for related cell death. Complement activation was correlated with clinical and other histological parameters. Electromicroscopy and immunoelectron microscopy were used for locating MAC depositions at the ultrastructural level. RESULTS: MAC localized consistently in a decellularized layer in the outer SCAA wall, and was found in all SCAA samples. The percentage of MAC-positive area relative to the total SCAA wall surface area (range, 5-77%) was greater in ruptured (n = 25; median, 39%) than in unruptured SCAAs (n = 18; median, 20%; P = 0.005). It also associated significantly with SCAA wall degeneration (P < 0.001), de-endothelialization(P < 0.001), and CD163+ macrophage (P = 0.023) and T-lymphocyte (P = 0.030) infiltrations. Apoptotic terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling-positive nuclei and MAC were located at the same wall areas in four out of 14 double-stained samples, but no double-positive cells were found. Electromicroscopy and immunoelectron microscopy of an unruptured SCAA showed cell death in the MAC-positive layers in the outer SCAA wall. CONCLUSION: These data suggests that complement activation and MAC formation are involved in SCAA wall degeneration and rupture.

Adolescent↗

PubMed2005

Rhinovirus/enterovirus RNA in tonsillar tissue of children with tonsillar disease.

BACKGROUND: Human rhinoviruses (HRVs) together with the closely related human enteroviruses (HEVs) cause most of the acute respiratory illnesses throughout the year. HRVs have been detected in most parts of the respiratory tract but not in pharyngeal tonsils. OBJECTIVES: We aimed to find out whether HRVs were detectable in tonsillar tissue and if their presence correlated to the tonsillar disease. STUDY DESIGN: Thirty-three tonsillar samples collected in February-March 2003 from children with no acute respiratory symptoms were studied with HRV in situ hybridization (HRV-ISH). Ten tonsillar samples were further examined in a separate laboratory by two different reverse transcription polymerase chain reaction (RT-PCR) methods designed for detection of HRV/HEV RNA. RESULTS: Twenty of the 33 samples (62%) were positive by HRV-ISH. Five positive and five negative HRV-ISH samples were investigated by two different PCR methods. HRV/HEV RNA was detected in 9 of the 10 specimens by a hanging drop-nested PCR. One HRV-ISH negative sample was positive by a conventional non-nested PCR. One of the samples studied by all three methods, from a patient with recurrent tonsillitis, had no detectable HRV/HEV RNA. Positive result in HRV-ISH did not correlate significantly with underlying tonsillar disease, history of respiratory infections or bronchial asthma. Altogether HRV/HEV RNA was detected in 75% of the tonsils with no correlation to patients' operation indication or history of respiratory diseases. CONCLUSIONS: In February-March, HRV/HEV RNA was frequently found in tonsillar tissue in children irrespective of the tonsillar pathology. Whether detection of the RNA is a marker of chronic infection or is merely remnant of past infection is not known.

Adolescent↗

PubMed2005

Complement regulator-acquiring surface protein 1 imparts resistance to human serum in Borrelia burgdorferi.

Factor H and factor H-like protein 1 (FH/FHL-1) are soluble serum proteins that negatively regulate the alternative pathway of complement. It is now well recognized that many pathogenic bacteria, including Borrelia burgdorferi, bind FH/FHL-1 on their cell surface to evade complement-mediated destruction during infection. Recently, it was suggested that B. burgdorferi open reading frame bbA68, known as complement regulator-acquiring surface protein 1 (CRASP-1), encodes the major FH/FHL-1-binding protein of B. burgdorferi. However, because several other proteins have been identified on the surface of B. burgdorferi that also can bind FH/FHL-1, it is presently unclear what role CRASP-1 plays in serum resistance. To examine the contribution of CRASP-1 in serum resistance, we generated a B. burgdorferi mutant that does not express CRASP-1. The B. burgdorferi CRASP-1 mutant, designated B31cF-CRASP-1, was found to be as susceptible to human serum as a wild-type strain of Borrelia garinii 50 known to be sensitive to human serum. To further examine the role of CRASP-1 in serum resistance, we also created a shuttle vector that expresses CRASP-1 from the native B. burgdorferi gene, which was designated pKFSS-1::CRASP-1. When the pKFSS-1::CRASP-1 construct was transformed into the B. burgdorferi B31cF-CRASP-1 mutant, wild-type levels of serum resistance were restored. Additionally, when pKFSS-1::CRASP-1 was transformed into the serum-sensitive B. garinii 50 isolate, human serum resistance was imparted on this strain to a level indistinguishable from wild-type B. burgdorferi. The combined data led us to conclude that CRASP-1 expression is necessary for B. burgdorferi to resist killing by human serum.

