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Biomedical subjects

C E Hack

Publications and source records attributed to C E Hack.

At least 55 records · Page 3Linked to original sources
PubMed2001

Therapeutic efficacy of intravenous immunoglobulin preparations depends on the immunoglobulin G dimers: studies in experimental immune thrombocytopenia.

The clinical benefit of intravenous immunoglobulin (IVIG) preparations in the treatment of immune thrombocytopenic purpura (ITP) is supposed to be mediated by blockade of Fc gamma receptor--bearing phagocytes. In 2 experimental models for ITP, it is shown that the therapeutic efficacy of IVIG preparations is related to the IgG dimer content present in these preparations. A rat monoclonal antibody (mAb; MWReg30) directed to the murine platelet-specific integrin alpha(IIb)beta(3) (gpIIb/IIIa) was administered intraperitoneally either as bolus injection or continuous infusion. With bolus injection, the circulating platelet count dropped to almost zero within 3 hours. Pretreatment with cobra venom factor did not affect platelet depletion, whereas pretreatment with anti-Fc gamma RII/III mAb 2.4G2 or IVIG greatly reduced platelet clearance. With continuous infusion, platelet numbers reached a steady state after 4 days, at approximately 25% of control. This reduction in platelets was, however, not observed in mice deficient for the FcR gamma-chain, lacking Fc gamma RI, Fc gamma RIII, and Fc gamma RIII(-/-) mice. Infusion of a single dose of IVIG with a high IgG dimer content on the 4th day--ie, mimicking therapeutic administration--resulted in a platelet increase for several days. IVIG predominantly consisting of monomeric IgG had no effect on platelet numbers. In conclusion, continuous infusion of MWReg30 induces thrombocytopenia in mice by enhancing Fc gamma receptor--mediated clearance of platelets. In this model, it is shown that IgG dimers present in IVIG preparations are responsible for the increase in platelet counts. (Blood. 2001;98:1095-1099)

Animals↗
PubMed2001

Chromatin-independent binding of serum amyloid P component to apoptotic cells.

Human serum amyloid P component (SAP) is a glycoprotein structurally belonging to the pentraxin family of proteins, which has a characteristic pentameric organization. Mice with a targeted deletion of the SAP gene develop antinuclear Abs, which was interpreted as evidence for a role of SAP in controlling the degradation of chromatin. However, in vitro SAP also can bind to phosphatidylethanolamine, a phospholipid which in normal cells is located mainly in the inner leaflet of the cell membrane, to be translocated to the outer leaflet of the cell membrane during a membrane flip-flop. We hypothesized that SAP, because of its specificity for phosphatidylethanolamine, may bind to apoptotic cells independent of its nuclear binding. Calcium-dependent binding of SAP to early, nonpermeable apoptotic Jurkat, SKW, and Raji cells was indeed observed. Experiments with flip-flopped erythrocytes confirmed that SAP bound to early apoptotic cells via exposed phosphatidylethanolamine. Binding of SAP was stronger to late, permeable apoptotic cells. Experiments with enucleated neutrophils, with DNase/RNase treatment of late apoptotic Jurkat cells, and competition experiments with histones suggested that binding of SAP to late apoptotic cells was largely independent of chromatin. Confocal laser microscopic studies indeed suggested that SAP bound to these apoptotic cells mainly via the blebs. Thus, this study shows that SAP binds to apoptotic cells already at an early stage, which raises the possibility that SAP is involved in dealing with apoptotic cells in vivo.

Animals↗
PubMed2001

Tissue factor pathway inhibitor does not influence inflammatory pathways during human endotoxemia.

Activation of coagulation induces a proinflammatory response in in vitro and animal experiments. Inhibition of the tissue factor-dependent pathway of coagulation inhibits cytokine release and prevents death in gram-negative sepsis models in primates. This study investigated the influence of blocking the coagulation system by tissue factor pathway inhibitor (TFPI) on endotoxin-induced inflammatory responses in healthy humans. Eight men were studied in a double-blind, randomized, placebo-controlled cross-over study. They received a bolus intravenous injection of 4 ng/kg of endotoxin, followed by a 6-h continuous infusion of either TFPI (0.2 mg/kg/h after a bolus of 0.05 mg/kg) or placebo. Endotoxin induced-activation of coagulation was prevented completely by TFPI. In contrast, TFPI did not influence leukocyte activation, chemokine release, endothelial cell activation, or the acute phase response. Thus, complete prevention of coagulation activation by TFPI does not influence activation of inflammatory pathways during human endotoxemia.

