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J Gabert

Publications and source records attributed to J Gabert.

17 recordsLinked to original sources
PubMed1992

Shift from posttranscriptional to predominant transcriptional control of the expression of the GM-CSF gene during activation of human Jurkat cells.

The expression of the granulocyte-macrophage colony-stimulating factor (GM-CSF) gene is differentially regulated in various cell types. We investigated the mechanisms controlling its expression in 12-O-tetradecanoylphorbol-13-acetate plus phytohemagglutinin-stimulated Jurkat cells, a human T-cell line. In unstimulated cells, GM-CSF mRNA was undetectable by Northern blot. Upon activation, it was detected from 3 h onward, with a progressive increase in the levels of the transcript up to 24 h of stimulation. Whereas cycloheximide treatment at the time of stimulation blocked mRNA induction, its addition at later times resulted in a marked increase in transcript levels. Run-on analysis showed that transcription of the GM-CSF gene was low to undetectable in unstimulated cells; stimulation led to transcriptional activation, which was weak at 6 h but had increased 16-fold at 24 h. In addition, the mRNA half-life decreased during activation, from 2.5 h at 6 h down to 45 min at 24 h. Cycloheximide treatment increased GM-CSF mRNA half-life (3- and 4-fold, respectively). Our results show: (a) both transcriptional and posttranscriptional signals regulate GM-CSF mRNA levels in activated Jurkat cells, (b) de novo protein synthesis is required for mRNA induction, whereas destabilizing labile proteins control the transcript stability, and (c) a shift from a posttranscriptional to a predominant transcriptional control of GM-CSF gene expression occurs during activation.

Cell Line↗
PubMed1991

Lambda-like and V pre-B genes expression: an early B-lineage marker of human leukemias.

V pre-B and lambda-like genes are selectively expressed in human pre-B cells and encode polypeptide chains that associate in a mu-pseudolight chain complex that may regulate some crucial steps of early B-cell differentiation. We have followed by polymerase chain reaction and Northern blot analysis the expression of these "pre-B-specific" genes in correlation with the status (rearranged v germline) of Ig gene loci (H, kappa, lambda) in a panel of 32 leukemias pertaining mostly to the B lineage and including a number of ambiguously characterized samples. All cells that had rearranged the H locus only expressed V pre-B and lambda-like transcripts, in agreement with a pre-B status. In this group, some biphenotypic leukemias (mostly My/B) might, in fact, be already engaged in the B lineage. Rearrangement of V kappa or V lambda loci correlated with the disappearance of the pre-B gene products. In a pre-B acute lymphoblastic leukemia cell line that was induced to mature to the B-cell stage in culture upon kappa gene rearrangement, the mu-pseudolight chain complex was actually replaced by the classical mu-kappa molecule. Finally, V pre-B and lambda-like genes were found expressed in two leukemic cells that had retained all Ig loci in germline configuration. This finding raises the possibility of having an early pro-B progenitor in which V pre-B and lambda-like products associate with a H chain surrogate in a complex that would trigger an early event of B-cell differentiation such as the H locus rearrangements.

Antigens, CD↗
PubMed1991

Activation of the granulocyte-monocyte colony stimulating factor gene in acute myeloid leukaemia cells is not related to gene rearrangement.

Several reports have documented that leukaemic blasts produce a number of cytokines among them the granulocyte-monocyte colony stimulating factor (GM-CSF). We analysed the structure of the gene that codes for GM-CSF in 44 acute myeloid leukaemia (AML) cases in an attempt to establish whether the autocrine production of GM-CSF was due to a structural gene alteration. No structural alteration was detected in the GM-CSF gene in any of the 44 cases studied. We, therefore, conclude that the autocrine production of GM-CSF by leukaemia blasts is not dependent on gene rearrangement.

Gene Expression Regulation, Neoplastic↗
PubMed1991

Wild type and tailless CD8 display similar interaction with microfilaments during capping.

We examined the influence of the intracytoplasmic region of CD8 alpha on capping and interaction with microfilaments. We used cell clones obtained by transfecting a CD4+ T-cell hybridoma with (a) T-cell receptor (TCR) alpha and beta chains from a cytolytic clone and (b) CD8 alpha genes that were either native or modified by extensive deletion of the intracytoplasmic region or replacement of the transmembrane and intracytoplasmic domains with those of a class I major histocompatibility complex gene (Letourneur et al. (1990). Proc. natn. Acad. Sci. U.S.A. 87, 2339-2343). Different cell surface structures were cross-linked with anti-T-cell receptor, anti-CD8 or anti-class I monoclonal antibodies and anti-immunoglobulin (Fab')2. Double labeling and quantitative image analysis were combined to monitor fluorescence anisotropy and correlation between different markers. Microfilaments displayed maximal polarization within two minutes. The correlation between these structures and surface markers was then maximal and started decreasing, whereas the redistribution of surface markers remained stable or continued. Furthermore, wild type and altered CD8 alpha exhibited similar ability to be capped and to induce co-capping of TCR and MHC (major histocompatibility complex) class I: the fraction of cell surface label redistributed into a localized cap ranged between 40% and 80%. Finally, cytochalasin D dramatically decreased CD8 capping in all tested clones. It is concluded that the transmembrane and/or intracellular domains of CD8 molecules are able to drive the extensive redistributions of membrane structures and cytoskeletal elements that are triggered by CD8 cross-linking.

