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K M Debatin

Publications and source records attributed to K M Debatin.

At least 109 records · Page 6Linked to original sources
PubMed1997

Activation of the CD95 system increases with disease progression in human immunodeficiency virus type 1-infected children and adolescents.

BACKGROUND: Increased apoptosis in infected as well as noninfected cells has been invoked in CD4+ T helper cell depletion during HIV-1 infection. A strong increase in the expression of CD95 (APO-1/Fas) and CD95 ligand, key regulators of apoptosis in normal T cells, has previously been described in freshly isolated T cells from HIV-1-positive children when compared with healthy age-matched controls. We also found an increase in spontaneous as well as specific CD95-mediated apoptosis in CD4+ and CD8+ T cells from these patients. However, the relationship of these findings to disease progression in children with HIV infection is not known. MEASUREMENTS AND SUBJECTS: We studied expression of CD95 and CD95 ligand as well as sensitivity towards spontaneous and anti-CD95-triggered apoptosis of T cells in 33 HIV-1-positive children and adolescents in different disease stages. RESULTS: Loss of CD4+ T cells in vivo was paralleled by an increase in the percentage of CD95 high T cells and an increase in anti-CD95-induced apoptosis of CD4+ T cells. CD95L mRNA was constantly up-regulated in T cells from patients in intermediate disease stages whereas patients with normal CD4 counts and patients with advanced T cell loss showed CD95 ligand-mRNA levels in or slightly above the range of normal controls. CONCLUSIONS: Disturbed regulation of the CD95 system may play an important role in the development of immunodeficiency during the course of HIV infection in children.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Whole genome amplification of single cells from clinical peripheral blood smears.

Molecular analysis of clinical samples has been hampered by the lack of fresh or frozen specimens and the presence of contaminating background cells within samples obscuring the molecular analysis of the pathological cells of interest. Routine cytology specimens are a ubiquitous and abundant, yet largely untapped, source of clinical samples for molecular analysis. Morphologically defined single cells from peripheral blood smears can be microdissected from contaminating background cells and their whole genome amplified by primer extension preamplification, followed by polymerase chain reaction analysis of the specific DNA of interest. Thus, molecular information can be traced back to the cell of origin in these clinical specimens. This should allow studies on clonality, loss of heterozygosity, mutation, or amplification of multiple loci from one single cell in haematological smears and possibly other clinical cytology specimens.

Blood Specimen Collection↗
PubMed1997

CD95-induced apoptosis contributes to loss of primed/memory but not resting/naive T cells in children infected with human immunodeficiency virus type 1.

Increased apoptosis of uninfected CD4+ T cells is involved in CD4+ T cell depletion in HIV-1+ individuals. Recently, a progressive loss of resting naive T cells has been shown during the asymptomatic stage of HIV infection in children and adults. The CD95 receptor/ligand system is a key regulator of T cell apoptosis. To elucidate the role of this system in the depletion of resting naive T cells, we studied expression of CD95 and sensitivity toward CD95-triggered apoptosis in T cell subsets defined by CD45 (leukocyte common antigen) isoforms and CD62L (lymphocyte homing receptor L-selectin) in a cohort of HIV-1+ children. In patients and healthy control subjects the level of CD95 expression increased from resting/naive (L-selectin(bright) CD45RA+) T cells to primed/memory (CD45RO+ CD45RA-) T cells. In HIV-1+ children the susceptibility of peripheral blood T cells for CD95-mediated apoptosis also increased with progressive differentiation toward primed/memory T cells. Resting/ naive T cells were resistant to spontaneous and anti-CD95-induced apoptosis. Loss of naive (CD45RA+ CD45RO-) T cells in HIV-1+ patients in vivo was found to be paralleled by an increase in the percentage of CD95high T cells as well as an increase in anti-CD95-induced apoptosis of CD4+ and CD8+ T cells. We conclude that loss of naive unprimed T cells during the asymptomatic phase of HIV-1 infection is caused by continuous generation of primed cells that exhibit increased sensitivity toward CD95-mediated apoptotic cell death in vitro.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Activation of the CD95 (APO-1/Fas) system in T cells from human immunodeficiency virus type-1-infected children.

