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PubMed1996

Biotinylation of proteins via amino groups can induce binding to U937 cells, HL-60 cells, monocytes and granulocytes.

The use of biotinylated ligands for the flow cytometric detection of cell surface receptors has become a popular alternative to radioreceptor assays. Although the biotinylation of a protein is a relatively mild chemical reaction several reports have mentioned the fact that the number and location of biotin moieties coupled to amino groups of a protein can alter its physicochemical properties and impair biological activity. In the present study we show for a variety of biotinylated functionally unaltered ligands that biotinylation by N-hydroxysuccinimide (NHS) esters of biotin can induce a binding to cell surfaces, which is not specific for the respective unlabelled ligand. C1q, C1 inhibitor (C1-INH), alpha 1-antitrypsin (AT), ovalbumin (OV), transferrin and soybean trypsin inhibitor (STI) were labelled with S-NHS-LC-biotin and activated C1s (C1s) with NHS-biotin. Biotinylation of C1q, C1s and C1-INH exerted negligible effects on biological function, antigenicity or electrophoretic mobility but when labelled and unlabelled proteins were assayed for binding to monocytic U937 cells, promyelocytic HL-60 cells, monocytes and granulocytes, a remarkable binding was observed for biotinylated C1q, C1-INH and C1s. In contrast, no binding was observed when we used unlabelled C1q, C1s and C1-INH and employed specific antibodies, alpha-mouse-FITC or alpha-rabbit-FITC for detection. Increasing molar ratios of biotin-to-protein (B : P) for biotinylated AT, OV and STI evoked increased fluorescence intensities of the cells. Most importantly the unlabelled ligands did not compete for cell binding with their biotinylated derivatives, with the exception of transferrin. Preincubation of the cells with an excess of free d-biotin did not reduce binding of biotinylated proteins, thus excluding a potential involvement of biotin receptors. Hydrophobic interaction chromatography revealed a remarkable increase in hydrophobicity of the biotinylated proteins compared to their unlabelled counterparts, suggesting that the biotinylation-induced binding is due to increased hydrophobicity. Our findings indicate that biotinylation by the common amino acid esterification method may be critical for proteins if they are to be used as ligands for receptor binding studies.

Amino Acids↗

PubMed1987

Platelet-mediated cytotoxicity. Role of antibody and C3, and localization of the cytotoxic system in membranes.

Platelets are one of several cell types capable of mediating antibody-dependent cellular cytotoxicity. We have developed a plasma-free system in which washed mouse platelets lyse washed antibody and complement-sensitized SRBC targets in the presence of EDTA. The dose-response curve is concave to the abscissa, indicating that lysis is a one-hit reaction. Determination of the actual number of platelets required to lyse a target shows that each platelet could lyse a single target. A limited degree of lysis is observed when platelets are incubated with SRBC sensitized with monoclonal IgG2a alone, but no lysis occurs with SRBC bearing comparable amounts of other isotypes. In the presence of C1 through C3, but not C1 through C2, efficient lysis is triggered by complement-fixing monoclonal IgG2a, IgG2b, and IgG3. In contrast, IgM and non-complement-fixing IgG1 and IgE are inactive. To achieve efficient lysis, it appears that platelets require both target cell-bound antibody and C3 fragments in close proximity. It is unlikely that proteases, pore-forming proteins, or toxic oxygen metabolites are involved in platelet-mediated lysis. Freezing and thawing of platelets, sonication, or sonication followed by hypotonic shock causes severe depletion of cytoplasmic and granular contents, as shown by electron microscopy and marker assays. However, the membrane fraction of these preparations retains cytolytic activity. When platelets are treated with trypsin or heated, lytic activity is eliminated, indicating that at least one component of this system is protein. These findings, as well as the fact that platelets do not lyse unsensitized innocent bystander SRBC, suggest that the complete cytotoxic system of platelets capable of specific recognition and lysis resides in their membranes.

Animals↗

PubMed1991

C1-esterase inhibitor in uncomplicated pregnancy and mild and moderate preeclampsia.

