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D Kabelitz

Publications and source records attributed to D Kabelitz.

At least 37 records · Page 2Linked to original sources
PubMed2001

Staurosporine and conventional anticancer drugs induce overlapping, yet distinct pathways of apoptosis and caspase activation.

Apoptosis can be induced by various stimuli including DNA-damaging anticancer drugs and the protein kinase inhibitor staurosporine. It is generally believed that the molecular events during execution of apoptosis are shared, as both anticancer drugs and staurosporine derivatives induce mitochondrial damage, cytochrome c release and the activation of the caspase-9 proteolytic cascade. In the present study we show that overexpression of a dominant-negative caspase-9 mutant abolished the activation of endogenous caspase-9, caspase-3 and the cleavage of the caspase substrate Bid in response to anticancer drug treatment. Surprisingly, however, only marginal effects were observed during staurosporine-induced apoptosis. Furthermore, we describe a Jurkat T-cell clone that is completely resistant towards different anticancer drugs, but remains sensitive towards staurosporine-induced apoptosis. In these cells only staurosporine, but neither anti-CD95 nor anticancer drugs were able to trigger caspase activity and the cleavage of caspase substrates. Our results therefore suggest that the mechanism of staurosporine-induced apoptosis is more complex and at least partially differs from anticancer drug-induced caspase activation. These distinct features of staurosporine may allow to bypass chemoresistance of tumor cells and may encourage further clinical trials for the use of staurosporine derivatives in antitumor therapy.

Antineoplastic Agents↗
PubMed2001

Inhibition of protein synthesis by the T cell receptor-inducible human TDAG51 gene product.

The T cell death associated gene 51 (TDAG51) was shown to be required for T cell receptor (TCR)-dependent induction of Fas/Apo1/CD95 expression in a murine T cell hybridoma. Despite the absence of a nuclear localization sequence and a nucleic acid binding domain, it was suggested to be localized in the nucleus and to function as a transcription factor regulating Fas-expression. However, we demonstrate that the human (h)TDAG51 protein is localized in the cytoplasm and the nucleoli, suggesting a role in ribosome biogenesis and/or translation regulation. Indeed, it strongly inhibited translation of a luciferase mRNA in a reticulocyte translational extract. Furthermore, cotransfection of hTDAG51 and the luciferase gene into 293T cells resulted in a strong inhibition of luciferase mRNA translation. Our findings were further strengthened by isolating in a yeast two-hybrid screen three proteins which are involved in the regulation of translation. We speculate that hTDAG51 couples TCR signaling to inhibition of protein biosynthesis in activated T lymphocytes.

Animals↗
PubMed2001

Treatment of aggressive, or progressing indolent peripheral T- and NK-cell neoplasias by combination of fludarabine, cyclophosphamide and doxorubicine.

BACKGROUND: Regarding standardization of treatment, classification, and pathophysiology of peripheral T- and NK-cell neoplasias the current knowledge is markedly behind that of B-cell lymphomas, which are approximately 10 times more frequent. In May 2000, the study group 'Peripheral T- and NK-cell Neoplasias' was founded in Frankfurt/M. This group decided on a clinical protocol and a scientific program for research on the pathophysiology of these entities. Rationales for the therapeutic regimen are the efficacy of cyclophosphamide and doxorubicine as shown in protocols for treatment of high grade lymphoma, the synergism of cyclophosphamide and fludarabine, and reports demonstrating the efficacy of fludarabine in T-cell neoplasias. PATIENTS AND METHODS: Patients will be treated with a combination of fludarabine (30 mg/m(2) days 1-3), cyclophosphamide (1000 mg/m(2) day 1) doxorubicine (25 mg/m(2) day 2+3) (FCD). For patients > or =65 years a dose-reduced FCD regimen will be administered. In patients included in the treatment study and additionally in patients with indolent disease not requiring therapy, scientific projects on the biology of peripheral T- and NK-cell neoplasias will be performed. CONCLUSIONS: Expected conclusions of the projected study are the establishment of treatment and diagnostic standards, and improvement of classification of these entities by clinical, morphologic and biologic parameters.

