Polyphosphate is a novel cofactor for regulation of complement by a serpin, C1 inhibitor.

The complement system plays a key role in innate immunity, inflammation, and coagulation. The system is delicately balanced by negative regulatory mechanisms that modulate the host response to pathogen invasion and injury. The serpin, C1-esterase inhibitor (C1-INH), is the only known plasma inhibitor of C1s, the initiating serine protease of the classical pathway of complement. Like other serpin-protease partners, C1-INH interaction with C1s is accelerated by polyanions such as heparin. Polyphosphate (polyP) is a naturally occurring polyanion with effects on coagulation and complement. We recently found that polyP binds to C1-INH, prompting us to consider whether polyP acts as a cofactor for C1-INH interactions with its target proteases. We show that polyP dampens C1s-mediated activation of the classical pathway in a polymer length- and concentration-dependent manner by accelerating C1-INH neutralization of C1s cleavage of C4 and C2. PolyP significantly increases the rate of interaction between C1s and C1-INH, to an extent comparable to heparin, with an exosite on the serine protease domain of the enzyme playing a major role in this interaction. In a serum-based cell culture system, polyP significantly suppressed C4d deposition on endothelial cells, generated via the classical and lectin pathways. Moreover, polyP and C1-INH colocalize in activated platelets, suggesting that their interactions are physiologically relevant. In summary, like heparin, polyP is a naturally occurring cofactor for the C1s:C1-INH interaction and thus an important regulator of complement activation. The findings may provide novel insights into mechanisms underlying inflammatory diseases and the development of new therapies.

Identification and characterization of C1 inhibitor in Nile tilapia (Oreochromis niloticus) in response to pathogenic bacteria.

C1 inhibitor (C1INH) is a multi-functional serine protease inhibitor in plasmatic cascades, not only inactivating various proteases, but also regulating both complement and contact system activation. In this study, we described the identification and characterization of a C1INH ortholog from Nile tilapia (Oreochromis niloticus) at molecular, protein and cellular levels. The full-length cDNA of Oreochromis niloticus C1INH (OnC1INH) consisted of 1791 bp of nucleotide sequence encoding polypeptides of 596 amino acids. The deduced protein possessed a serpin domain at the C-terminal domain, and two Ig-like domains in the N-terminal domain with significant homology to teleost. Expression analysis revealed that the OnC1INH was extremely highly expressed in the liver; however, much weakly exhibited in other tissues including spleen, kidney, blood and heart. After the in vivo challenges of the lipopolysaccharide (LPS) and Streptococcus agalactiae, the expression of OnC1INH was significantly up-regulated in liver and spleen at the late phase, which was confirmed at the protein level with immunohistochemical analysis. The up-regulation of OnC1INH expression was also demonstrated in head kidney monocytes/macrophages in vitro stimulated with LPS, Aeromonas hydrophila and Streptococcus agalactiae, which was positively correlated with the protein expression pattern in the culture media. Taken together, the results of this study indicated that OnC1INH might be involved in the immune response of Nile tilapia against to bacterial challenge.

The Levels of the Lectin Pathway Serine Protease MASP-1 and Its Complex Formation with C1 Inhibitor Are Linked to the Severity of Hereditary Angioedema.