Routine coagulation tests and measurement of the plasma levels of C1-esterase inhibitor (C1-INH) and antithrombin III were performed in 17 women with mild preeclampsia, 10 women with moderate preeclampsia and 20 women with uncomplicated pregnancy. All pregnant probands were within the third trimester of pregnancy. 20 non-pregnant women were used as controls. The groups were matched in age and the pregnant ones were also matched in gestational age. C1-INH activity and antigen were significantly reduced (p less than 0.002) in normally pregnant women as compared with non-pregnant ones. Further, C1-INH activity was lower in women with mild preeclampsia and significantly lower in women with moderate preeclampsia (p less than 0.05) as compared with normally pregnant women. None of the plasmatic coagulation tests was indicative of a consumption reaction. We conclude that C1-INH activity and antigen reductions are commonly associated with pregnancy. Furthermore, as markedly lower values can be found in mild and moderate preeclampsia, measurement of the C1-INH activity in pregnant women within the third trimester might proof useful to establish the diagnosis of a preeclamptic condition.

Adult↗

PubMed2001

Complement 1 inhibitor is a regulator of the alternative complement pathway.

We studied complement 1 inhibitor (C1-INH) as an inhibitor of the alternative complement pathway. C1-INH prevented lysis, induced by the alternative complement pathway, of paroxysmal nocturnal hemoglobinuria (PNH) erythrocytes in human serum. It inhibited the binding of both factors B and C3 to PNH and rabbit erythrocytes and blocked the ability of factor B to restore alternative-pathway function in factor B-depleted serum. C1-INH did not bind to factors B or D but did bind to immobilized C3b and cobra venom factor (CVF), a C3b analogue. C1-INH prevented factor B from binding to CVF-coated beads and dissociated bound factor B from such beads. Factor B and C1-INH showed cross competition in binding to CVF-coated beads. Factor D cleaved factor B into Bb and Ba in the presence of C3b. Cleavage was markedly inhibited when C3b was preincubated with C1-INH. C1-INH inhibited the formation of CVFBb and decreased the C3 cleavage. Removal of C1-INH from serum, in the presence of Mg-EGTA with an anti-C1-INH immunoabsorbant, markedly increased alternative-pathway lysis. C1-INH interacts with C3b to inhibit binding of factor B to C3b. At physiologic concentrations, it is a downregulator of the alternative pathway convertase.

Absorption↗

PubMed1983

[Hereditary deficiency of C1 esterase inhibitor. Lupus and glomerulonephritis].

Congenital deficit of the inhibitor of C1 esterase (C1 INH) usually presents by oedema of the lower limbs, abdomen and glottis (sometimes lethal), which explains its clinical denomination of angioneurotic oedema. The association of this condition with disseminated lupus erythematosis has been reported in 4 cases and with discoid lupus in 4 cases. Antinuclear factors were found in all these cases but there were only two documented cases of nephropathy (one diffuse proliferative glomerulonephritis and one local glomerulonephritis). The association of a deficit of C1 INH and membrano-proliferative glomerulonephritis has only been reported in 2 cases (one lobular glomerulonephritis and one glomerulonephritis with dense basal membrane deposits). Our case had C1 INH deficiency and proliferative lupic glomerulonephritis in the absence of other clinical and immunological signs of DLE. Nephropathy was not looked for in 9 cases of association of C1 INH deficiency and C3-shearing autoantibody (C3 NEF). A common genetic mechanism for these associations seems very improbable. The aptitude of patients with C1 INH deficiency to synthesise autoantibodies under the influence of infections factors, for example, could explain the higher incidence of lupus and glomerulopathies in these patients.

Adolescent↗

PubMed1993

C1q inhibitor (chondroitin-4-sulfate proteoglycan): structure and function.