Aged↗
PubMed2001

Dual TCR-expressing T lymphocytes in health and disease.

The authors briefly review recent experimental advances in elucidating the role of dual T cell receptor (TCR)-expressing lymphocytes in the development of diseases with special emphasis on autoimmunity. Moreover, they summarize present knowledge about these cells concerning their proportion among peripheral blood mononuclear cells, their functionality, and their impact on allorecognition and memory both in humans and in mice. Finally, they describe disease-associated clonal expansions of dual TCR-expressing cells in humans, most of which have been observed in peripheral T cell malignancies. Other cases occurred in inflammatory bowel disease and in HIV infection. They propose that expression of two distinct TCR on malignant T lymphocytes might be much higher than is suggested by the few cases described so far, and that their presence might impinge on therapeutic immunization strategies which make use of the TCR itself as a target.

Animals↗
PubMed2000

Identification of the T-cell receptor alpha variable (TRAV) gene(s) in T-cell malignancies.

Due to the lack of a complete range of monoclonal antibodies (mAb) it is often impossible to rapidly identify by flow cytometry the T-cell receptor variable genes in patients suffering from T-cell malignancies. This applies especially to the alpha variable genes (TRAV), since only very few anti-TcR variable alpha mAb are available. We describe a very rapid method for inverse PCR amplification of the TcR alpha chain without prior purification of the double-stranded cDNA, provide the sequences for appropriate oligonucleotides, and describe a buffer system that dramatically enhances the amplification efficiency as compared to standard conditions.

Buffers↗
PubMed2000

Sensitization to death receptor cytotoxicity by inhibition of fas-associated death domain protein (FADD)/caspase signaling. Requirement of cell cycle progression.

Upon binding of their ligands, death receptors belonging to the tumor necrosis factor (TNF) receptor family initiate a signaling pathway leading to the activation of caspases and ultimately apoptosis. TNF, however, in parallel elicits survival signals, protecting many cell types from cell death that can only be induced by combined treatment with TNF and inhibitors of protein synthesis. Here, we report that in NIH3T3 cells, apoptosis in response TNF and cycloheximide is not inhibited by the broad spectrum caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (zVAD. fmk). Moreover, treatment with zVAD.fmk sensitizes the cells to the cytotoxic action of TNF. Sensitization was also achieved by overexpression of a dominant-negative mutant of Fas-associated death domain protein and, to a lesser extent, by specific inhibition of caspase-8. A similar, but weaker sensitization of zVAD.fmk to treatment with the TNF-related apoptosis-inducing ligand (TRAIL) or anti-CD95 antibody was demonstrated. The unexpected cell death in response to TNF and caspase inhibition occurs despite the activation of nuclear factor kappaB and c-Jun N-terminal kinases. The mode of cell death shows several signs of apoptosis including DNA fragmentation, although activation of caspase-3 was excluded. TNF/zVAD.fmk-induced cell death is preceded by an accumulation of cells in the G(2)/M phase of the cell cycle, indicating an important role of cell cycle progression. This hypothesis is further strengthened by the observation that arresting the cells in the G(1) phase of the cell cycle inhibited TNF/zVAD.fmk-induced cell death, whereas blocking them in the G(2)/M phase augmented it.

3T3 Cells↗
PubMed2000

FasL:Fas ratio--a prognostic factor in breast carcinomas.

Programmed cell death (apoptosis) is primarily mediated by Fas ligand (FasL; CD95L) and the Fas receptor (Fas; CD95). In this study, FasL was detected by immunohistochemical analysis in 85% of breast carcinomas and 14% of fibroadenomas randomly chosen, indicating that high expression of FasL might play a role in tumor pathology. FasL and Fas levels as well as FasL:Fas ratios were further ascertained in 215 human breast tumors, including 199 invasive ductal carcinomas, by real-time quantitative reverse transcription-PCR and compared with expression levels and ratios found in 25 normal human tissues, in 37 fibroadenomas, and in 5 normal breast tissues. Among breast carcinomas, high FasL mRNA expression seems to be positively correlated with histological grading (n = 212; P<0.0001). A ratio of FasL:Fas mRNA transcripts >1 is found to be significantly associated with decreased patient's disease-free survival (n = 211; P<0.03) and increased mortality (n = 211; P = 0.19). A FasL:Fas ratio >1 is related to tumor progression scored by histological grading (n = 212; P<0.02). The selection process leading to highly aggressive breast tumor variants might be enhanced by FasL-mediated tumor fratricide, eventually a possible target for novel therapeutic strategies.