C1 inhibitor (C1-INH) is known to form complexes with the lectin complement pathway serine proteases MASP-1 and MASP-2. Deficiency of C1-INH is associated with hereditary angioedema (HAE), an autosomal inherited disease characterized by swelling attacks caused by elevated levels of bradykinin. MASP-1 was shown to cleave high m.w. kininogen into bradykinin; therefore, we hypothesized that MASP-1 levels and the quantity of MASP-1/C1-INH complexes might be associated with different paraclinical and clinical outcomes of HAE. We measured MASP-1 serum concentrations and endogenous MASP-1/C1-INH complex levels in 128 HAE patients and 100 controls. Relatively high levels of pre-existing MASP-1/C1-INH complexes were observed in normal serum, and we found that both the serum levels of MASP-1 and the complex formation between MASP-1 and C1-INH were significantly reduced in HAE patients compared with matched controls (p < 0.0001). The level of MASP-1 and MASP-1/C1-INH complexes in HE patients correlated with the level of C1-INH (p = 0.0009 and p = 0.0047, respectively), the level of C4 (p = 0.0084 and p < 0.0001, respectively), and the number of attacks in the year of blood sampling (p = 0.0075 and p = 0.0058, respectively). In conclusion, we show that MASP-1/C1-INH complexes circulate in normal human blood. The levels of MASP-1 and MASP-1/C1-INH complexes are reduced in HAE patients compared with controls. Both MASP-1 and MASP-1/C1-INH complexes are related to the degree of complement C4 consumption, as well as the severity of disease. These results suggest that MASP-1 may exert a previously unrecognized role in the pathophysiology of HAE.

Human C1-Inhibitor Suppresses Malaria Parasite Invasion and Cytoadhesion via Binding to Parasite Glycosylphosphatidylinositol and Host Cell Receptors.

Plasmodium falciparum-induced severe malaria remains a continuing problem in areas of endemicity, with elevated morbidity and mortality. Drugs targeting mechanisms involved in severe malaria pathology, including cytoadhesion of infected red blood cells (RBCs) to host receptors and production of proinflammatory cytokines, are still necessary. Human C1-inhibitor (C1INH) is a multifunctional protease inhibitor that regulates coagulation, vascular permeability, and inflammation, with beneficial effects in inflammatory disease models, including septic shock. We found that human C1INH, at therapeutically relevant doses, blocks severe malaria pathogenic processes by 2 distinct mechanisms. First, C1INH bound to glycan moieties within P. falciparum glycosylphosphatidylinositol (PfGPI) molecules on the parasite surface, inhibiting parasite RBC invasion and proinflammatory cytokine production by parasite-stimulated monocytes in vitro and reducing parasitemia in a rodent model of experimental cerebral malaria (ECM) in vivo. Second, C1INH bound to host CD36 and chondroitin sulfate A molecules, interfering with cytoadhesion of infected RBCs by competitive binding to these receptors in vitro and reducing sequestration in specific tissues and protecting against ECM in vivo. This study reveals that C1INH is a potential therapeutic antimalarial molecule able to interfere with severe-disease etiology at multiple levels through specific interactions with both parasite PfGPIs and host cell receptors.

C1-inhibitor polymers activate the FXII-dependent kallikrein-kinin system: Implication for a role in hereditary angioedema.

BACKGROUND: The FXII-dependent kallikrein-kinin system (KKS) is tightly regulated by the serine protease inhibitor (serpin) C1-inhibitor (C1-inh). When regulation of the FXII-dependent KKS fails, which is the case in hereditary angioedema (HAE), patients consequently experience invalidating edema attacks. HAE is caused by mutations in the C1-inh encoding gene, and we recently demonstrated that some mutations give rise to the presence of polymerized C1-inh in the plasma of HAE patients. METHODS: C1-inh polymers corresponding to the size of polymers observed in vivo were produced using heat denaturation and gel filtration. The ability of these polymers to facilitate FXII activation was assessed in vitro in an FXII activation bandshift assay. After spiking of plasma with C1-inh polymers, kallikrein generation was analyzed in a global kallikrein generation method. Prekallikrein consumption in the entire Danish HAE cohort was analyzed using an ELISA method. RESULTS: C1-inh polymers mediated FXII activation, and a dose dependent kallikrein generation in plasma spiked with C1-inh polymers. An increased (pre)kallikrein consumption was observed in plasma samples from HAE patients presenting with C1-inh polymers in vivo. CONCLUSION: Polymerization of the C1-inh transforms the major inhibitor of the FXII-dependent KKS, into a potent activator of the very same system. GENERAL SIGNIFICANCE: The C1-inh polymers might play a role in the pathophysiology of HAE, but several diseases are characterized by the presence of serpin polymers. The role of serpin polymers has so far remained elusive, but our results indicate that such polymers can play a role as inflammatory mediators through the FXII-dependent KKS.