The serum C1q inhibitor (C1q INH) is a chondroitin 4-sulfate proteoglycan which is composed of several polyanionic components ranging in size from 21-750 kDa. Although the activity of C1q INH has been described in terms of its ability to precipitate C1q and inhibit its hemolytic activity, not much is known about either the mechanisms of its action or its role in health and disease. This report provides evidence that a 30 kDa core protein component of the proteoglycan macromolecule contains most of the C1q inhibitory activity. This inhibitory activity occurs as a result of C1q INH binding to the C1q "heads" (gC1q) as well as to the collagen "tail" (cC1q). What may be more significant in terms of perpetuation of inflammatory processes is the ability of C1q INH to moderately activate the classical pathway leading to C2 and C4 consumption. The binding of C1q INH to C1q is enhanced at low ionic strength, but significant binding does occur under physiologic conditions which makes it likely for the inhibitor to participate in inflammatory processes especially in microenvironments of high inhibitor concentration. Such elevated concentration does occur in patients with active rheumatoid arthritis and systemic lupus erythematosus either as a result of unregulated proteoglycan synthesis or disturbances in connective tissue metabolism. Another important function of serum C1q INH is its ability to prolong the clotting time of plasma and fibrinogen solutions containing or lacking CaCl2. This potent anticoagulant activity is again displayed by the 30 kDa putative protein core which specifically binds to both the E and D domains of fibrinogen. However, the epitope(s) on the 30 kDa which binds to C1q appears to be distinct from that which binds to fibrinogen. The known presence of proteoglycans on the basement membranes and other sites may explain at least in part the presence of fibrinogen in atheromatous lesions. Furthermore, by binding to fibrinogen, soluble C1q INH-and C1q-C1q INH complexes may limit fibrin gelation in inflammatory and tissue repair microenvironments.

Chondroitin Sulfate Proteoglycans↗

PubMedDate not supplied

[Hereditary angioedema: clinical and laboratory aspects of 7 cases].

Hereditary angioedema is caused by a defect in C1 inhibitor activity (C1INH). Its occurrence is rare and it is associated with an autosomal dominant mode of inheritance. We describe seven patients (4M:3F), age from 12 to 50 years old, who are affected by hereditary angioedema; four of them belong to the same family. The main clinical manifestations were: angioedema of face, hands and feet (6/7) and abdominal pain (2/7). No triggering factors were associated with symptoms in 4/7 patients and trauma (2/7) and menses (1/7) were reported in the other three ones. One patient was submitted to laparotomy for partial intestinal resection, before diagnosis. Laboratory complement analysis revealed the absence of hemolytic function of complement, reduced C4 (6/7) and low C1INH levels. All patients received Danazol (100 mg/day) with clinical control. Hereditary angioedema has to be considered in the differential diagnosis of angioedema, since an early diagnosis of this immunodeficiency, leading to specific treatment in order to decrease the complications.

Adult↗

PubMed1993

Endotoxin-induced pulmonary dysfunction is prevented by C1-esterase inhibitor.

In septic shock, hypotension, disseminated intravascular coagulation, and neutrophil activation are related to the activation of the blood coagulation contact system. This study evaluates in dogs the effect of the C1-esterase inhibitor (C1-INH), a main inhibitor of the blood coagulation contact system, on the cardiovascular and respiratory dysfunction associated with endotoxic shock. Two groups were included: controls, which received Escherichia coli endotoxin, and a C1-INH group in which C1-INH was infused before E. coli endotoxin administration. In both groups, endotoxin produced hypodynamic shock; however, the decrease in the systolic index and the ventricular systolic work indexes were greater in controls than the C1-INH group. In controls, the arterial O2 partial pressure decreased by 30% and the alveolo-arterial O2 difference increased by 625%, these parameters remained unchanged in the C1-INH group. Hypoxemia was associated with increased intrapulmonary shunt, decreased blood coagulation contact factors, and decreased C3c. In contrast, C1-INH administration prevented endotoxin-induced hypoxemia, the increase in intrapulmonary shunt, and the decrease in blood coagulation contact factors. This study shows that, in dogs with endotoxic shock, pulmonary dysfunction is associated with an activation of the blood coagulation contact phase system. An inhibition of this system by C1-INH prevented the hypoxemia induced by endotoxic shock.

Animals↗

PubMed1993

C1 subcomponent complexes: basic and clinical aspects.

C1 subcomponents form a variety of complexes that can be detected in normal and pathological sera. Since aberrations of C1 subcomponents in disease could reflect in vivo interactions with influence on complement function, studies of C1 subcomponent complexes might provide insight into pathogenetic mechanisms. C1 inhibitor (C1Inh)-dependent dissociation of the C1q(C1r-C1s)2 complex gives rise to C1Inh-C1r-C1s or C1Inh-C1r-C1s-C1Inh complexes. Increased concentrations of C1Inh-C1r-C1s probably signify prevention of C1 activation, while C1Inh-C1r-C1s-C1Inh appears to be a clinically useful marker of efficient classical pathway activation. "Free" C1q as found in some pathological sera, and in joint fluids of patients with rheumatoid arthritis could be a result of C1Inh-dependent dissociation of C1q(C1r-C1s)2. The presence in serum of zymogen (C1r-C1s)2 is an expected finding in various conditions with low C1q concentrations without evidence of C1 activation. It is not excluded that circulating (C1r-C1s)2 might sometimes be acquired due to factors capable of interacting with the collagenous part of the C1q molecule.

