Biomedical subjects

S Depraetere

Publications and source records attributed to S Depraetere.

11 recordsLinked to original sources

PubMed2003

Enhanced soluble interleukin-5 receptor alpha expression in nasal polyposis.

BACKGROUND: Alternative splicing of the interleukin-5 receptor alpha (IL-5Ralpha)-subunit leads to the generation of a signalling, membrane-anchored (TM) isoform, or a secreted [soluble (SOL)], antagonistic variant. Given the key role of IL-5 in eosinophil function, we investigated SOL IL-5Ralpha expression pattern in an eosinophil-associated disease such as nasal polyposis (NP). METHODS: An SOL IL-5Ralpha enzyme-linked immunosorbent assay and quantitative real-time polymerase chain reaction (PCR) were established and applied in serum, nasal secretion and nasal tissue of controls (n = 12), and NP patients (n = 42) with or without asthma. RESULTS: Analysis of serum, nasal secretion, and nasal tissue samples revealed that SOL IL-5Ralpha protein concentrations were significantly increased in NP vs control tissue. Within the NP group, there was a significant up-regulation of SOL IL-5Ralpha in patients with systemic airway disease. These findings were confirmed at the mRNA level, using an optimized real-time reverse-transcriptase PCR procedure. CONCLUSIONS: This report demonstrates SOL IL-5Ralpha transcript and protein up-regulation in NP. Soluble IL-5Ralpha differentiates nasal polyps with or without concomitant asthma. As SOL IL-5Ralpha is strongly up-regulated for disease and has antagonistic properties in vitro, our studies shed new light on the mechanisms of specific immunomodulatory therapies, such as anti-IL-5.

Adult↗

PubMed2001

Human B cell growth and differentiation in the spleen of immunodeficient mice.

Human mAbs (HumAbs) have therapeutic potential against infectious diseases and cancer. Heretofore, their production has been hampered by ethical constraints preventing the isolation of Ag-specific activated B cells by in vivo immunization. Alternatively, severe combined immune deficient (SCID) mice, transplanted i.p. with human (Hu)-PBLs, allow the in vivo stimulation of human Ab responses without the usual constraints. Unfortunately, human B cells only represent a minor fraction of the surviving graft, they are scattered all over the animal body, and thus are hard to isolate for subsequent immortalization procedures. To prevent this dispersion and to provide the human B cells with a niche for expansion and maturation, SCID mice were engrafted with Hu-PBL directly into the spleen. Simultaneously endogenous murine NK cell activity was depleted by treatment with an anti-mouse IL-2 receptor beta-chain Ab. During engraftment, human B lymphocytes became activated, divided intensely, and differentiated into plasmacytoid cells. In vivo exposure to a recall Ag after cell transfer induced expansion of Ag-specific B cell clones. One week after inoculation, human B cells were abundant in the spleen and could easily be recovered for fusion with a heteromyeloma line. This resulted in the formation of stable hybridoma cell lines that secreted Ag-specific HumAbs. Thus transplantation of human lymphoid cells in the spleens of immune deficient mice represents a model for the study of human T cell-dependent B cell activation and proves to be an excellent tool for the successful production of HumAbs.

Animals↗

PubMed2000

Mouse strain and conditioning regimen determine survival and function of human leucocytes in immunodeficient mice.

The innate immune system of severe combined immunodeficient (SCID) mice represents an important barrier to the successful engraftment of human cells. Different genetic and pharmacological strategies improve the graft survival. Non-obese diabetic (NOD)-SCID mice are better hosts for reconstitution with human peripheral blood leucocytes (Hu-PBL) because of their reduced natural killer cell and macrophage activity next to defective T and B cell functions. We investigated effects of TM-beta1, a rat monoclonal antibody recognizing the mouse IL-2 receptor beta-chain, on Hu-PBL survival and function in NOD-SCID and SCID mice. Relative to untreated littermates, TM-beta1 improved Hu-PBL survival in SCID and NOD-SCID mice. Moreover, TM-beta1-pretreated NOD-SCID mice displayed significantly better Hu-PBL survival and tissue distribution than TM-beta1-pretreated SCID mice. Irradiation of NOD-SCID mice further enhanced the effects of TM-beta1. However, these animals died within 3 weeks post-grafting due to graft-versus-host disease. Secondary immune responses were evaluated with Hu-PBL from a donor immune to hepatitis B surface antigen (HBsAg). In TM-beta1-pretreated NOD-SCID mice, human HBsAg-specific memory B cells produced high titres of anti-HBsAg immunoglobulin irrespective of the administration of a secondary antigen booster dose. This contrasts with secondary immune responses in TM-beta1-pretreated SCID mice where high titred antigen-specific immunoglobulins were produced when the appropriate antigen booster was given. In conclusion, reducing the function of the innate immune system in immunodeficient mice improves survival of the human graft and can result in an activation of the memory B cells without the need for recall antigen exposure.