Complement is activated in progressive multiple sclerosis cortical grey matter lesions.

BACKGROUND: The symptoms of multiple sclerosis (MS) are caused by damage to myelin and nerve cells in the brain and spinal cord. Inflammation is tightly linked with neurodegeneration, and it is the accumulation of neurodegeneration that underlies increasing neurological disability in progressive MS. Determining pathological mechanisms at play in MS grey matter is therefore a key to our understanding of disease progression. METHODS: We analysed complement expression and activation by immunocytochemistry and in situ hybridisation in frozen or formalin-fixed paraffin-embedded post-mortem tissue blocks from 22 progressive MS cases and made comparisons to inflammatory central nervous system disease and non-neurological disease controls. RESULTS: Expression of the transcript for C1qA was noted in neurons and the activation fragment and opsonin C3b-labelled neurons and glia in the MS cortical and deep grey matter. The density of immunostained cells positive for the classical complement pathway protein C1q and the alternative complement pathway activation fragment Bb was significantly increased in cortical grey matter lesions in comparison to control grey matter. The number of cells immunostained for the membrane attack complex was elevated in cortical lesions, indicating complement activation to completion. The numbers of classical (C1-inhibitor) and alternative (factor H) pathway regulator-positive cells were unchanged between MS and controls, whilst complement anaphylatoxin receptor-bearing microglia in the MS cortex were found closely apposed to cortical neurons. Complement immunopositive neurons displayed an altered nuclear morphology, indicative of cell stress/damage, supporting our finding of significant neurodegeneration in cortical grey matter lesions. CONCLUSIONS: Complement is activated in the MS cortical grey matter lesions in areas of elevated numbers of complement receptor-positive microglia and suggests that complement over-activation may contribute to the worsening pathology that underlies the irreversible progression of MS.

Serial change of C1 inhibitor in patients with sepsis--a preliminary report.

OBJECTIVE: C1 inhibitor (C1INH) regulates not only the complement system but also the plasma kallikrein-kinin, fibrinolytic, and coagulation systems. The biologic activities of C1INH can be divided into the regulation of vascular permeability and anti-inflammatory functions. The objective was to clarify the serial change of C1INH in patients with sepsis. METHODS: We serially examined C1INH activity values (reference range, 70%-130%) and quantitative values (reference range, 160-330 µg/mL) in patients with sepsis admitted into the intensive care unit of the Trauma and Acute Critical Care Center at Osaka University Hospital (Osaka, Japan) during the period between December 2012 and February 2013. We also analyzed their clinical course. We defined "refractory shock" as septic shock requiring steroid administration to maintain hemodynamics. RESULTS: The serial change of C1INH was evaluated in 5 patients (4 survivors and 1 nonsurvivor). Two patients were diagnosed as having refractory shock. In the nonsurvivor after refractory shock, C1INH activity on admission was 97.2%, and the quantitative value was 133.1 µg/mL. In the other patient with refractory shock, C1INH activity on admission was 94.4%, and the quantitative value was 126.7 µg/mL. This patient's general condition had improved by day 6, with increases in C1INH activity (139.9%) and quantitative value (250.1 µg/mL). In the 3 nonrefractory shock patients, C1INH activity on admission was 130.6%±8.7%, and the quantitative value was 215±26.5 µg/mL. CONCLUSIONS: Enhancement of C1INH activity was not observed in the refractory shock patients, and the C1INH quantitative values were low. Further evaluation of the serial change of C1INH and the validity of C1INH replacement therapy in patients with septic shock may lead to a new strategy for sepsis management.

C1 inhibitor function using contact-phase proteases as target: evaluation of an innovative assay.