Antigen-Antibody Complex↗

PubMed2001

Ex-vivo hemoperfusion (eHPS) of pig-lungs with whole human blood: effects of complement inhibition with a soluble C1-esterase-inhibitor.

OBJECTIVES: Xenotransplantation could be a future alternative to allotransplantation due to increasing organ shortage. Complement activation plays a major role in hyperacute rejection (HAR) in pig-to-human combinations. We developed an ex-vivo hemoperfusion (EHP) system to investigate pathophysiology of HAR in the lung. After standardizing the model, the effect of a soluble complement inhibitor (C1-INH, Berinert) was investigated. METHODS: Pig lungs were harvested following cold perfusion with Celsior preservation solution. EHP was performed using fresh heparinized human blood plus C1-INH (n = 6) or heparinized human blood as control (n = 4). Bloodgas analyses (BGA), pulmonalarterial pressure (PAP) were monitored. P-selectin and L-selectin were measured. Tissue samples were taken and microscopic changes evaluated. RESULTS: BGA, PAP, macroscopic and microscopic changes in the control group showed HAR, while the C1-INH group showed significantly longer function. Leucocytes and platelets were markedly activated in the control, whereas in the treated group L-selectin and P-selectin values indicated lower activation. HE stainings showed maintained lung architecture after perfusion of pig-lungs with human blood plus C1-INH. Immunohistochemistry showed less C1q, C3, C5b-9 activation in the C1-INH group. CONCLUSIONS: Investigation of interaction of human blood with pig lung endothelium could be done in this model. C1-INH attenuates HAR in a pig-to-human lung transplantation model by decreasing the activation of adhesion molecules. C1-INH could play a role in induction therapy of future lung xenotransplantation.

Animals↗

PubMed2000

A monoclonal antibody raised against human beta-factor XIIa which also recognizes alpha-factor XIIa but not factor XII or complexes of factor XIIa with C1 esterase inhibitor.

A monoclonal antibody (mAb 2/215) against human beta-factor XIIa (beta-FXIIa), was shown by equilibrium binding studies to have a high affinity for alpha-factor XIIa (alpha-FXIIa) (Kd 1.8 nM) and beta-FXIIa (Kd 0.65 nM) but no detectable reaction with FXII zymogen or alpha-FXIIa:C1 esterase inhibitor (C1-INH) complex. Surface plasmon resonance studies showed that the mAb 2/215 bound to immobilized alpha-FXIIa with high affinity (KD 3.93 +/- 1.46 x 10(-11) M). Western blots employing mAb 2/215 indicated that human plasma contained small amounts of alpha-FXIIa but no beta-FXIIa. mAb 2/215 did not inhibit the amidolytic activity of beta-FXIIa and protected beta-FXIIa from inhibition by C1-INH. The recovery by ELISA,employing mAb 2/215 as the capture antibody, of alpha-FXIIa added to plasma was 11.3%, 42% after inhibition of alpha-FXIIa with 3:4dichloroisocoumarin, and 82% when 0.5% Triton-X100 was added to the assay. Gel filtration showed that the majority of plasma alpha-FXIIa existed as a complex (Mr approximately 170,000). This distinctive mAb increases the capacity to study the contact system in health and disease.

Amidohydrolases↗

PubMed2001

[The effect of C 1 esterase inhibitor on ischemia: reperfusion injury in the rat brain].

