PubMed Health⌕ Search

Biomedical subjects

N Glaichenhaus

Publications and source records attributed to N Glaichenhaus.

35 records · Page 2Linked to original sources
PubMed1997

Immunological tolerance to a pancreatic antigen as a result of local expression of TNFalpha by islet beta cells.

Recent experiments have suggested that tumor necrosis factor alpha (TNFalpha) can down-regulate islet-specific T cells and prevent the development of autoimmune diabetes. Here we demonstrate that transgenic mice expressing both TNFalpha and the Leishmania major LACK antigen in the pancreas (RIP-TNFalpha/RIP-LACK) exhibit an impaired ability to mount a CD4+ T cell response against LACK. In addition, peripheral CD4+ T cells from TCR transgenic mice (TCR-LACK/RIP-TNFalpha/RIP-LACK) produced reduced interleukin-2 but elevated levels of T helper 2 cytokines in response to LACK peptide in vitro. Taken together, our data suggest that TNFalpha may act in vivo to modulate a potentially damaging self-reactive T cell response by inducing tolerance to pancreatic antigens.

Animals↗
PubMed1996

Resistance to Leishmania major induced by tolerance to a single antigen.

In mice, susceptibility to Leishmania major is associated with the early expansion of T helper 2 cells (TH2) cells, but nothing is known of the specificity of these cells. A previously identified antigen, Leishmania homolog of receptors for activated C kinase (LACK), was found to be the focus of this initial response. Mice made tolerant to LACK by the transgenic expression of the antigen in the thymus exhibited both a diminished TH2 response and a healing phenotype. Thus, T cells that are activated early and are reactive to a single antigen play a pivotal role in directing the immune response to the entire parasite.

Amino Acid Sequence↗
PubMed1996

Presentation of the protective parasite antigen LACK by Leishmania-infected macrophages.

Macrophages are apparently the only cells that in vivo allow the growth of the intracellular pathogen Leishmania. They are thus generally considered as likely candidates for the presentation of parasite Ag to CD4+ T lymphocytes known to be involved in protective and counterprotective immune responses. In the present study, we examined whether mouse macrophages infected with Leishmania were capable of stimulating T cell hybrids and a T cell clone reacting with the previously identified protective Ag LACK (Leishmania homologue of receptors for Activated C Kinase). This parasite protein is expressed in both promastigote and amastigote stages of Leishmania. We found that IFN-gamma-treated macrophages recently infected with live Leishmania promastigotes were fully competent to activate LACK-reactive T cells. However, at later times of infection, permissive macrophages infected with promastigotes were no longer able to present LACK, in spite of the presence of numerous intracellular parasites. This punctual presentation of LACK was apparently linked with the destruction, at least partial, of the intracellular parasites. In contrast, macrophages infected with live Leishmania amastigotes were always unable to stimulate the LACK-specific T cells. Amastigote-infected macrophages could, however, reactivate the T cells if LACK-delta(1), a recombinant form of LACK, was added as an exogenous protein in the culture medium. Similar results were obtained with all combinations tested involving macrophages from various origins, different activating cytokines (IFN-gamma, granulocyte-macrophage CSF, IL-4), several Leishmania species (L. amazonensis, L. major, L. donovani), and 15 different LACK-reactive T cell hybrids and clones. From these data, it is tempting to propose that the differentiation of promastigotes into amastigotes, which leads to a better survival of the parasites within macrophages, also allows them to go unnoticed by the immune system.

Animals↗
PubMed1995

Expression cloning of a protective Leishmania antigen.

Parasite-specific CD4+ T cells have been shown to transfer protection against Leishmania major in susceptible BALB/c mice. An epitope-tagged expression library was used to identify the antigen recognized by a protective CD4+ T cell clone. The expression library allowed recombinant proteins made in bacteria to be captured by macrophages for presentation to T cells restricted to major histocompatibility complex class II. A conserved 36-kilodalton member of the tryptophan-aspartic acid repeat family of proteins was identified that was expressed in both stages of the parasite life cycle. A 24-kilodalton portion of this antigen protected susceptible mice when administered as a vaccine with interleukin-12 before infection.