BACKGROUND: Controlling prekallikrein activation by C1 inhibitor (C1Inh) represents the most essential mechanism for angioedema patient protection. C1Inh function in the plasma is usually measured based on the residual activity of the C1s protease not involved in the pathological process. We have hereby proposed an alternative enzymatic measurement of C1Inh function based on contact-phase activation and correlation with angioedema diagnostic requirements. METHODS: The contact phase was reconstituted using the purified components, with C1Inh standard or plasma sample. The kinetics of the amidase activity were monitored using Pro-Phe-Arg-pNA, independently of alpha2-macroglobulin. We prevented any interference from a possible high plasma kininogenase activity by preincubating the samples with protease inhibitor. Receiver operating characteristics (ROC) were used to calculate the assay's diagnostic performance. RESULTS: The calibration curve was built using C1Inh standard (threshold limit 0.10 × 10(-3) U, i.e., 0.2 pmol), and C1Inh function was quantified in the sample, with a reference interval established based on healthy individuals (n = 281; men: 0.61-1.10 U/ml, median: 0.85 U/ml; women: 0.42-1.08 U/ml, median: 0.74 U/ml). The median values of female donors were lower than those of the others due to estrogen, yet C1Inh function remained within the reference interval. The ROC curve calculation provided the following optimum diagnostic cutoff values: women 0.36 U/ml (area under curve [AUC]: 0.99; sensitivity: 93.48%; specificity: 99.37%); and men 0.61 U/ml (AUC: 1; sensitivity: 100.0%; specificity: 100.0%). CONCLUSION: The performance outcome provided features suitable for angioedema diagnostic or follow-up. Established by means of the kinin formation process, this assay should be preferred over the method based on a C1s protease target.

Hereditary angioedema with F12 mutation: factors modifying the clinical phenotype.

BACKGROUND: Hereditary angioedema (HAE) with normal C1 inhibitor (C1Inh) associated with the c.983C>A and c.983C>G mutations of the F12 gene (FXII-HAE) is a rare condition, and presents with highly variable clinical expression. On the basis of data gathered from a large carrier cohort, we assessed the modifiers affecting the clinical phenotype. METHODS: We analyzed clinical and biological data recorded from 118 mutation carriers (80 symptomatic and 38 asymptomatic), 58 noncarrier relatives from 40 families, and 200 healthy donors. Disease severity was scored in relation to frequency and location of edema, as well as age at disease onset. To predict FXII-HAE disease severity, we analyzed the biological phenotype [C1Inh, C4, spontaneous amidase, angiotensin-I-converting enzyme (ACE), aminopeptidase P (APP), and carboxypeptidase N/M (CPN)] by means of logistic regression (Akaike information criterion) and odds ratio (OR). RESULTS: Meaningful variables contributed to FXII-HAE, with the kinin catabolism enzymes ACE and CPN exhibiting a significant inverse relationship with disease severity (OR = 0.36, 95% CI 0.23-0.59, P < 0.001; OR = 0.58, 95% CI 0.36-0.91, P < 0.05, respectively). CPN activities were 37.5 (28.5-41.3) nmol/ml/min and 38.5 (32.8-45.6) for FXII-HAE asymptomatic and symptomatic carriers, respectively, and 37.9 (30.5-43.7) nmol/ml/min for noncarriers. Angiotensin-I-converting enzyme activities were 58 (44-76) and 49 (35-59) nmol/ml/min for FXII-HAE asymptomatic and symptomatic carriers, respectively, and 56 (49-66) nmol/ml/min for noncarriers. CONCLUSIONS: The FXII-HAE is associated with modifiers, for example kinin catabolism enzymes, ACE and CPN, different from those recognized in HAE with C1Inh deficiency.

Upper airway edema in 43 patients with hereditary angioedema.