Bacterial Proteins↗

PubMed2005

Comparison of surface recognition and C3b binding properties of mouse and human complement factor H.

Factor H (FH) is a central complement regulator both in plasma and on certain cellular and acellular surfaces that are in contact with plasma. Although FH deficiency has been shown to lead to similar diseases in man and mice (membranoproliferative glomerulonephritis or dense deposit disease) little is known about the similarity between the human and murine FH functions. We here characterize the interactions of murine FH (mFH) with C3b, glycosaminoglycans, and endothelial cells and compare these interactions with those of human FH (hFH). To achieve this we purified mFH and murine C3 from plasma, prepared murine C3b, and expressed recombinant mFH constructs containing domains 1-5 and 18-20 (mFH1-5 and mFH18-20). For comparisons, hFH, human C3b, and recombinant hFH1-5 and hFH18-20 were used. We demonstrate that mFH and mFH1-5 do act as cofactors for factor I-mediated cleavage of human C3b. Surface plasmon resonance analysis showed binding of mFH18-20 to murine C3b and weak binding to human C3b. The mFH18-20 construct bound to heparin in a manner comparable to hFH18-20. It was demonstrated by flow cytometry that mFH and mFH18-20 bind to human endothelial cells in a similar manner to hFH and hFH18-20. Taken together, locations of the key functions of mFH, i.e. complement regulation and surface recognition, are comparable to hFH. Recently, mutations in the carboxy-terminal end of hFH have been found to be associated with atypical hemolytic uremic syndrome (aHUS). Based on the results in this report it is conceptually attractive to establish a murine model for aHUS.

Animals↗

PubMed2005

Binding of the complement inhibitor C4bp to serogroup B Neisseria meningitidis.

Neisseria meningitidis (meningococcus) is an important cause of meningitis and sepsis. Currently, there is no effective vaccine against serogroup B meningococcal infection. Host defense against neisseriae requires the complement system (C) as indicated by the fact that individuals deficient in properdin or late C components (C6-9) have an increased susceptibility to recurrent neisserial infections. Because the classical pathway (CP) is required to initiate efficient complement activation on neisseriae, meningococci should be able to evade it to cause disease. To test this hypothesis, we studied the interactions of meningococci with the major CP inhibitor C4b-binding protein (C4bp). We tested C4bp binding to wild-type group B meningococcus strain (H44/76) and to 11 isogenic mutants thereof that differed in capsule expression, lipo-oligosaccharide sialylation, and/or expression of either porin (Por) A or PorB3. All strains expressing PorA bound radiolabeled C4bp, whereas the strains lacking PorA bound significantly less C4bp. Increased binding was observed under hypotonic conditions. Deleting PorB3 did not influence C4bp binding, but the presence of polysialic acid capsule reduced C4bp binding by 50%. Bound C4bp remained functionally active in that it promoted the inactivation of C4b by factor I. PorA-expressing strains were also more resistant to C lysis than PorA-negative strains in a serum bactericidal assay. Binding of C4bp thus helps Neisseria meningitidis to escape CP complement activation.

Amino Acid Sequence↗

PubMed2005

C-reactive protein binds to the 3beta-OH group of cholesterol in LDL particles.

C-reactive protein (CRP) has been suggested to contribute to the development of atherosclerosis. We previously found binding of CRP to cholesterol in modified low density lipoprotein (LDL) particles. Here, we characterize the interaction between CRP and cholesterol in more detail. When lipids of native LDL were separated by thin-layer chromatography, CRP bound only to cholesterol. When various cholesterol analogues were compared for their ability to bind CRP, we found that any modification of the 3beta-OH group blocked binding of CRP to cholesterol. Similarly, enrichment of LDL with cholesterol but not with its analogues triggered the binding of CRP to LDL. Finally, with the aid of anti-CRP monoclonal antibodies and by molecular modeling, we obtained evidence for involvement of the phosphorylcholine-binding site of CRP in cholesterol binding. Thus, CRP can bind to cholesterol, and the interaction is mediated by the phosphorylcholine-binding site of CRP and the 3beta-hydroxyl group of cholesterol.

C-Reactive Protein↗

PubMed2005

IFN-alpha enhances TLR3-mediated antiviral cytokine expression in human endothelial and epithelial cells by up-regulating TLR3 expression.