Acute-Phase Reaction↗
PubMed2001

The granzyme B inhibitor, protease inhibitor 9, is mainly expressed by dendritic cells and at immune-privileged sites.

Granzyme B is released from CTLs and NK cells and an important mediator of CTL/NK-induced apoptosis in target cells. The human intracellular serpin proteinase inhibitor (PI)9 is the only human protein able to inhibit the activity of granzyme B. As a first step to elucidate the physiological role of PI9, PI9 protein expression in various human tissues was studied. A mAb directed against human PI9 was developed, which specifically stained PI9-transfected COS-7 cells, and was used for immunohistochemistry. Both in primary lymphoid organs and in inflammatory infiltrates, PI9 was present in different subsets of dendritic cells. Also T-lymphocytes in primary and organ-associated lymphoid tissues were PI9 positive. Endothelial cells of small vessels in most organs tested as well as the endothelial layer of large veins and arteries showed strong PI9 staining. Surprisingly, high PI9 protein expression was also found at immune-privileged sites like the placenta, the testis, the ovary, and the eye. These data fit with the hypothesis that PI9 is expressed at sites where degranulation of CTL or NK cells is potentially deleterious.

Animals↗
PubMed2001

IC14, an anti-CD14 antibody, inhibits endotoxin-mediated symptoms and inflammatory responses in humans.

CD14 is a receptor for cell wall components of Gram-negative and Gram-positive bacteria that has been implicated in the initiation of the inflammatory response to sepsis. To determine the role of CD14 in LPS-induced effects in humans, 16 healthy subjects received an i.v. injection of LPS (4 ng/kg) preceded (-2 h) by i.v. IC14, a recombinant chimeric mAb against human CD14, at a dose of 1 mg/kg over 1 h, or placebo. In subjects receiving IC14, saturation of CD14 on circulating monocytes and granulocytes was >90% at the time of LPS injection. IC14 attenuated LPS-induced clinical symptoms and strongly inhibited LPS-induced proinflammatory cytokine release, while only delaying the release of the anti-inflammatory cytokines soluble TNF receptor type I and IL-1 receptor antagonist. IC14 also inhibited leukocyte activation, but more modestly reduced endothelial cell activation and the acute phase protein response. The capacity of circulating monocytes and granulocytes to phagocytose Escherichia coli was only marginally reduced after infusion of IC14. These data provide the first proof of principle that blockade of CD14 is associated with reduced LPS responsiveness in humans in vivo.

Acute-Phase Proteins↗
PubMed2001

Complement activation in patients with rheumatoid arthritis mediated in part by C-reactive protein.

OBJECTIVE: Complement activation in patients with rheumatoid arthritis (RA) is considered to be triggered by immune complexes. Recently, it was shown that C-reactive protein (CRP) can activate the complement system in vivo. We therefore hypothesized that part of the complement activation in RA is due to CRP. The aim of this study was to investigate CRP-mediated complement activation in RA, and to assess its correlation with disease activity. METHODS: Complexes between CRP and the activated complement components C3d (C3d-CRP) and C4d (C4d-CRP), which reflect CRP-mediated complement activation, as well as the overall levels of activated C3 and C4 were measured in the plasma of 107 patients with active RA and 177 patients with inactive RA. Inactive RA was defined according to the American College of Rheumatology criteria for clinical remission. Disease activity was assessed by the modified Disease Activity Score (DAS28). RESULTS: Plasma levels of C3d-CRP and C4d-CRP were increased in the majority of the patients, and were significantly higher in patients with active disease versus those with inactive RA (P < 0.001). In patients with active RA, the plasma concentrations of C3d-CRP and C4d-CRP correlated significantly with the DAS28 (Spearman's rho 0.61 and 0.55, respectively; P < 0.001), whereas these correlations were less pronounced in patients with inactive RA (Spearman's rho 0.28 [P < 0.001] and 0.25 [P = 0.001], respectively). Levels of activated C3 and C4 were also increased in the majority of the patients, particularly in patients with active RA. CONCLUSION: Part of the activation of complement in RA is mediated by CRP and is correlated with disease activity. We suggest that this activation is involved in the pathogenesis of RA.

Adolescent↗
PubMed2001

Increased systemic activation of neutrophils but not complement in preeclampsia.