Actin Cytoskeleton↗
PubMed1991

Prevention of acute GVHD by in vivo use of anti-interleukin-2 receptor monoclonal antibody (33B3.1): a feasibility trial in 15 patients.

Results of allogeneic bone marrow transplantation (BMT) are still impaired due mainly to acute graft-versus-host disease (GVHD). Successful T cell depletion may abolish GVHD but causes increased rates of rejection and relapse. In vivo blocking of the CD25 receptor on T cells induces efficient and selective immunosuppression. We present results of a pilot trial studying the use of a CD25 MoAb (33B3.1) to prevent acute GVHD after allogeneic BMT. Fifteen patients were included in the study; 14 had a fully HLA matched sibling donor. In association with short methotrexate and cyclosporin A post-graft immunosuppression, the patients received 10 mg of 33B3.1 monoclonal antibody daily according to three successive schedules to study toxicity on marrow graft. No major adverse clinical experiences occurred. Engraftment was not delayed; after 4 months, full chimerism was documented in 14/15 studied patients. No human anti-rat antibody was detected during treatment period. No GVHD occurred during the period of antibody administration. Two patients relapsed; seven are alive and well with a median follow-up of 650 days. This study justifies a prospective controlled study to determine the real impact of 33B3.1 on GVHD prophylaxis.

Acute Disease↗
PubMed1990

A signaling role for the cytoplasmic segment of the CD8 alpha chain detected under limiting stimulatory conditions.

To test for the functional importance of the cytoplasmic segment of the CD8 molecule, a mouse T-cell hybridoma expressing a T-cell receptor specific for the class I major histocompatibility complex product H-2Kb was transfected with a set of CD8 alpha-chain (Ly-2) and/or beta-chain (Ly-3) genes encoding polypeptides with carboxyl-terminal truncations or substitutions. When challenged with Kb-positive splenocytes, transfectants expressing Ly-2 homodimers that lacked cytoplasmic tails responded nearly as effectively as wild-type Ly-2 transfectants. However in marked contrast to the wild-type Ly-2 transfectants, tailless Ly-2 transfectants were greatly impaired in their ability to respond to Kb-transfected L cells. Coexpression of the Ly-3 gene did not restore this impaired response. The unique functional property of the Ly-2 alpha cytoplasmic segment was further supported by the analysis of a chimeric Ly-3 subunit in which the cytoplasmic segment was replaced by the one from the Ly-2 alpha subunit. When associated with a soluble Ly-2 subunit lacking a transmembrane segment, the chimeric Ly-3 was indeed sufficient to restore the response to Kb-transfected L cells. Since the lateral mobility of the tailless Ly-2 molecules on the cell surface was nearly identical to that of the wild-type Ly-2 molecules, their partially impaired function may indicate that they have lost their cis-acting signaling properties but retained their ability to bind class I products of the major histocompatibility complex.

Amino Acid Sequence↗
PubMed1989

Detection of residual bcr/abl translocation by polymerase chain reaction in chronic myeloid leukaemia patients after bone-marrow transplantation.

The polymerase chain reaction was used to evaluate minimum residual disease in chronic myelogenous leukaemia (CML) patients after bone-marrow transplantation, by amplification of the transcript of the specific bcr/abl hybrid gene. Strict precautions were taken to avoid contamination. Peripheral blood cells from 22 patients transplanted for haematological malignant disorders were analysed. The results were clearcut for positive controls (patients with CML in relapse) and negative controls (patients with malignant disorders other than CML). In 11 of 12 CML patients in clinical and cytogenetic remission the bcr/abl transcript was detected 3 months to 6 years after transplantation. Thus, it appears that cells expressing the bcr/abl mRNA are not eradicated from the blood of CML patients in complete clinical remission even years after bone-marrow transplantation.

Adolescent↗
PubMed1989

Comparison of phosphorylation and internalization of the antigen receptor/CD3 complex, CD8, and class I MHC-encoded proteins on T cells. Role of intracytoplasmic domains analyzed with hybrid CD8/class I molecules.

We analyzed the phosphorylation and the dynamics of TCR/CD3, CD8 and MHC class I molecules during the activation of a CD8+ cytotoxic T lymphocyte clone and of CD8- T helper hybridomas transfected with the gene coding for the native (J. Gabert, C. Langlet, R. Zamoyska, J.R. Parnes, A.M. Schmitt-Verhulst, and B. Malissen. 1987. Reconstitution of MHC class I specificity by transfer of the T cell receptor and Lyt-2 genes. Cell 50:545) or truncated CD8 alpha molecule. The CD3 components gamma and epsilon and the CD8 alpha subunit were phosphorylated after activation of the CTL clone with the protein kinase C activator PMA. Class I MHC molecules were phosphorylated irrespective of PMA activation. Constitutive phosphorylation of the MHC class I products was found to be intrinsic to the transmembrane/cytoplasmic portion of the molecules because it was transferred to the CD8 alpha hybrid molecules composed of extracellular CD8 and MHC class I transmembrane and intracytoplasmic domains (CD8-e/MHC-t-i). Measurements of the dynamics of these cell surface molecules by using radiolabeled mAb revealed distinct behaviors: TCR/CD3 complex ligand internalization was increased (around 50% after 40 to 60 min) after PMA activation, whereas the ligand of class I MHC molecules was internalized at constant rate irrespective of PMA activation. Ligand bound to native CD8 molecules was poorly internalized, irrespective of the activation of the T cells with PMA. The same ligand bound to the CD8-e/MHC-t-i hybrid molecule was internalized at the same rate as a class I MHC molecule ligand, indicating that the behavior of the hybrid molecule was characteristic of the transmembrane/cytoplasmic portion of MHC class I molecules.