Animals↗

PubMed2000

Long term response to interferon treatment in chronic hepatitis C patients is associated with a significant reduction in anti-E1 envelope antibody titers.

Interferon (IFN) alfa has been used widely for the treatment of chronic hepatitis C virus (HCV) infections but only a small number of patients treated have shown a sustained biochemical and virological response. Anti-envelope E1 and E2 antibody titers were assessed retrospectively before, during, and after treatment with IFN in order to evaluate their usefulness for the prediction and monitoring of therapy outcome in 115 patients infected chronically with HCV genotype 1b. At baseline, E2 induced more frequent and stronger immunogenic responses than E1, irrespective of patient response to therapy. E1 and E2 antibodies also tended to be higher in patients with a long-term or a transient response to IFN treatment than in patients who were absolute non-responders. In most patients, E1 and E2 antibody levels tended to be lower after treatment. This reduction was most pronounced and occurred most frequently in long-term responders to therapy. In this patient group, the reduction of E1 antibodies was more pronounced than that of E2 antibodies. In contrast to E2 antibodies, the decrease of E1 antibodies could already be observed at the end of therapy (week 24) and was significantly larger (p<0.05) than that observed in relapsers and non-responders. Thus, a sustained elevation of E1 antibodies seems to be associated with ongoing infection even when HCV RNA levels were undetectable in serum. Monitoring of E1 antibody titers may represent a useful additional marker to discriminate sustained responders from those who relapse in patients receiving interferon therapy.

Antigens, Viral↗

PubMed1999

N-Confused Calix

Next to the "normal" calix[4]pyrrole 1, the N-confused calix[4]pyrrole 2 is formed in substantial amounts (up to 22 % yield) as side product in the acid-catalyzed condensation reaction of ketones and pyrrole. In some cases, doubly N-confused calix[4]pyrroles are also formed.

Journal Article↗

PubMed1998

Murine IL-2 receptor beta chain blockade improves human leukocyte engraftment in SCID mice.

Severe combined immunodeficient (SCID) mice accept human xenografts and can act as a model for human immune functions. Murine natural killer cells (NK), however, represent an important barrier for the reconstitution of SCID mice with human peripheral blood leukocytes (Hu-PBL). We investigated the effect on Hu-PBL survival of pretreatment with TM-beta1, a rat monoclonal antibody for the mouse IL-2 receptor beta chain. TM-beta1 greatly improved the survival of Hu-PBL. Human lymphocytes, predominantly T cells, survived in the peritoneum and infiltrated spleen and lungs already 1 week after engraftment and liver and thymus from 2 weeks on. Secondary humoral responses were evaluated with Hu-PBL from a donor immune to hepatitis-B surface Ag (HBsAg) and tetanus toxoid (TT). TM-beta1 pretreatment enhanced the recall Ig response to HBsAg and did not affect the baseline anti-TT Ig production. In conclusion, TM-beta1 pretreatment of SCID mice significantly improves the survival and functionality of the Hu-PBL graft.

Animals↗

PubMed1995

Polar agents with differentiation inducing capacity potentiate tumor necrosis factor-mediated cytotoxicity in human myeloid cell lines.

Cotreatment or pretreatment of several human myeloid cell lines (KG1, HL60, U937, THP1) with the differentiation inducer DMSO was found to potentiate the antiproliferative and cytotoxic effects of TNF. In addition, TNF-resistant monocytic cell lines could be sensitized to TNF cytotoxicity by DMSO treatment. Other highly polar molecules, known to be potent differentiation inducers, showed similar effects to those of DMSO. The potentiating effect of DMSO was related neither to an up-regulation of TNF receptor expression nor to an alteration in the rate of TNF internalization and degradation. We present evidence that the TNF activities are p55 TNF receptor-mediated and are not due to insertion of TNF into lipid bilayers, an effect that could be susceptible to DMSO, as this component has been described to modify cell membrane characteristics. DMSO-induced potentiation of TNF cytostasis/cytotoxicity was restricted to myeloid leukemia cell lines. In non-myeloid cells such as fibrosarcomas, myosarcomas, thymomas, or carcinomas, DMSO was found either not to alter or to inhibit TNF-induced cell death. The latter results are in good agreement with data reported by others who suggested that DMSO could act as a scavenger of TNF-induced toxic radical formation. The potential correlation in myeloid cells between DMSO-induced changes in the cells' differentiation status and DMSO-enhanced TNF-susceptibility is discussed.