OBJECTIVE: To investigate whether neutrophils and systemic complement are activated in pregnancies complicated by preeclampsia more than in normal pregnancies. METHODS: We measured native complement components and activation products in plasma by enzyme immunoassays in 19 women with uncomplicated pregnancies, 15 with preeclampsia before cesarean deliveries, and 16 nonpregnant women. Neutrophil activation was measured by specific enzyme immunoassays for myeloperoxidase and lactoferrin. RESULTS: Myeloperoxidase was significantly higher in women with preeclampsia (197 microg/L, 95% confidence interval [CI] 94, 646) than in women with uncomplicated pregnancies (124 microg/L, 95% CI 70, 289; P =.009), whereas lactoferrin did not differ between groups. C4 was decreased in preeclamptic women (0.16 g/L, 95% CI 0.07, 0.48) compared with women with uncomplicated pregnancies (0.21, 95% CI 0.10, 0.30, P <.001). There were no differences for the other native complement components. There was a significant decrease in C1rs-C1 inhibitor, 13 AU/mL (95% CI 9, 34) versus 19 (95% CI 13, 38) (P < or =.001) in normal pregnant women compared with nonpregnant women. There also was an increase in C3, C4, C9 (data not shown), C4bp, 132% (95% CI 94%, 161%) versus 91% (95% CI 57%, 128%); C3bc (7.4 AU/mL, 95% CI 4.2, 10.7) versus 4.8 AU/mL (95% CI 3.2, 7.3) and C4bc (8.6 AU/mL, 95% CI 5.7, 14.0) versus 3.5 AU/mL (95% CI 2.2, 6.7) in normal pregnant women compared with nonpregnant women (P < or =.001). CONCLUSION: Neutrophil activation in preeclampsia was shown by systemic increases in myeloperoxidase. Except for a decrease in C4, systemic complement activation could not be detected in preeclampsia.

Adult↗
PubMed2001

The potentiation of human C1-inhibitor by dextran sulphate is transient in vivo: studies in a rat model.

C1-inhibitor (C1-Inh) is an important regulator of inflammatory reactions because it is a potent inhibitor of the contact and complement system. C1-Inh application in inflammatory disease is, however, restricted because of the high doses required. The glycosaminoglycan-like molecule dextran sulphate (DXS) enhances C1-Inh function in vitro. Hence, we investigated whether co-administration with dextran sulphate reduces the amount of C1-Inh required, through enhancement in vivo. C1-Inh potentiation was measured in a newly developed C1s-inactivation assay that is based on activation of C4 by purified C1s. Activated C4 in rat plasma was quantified with a newly developed ELISA. Human C1-Inh (2.5 microM) inhibited C1s in rat plasma 55-fold faster in the presence of dextran sulphate (15 kDa, 5 microM). To study the stability of the complex in vivo, rats were given a mixture of C1-Inh (10 mg/kg) and dextran sulphate (3 mg/kg). C1-Inh activity during 5 h was analyzed ex vivo with the C1s inactivation assay. The noncovalent C1-Inh-dextran sulphate complex resulted in a transient enhancement of the inhibitory capacity of C1-Inh, lasting for 60-90 min. Dextran sulphate did not affect plasma clearance of C1-Inh. We conclude that the enhanced inhibitory capacity of C1-Inh complexed to dextran sulphate is transient in vivo. Hence, co-administration of these compounds seems a feasible approach to achieve short-term inhibition of complement in vivo.

Animals↗
PubMed2001

Intravenous immunoglobulin preparations induce mild activation of neutrophils in vivo via triggering of macrophages--studies in a rat model.

Despite widespread use in various immune disorders, the in vivo mechanisms of action of intravenous immunoglobulin (IVIG) preparations are not well known. We previously reported that human neutrophils degranulate after incubation with IVIG in vitro as a result of interaction with FcgammaRII. The purpose of this study was to determine whether IVIG might stimulate neutrophils in vivo. Anaesthetized rats received a bolus intravenous injection of IVIG preparations, containing either high (aged IVIG) or low (fresh IVIG) amounts or IgG dimers at a dose of 250 mg/kg. Administration of aged IVIG induced neutrophil activation in vivo, whereas no effect was observed after infusion of fresh IVIG. Histological examination of lung tissue demonstrated mild influx of neutrophils into the pulmonary tissue after aged IVIG administration, though gross damage did not occur. Macrophage-depleted rats no longer showed activation of neutrophils after infusion of aged IVIG, suggesting that neutrophils become activated via an indirect macrophage dependent way. We conclude that IVIG induces a mild activation of neutrophils in vivo via triggering of macrophages depending on the amount of IgG dimers. For this reason, IVIG preparations with a high content of dimers may not always be as harmless as generally believed and may be responsible for some of the side-effects observed during IVIG infusions.