BACKGROUND: Upper airway edema (UAE) occurs infrequently in hereditary angioedema (HAE), but still results in significant morbidity and mortality. OBJECTIVE: To assess patients with HAE and UAE to determine whether unique features exist that can predict the risk of UAE. METHODS: Clinical, laboratory, and genetic data were compared between 43 patients with HAE and 743 UAE attacks and those without UAE and normal controls after ethics committee approval. RESULTS: Most patients had their first episode of UAE in the second (25.6%), third (27.9%), and fourth (23.3%) decades of life, and the mean age at onset was 27.3 years. Evolution of UAE from initial to maximum symptoms was 4.6 hours on average, and most cases (69.8%) progressed within 4 hours. Dyspnea was the most frequent manifestation in per-episode (92.2%) and per-patient (97.7%) analyses. Men developed more asphyxiation attacks (19 vs 2) and underwent more tracheotomies (12 vs 2) than did women. UAE was associated with facial edema in half the studied patients. Patients with a positive family history of UAE had a high risk of UAE attacks. CONCLUSION: Symptoms limited to the upper airway should be taken seriously. Dyspnea may be the only manifestation of UAE. UAE attacks most commonly start spontaneously and usually progress rapidly, as quickly as 30 minutes, from awareness of symptoms to maximum airway involvement. Patients with a positive UAE family history are predisposed to UAE attacks, and men appear to be more apt to develop asphyxiation than women.

Factor XII-independent activation of the bradykinin-forming cascade: Implications for the pathogenesis of hereditary angioedema types I and II.

BACKGROUND: We have previously reported that prekallikrein expresses an active site when it is bound to high-molecular-weight kininogen (HK) and can digest HK to produce bradykinin. The reaction is stoichiometric and inhibited by C1 inhibitor (C1-INH) or corn trypsin inhibitor. Addition of heat shock protein 90 leads to conversion of prekallikrein to kallikrein in a zinc-dependent reaction. OBJECTIVE: Our goal was to determine whether these reactions are demonstrable in plasma and distinguish them from activation through factor XII. METHODS: Plasma was incubated in polystyrene plates and assayed for kallikrein formation. C1-INH was removed from factor XII-deficient plasma by means of immunoadsorption. RESULTS: We demonstrate that prekallikrein-HK will activate to kallikrein in phosphate-containing buffers and that the rate is further accelerated on addition of heat shock protein 90. Prolonged incubation of plasma deficient in both factor XII and C1-INH led to conversion of prekallikrein to kallikrein and cleavage of HK, as was seen in plasma from patients with hereditary angioedema but not plasma from healthy subjects. CONCLUSIONS: These results indicate that C1-INH stabilizes the prekallikrein-HK complex to prevent HK cleavage either by prekallikrein or by prekallikrein-HK autoactivation to generate kallikrein. In patients with hereditary angioedema, kallikrein and bradykinin formation can occur without invoking factor XII activation, although the kallikrein formed can rapidly activate factor XII if it is surface bound.

C1-inhibitor efficiently inhibits Escherichia coli-induced tissue factor mRNA up-regulation, monocyte tissue factor expression and coagulation activation in human whole blood.

Both the complement system and tissue factor (TF), a key initiating component of coagulation, are activated in sepsis, and cross-talk occurs between the complement and coagulation systems. C1-inhibitor (C1-INH) can act as a regulator in both systems. Our aim in this study was to examine this cross-talk by investigating the effects of C1-INH on Escherichia coli-induced haemostasis and inflammation. Fresh human whole blood collected in lepirudin was incubated with E. coli or ultrapurified E. coli lipopolysaccharide (LPS) in the absence or presence of C1-INH or protease-inactivated C1-INH. C3 activation was blocked by compstatin, a specific C3 convertase inhibitor. TF mRNA was measured using reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and TF surface expression was measured by flow cytometry. In plasma, the terminal complement complex, prothrombin F1·2 (PTF1·2) and long pentraxin 3 (PTX3) were measured by enzyme-linked immunosorbent assay (ELISA). Cytokines were analysed using a multiplex kit. C1-INH (1·25-5 mg/ml) reduced both LPS- and E. coli-induced coagulation, measured as a reduction of PTF1·2 in plasma, efficiently and dose-dependently (P < 0·05). Both LPS and E. coli induced marked up-regulation of TF mRNA levels and surface expression on whole blood monocytes. This up-regulation was reduced efficiently by treatment with C1-INH (P < 0·05). C1-INH reduced the release of PTX3 (P < 0·05) and virtually all cytokines measured (P < 0·05). Complement activation was inhibited more efficiently with compstatin than with C1-INH. C1-INH inhibited most of the other readouts more efficiently, consistent with additional non-complement-dependent effects. These results indicate that complement plays a role in activating coagulation during sepsis and that C1-INH is a broad-spectrum attenuator of the inflammatory and haemostatic responses.