Increased apoptosis of CD4+ T cells is considered to be involved in CD4+ T-cell depletion in human immunodeficiency virus type-1 (HIV-1)-infected individuals progressing toward acquired immunodeficiency syndrome (AIDS). We have recently shown that CD95 (APO-1/Fas) expression is strongly increased in T cells of HIV-1-infected children. In this report we provide further evidence for a deregulated CD95 system in AIDS. CD95 expression in HIV-1+ children is not restricted to previously activated CD45RO+ T cells but is also increased on freshly isolated naive CD45RA+ T cells. In addition, specific CD95-mediated apoptosis is enhanced in both CD4+ and CD8+ T cells. Furthermore, levels of CD95 ligand mRNA are profoundly increased. Specific T-cell receptor/CD3-triggered apoptosis in HIV-1+ children is more enhanced in CD8+ than in CD4+ T cells. Accelerated activation induced cell death of T cells could partially be inhibited by blocking anti-CD95 antibody fragments. These data suggest an involvement of the CD95 receptor/ligand system in T-cell depletion and apoptosis in AIDS and may open new avenues of rational intervention strategies.

Adult↗
PubMed1996

Involvement of the CD95 (APO-1/FAS) receptor/ligand system in drug-induced apoptosis in leukemia cells.

Cytotoxic drugs used in chemotherapy of leukemias and solid tumors cause apoptosis in target cells. In lymphoid cells the CD95 (APO-1/Fas)/CD95 ligand (CD95-L) system is a key regulator of apoptosis. Here we describe that doxorbicin induces apoptosis via the CD95/CD95-L system in human leukemia T-cell lines. Doxorubicin-induced apoptosis was completely blocked by inhibition of gene expression and protein synthesis. Also, doxorbicin strongly stimulates CD95-L messenger RNA expression in vitro at concentrations relevant for therapy in vivo. CEM and jurkat cells resistant to CD95-mediated apoptosis were also resistant to doxorbicin-induced apoptosis . Furthermore, doxorbicin-induced apoptosis was inhibited by blocking F(ab')2 anti-APO-1 (anti-CD95) antibody fragments. Expression of CD95-L mRNA and protein in vitro was also stimulated by other cytotoxic drugs such as methotrexate. The finding that apoptosis caused by anticancer drugs may be mediated via the CD95 system provides a new molecular insight into resistance and sensitivity toward chemotherapy in malignancies.

Antibiotics, Antineoplastic↗
PubMed1996

Resistance of chimpanzee T cells to human immunodeficiency virus type 1 Tat-enhanced oxidative stress and apoptosis.

CD4+ T-cell depletion in AIDS patients involves induction of apoptosis in human immunodeficiency virus (HIV)-infected and noninfected T cells. The HIV type 1 (HIV-1)-transactivating protein Tat enhances apoptosis and activation-induced cell death (AICD) of human T cells. This effect is mediated by the CD95 (APO-1/Fas) receptor-CD95 ligand (CD95L) system and may be linked to the induction of oxidative stress by Tat. Here we show that HIV-1 Tat-induced oxidative stress is necessary for sensitized AICD in T cells caused by CD95L expression. Tat-enhanced apoptosis and CD95L expression in T cells are inhibited by neutralizing anti-Tat antibodies, antioxidants, and the Tat inhibitor Ro24-7429. Chimpanzees infected with HIV-1 show viral replication resembling early infection in humans but do not show T-cell depletion or progression towards AIDS. The cause for this discrepancy is unknown. Here we show that unlike Tat-treated T cells in humans, Tat-treated chimpanzee T cells do not show downregulation of manganese superoxide dismutase or signs of oxidative stress. Chimpanzee T cells are also resistant to Tat-enhanced apoptosis, AICD, and CD95L upregulation.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Disturbances of the CD95 (APO-1/Fas) system in disorders of lymphohaematopoietic cells.

