Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.27.1 (RNase)
 16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The induction of immunoglobulin E (IgE) switching in B cells requires at least two signals. The first is given by either of the soluble lymphokines interleukin 4 (IL-4) or IL-13, whereas the second is contact dependent. It has been widely reported that a second signal can be provided by the CD40 ligand (CD40L) expressed on the surface of T cells, mast cells, and basophils. A defect in the CD40L has been shown recently to be responsible for the lack of IgE, IgA, and IgG, characteristic of the childhood X-linked immunodeficiency, hyper IgM syndrome (HIGM1). IgE can however be detected in the serum of some HIGM1 patients. In this study, we isolated T cell clones and lines using phytohemagglutinin (PHA) and allergen, respectively, from the peripheral blood of one such patient who expressed a truncated form of CD40L, and investigated their ability to induce IgE switching in highly purified, normal tonsillar B cells in vitro. Unexpectedly, 4 of 12 PHA clones tested induced contact-dependent IgE synthesis in the presence of exogenous IL-4. These clones were also shown to strongly upregulated IL-4-induced germline epsilon RNA and formed dense aggregates with B cells. Of the four helper clones, three were CD8+, of which two were characteristic of the T helper cell 2 (Th2) subtype. Two allergen-specific HIGM1 T cell lines, both of the Th0 subtype, could also drive IgE synthesis when prestimulated using specific allergen. All clones and lines were negative for surface expression of CD40L, and the mutated form of CD40L was confirmed for a representative clone by RNase protection assay and sequencing. The IgE helper activity could not be attributed to membrane tumor necrosis factor alpha (TNF-alpha) although it was strongly expressed on activated clones, and the addition of neutralizing anti-TNF-alpha antibody did not abrogate IgE synthesis. These results therefore suggest the involvement of T cell surface molecules other than CD40L in the induction of IgE synthesis, and that these molecules may also be implicated in other aspects of T-B cell interactions.
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PMID:T cell clones from an X-linked hyper-immunoglobulin (IgM) patient induce IgE synthesis in vitro despite expression of nonfunctional CD40 ligand. 796 60

Rapid advances in our ability to localize and quantify macromolecular changes in health and disease are being brought about by the availability of genetically altered animals (mutants), purified reagents such as monoclonal antibodies, and new molecular methods. Targeted gene deletion (knockouts) and gene insertions (transgenics) in animals can allow identification of the importance and function of macromolecules. Monoclonal antibodies and fluorescent labels coupled with advances in microscopy provide exacting and multi-dimensional information about localization and cellular changes in proteins, carbohydrates, and lipids using immunohistochemistry, fluorescent activated cell sorting, and immunoprecipitation. Similarly, new applications of molecular methods can be used to identify and localize nucleic acids in tissues via in situ hybridization, polymerase chain reaction (PCR), reverse transcription (RT) PCR, differential display RT-PCR, RNase protection assays, and microchip arrays. The ligand for CD40 (CD40L), an important immunoregulatory molecule, is an example of the successful application of mutants, monoclonal antibodies, and molecular methods to cloning and biological characterization of new molecules. CD40L knockout mice, monoclonal antibodies, and several molecular methods were used to identify mutations in CD40L as the genetic basis for hyper-IgM syndrome in humans, to provide new insights into the pathobiology of Pneumocystis carinii infection, and to evaluate CD40L for immunotherapy of tumors and opportunistic infections.
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PMID:Mechanisms of disease and injury: utilization of mutants, monoclonals, and molecular methods. 1036 85

This study addresses a mechanism by which lymphocytes may promote vascular endothelial growth factor (VEGF) expression and angiogenesis in immune inflammation. Resting human umbilical endothelial cells (HUVECs) were found to express low levels of VEGF messenger RNA (mRNA) by reverse transcription polymerase chain reaction and ribonuclease protection assay with little or no change in expression following activation by cytokines, including tumor necrosis factor-alpha, interleukin (IL)-1, interferon gamma, or IL-4. In contrast, treatment of HUVECs and monocytes with soluble CD40 ligand (sCD40L) resulted in a marked dose-dependent induction of VEGF mRNA (approximately 4-fold), which peaked between 1 and 5 hours post-stimulation. Transient transfection of HUVECs was performed with a luciferase reporter construct under the control of the human VEGF promoter. Treatment of transfected HUVECs with sCD40L was found to enhance luciferase activity (approximately 4-fold) compared with controls, similar to the relative fold induction in mRNA expression in parallel cultures. Thus, CD40-dependent VEGF expression was a result of transcriptional control mechanisms. Treatment of HUVECs with sCD40L was also found to function in vitro to promote growth and proliferation in a VEGF-dependent manner, and CD40-dependent HUVEC growth was comparable to that found following treatment with recombinant human VEGF. Furthermore, subcutaneous injection of sCD40L in severe combined immunodeficient and nude mice induced VEGF expression and marked angiogenesis in vivo. Taken together, these findings are consistent with a function for CD40L-CD40 interactions in VEGF-induced angiogenesis and define a mechanistic link between the immune response and angiogenesis. (Blood. 2000;96:3801-3808)
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PMID:Ligation of CD40 induces the expression of vascular endothelial growth factor by endothelial cells and monocytes and promotes angiogenesis in vivo. 1109 63