Analysis of Variance↗
PubMed2001

Activation of coagulation factor XI, without detectable contact activation in dengue haemorrhagic fever.

A prospective cohort study was performed in 50 patients with dengue haemorrhagic fever (DHF) to determine the potential role of the contact activation system and factor XI activation (intrinsic pathway) in the coagulation disorders in DHF. To establish whether TAFI (thrombin-activatable fibrinolysis inhibitor) was involved in the severity of the coagulation disorders, the TAFI antigen and activity levels were also determined. Markers of contact activation (kallikrein--C1-inhibitor complexes), the intrinsic pathway of coagulation (factor XIa--C1-inhibitor complexes) and TAFI were measured and correlated to thrombin generation markers (thrombin--anti-thrombin complexes (TAT), prothrombin fragment 1+2 (F1+2)) and a marker for fibrinolysis [plasmin--alpha 2--anti-plasmin complexes (PAP)]. Activation of the intrinsic pathway of coagulation was clearly demonstrated by elevated levels of factor XIa--C1-inhibitor complexes, without evidence of contact activation, reflected by undetectable kallikrein--C1-inhibitor complexes. Both TAFI antigen and activity levels were decreased in all patients, which may contribute to the severity of bleeding complications in DHF because of the impaired capacity of the coagulation system to protect the fibrin clot from fibrinolysis. These findings in a human viral infection model are in accordance with earlier findings in bacterial sepsis.

Autoantigens↗
PubMed2001

Complement activation plays a key role in the side-effects of rituximab treatment.

Treatment with rituximab, a chimaeric anti-CD20 monoclonal antibody, can be associated with moderate to severe first-dose side-effects, notably in patients with high numbers of circulating tumour cells. The aim of this study was to elucidate the mechanism of these side-effects. At multiple early time points during the first infusion of rituximab, complement activation products (C3b/c and C4b/c) and cytokines [tumour necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6) and IL-8] were measured in five relapsed low-grade non-Hodgkin's lymphoma (NHL) patients. Infusion of rituximab induced rapid complement activation, preceding the release of TNF-alpha, IL-6 and IL-8. Although the study group was small, the level of complement activation appeared to be correlated both with the number of circulating B cells prior to the infusion (r = 0.85; P = 0.07) and with the severity of the side-effects. We conclude that complement plays a pivotal role in the pathogenesis of side-effects of rituximab treatment. As complement activation can not be prevented by corticosteroids, it might be relevant to study the possible role of complement inhibitors during the first administration of rituximab.

Adult↗
PubMed2001

Interferon-gamma in healthy subjects: selective modulation of inflammatory mediators.

BACKGROUND: It is suggested that interferon-gamma (IFN-gamma), like other cytokines, is a mediator in the host inflammatory response, which could be of importance in the pathophysiology of sepsis. The role of IFN-gamma in human host inflammatory responses, however, has not been studied. DESIGN: In a placebo-controlled trial we studied the acute effects of IFN-gamma administration on host inflammatory mediators in healthy men: i.e. the cytokine/chemokine cascade system, acute-phase proteins, activation markers of the innate cellular immunity and coagulation/fibrinolysis parameters. RESULTS: IFN-gamma increased plasma levels of interleukin-6 (IL-6), IL-8 and IFN-gamma-inducible protein-10 (IP-10) (P < 0.05), but did not affect plasma levels of other cytokines (IL-4, IL-10, tumour necrosis factor-alpha, IL-12p40/p70). Plasma concentrations of C-reactive protein and secretory phospholipase A2 both increased (P < 0.05). Plasma levels of the leucocyte activation marker elastase-alpha1-antitrypsin complexes increased after IFN-gamma administration (P < 0.05), IFN-gamma increased the percentage of high-affinity Fcgamma-receptor (FcgammaRI) -positive neutrophils (P < 0.05), but did not affect the mean fluorescence intensity of FcgammaRI on neutrophils. Procoagulant and profibrinolytic effects of IFN-gamma were evidenced by increased plasma levels of prothrombin fragment F1 + F2, tissue-plasminogen activator and plasmin-alpha2-antiplasmin complexes (P < 0.05). CONCLUSION: We conclude that IFN-gamma selectively affects host inflammatory mediators in humans.