Control of tissue homeostasis is maintained through programs that balance proliferation and cell death. Physiologic cell death is primarily mediated through apoptosis. Deregulations of the cellular programs and genes that determine apoptosis have recently been considered to be involved in a variety of human diseases. One of the central regulatory systems for apoptosis is the CD95 (APO-1/Fas) system. Defects in the CD95 cell surface receptor and deregulated expression of CD95 and the CD95 ligand have been shown to be involved in diseases such as lymphoproliferation, AIDS and haematopoietic failure. This review summarizes our current knowledge on the implication of the CD95 system especially in lymphohaematopoietic diseases in humans.

Journal Article↗
PubMed1996

Monitoring of CD95 (APO-1/Fas) ligand expression in human T cells by quantitative RT-PCR.

CD95 (APO-1/Fas) receptor/ligand interaction is a key regulatory pathway for apoptosis in lymphoid cells. We developed a quantitative RT-PCR for the human CD95-L to determine expression levels in lymphoid cell lines and in lymphocytes derived from blood of healthy individuals. In untreated peripheral blood T lymphocytes and T cell lines constitutive expression of the CD95-L mRNA was found at low levels. Stimulation of T cells by treatment with PMA and ionomycine (P/I) lead up to a 100-fold maximal increase in CD95-L mRNA after 4 h. CD95-L mRNA is produced by activated CD8 and CD4T cells. In vivo increased CD95-L mRNA expression was found in freshly isolated T cells during the acute phase of EBV infection. In contrast to T cells, CD95-L mRNA could be induced in some B lineage cell lines only after five days of stimulation. Since defective or accelerated CD95/CD95-L interaction is considered to be involved in the pathogenesis of lymphoproliferation, autoimmunity and AIDS, the quantitative RT-PCR assay described in this paper may provide a powerful tool for monitoring CD95-L expression in these diseases.

Journal Article↗
PubMed1996

Activation of T cell cytotoxicity against autologous common acute lymphoblastic leukemia (cALL) blasts by CD3xCD19 bispecific antibody.

To develop an effective immunotherapy for B-lineage acute lymphoblastic leukemia (ALL), bispecific monoclonal antibodies (bsAb) were raised by cell fusion of two hybridoma cell lines secreting CD3 and CD19 antibodies. The resulting bispecific antibody contains two different specificities within a single antibody molecule. One binding site (CD3) activates the T cells via the T cell receptor complex, whereas the second binding site (CD19) targets the cytolytic T cells to malignant B cells. Leukemic blasts from children with B-lineage ALL showed stable and strong CD19 expression. CD3xCD19 bsAb were used to activate peripheral blood mononuclear cells (PBMC) from healthy donors or from patients with ALL during remission. Cytotoxic activity against autologous ALL cells by PBMC was induced upon addition of 100 ng/ml CD3xCD19 bsAb after 3 days of preincubation. Costimulation through CD28 increased T cell proliferation to some extent, but did not increase cytotoxic activity of PBMC against leukemic blasts. We present evidence for an effective and specific activation of resting human T lymphocytes by CD3xCD19 bsAb in vitro. Activation of cytotoxic effector T cells is feasible by preincubation with bsAb CD3xCD19 alone and does not rely on additional external costimulation. Thus, targeting of T cell cytotoxicity towards leukemic blasts via CD3xCD19 bsAb may represent a promising strategy for immunotherapy of B-lineage ALL.

Antibodies, Bispecific↗
PubMed1995

Sensitization of T cells to CD95-mediated apoptosis by HIV-1 Tat and gp120.