This study aimed to determine the effects of anti-CD154 on T cell cytokine profiles and ocular chemokine gene expression after high-risk corneal transplantation and to specifically determine if CD154 blockade is associated with a switch from a Th1 to a Th2 alloimmune response. Mice were used as recipients of syngeneic or multiple minor H or MHC antigen-mismatched corneal grafts. Recipient beds were neovascularized (high-risk). Hosts were randomized to receive either anti-CD154 antibody or control immunoglobulin (Ig) perioperatively. Two weeks after corneal transplantation, allospecific delayed-type hypersensitivity (DTH) was evaluated. Frequencies of interferon-gamma (IFN-gamma)-, interleukin-2 (IL-2)-, IL-4-, and IL-5-secreting T cells in the hosts were measured by enzyme-linked immunospot (ELISPOT) assay. Ocular chemokine gene expression in anti-CD154-treated and control hamster Ig-treated groups was determined using a multiprobe ribonuclease protection assay (RPA). Leukocyte infiltration of corneal grafts was evaluated microscopically. Anti-CD154-treated mice did not exhibit allospecific DTH. The frequencies of Th1 cytokine-producing but not Th2 cytokine-producing T cells were significantly reduced in anti-CD154-treated hosts. Postoperative mRNA levels of RANTES and macrophage inflammatory protein-1beta (MIP-1beta) in anti-CD154-treated eyes were substantially suppressed compared with hamster Ig-treated controls. Leukocyte infiltration was profoundly suppressed in grafts of anti-CD154-treated hosts. These data demonstrate that blockade of the CD40-CD154 costimulatory pathway after corneal transplantation inhibits Th1-mediated responses but does not induce a switch to a Th2-specific response. In addition, anti-CD154 therapy suppresses ocular chemokine gene expression and leukocytic infiltration into allografts.
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PMID:Mechanisms of immunotherapeutic intervention by anti-CD154 (CD40L) antibody in high-risk corneal transplantation. 1258 95

Recent studies affirm costimulatory blockade as a beneficial means of preventing allograft rejection. The precise molecular effects of these pathways, however, are not entirely understood. A striking example is in the costimulatory pathways, 4-1BB/4-1BBL, CD40/CD40L, and B7/CD28. Blocking any one of these prolongs graft survival, yet each operates via distinct immunomodulatory signals. To examine the mechanistic relationships among these signals, our approach was a comprehensive investigation of their molecular constituents. Using a model of heterotopic heart transplantation in mice with a costimulatory pathway deficiency, we analyzed the expression profiles of a large panel of immune and inflammatory genes using ribonuclease protection assays coupled with algorithms. We found that while graft survival was prolonged in all groups, each pathway modulates a unique profile of expressed genes. There were 19 genes, for example, with significant changes in expression compared to the control, yet none of these were similarly modulated in all three groups. Our study reveals that despite similar delays of allograft rejection, the molecular basis for this effect is distinct in all three costimulatory pathways. Furthermore, we underscore the existence of numerous molecular mechanisms affecting graft survival. This, in turn, provides crucial implications for clinical treatment post-transplant where inhibitors would be designed to target multiple mechanisms.
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PMID:Analysis of costimulation by 4-1BBL, CD40L, and B7 in graft rejection by gene expression profiles. 1293 98

The cellular and molecular mechanisms underlying the blunted allo-responsiveness of umbilical cord blood (UCB) T cells have not been fully elucidated. Protein expression of NFATc2 (nuclear factor of activated T cells c2), a critical transcription factor necessary for up-regulation of multiple cytokines known to amplify T-cell allogeneic responses, is reduced in UCB T cells. Affymetrix oligonucleotide microarrays were used to compare gene expression of primary purified CD4+ UCB T cells to adult peripheral blood CD4+ T cells (AB) at baseline, 6, and 16 hours of primary stimulation. NFAT-regulated genes exhibited lower expression in UCB CD4+ T cells including the following: granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), interleukin 3 (IL-3), IL-4, IL-5, IL-13, IL-2 receptor alpha (IL-2Ralpha; CD25), CD40L, and macrophage inflammatory protein 1 alpha (MIP-1alpha). Transcription factors involved in the NFAT pathway including C/EBPbeta, JunB, and Fosl1 (Fra-1), as well as Th1- and Th2-related transcription factors STAT4 (signal transducers and activators of transcription 4), T-bet, and c-maf showed reduced expression in UCB compared with AB during primary stimulation. Reduced cytokine, chemokine, and receptor expression was also found in UCB. Gene array data were confirmed using RNase protection assays, flow cytometry, and quantitative multiplexed cytokine measurements. Reduced global expression of NFAT-associated genes, as well as cytokines and chemokines, in UCB CD4+ T cells may contribute to the decreased graft-versus-host disease (GVHD) observed after UCB transplantation.
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PMID:Reduced expression of NFAT-associated genes in UCB versus adult CD4+ T lymphocytes during primary stimulation. 1294 96