Adolescent↗
PubMed2000

V delta repertoire during thymic ontogeny suggests three novel waves of gamma delta TCR expression.

Taking advantage of a PCR technique that allows amplification of all variable region genes with equal efficiency, we defined three novel waves of TCR delta-chain transcription during thymic ontogeny. The canonical DV101-D2-J2 rearrangement was confined to a narrow window from days 14 to 18 of gestation, indicating that the postulated two consecutive gamma delta precursor waves bearing this canonical DV101 rearrangement will coincide on day 16. Neonatal delta-chain transcripts used a second wave of diverse V alpha gene segments that are exclusively located in the delta locus-proximal gene cluster of intermingled single members of different V alpha subfamilies. In the adult, only expression of a clan of three homologous subfamilies, ADV7, DV104, and ADV17, persists. The members of the ADV7 subfamily are also scattered across the alpha locus, but their usage does not show the position-dependent bias of the other V alpha-to-delta rearrangements.

Aging↗
PubMed2000

Role of apoptosis in cardiac allograft vasculopathy.

Cardiac allograft vasculopathy (CAV) is a major long-term complication of heart transplantation. Coronary endothelial injury provokes immunological reactions leading to inflammation and proliferation of vascular smooth muscle cells. Recent studies suggest that cell death of endothelial cells during early phases of transplant arteriopathy development proceeds via programmed cell death (apoptosis). The potential role of apoptosis in CAV is discussed. Based on these concepts, therapeutic strategies might be envisaged aimed at the prevention of apoptosis during the initiating phase of CAV.

Animals↗
PubMed2000

Expression of the apoptosis-inducing ligands FasL and TRAIL in malignant and benign human breast tumors.

Apoptosis-inducing ligands such as Fas ligand (FasL) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) have been found to play an important role in cell regulation. Different malignant tumors show an altered expression of these ligands and their respective receptors compared to normal tissues. The purpose of this study was therefore to investigate expression of TRAIL, FasL, and its receptor Fas on protein and mRNA levels in breast carcinomas (n=40), fibroadenomas (n=7), and normal breast tissues (n=5). Immunohistochemical reaction demonstrated that FasL was strongly expressed in breast cancer tissues (34/40) while only one fibroadenoma and one normal breast tissue reacted weakly positive for FasL. All fibroadenomas and normal breast tissues as well as the majority of breast cancer tissues expressed Fas on protein level. Quantitative RT-PCR analysis detected high expression of FasL mRNA in breast cancer tissues and fibroadenomas, whereas fibroadenomas showed the highest Fas mRNA copy numbers, followed by breast cancer tissues and normal breast tissues (P<0.05). Compared to FasL expression, TRAIL could be detected in less breast cancer tissues on protein level (21/40) and was found in only one fibroadenoma and none of the normal breast tissues. Thus, it can be concluded that malignant breast tumors show an altered expression of the two apoptosis-inducing ligands FasL and TRAIL.

Apoptosis↗
PubMed2000

Regulation of activation-induced cell death of mature T-lymphocyte populations.

Resting mature T lymphocytes are activated when triggered via their antigen-specific T-cell receptor (TCR) to elicit an appropriate immune response. In contrast, preactivated T cells may undergo activation-induced cell death (AICD) in response to the same signals. along with cell death induced by growth factor deprivation, AICD followed by the elimination of useless or potentially harmful cells preserves homeostasis, leads to the termination of cellular immune responses and ensures peripheral tolerance. T-cell apoptosis and AICD are controlled by survival cytokines such as interleukin-2 (IL-2) and by death factors such as tumor necrosis factor (TNF) and CD95 ligand (CD95L). In AICD-sensitive T cells, stimulation upregulates expression of one or several death factors, which in turn engage specific death receptors on the same or a neighboring cell. Death receptors are activated by oligomerization to rapidly assemble a number of adapter proteins and enzymes to result in an irreversible activation of proteases and nucleases that culminates in cell death by apoptosis. Increased knowledge of the molecular mechanisms that regulate AICD of lymphocytes opens new immunotherapeutic perspectives for the treatment of certain autoimmune diseases, and has implications in other areas such as transplantation medicine and AIDS research.