The depletion of CD4+ T cells in AIDS is correlated with high turnover of the human immunodeficiency virus HIV-1 and associated with apoptosis. The molecular mechanism of apoptosis in HIV infection, however, is largely unknown. T-cell apoptosis might be affected by viral proteins such as HIV-1 Tat and gp120 (refs 10, 11). T-cell-receptor (TCR)-induced apoptosis was recently shown to involve the CD95 (APO-1/Fas) receptor. We show here that HIV-1 Tat strongly sensitizes TCR- and CD4(gp120)-induced apoptosis by upregulation of CD95 ligand expression. Concentrations of Tat found to be effective in cultures of HIV-1-infected cells were also observed in sera from HIV-1-infected individuals. Taken together, our results indicate that HIV-1 Tat and gp120 accelerate CD95-mediated, activation-induced T-cell apoptosis, a mechanism that may contribute to CD4+ T-cell depletion in AIDS.

Antigens, Surface↗
PubMed1995

Mutations in Fas associated with human lymphoproliferative syndrome and autoimmunity.

Fas (also known as Apo1 and CD95) is a cell surface receptor involved in apoptotic cell death. Fas expression and function were analyzed in three children (including two siblings) with a lymphoproliferative syndrome, two of whom also had autoimmune disorders. A large deletion in the gene encoding Fas and no detectable cell surface expression characterized the most affected patient. Clinical manifestations in the two related patients were less severe: Fas-mediated apoptosis was impaired and a deletion within the intracytoplasmic domain was detected. These findings illustrate the crucial regulatory role of Fas and may provide a molecular basis for some autoimmune diseases in humans.

Amino Acid Sequence↗
PubMed1995

Identification of soluble APO-1 in supernatants of human B- and T-cell lines and increased serum levels in B- and T-cell leukemias.

The cell-surface protein APO-1 is a member of the nerve growth factor (NGF)/tumor necrosis factor (TNF) receptor superfamily. APO-1 mediates apoptosis in susceptible cells upon stimulation with the monoclonal antibody anti-APO-1 or upon binding of its natural ligand. Soluble receptors had previously been identified for most members of the NGF/TNF receptor superfamily. Recently, a soluble form of APO-1 (sAPO-1) was described. We established a sandwich enzyme-linked immunosorbent assay to detect sAPO-1 in culture supernatants of human cell lines and in human sera. sAPO-1 was found in culture supernatants of different human B- and T-cell lines. Molecular weights of sAPO-1 and membrane APO-1 were similar. In addition, in comparison to healthy donors, sera from patients with different high- and low-grade malignant B- and T-cell leukemias and lymphomas contained increased levels of sAPO-1. These findings may have implications for the growth of leukemias and the diagnostic monitoring of individual patients.

Animals↗
PubMed1995

Autocrine T-cell suicide mediated by APO-1/(Fas/CD95)

The APO-1/(Fas/CD95) cell surface receptor is a member of the nerve growth factor (NGF)/tumour necrosis factor (TNF) receptor superfamily and mediates apoptosis. Peripheral activated T cells (ATC) from lymphoproliferation (lpr/lpr) mutant mice that express a reduced number of APO-1 receptors have a defect in T-cell receptor (TCR)-induced apoptosis. This suggests that TCR-induced apoptosis involves APO-1. We tested this hypothesis in various human T cells: (1) malignant Jurkat cells, (2) an alloreactive T-cell clone (S13), and (3) peripheral ATC. TCR triggering through immobilized anti-CD3 antibodies or Staphylococcus enterotoxin B (SEB) superantigen induced expression of the APO-1 ligand and apoptosis in these cells. Anti-CD3-induced apoptosis of Jurkat cells was demonstrated even in single-cell cultures. In all cases apoptosis was substantially inhibited by blocking anti-APO-1 antibody fragments and soluble APO-1 receptor decoys. The APO-1 ligand was found in the supernatant of activated Jurkat cells as a soluble cytokine. We propose that TCR-induced apoptosis in ATC can occur through an APO-1 ligand-mediated autocrine suicide. These results provide a mechanism for suppression of the immune response and for peripheral tolerance by T-cell deletion.