Animals↗

PubMed1995

Potentiation of tumor necrosis factor-mediated cytotoxicity on human myeloid cell lines: effects of interferons versus dimethylsulphoxide.

After prolonged incubation times of 72 h IFN alpha 2a and IFN beta 1 significantly reduced cell growth in the myelomonocytic U937 and THP1 cell lines. IFN gamma showed only slight growth inhibitory activities. IFN activities were potentiated by the highly polar differentiation inducer dimethylsulphoxide, which is similar to our previous study on tumor necrosis factor (TNF). However, in contrast with TNF, none of the interferon types induced cell cytotoxicity or DNA fragmentation. Like DMSO, all interferons potentiated TNF-induced cytotoxicity, IFN beta 1 and IFN gamma being the most potent in this respect. When applied together, DMSO and IFN gamma enhanced TNF-mediated cell lysis in either an additive (in the case of U937, THP1, HL60 cells) or a synergistic (in the case of KG1) manner, suggesting that the mechanisms of the potentiating activity of DMSO and IFN gamma are different. The potential role of the simultaneous use of DMSO-related molecules, and TNF and/or IFN in leukemic cancer chemotherapy is discussed.

Antineoplastic Agents↗

PubMed1994

Polar agents with differentiation-inducing capacity prime myelomonocytic cell lines to lipopolysaccharide-induced cytolysis: the role of endogenous tumor necrosis factor.

Treatment of the human myelomonocytic U937 and THP1 cell lines for 24 h with 180 mM of the differentiation inducer DMSO, resulted in priming these cells to subsequent LPS-induced cytolysis. The observed cytotoxicity was LPS dose-dependent and characterized by a prolonged lag phase with detectable effects only appearing after 8 h. LPS-induced apoptotic cell death in DMSO-pretreated U937 cells as indicated by the appearance of 200 basepair DNA fragments upon agarose gel electrophoresis of total cellular DNA. Furthermore, DMSO pretreatment potentiated the cells' capacity to produce cytokines, especially TNF, upon LPS stimulation. This endogenously present TNF was metabolized by the cells. These observations suggested that the LPS-induced cytostasis/cytotoxicity was mediated through TNF. Indeed, medium conditioned by LPS-stimulated U937-DMSO cells was found to exert a cytotoxic effect on U937-DMSO cells that was completely neutralized by anti-human TNF antiserum. Such TNF-like activities were not only present in the supernatant but also at the level of the cell membrane of LPS-stimulated U937-DMSO cells. Apart from TNF, other exogenously applied recombinant cytokines (IL1, IL6, IFN gamma, GM-CSF) were not cytotoxic to U937-DMSO cells. Thus, DMSO-pretreated myelomonocytic cells become sensitive to LPS-induced cytotoxicity, which is, at least in part, mediated through endogenous TNF.

Cell Death↗

PubMed1992

"In vitro" effect of interleukin-1 beta on human glioma cell lines: regulation of cell proliferation and IL-6 production.

The human glioma cell lines U251 and HP591 were chosen as "in vitro" models for functional astrocytes. When cultured in the presence of IL-1 beta these cell lines demonstrated a marked increase in interleukin-6 production and in [3H]-thymidine uptake. The addition of dbcAMP could mimic the first effect of IL-1 beta but at the same time suppressed cell proliferation. These results suggest that IL-1 beta possibly exerts one of its biological effects (IL-6 synthesis) by means of the cyclic AMP pathway.

Bucladesine↗

PubMed1991

Stimulation of CRP secretion in HepG2 cells: cooperative effect of dexamethasone and interleukin 6.

This report described the capability of the human. human acute phase reactant, C-reactive protein (CRP). Its secretion is stimulated by interleukin 6 (IL-6) in a dose-dependent fashion and can further be positively modulated by dexamethasone. The way in which this glucocorticoid influences the CRP response depends on its time of application. Incubation of HepG2 cells simultaneously with IL-6 and dexamethasone increases the magnitude of CRP release significantly above that seen with IL-6 alone. After preincubation with dexamethasone, the kinetics of CRP release, induced by IL-6, are increased and approach that observed in the case of alpha 1-acid glycoprotein (alpha 1-AGP) without dexamethasone pretreatment. Conditions for optimal secretion of CRP were determined.

C-Reactive Protein↗