Amino Acid Sequence↗
PubMed1993

Coordinated posttranscriptional control of gene expression by modular elements including Alu-like repetitive sequences.

We previously reported that in rat fibroblasts, accumulation of a set of mRNAs ("pIL genes") was modulated as a function of cell growth and transformation, at a posttranscriptional stage, and by a mechanism that depends on a short nucleotide sequence containing an ID repetitive element. In mouse fibroblasts, hybridization with rat pIL probes identified mRNAs with the same pattern of expression, which did not contain ID sequences but contained a different regulatory element, encompassing a repetitive sequence of the B1 family. Expression in mouse cells of a reporter beta-globin gene carrying this element inserted in its 3' noncoding region was growth- and transformation-dependent. The nucleotide sequences of two murine and of three rat pIL cDNAs showed clear similarities in the region immediately adjacent to the ID and B1 repeats. Both the repeat and the flanking sequence were required to confer on beta-globin constructs the pattern of expression characteristic of the pIL genes. The hypothesis is presented that repetitive sequences in the eukaryotic genome might be modular parts of complex regulatory elements ensuring the coordinated expression of various mRNA species.

3T3 Cells↗
PubMed1991

A novel strategy for the generation of T cell lines lacking expression of endogenous alpha- and/or beta-chain T cell receptor genes.

Mutant T cell lines that do not express the endogenous alpha- and/or beta-chain genes of the TCR were generated from the alpha beta TCR/CD3+ tumor cell line C6VL with a combination of classical mutagenesis methods and selection of somatic hybrid variants. This novel strategy obviated the need for repeated mutagenesis and screening of a large number of individual clones. The loss of either the alpha- or the beta-chain expression in the mutant cells was associated with the loss of surface TCR/CD3 complex, which could be rescued by the transfection of appropriate exogenous alpha- and/or beta-chain gene constructs. Because these cells express a single TCR molecule on the cell surface, they are useful for the study of the assembly and function of the alpha beta TCR. This strategy is also generally applicable for the generation of homozygous mutant cell lines lacking other gene products.

Animals↗
PubMed1991

Requirement for association of p56lck with CD4 in antigen-specific signal transduction in T cells.

The T cell-specific transmembrane glycoprotein CD4 interacts with class II MHC molecules via its external domain and is associated with tyrosine kinase p56lck via a cysteine motif in its cytoplasmic domain. We have assessed the ability of CD4 to synergize with the antigen-specific T cell receptor (TCR) for induction of transmembrane signals that result in lymphokine production. Mutant CD4 molecules were introduced into T cells that lacked endogenous CD4 but expressed TCRs specific for lysozyme peptides or the superantigen SEA bound to Ab or Abm12 class II MHC molecules. With either ligand, T cell activation occurred only when CD4 was associated with p56lck. These results demonstrate that residues within the cytoplasmic domain of CD4 are required for its coreceptor function in TCR-mediated signal transduction and strongly support the notion that the association of CD4 with p56lck is critical in this process.

Amino Acid Sequence↗
PubMed1987

A role for ID repetitive sequences in growth- and transformation-dependent regulation of gene expression in rat fibroblasts.

A set of mRNAs tagged by repetitive sequences of the ID family were found to accumulate following growth-factor-induced transition of normal (FR3T3) rat fibroblasts from a quiescent to a proliferative state. The levels of the same transcripts were also increased following transformation by polyoma virus and by ras and myc oncogenes. The presence of the ID element appeared to be determinant, since a similar pattern of expression was observed for a construct where one element had been inserted in the 3' noncoding region of a rabbit beta-globin gene expressed under control of an SV40 promoter.