Animals↗
PubMed1995

Resistance to APO-1 (CD95) induced apoptosis in T-ALL is determined by a BCL-2 independent anti-apoptotic program.

Selective induction of programmed cell death, apoptosis, may represent a new approach to the treatment of cancer. Apoptosis can be induced by the monoclonal antibody anti-APO-1 directed against the cell surface receptor APO-1, a member of the nerve growth factor (NGF) receptor/tumor necrosis factor (TNF) receptor superfamily. We determined APO-1 expression and sensitivity to anti-APO-1 mediated apoptosis in childhood acute lymphoblastic leukemia cells of T lymphocyte precursor phenotype (T-ALL). APO-1 was constitutively expressed by 21 of 30 T-ALL and by all T-ALL cell lines investigated. However, most APO-1 positive T-ALL were resistant to anti-APO-1 mediated apoptosis. Sensitivity to anti-APO-1 mediated apoptosis was independent of the density of APO-1 expression on the cell surface and independent of the amount of Bcl-2. Incubation of resistant T-ALL with the protein synthesis inhibitor cycloheximide reversed resistance and induced sensitivity to anti-APO-1 mediated apoptosis in most T-ALL. These data suggest that resistance to anti-APO-1 mediated apoptosis in T-ALL is maintained by an active cellular program. Reversion of resistance to sensitivity towards induction of apoptosis in tumors may provide a new basis for successful therapeutic intervention.

Antibodies, Monoclonal↗
PubMed1995

Molecular mechanisms of APO-1/Fas(CD95)-mediated apoptosis in tolerance and AIDS.

The cell surface molecule APO-1/Fas(CD95), a member of the Tumor Necrosis Factor (TNF) receptor/Nerve Growth Factor (NGF) receptor superfamily mediates apoptosis upon cross-linking by agonistic antibodies or its ligand. Recent findings suggest that APO-1/Fas(CD95) and its ligand are the key molecules for antigen receptor-induced apoptosis in activated mature T cells. Here we propose a mechanism for antigen receptor-induced apoptosis of activated T cells via APO-1 ligand mediated autocrine suicide. This mechanism may also contribute to the depletion of CD4+ T cells in AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Apoptotic cell death induced by a mouse-human anti-APO-1 chimeric antibody leads to tumor regression.

The murine anti-APO-1 antibody (gamma 3, kappa) induces programmed cell death (apoptosis) following binding to the APO-1 antigen (m.w., 48 kDa) expressed, e.g., on activated or malignant lymphocytes. APO-1 expression on malignant cell lines and tissues suggested potential clinical utility supported by anti-APO-1-mediated tumor regression in a nude mouse model. A mouse-human anti-APO-1 chimeric antibody (gamma 3, kappa) with an affinity similar to that of the murine antibody was produced. Chimeric anti-APO-1 showed the same potential to inhibit growth of the SKW6.4 B-lymphoblastoid cell line as murine anti-APO-1. In addition, both the chimeric and murine anti-APO-1 antibodies were equally capable of mediating complete macroscopic tumor regression of a SKW6.4 xenotransplant in SCID mice by induction of apoptosis. Induction of apoptosis was the only mechanism for tumor regression because neither murine nor chimeric anti-APO-1 showed anti-tumor activity against solid H53 tumor (APO-1 antigen-positive, anti-APO-1-resistant) xenotransplants. Our results indicate that the chimeric anti-APO-1 antibody effectively induces apoptosis and suggest that chimeric anti-APO-1 should be evaluated for the treatment of malignant cells expressing the APO-1 antigen. However, chimeric anti-APO-I might only be used therapeutically when the antibody can be targeted specifically to tumor cells.

Animals↗