Amino Acid Sequence↗
PubMed1988

Gene transfer of the Ly-3 chain gene of the mouse CD8 molecular complex: co-transfer with the Ly-2 polypeptide gene results in detectable cell surface expression of the Ly-3 antigenic determinants.

The CD8 molecule is a glycoprotein expressed on a subset of mature T lymphocytes. It has been postulated to be a receptor for class I major histocompatibility complex molecules. In the mouse, CD8 is a heterodimer composed of Ly-2 and Ly-3 chains. We have isolated and analyzed cDNA and cosmid clones corresponding to the Ly-3 subunit. One of the isolated, cosmid clones was subsequently transfected, alone or in combination with the Ly-2 gene, into mouse Ltk- cells. Analysis of the Ly-2,3 molecules expressed at the surface of the double transfectants indicated that they are serologically and biochemically indistinguishable from their normal counterparts expressed on lymphoid cells. Ltk- cells transfected with the Ly-2 gene alone were shown to react with a subset of anti-CD8 monoclonal antibodies whereas Ly-3 transfectants did not stain with any of the anti-Ly-3 antibodies employed in this study. Since at least one of these antibodies (53-5.8) has been previously shown to recognize an epitope which is retained on the Ly-3 subunit after dissociation of the heterodimeric Ly-2,3 complex, these observations suggest that the expression of the Ly-2 polypeptide is required to permit the detectable cell surface expression of the antigenic determinants carried by the Ly-3 subunit.

Amino Acid Sequence↗
PubMed1987

Reconstitution of MHC class I specificity by transfer of the T cell receptor and Lyt-2 genes.

The T cell receptor alpha and beta chain genes donated by an H-2 class I-specific, CD8-dependent cytotoxic T cell clone were transferred, alone or in combination with the Lyt-2 gene, into a class II-restricted, CD4+ T cell hybridoma. Two important points emerged. First, the alpha and beta T cell receptor genes endowed the recipient with the H-2 class I specificity of the donor only if the same cell had also been transfected with the Lyt-2 gene. Second, the functional Lyt-2 molecule was expressed on the transfected cells in the absence of the Lyt-3 polypeptide. These results demonstrate that, besides the T cell receptor, the Lyt-2 polypeptide is the only subset-specific molecule required to retarget a class II-reactive, CD4+ T cell line toward H-2 class I molecules.

Animals↗
PubMed1972

Sociomedical study of patients over 75 in general practice.

In a survey of people of 75 years and over in a general practice situated in the north-west of England a total of 297 patients was examined. Among the many previously unreported medical conditions and social needs were seven unknown malignant conditions, 28 patients with heart failure, five with diabetes, and one with myxoedema. A high incidence of nutritional anaemia was also found. It is concluded that such a survey can detect much hidden illness and disability and that general practice is the right setting for it.

Aged↗
PubMedDate not supplied

Recombinant interleukin-2 (rIL-2) after autologous bone marrow transplantation (BMT): a pilot study in 19 patients.

In vivo use of rIL-2 autologous BMT may be the means of reproducing a kind of "adoptive immunotherapy" from grafted cells after allogeneic BMT. This approach may enhance the spontaneous generation of cytotoxic T-cells and NK cells which are presumably involved in this immunotherapy. Potential risks of such an approach would be to increase the usual toxicity of rIL-2 and to jeopardize the hemopoietic reconstitution. To determine the feasibility of this approach we have treated 19 poor prognosis patients with a succession of autologous BMT followed 78 +/- 12 days later by a continuous infusion of rIL-2. Eighteen million international units (IU) per m2 per day of Proleukine (CETUS, Amsterdam, The Netherlands) were administrated over 6 or 12 days. No patient died of the procedure. Clinical toxicity related to rIL-2 was not increased. Hemopoietic toxicity, significant both for platelets and granulocytes, was transient. Immune stimulation was dramatic for lymphocytes and subpopulations (CD3+ and NK cells) and for cytolytic functions (NK and LAK activity). This trial establishes the feasibility of administration of high doses of rIL-2, 2 months after autologous BMT. In this setting a 6 day period of continuous infusion of 18 million per m2 per day of Proleukine appears to be a regularly tolerable dosage conducting to a major immune activation and invites further studies to determine the clinical impact of such an approach.

Adjuvants, Immunologic↗