Acquired angioedema--occurrence, clinical features and associated disorders in a Danish nationwide patient cohort.

BACKGROUND: The prevalence of acquired angioedema (AAE) is hitherto unknown and, to date, less than 200 patients have been reported worldwide. AAE is associated with lymphoproliferative conditions and autoantibodies against C1 inhibitor (C1INH). Rituximab (RTX) is increasingly used in the treatment of AAE patients. METHODS: A nationwide study of AAE patients was performed in Denmark. Clinical features, associated disorders, treatments and outcomes were registered. RESULTS: Eight AAE patients were identified. The diagnostic delay was on average 1 year and 8 months. Patients were treated with C1INH concentrate or icatibant on demand. Six patients were diagnosed with a clonal B-cell disorder during follow-up, on average 2.5 years after the first swelling. Two patients had monoclonal B-cell lymphocytosis (MBL). Two patients received RTX. CONCLUSIONS: AAE is a rare condition occurring in less than 10% of patients with C1INH deficiency in Denmark. AAE is highly associated with haematologic disorders, and we recommend yearly follow-up visits with clinical examination and blood tests including flow cytometry to diagnose B-cell conditions at an early stage. We report 2 patients with AAE and associated MBL, which is a benign expansion of clonal B lymphocytes. MBL can be the precursor of chronic lymphocytic leukaemia or is associated with non-Hodgkin's lymphoma. If angioedema is poorly controlled with standard treatment regimens, we suggest treatment of the associated haematologic disorder. Based on a review of the literature and our own data, we recommend therapy with RTX, especially in patients with anti-C1INH autoantibodies.

Recombinant expression of the autocatalytic complement protease MASP-1 is crucially dependent on co-expression with its inhibitor, C1 inhibitor.

MASP-1 is a protease of the lectin pathway of complement. It is homologous with MASP-2, previously thought both necessary and sufficient for lectin pathway activation. Recently MASP-1 has taken centre stage with the observation that it is crucial to the activation of MASP-2 and thus central to complement activation. Numerous additional functions have been suggested for MASP-1 and its importance is obvious. Yet, thorough analyses of proteolytic activities and physiological roles in the human scenario have been hampered by difficulties in purifying or producing full-length human MASP-1. We present the successful expression of full-length recombinant human MASP-1 entirely in the zymogen form in a mammalian expression system. We found that the catalytic activity of MASP-1 suppresses its expression through rapid auto-activation and auto-degradation. This auto-degradation was not inhibited by the addition of inhibitors to the culture medium, and it was subsequently found to occur intracellularly. Numerous mutations aimed at attenuating auto-activation or preventing auto-degradation failed to rescue expression, as did also attempts at stabilizing the protease by co-expression with MBL or ficolins or expression in hepatocyte cell lines, representing the natural site of synthesis. The active protease was finally produced through co-expression with the serine protease inhibitor C1 inhibitor. We demonstrate that the expressed protease is capable of binding MBL and auto-activating, and is catalytically active. We have generalized the concept to the expression also of MASP-2 entirely in its zymogen form and with improved yields. We suggest a general advantage of expressing aggressive, autocatalytic proteases with their cognate inhibitors.

The burden of illness in patients with hereditary angioedema.