Animals↗
PubMed1987

Study of a growth hormone-regulated protein secreted by rat hepatocytes: cDNA cloning, anti-protease activity and regulation of its synthesis by various hormones.

GHR-P63 ('growth hormone-regulated protein of 63,000 daltons') is an acidic glycoprotein secreted by rat hepatocytes whose synthesis is abolished upon hypophysectomy. The sequence of its mRNA including the entire coding and 3' untranslated regions was determined from a nearly full-length lambda gt11-cDNA clone. The sequence contained two ATGs in frame giving rise to two overlapping coding regions which could encode precursor polypeptides of 416 and 406 amino acid residues (MrS = 46549 and 45371). These potential translation initiation codons appeared to be functional both in vitro and in intact cells since two precursors of the correct size were immunoprecipitated as products of mRNA translation. The unglycosylated precursors were converted into intermediate intracellular forms of about 56,000 daltons containing N-linked oligosaccharide side chains and thereafter into the secretory form of approximately equal to 63,000 daltons. Strong sequence homologies, both at the nucleotide and the amino acid levels were found between GHR-P63 and several serum protease inhibitors, more particularly mouse contrapsin and human alpha 1-antichymotrypsin. In agreement with sequence data, GHR-P63 purified from rat blood by affinity chromatography was found to carry an anti-trypsin activity. GHR-P63 mRNA, virtually undetectable in hepatocytes from hypophysectomized rats, could be hormonally re-induced to subnormal levels both in vivo by treating animals with hormones and in vitro by incubating the defective cells with hormones. Growth hormone was absolutely required but had a weak effect when used alone. Glucocorticoids which had no effect per se, strongly potentiated the action of growth hormone. Nuclear run-off experiments suggest that hormones regulated GHR-P63 mRNA levels by acting mostly, if not exclusively, on gene transcription.

Acute-Phase Proteins↗
PubMed1986

Increased levels of mitochondrial gene expression in rat fibroblast cells immortalized or transformed by viral and cellular oncogenes.

Steady-state levels of the mitochondrial (mt) mRNA encoding subunit II of cytochrome oxidase (COII) were increased 5-10 fold in fully transformed cell lines derived from rodent embryonic fibroblasts after transfer of polyoma virus DNA, and in immortalized cell lines established by transfer of plt (polyoma large T protein), E1A (adenovirus) and myc oncogenes. Increased mitochondrial gene expression was not related with active growth per se: it was low in fast-growing rat embryo cells, and it did not change upon serum starvation and subsequent stimulation of FR3T3 cells. The number of copies of mtDNA did not vary, and different mitochondrial mRNAs and rRNAs were increased in the same proportions, suggesting a change in the rate of accumulation of their common precursor.

Animals↗
PubMed1985

Epidermal growth factor and oncogenes induce transcription of the same cellular mRNA in rat fibroblasts.

We have isolated and sequenced a cloned cDNA corresponding to an mRNA present in significantly higher levels in rat cells transformed by polyoma virus, Rous sarcoma virus, and the cellular oncogene H-ras than in the normal parental cell lines. The mRNA transcript is also rapidly induced by the polypeptide growth factor epidermal growth factor, providing a new link between oncogenes and growth factors. Both the growth factor and the oncogenes control expression of the corresponding gene at the transcriptional level. Our results point to the existence of intracellular mechanisms that are common to the action of both growth factors and oncogenes.

Animals↗
PubMed1982

The roles of individual polyoma virus early proteins in oncogenic transformation.

The expression in normal rat cells of modified polyoma virus genomes, separately encoding large T, middle T or small T antigens, has allowed the investigation of the roles of these proteins in oncogenic transformation. Middle T is sufficient to transform cells of established lines but the transformants are serum dependent. Large T lacks intrinsic oncogenic potential but can relieve the serum dependence of normal and transformed cells. Middle T alone cannot transform primary rat embryo fibroblasts.

Animals↗