TLRs play a critical role in early innate immune response to virus infection. TLR3 together with TLR7 and TLR8 constitute a powerful system to detect genetic material of RNA viruses. TLR3 has been shown to bind viral dsRNA whereas TLR7 and TLR8 are receptors for viral single-stranded RNA. In this report we show that TLR7 or TLR8 are not expressed in human epithelial A549 cells or in HUVECs. Accordingly, A549 cells and HUVECs were unresponsive to TLR7/8 ligand R848. TLR3 was expressed at a higher level in HUVECs than in A549 cells. The TLR3 ligand poly(I:C) up-regulated IFN-beta, IL-28, IL-29, STAT1, and TLR3 expression in HUVECs but not in A549 cells. An enhanced TLR3 expression by transfection or by IFN-alpha stimulation conferred poly(I:C) responsiveness in A549 cells. Similarly, IFN-alpha pretreatment strongly enhanced poly(I:C)-induced activation of IFN-beta, IL-28, and IL-29 genes also in HUVECs. In conclusion, our results suggest that IFN-alpha-induced up-regulation of TLR3 expression is involved in dsRNA activated antiviral response in human epithelial and endothelial cells.

Cell Line, Tumor↗

PubMed2005

Membranoproliferative glomerulonephritis type II (dense deposit disease): an update.

Membranoproliferative glomerulonephritis type II (MPGN II) is a rare disease characterized by the deposition of abnormal electron-dense material within the glomerular basement membrane of the kidney and often within Bruch's membrane in the eye. The diagnosis is made in most patients between the ages of 5 and 15 yr, and within 10 yr, approximately half progress to end-stage renal disease, occasionally with the late comorbidity of visual impairment. The pathophysiologic basis of MPGN II is associated with the uncontrolled systemic activation of the alternative pathway (AP) of the complement cascade. In most patients, loss of complement regulation is caused by C3 nephritic factor, an autoantibody directed against the C3 convertase of the AP, but in some patients, mutations in the factor H gene have been identified. For the latter patients, plasma replacement therapy prevents renal failure, but for the majority of patients, there is no proven effective treatment. The disease recurs in virtually all renal allografts, and a high percentage of these ultimately fail. The development of molecular diagnostic tools and new therapies directed at controlling the AP of the complement cascade either locally in the kidney or at the systemic level may lead to effective treatments for MPGN II.

Child↗

PubMed2005

Complement factor H as a marker for detection of bladder cancer.

BACKGROUND: The BTA TRAK and BTA stat tests for bladder cancer use monoclonal antibodies (mAbs) X13.2 and X52.1 to detect factor H (FH)-related material in urine. The exact ligands remain unknown. METHODS: Western blot analyses of purified FH, recombinant factor H-related protein 1 (FHR-1), and serum and urine samples were used to identify the ligands of X13.2 and X52.1. Recombinant FH constructs were used to identify the target sites of X13.2 and X52.1. To analyze whether natural ligands of FH could compete with its recognition by the capture mAb X52.1, we used surface plasmon resonance analysis. The role of the ligands of X52.1 in the BTA TRAK assay was tested with use of purified proteins and FH-depleted samples. RESULTS: X13.2 bound to domain 3 of FH and FH-like protein 1, whereas X52.1 bound to domain 18 of FH and to FHR-1. Using specific FH depletion from a bladder cancer patient's urine and purified FH, we demonstrated that FH is the ligand recognized by the BTA TRAK test. By contrast, FHR-1 in urine reduced the FH-dependent test signal. CONCLUSIONS: FH is a tumor marker for bladder cancer. To reveal the presence of bladder cancer, the BTA TRAK assay detects FH, whereas FHR-1 is able to partly inhibit this detection. This indicates a special mechanism for a diagnostic immunoassay based on the combined effect of simultaneous positive and negative signals in a single sample.

Antibodies, Monoclonal↗

PubMed2005

Human keratinocytes produce the complement inhibitor factor H: synthesis is regulated by interferon-gamma.

Locally synthesized complement is believed to play an important role in host defense and inflammation at organ level. In the epidermis, keratinocytes have so far been shown to synthesize two complement components, C3 and factor B. Here, we studied the synthesis of factor H by human keratinocytes. We also studied the regulation of factor H synthesis in keratinocytes by several cytokines, namely IL-1alpha, IL-2, IL-6, TGF-beta1, TNF-alpha and IFN-gamma. Human keratinocytes expressed factor H mRNA and constitutively released small amounts of factor H protein into the culture medium. This release was strongly upregulated by IFN-gamma but not by other cytokines tested. Western blot analysis revealed that IFN-gamma augments the synthesis of both molecular species, factor H (FH; 155kDa) and factor H-like protein-1 (FHL-1; 45kDa), of factor H. Factor H released in response to IFN-gamma was functionally active. In conclusion, we demonstrate that keratinocytes are capable of synthesizing factor H and that this synthesis is regulated by IFN-gamma.

Blotting, Western↗