OBJECTIVE: Hereditary angioedema (HAE) is a rare genetic disease characterized by long-term recurrent attacks of subcutaneous or submucosal edema in different parts of the body. A comprehensive review of the literature on burden of illness for patients with HAE is presented. DATA SOURCES: A Boolean search was performed using MEDLINE and EMBASE databases and the Internet. STUDY SELECTION: Articles discussing aspects of the burden of illness in HAE were selected. Topics focused on the course of the disease, nature of attacks, treatment, quality of life, and costs. RESULTS: Hereditary angioedema is associated with a significant and multifaceted disease burden. Diagnosis is often delayed for years, with patients receiving ineffective treatment and unnecessary medical procedures before diagnosis. HAE attacks are painful, unpredictable, and debilitating and often require emergency medical attention. Attacks can affect a patient's daily activities, including work or schooling. Depression and anxiety are prevalent in patients with HAE. Recent advances in treatment provide patients with effective and well-tolerated prophylactic and on-demand therapeutic options. However, end points specific to HAE that better measure the impact of treatment on disease burden are lacking. Furthermore, there is a notable paucity of literature directed toward physicians who are instrumental in diagnosing and treating patients with HAE (eg, emergency department). CONCLUSION: More publications are broadening the understanding of HAE. However, important gaps remain. Effective management of HAE requires a more comprehensive understanding of the disease burden so that disease management can be individualized to meet specific patient needs.

Cloning and molecular characterization of complement component 1 inhibitor (C1INH) and complement component 8ß (C8ß) in Nile tilapia (Oreochromis niloticus).

Nile tilapia (Oreochromis niloticus), one of the most important groups of food fishes in the world, has frequently suffered from serious challenge from pathogens in recent years. Immune responses of Nile tilapia should be understood to protect the aquaculture industry of this fish. The complement system has an important function in recognizing bacteria, opsonizing these pathogens by phagocytes, or killing them by direct lysis. In this study, two Nile tilapia complement component genes, complement component 1 inhibitor (C1INH) and complement component 8ß subunit (C8ß), were cloned and their expression characteristics were analyzed. C1INH cDNA was found containing a 1791 bp open reading frame (ORF) encoding a putative protein with 597 amino acids, a 101 bp 5'-untranslated region (UTR) and a 236 bp 3'-UTR. The predicted protein structure for this gene consisted of two Ig-like domains and glycosyl hydrolase family-9 active site signature 2. The C8ß cDNA consisted of a 1761 bp ORF encoding 587 amino acids, a 15 bp 5'-UTR and a 170 bp 3'-UTR. The predicted protein of C8ß contained three motifs, thrombospondin type-1 repeat, membrane attack complex/perforin domain, and LDL-receptor class A. Expression analysis revealed that these two complement genes were highly expressed in the liver, however, were weakly expressed in the gill, heart, brain, kidney, intestine, spleen and dorsal muscle tissues. The present study provided insights into the complement system and immune functions of Nile tilapia.

Angioedema with normal laboratory values: the next step.

When faced with a patient with recurrent swelling, a thorough laboratory evaluation to determine the underlying etiology ensues. When the laboratory work-up is unrevealing, health care practitioners are frequently left in a quandary. This review will attempt to provide up-to-date information on how to approach the diagnosis and management of angioedema in a patient with normal laboratory values. The subtypes that will be reviewed in detail include: hereditary angioedema with normal C1 inhibitor (HAE with normal C1INH), drug-induced angioedema, and idiopathic angioedema. We present literature to aid the physician in the diagnosis and treatment of these disorders.

C1 inhibitor hinge region mutations produce dysfunction by different mechanisms.

Heterozygosity for a mutant dysfunctional C1 inhibitor protein, a member of the serine proteinase inhibitor (serpin) superfamily, results in type II hereditary angioneurotic oedema. We identified a "hinge" region mutation in C1 inhibitor with a Val to Glu replacement at P14 Val-432. Recombinant C1 inhibitors P10 Ala-->Thr and P14Val-->Glu did not form stable complexes with fluid phase C1s or kallikrein. The P14 Val-->Glu mutant, however, was cleaved to a 96K form by C1s, while the P10 Ala-->Thr mutant was not. The recombinant P10 mutant also did not complex with C1s, kallikrein or beta-factor Xlla-Sepharose. The two mutations, therefore, result in dysfunction by different mechanisms: in one (P14 Val-->Glu), the inhibitor is converted to a substrate, while in the other (P10 Ala-->Thr), interaction with target protease is blocked.