BACKGROUND: Despite the current interest in thrombolytic therapy for acute stroke, ischemia-reperfusion injury remains a potentially hazardous complication. The complement system is thought to play a major role in initiating some of the inflammatory events occurring in the reperfusion injury. This study was conducted to explore the effect of C 1 esterase inhibitor (C 1 INH) on the reperfusion injury in rat middle cerebral artery (MCA) occlusion-reperfusion model. METHODS: Twenty-nine male Wistar rats were used. Intraluminal MCA occlusion was performed for 60 minutes. Just before the reperfusion, C 1 INH(50 IU/kg, C 1 INH group, n = 15) or saline (control group, n = 14) was administrated. Forty-eight hours after the reperfusion, infarct volume and myeloperoxidase(MPO) activity of the brain were evaluated. RESULT: Infarct volume and MPO activity were significantly smaller in the C 1 INH group(86.5 +/- 76.8 mm3, 0.38 +/- 0.30 U/g) than in control group(179 +/- 92.8 mm3, 1.37 +/- 0.46 U/g) (p < 0.01). CONCLUSION: The results of this study provided the first evidence that C 1 INH reduced polymorphonuclear leukocytes(PMN) accumulation and reperfusion damage in the brain.

Animals↗

PubMed1997

C1-esterase inhibitor prevents early pulmonary dysfunction after lung transplantation in the dog.

The success of lung transplantation to a large extent depends on effective protection of the graft from ischemic injury after reperfusion. Although mechanisms have not been clarified, the pathologic findings of ischemic injury after reperfusion are similar to adult respiratory distress syndrome, a condition in which the blood coagulation contact system is activated. This study evaluates the effect of C1-esterase inhibitor (C1-INH), the main inhibitor of the blood coagulation contact system, on short-term lung function in a dog model of orthotopic lung transplantation. Twelve lung transplantations were performed after 24 h of ischemic time. Dogs were randomly assigned to receive either vehicle (Control) or C1-INH. After the lung transplantation in the control group, Pao2 decreased by 84% and both the AaPO2 and the Qs/Qt% increased (340 and 530%, respectively, p < 0.01); these parameters remained unchanged in the C1-INH group. The hypoxemia observed in control animals was associated with decreased blood coagulation contact factors, complement consumption, increased expression of adhesion glycoproteins in leukocytes, and extensive intraalveolar and interstitial neutrophil infiltration. In contrast, C1-INH administration prevented hypoxemia, the decrease in blood coagulation contact factors, the activation of the complement system, the increase in expression of leukocyte adhesion molecules, and inflammatory cell infiltrate. This study has demonstrated that in a dog model of lung transplantation, the administration of C1-INH prevents early pulmonary dysfunction, and it suggests that activation of blood coagulation contact system and complement are important mechanisms causing ischemic injury after reperfusion.

Animals↗

PubMed1984

Quantification of C1-inhibitor functional activities by immunodiffusion assay in plasma of patients with hereditary angioedema--evidence of a functionally critical level of C1-inhibitor concentration.

The relationship of C1-inhibitor (C1-INH) concentration and apparent functional activity was investigated in 111 plasma samples from 21 patients with the common form of hereditary angioedema (HAE). Functional C1-INH was analyzed by means of a modified version of immunodiffusion assay. Down to a C1-INH level of approximately 0.075 g/l (38% of normal) apparent C1-INH functions were found within the normal range, while below this level functional adequacy of C1-INH could no longer be ascertained. When C4 concentrations, considered to reflect approximately functional C1-INH, were related to C1-INH antigen levels of individual samples, a relationship emerged which was identical to that between C1-INH concentration and apparent function. No attacks of edema could be associated with C1-INH concentrations above 0.075 g/l, while it was possible to associate attacks with concentrations below this level. In experiments where patient plasma and normal plasma were mixed in various ratios or where HAE plasma was replaced by purified C1-INH, an increase in C1-INH antigen to concentrations of 0.06-0.08 g/l was followed by a sharp rise in apparent functions to normal values. The rise of functional C1-INH became moderate when C1-INH antigen further increased. The results supported the idea of a functionally critical level of C1-INH in the common form of HAE.

Angioedema↗

PubMed1986

The functional inhibition of activated C1 inhibitor in normal human serum causes spontaneous consumption of the complement components C2, C3, C4, and factor B.

The human complement components C1r, C1s, C4, C3, factor B, and/or activated C1INH were functionally blocked in normal human serum (NHS) and EGTA- or EDTA-treated NHS by polyclonal monospecific Fab'-fragments to the individual components. The results of inhibition experiments are compatible with the formation of a classical pathway fluid-phase C3 convertase (C4b2a) spontaneously generated by the inhibition of activated C1INH. This process in both NHS and EGTA-NHS was accompanied by the consumption of C2, C4, C3, and factor B but only by poor enhancement of C5 conversion. Blocking subcomponent C1r, completely inhibited spontaneous activation of the complement components, indicating that the control of C1r hydrolysis is the essential role of activated C1INH as a regulator of C1 activation in NHS. Non-complement serum proteases were inactive during the initiation of the activation process. The presence of blood cells during functional inhibition of activated C1INH in NHS slightly decreased the consumption of C3 but not of C2 and C4.