Animals↗
PubMed2000

Bypassing hybridoma technology: HLA-C reactive human single-chain antibody fragments (scFv) derived from a synthetic phage display library (HuCAL) and their potential to discriminate HLA class I specificities.

The generation of discriminative, monospecific anti-HLA antibodies used to be a difficult endeavor. Phage display technology, using single-chain antibody fragments (scFv) offers a powerful alternative obtaining target-specific, genetically stable reagents. Most of scFv obtained to date have been enriched by panning phage libraries to solid-phase coupled antigens. In the present study, HLA-C-specific scFv were isolated using a synthetic phage library in combination with a Cw*0602 overexpressing cell line. ScFv from this procedure precipitated HLA-Cw*0602 heavy chains from whole cell lysates. Flow cytometry analysis revealed that scFv stained HLA-Cw*0602-positive cells, but not cells expressing HLA alleles Cw*0302, Cw*0802, A*0201, B*2705, or Gm1*01011, indicating the specificity of scFv. Similarly they showed an ability to discriminate Cw*0602-positive from Cw*0602-negative peripheral blood lymphocytes (PBL). The results of our study demonstrate the feasibility to genetically engineer single-chain HLA-class I-specific antibodies, by phage display technology. This approach might be a valuable tool to develop a broad range of novel monospecific antibodies against HLA-class I specificities.

Alleles↗
PubMed2000

Cell-surface expression of transrearranged Vgamma-cbeta T-cell receptor chains in healthy donors and in ataxia telangiectasia patients.

Transrearrangements between the T-cell receptor (TCR) VgammaI family and JbetaCbeta loci occur at increased frequencies in patients with ataxia telangiectasia (AT). We have used an optimized reverse transcriptase polymerase chain reaction (RT-PCR) approach to investigate the occurrence of TCRVgamma-JbetaCbeta transrearrangements involving the dominantly used Vgamma element in peripheral blood gammadelta T cells, i.e. Vgamma9. We detected in frame transcripts of Vgamma9-JbetaCbeta transrearrangements in 4/16 AT patients and in 3/13 healthy control donors. A panel of monoclonal antibodies (mAb) against all expressed TCRVgamma elements was used to monitor cell-surface expression of transrearranged TCR. A very low proportion (< 1%) of peripheral blood TCRalphabeta cells expressed Vgamma instead of Vbeta elements. For the first time, we have isolated and molecularly characterized alphabeta T cells with a Vgamma9-JbetaCbeta transrearrangement from two AT patients and we have shown that such TCR are functional. We conclude that functional TCR transrearrangements can also involve Vgamma9, the dominant Vgamma element in peripheral blood gammadelta T cells.

Ataxia Telangiectasia↗
PubMed2000

Differential regulation of activation-induced cell death in individual human T cell clones.

BACKGROUND: Restimulation of T lymphocytes via the TCR/CD3 complex can result in CD95/CD95L-dependent activation-induced cell death (AICD). Although the correlation of AICD sensitivity to the T helper 1 phenotype was confirmed in different studies, the underlying mechanism is still debated. Thus, it has been suggested that in Th2 cells, AICD resistance is controlled by a TCR-induced upregulation of the CD95-associated inhibitory phosphatase, FAP-1. We and others demonstrated that AICD resistance is associated with a reduced surface expression of CD95L upon restimulation. METHODS: Utilizing RT-PCR, Western blotting and flow cytometry, we analyzed time-dependent changes in levels of CD95L mRNA, cytosolic protein and surface expression in five long-term human T cell clones and polarized helper populations. RESULTS: We confirm that the inducible CD95L surface expression is lower or absent in all tested AICD-resistant clones as compared to sensitive cells. It is of interest that striking differences with respect to the activation-dependent inducibility of CD95L mRNA expression in individual resistant clones were observed. In addition, alterations in the expression of the inhibitory phosphatase FAP-1 or TCR-dependent changes in CD95 sensitivity in AICD-resistant clones could be ruled out as a mechanism for AICD resistance of human T cell clones. CONCLUSIONS: (1) The data presented strongly support the previous notion that AICD resistance of human T cell clones is mainly regulated by a differential expression of CD95L. (2) Differential expression of CD95L on individual resistant clones results from a lack of mRNA induction in one set and from a markedly decreased surface expression of translated protein in another set of clones.