Acute-Phase Proteins↗
PubMed2001

Fibrinolysis in disseminated intravascular coagulation.

Studies in experimental models for sepsis, the most common cause of disseminated intravascular coagulation (DIC), have put forward the concept of a procoagulant state that is characterized by thrombin generation exceeding that of plasmin. Convincing evidence indicates that this imbalance between coagulation and fibrinolysis is due to increased levels of plasminogen activator inhibitor type 1 (PAI-1). Levels of this fibrinolysis inhibitor indeed correlate with outcome and severity of multiple organ failure in patients with sepsis, as well as in patients with DIC from other causes. Hence we suggest that PAI-1 constitutes an important target for therapy in patients with DIC.

Animals↗
PubMed2001

Human granzyme B mediates cartilage proteoglycan degradation and is expressed at the invasive front of the synovium in rheumatoid arthritis.

OBJECTIVE: To investigate the cartilage-degrading capacity of granzyme B and the presence of granzyme B-positive cells at sites of erosion in the rheumatoid synovium. METHODS: Granzyme B was added to [(3)H]proline/[(35)S]sulphate-labelled cartilage matrices and to cartilage explants. Proteoglycan degradation was assessed by the release of (35)S and glycosaminoglycans into the medium and collagen degradation was assessed by the release of (3)H and hydroxyproline and by measuring the fraction of denatured collagen. Granzyme B expression was studied at the invasive front of the synovium by immunohistochemistry. RESULTS: Granzyme B induced loss of both newly synthesized, radiolabelled proteoglycans in cartilage matrices and resident proteoglycans of the cartilage explants. No effect on collagen degradation was found. Granzyme B-positive cells were present throughout the synovium and at the invasive front. CONCLUSION: The presence of granzyme B-positive cells at the invasive front of the synovium together with its ability to degrade articular proteoglycans supports the view that granzyme B may contribute to joint destruction in rheumatoid arthritis.

Animals↗
PubMed2001

In vitro interaction of C1-inhibitor with thrombin.

Previous observations of increased generation of thrombin during acute attacks of angioedema in plasma of patients with C1-inhibitor (C1-INH) deficiency prompted us to evaluate the interaction of C1-INH with thrombin in both purified systems and human plasma. For this purpose, we used several methods: (1) sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting analysis; (2) enzyme-linked immunosorbent assays to measure complexes between C1-INH and thrombin and inactivated C1-INH; and (3) kinetic studies using a chromogenic assay. We found that the interaction of purified C1-INH with thrombin is associated with the formation of bimolecular complexes of molecular weight (Mr) 130 000 and 120 000 as well as with the appearance of a cleaved form of C1-INH of Mr 97 000. The kinetic studies of inhibition of thrombin by C1-INH showed an average second-order rate constant of 19/s per mol/l, which was significantly increased in the presence of heparin. The addition of thrombin to human plasma was not associated with detectable C1-INH-thrombin complex formation or with cleavage of C1-INH. In conclusion, our data demonstrate that C1-INH upon interaction with thrombin, in part, forms enzyme-inhibitor complexes and, in part, is cleaved. The low second-order rate constant and the lack of a significant interaction in plasma suggest that the inhibition of thrombin by C1-INH has a minor role in circulating blood; however, its role might be important at the endothelial surface, where high concentrations of glycosaminoglycans occur.

Complement C1 Inactivator Proteins↗
PubMed2001

The endothelium in sepsis: source of and a target for inflammation.

OBJECTIVE: To discuss a possible role of the endothelium in sepsis. DATA SOURCES: Studies published in biomedical journals and our own experimental results. STUDY SELECTION: Studies on endothelial mechanisms in the context of sepsis. DATA EXTRACTION AND SYNTHESIS: Changes in endothelial cells on activation by inflammatory stimuli are reviewed briefly; potential mechanisms that lead to endothelial damage during sepsis are discussed. CONCLUSIONS: The endothelium is a key organ involved in the pathogenesis of sepsis. Dysfunction of or injury to the endothelium may be involved in the pathogenesis of multiple organ failure and should be discriminated from activation resulting from stimulation with inflammatory stimuli. Identification of the molecular mechanisms that contribute to endothelial dysfunction or damage is likely to provide novel targets for the treatment of sepsis.

Animals↗