Angioedema↗

PubMed1998

[Hereditary angioedema. A rare cause of acute abdominal pain with ascites].

HISTORY AND CLINICAL FINDINGS: Since the age of 16 years a now 25-year-old woman had been known to have C1-inhibitor (C1-INH) deficiency. She presented herself at the emergency department because of acute severe lower abdominal cramps. A urinary infection had been treated with antibiotics for the previous 4 days. There was marked pain on pressure over the lower abdomen, but there were no signs of peritonitis and bowel sound were normal. There had been no nausea or vomiting and the stools had been normal. INVESTIGATIONS: There was a leukocytosis of 10,200/microliter, moderately elevated C-reactive protein (44.8 mg/l), haemoglobin concentration of 17 g/dl and haematocrit of 51%. Radiology revealed oedema of the duodenum and sonography showed free fluid in the abdomen. TREATMENT AND COURSE: After excluding an acute abdomen and in view of the C1-INH deficiency treatment was symptomatic. All symptoms completely disappeared after 2 days. CONCLUSIONS: Exclusively gastrointestinal symptoms and ascites are rare in patients with hereditary angioedema. But knowledge of this manifestation of the disease is important because patients are sometimes operated under the false diagnosis of acute abdomen. In severe cases symptomatic treatment may have to be supplemented by C1-INH administration. Prevention with attenuated androgens should be started or modified, respectively.

Abdominal Pain↗

PubMed1981

Glomerular disease in two patients with urticaria-cutaneous vasculitis and hypocomplementemia.

We assessed the clinical, serologic, and renal abnormalities of two patients with the syndrome of hypocomplementemia, vasculitis, and urticaria. Both patients presented with recurrent urticaria and were found subsequently to have glomerulonephritis. Both manifested depletion of the early complement (C) components, and their Cl inhibitor levels were normal. Circulating immune complexes were detected by two of three assays in both patients. One patient had a high titer of Sm antibodies. The detectable immune complexes were of high molecular weight, and were more suggestive of classical lupus erythematosus than the low molecular weight (7S) Clq precipitins which characterize some cases of hypocomplementemia-vasculitis-urticaria syndrome. Biopsy of the skin lesions in both patients revealed leukocytoclastic vasculitis with immunoglobulin and C deposits at the dermal-epidermal junction. Renal biopsy specimens showed segmental or diffuse proliferative mesangial glomerulonephritis. The results suggest that patients with this syndrome do not conform to a discrete entity but rather exhibit a spectrum of diseases ranging from systemic lupus erythematosus to the syndrome of urticaria, hypocomplementemia, and low molecular weight Clq precipitins.

Adult↗

PubMed1984

Plasma prekallikrein, factor XII, antithrombin III, C1(-)-inhibitor and alpha 2-macroglobulin in critically ill patients with suspected disseminated intravascular coagulation (DIC).

In nine patients with suspected disseminated intravascular coagulation (DIC) and five controls, the following analyses were performed on admission and 7-29 hours later: Routine coagulation studies (fibrinogen, platelet count, fibrin(ogen) degradation products, ethanol gelation, reptilase time, Factor V) providing a semiquantitative DIC score, prekallikrein (PK), Factor XII, antithrombin III (AT-III), C1(-)-inhibitor and alpha 2-macroglobulin. Significant correlations were found: PK or AT III with the DIC-score, PK with AT-III and Factor XII, AT-III with Factor XII. The changes (expressed as a percentage of normal plasma) of PK and AT-III from the first to the second evaluation were nearly identical. The two patients with rapidly fatal irreversible shock showed the highest DIC score and a pronounced decrease of PK and AT-III, whereas in reversible shock stable or increasing PK and AT-III values were found. The other variables showed an overlap between reversible and irreversible shock. DIC in these shock patients, accompanied by a decrease in PK, probably was mediated via Factor XII activation. PK and AT-III might be of prognostic value in patients with (septic) shock.

Aged↗