Antibodies, Monoclonal↗
PubMed2000

Antigen recognition by human gammadelta T lymphocytes.

Mature T lymphocytes carrying the conventional alphabeta T cell receptor (TCR) recognize peptide antigens in the context of MHC class I (CD8+) and MHC class II (CD4+) antigens, respectively. In striking contrast, human gammadelta T lymphocytes recognize unconventional antigens via their heterodimeric TCR in a non-MHC-restricted fashion. In this brief review, we discuss recent progress in the identification of ligands that are specifically recognized by human gammadelta T cells. It appears that gammadelta T cells have evolved to supplement the cellular immune response towards antigens that are not seen by alphabeta T lymphocytes.

Amines↗
PubMed2000

Alloreactivity and apoptosis in graft rejection and transplantation tolerance.

Weissmann wrote as early as 1889 that higher organisms contain within themselves the germs of death [1]. However, the term, programmed cell death, or apoptosis as it is now known, was defined much later [2]. Thus, it was long recognized that damaged and old cells are eliminated within the body, but the underlying mechanisms are only now beginning to emerge. Apoptosis appears central to the process of negative selection of developing T-cells in the thymus. In regard to organ transplantation, apoptosis contributes to graft rejection and the establishment of graft tolerance. Thus, understanding the regulatory mechanisms of apoptosis may help establish a new protocol for the induction of transplantation tolerance.

Animals↗
PubMed2000

Cytotoxic hepatosplenic gammadelta T-cell lymphoma following acute myeloid leukemia bearing two distinct gamma chains of the T-cell receptor. Biologic and clinical features.

BACKGROUND AND OBJECTIVES: Hepatosplenic gd T-cell lymphoma is a rare entity of peripheral T-cell lymphomas. We characterized in detail the first case of hepatosplenic gd -T-cell lymphoma following acute myeloid leukemia. DESIGN AND METHODS: Hepatosplenic gd -T-cell lymphoma was diagnosed in a woman who had been in complete remission (CR) of acute myeloid leukemia (AML) for two years. Improvement but no objective response of the disease was observed after various types of chemotherapy. CR was achieved after related donor stem cell transplantation. Thirteen months later relapse of hepatosplenic gd T-cell lymphoma was diagnosed. While being prepared for a second transplantation the patient developed meningeal lymphoma and died. The patient's lymphoma cells were studied by immunologic, functional and molecular techniques. RESULTS: Lymphoma cells expressed the gd T-cell receptor (TCR), CD2, CD3, CD5, CD7, CD38, CD45, CD161 (NKR-P1), TIA and Ki67. Further analysis revealed expression of Vd1 and two distinct TCRg chains, Vg3 and Vg9, by the malignant cell clone. The clonality of the T-cells was confirmed by reverse transcriptase polymerase chain reaction (RT-PCR) followed by sequencing of TCR Vg3, Vg9 and Vd1 junctional regions. Clone-specific PCR was negative at diagnosis of AML and was positive at all times during follow-up of the hepatosplenic gd T-cell lymphoma. The lymphoma cells mediated strong natural killer cell-like cytotoxic activity, possibly explained by expression of CD161 and a lack of killer inhibitory receptor. INTERPRETATION AND CONCLUSIONS: Several so far undescribed features were observed in this case of hepatosplenic gd T-cell lymphoma, such as T-cell lymphoma following AML, expression of two distinct T-cell receptor g-chains, and an unexpected cytotoxic phenotype.

Acute Disease↗