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In the present study, an attempt was made to characterize the immunomodulating abilities of the cytostatic drugs cydophosphamide, ifosfamide, vinblastine, vincristine, procarbazine, dacarbazine, 6-mercaptopurine, methotrexate, 5-f/uor-uracil and adriamycine in a defined experimental model. Varying combinations of drug plus transplantation alloantigen, (C3H-lymphocytes) were injected into Balb/c mice at different time intervals in vivo. The resulting T-effector cell reactivity was determined in vitro with the microcytotoxicity assay on day + 5 for primary (r) and day + 7 for secondary (2°) sensitized mice. According to the type of drug (alkylating agent vs. vinca alkaloid vs. antimetabolite vs. cytostatic antibiotic), the dosage (20% LD50 vs. 60% LD50), the state of sensitization (r vs. 2° sensitized recipients), and the time of drug application in relation to the antigen treatment on day 0 (in varying steps from day -6 to day +4), so-called "pharmaconantigen- variation-effects" (PA VE) were established for each of the investigated drugs in form of reaction profiles. The results were as folIows: (1) For almost alt substances, characteristic reaction profiles involving immunostimulation and/or immunosuppression could be established. Similarities in the profiles of different substances made it possible to classify the drugs according to different reaction types. The reaction type however is not definitely correlated to the biochemical mechanism of drug action. (2) The PA VE are decisively inf/uenced by so me of the biological parameters, such as the time of drug application in relation to the antigen treatment and the state of sensitization but relatively !ittle by the dosage of the drug. (3) Considering the different processes occurring du ring primary and secondary immune responses, the PAVE may give hints for a distinct manipulation of the immunoregulation and thus information on the immunobiological mechanism of drug action.
As critical steps in the life cycle oJ measles virus (Mfl), the e.fficiency of uptake into and replication in susceptible host cells are governed by cellular determinants. Measles virus infections of cells of the human CNS are characterized by particular constraints imposed on v1:ral transcription and translation attenuating viral gene Junctions and thus contributing to the pathogenesis oJ MV persistence in these cells.
The expression of measles virus (MV) in six different permanent human glioma cell lines (D-54, U-251, U-138, U-105, U-373, and D-32) was analyzed. Although all celllines were permissive for productive replication of all MV strains tested, U-251, D-54, and D-32 cells spontaneously revealed restrictions of MV transcription similar to those observed for primary rat astroglial cells and brain tissue. In vitro differentiation of D-54 and U-251 cells by substances affecting tbe intracellular cyclic AMP Ievel caused a significant reduction of tbe expression of tbe viral proteins after 18, 72, and 144 b of infection. This pronounced restriction was not paralleled to a comparable Ievel by an inhibition of tbe syntbesis and biological activity in vitro of virus·specific mRNAs as sbown by quantitative Northem (RNA) blot analyses and in vitro translation. The block in viral protein syntbesis could not be attributed to tbe induction of type I interferon by any of tbe substances tested. Our findings indicate tbat down-regulation of MV gene expression in human brain cells can occur by a cell type-rlependent regulation of tbe viral mRNA transcription and a differentiation-dependent regulation of translation, botb of wbicb may be crucial for the establisbment of persistent MV infections in tbe centrat nervous system.
To probe into the functional properties of the major peripheral myelin cell surface glycoprotein P 0 , its ability to confer adhesion and neurite outgrowth-promoting properfies was studied in cell culture. Tothis aim, Po was expressed as integral membrane glycoprotein at the surface of CV -1 cells with the help of a recombinant vaccinia virus expression system. Furthermore, the immunoglobulin-like extracellular domain of P0 (P0 -ED) was expressed as soluble profein in a bacterial expression system and used as substrafe coated to plastic dishes or as competitor in cell adhesion and neurite outgrowth-promoting assays. The adhesion of P0 -expressing CV-1 cells to P0 -ED substrafe was specifically inhibitable by polyclonal Po antibodies (54% :t 6% ). In addition, the specific interaction between Po molecules could be reduced ( 49% ± 8%) by adding soluble P0 -ED to the culture medium, demonstrating that the homophilic inter~ction between recombinant Po molecules can be mediated, at least on one partner of interacting molecules, by the unglycosylated Ig-like domain. Substrate-coated p -ED also conferred adhesion and neurite outgrowth ability to dorsal root ganglion neurons with neurites of a mean length of about 150 ,_..m. This neurite outgrowth was specifically inhibitable by soluble P" (74% ± 14%) and P 0 antibodies (65% ± 9% ). These observations indicate that Po is capable of displaying two different types of functional roles in the myelination process of . peripheral nerves: The heterophilic interaction with neurons may be responsible for the recognition between axon and myelinating Schwann cell at the onset of myelination, whereas the homophilic interacton may indicate its roJe in the selfrecognition of the apposing loops of Schwann cell surface membranes during the myelination process and in the mature compact myelin sheath.
Human immunodeficiency virus (HIV-1) infection in the human brain Ieads to characteristic neuropathological changes, which may result indirectly from interactions of the envelope glycoprotein gp 120 with neurons and/or glial cells. We therefore investigated the binding of recombinant gp120 (rgp120) to human neural cells and its effect on int~acellular.s.ignallin~. Herewe pre~ent evidence that rgp120, besides binding to galactocerebroside or galactosyl-sulfatlde, spec1f1cally bmds to a protem receptor of a relative molecular mass of approximately 180,000 Da (180 kDa) pre~ent. on the CD4-negative glioma cells D-54, but not on Molt4 T lymphocytes. Binding of rgp120 to this receptor rap1dly 1nduced a tyrosine-specific protein kinase activity leading to tyrosine phosphorylation of 130- and 115-kDa p~oteins. The c~ncentration of intracellular calciumwas not affected by rgp120 in these cells. Our data suggest a novel Signal transduc1ng HIV-1 gp120 receptor on CD4-negative glial cells, which may contribute to the neuropathological changes observed in HIV-1-infected brains.
The effect of measles virus (MV) infection on mRNA expression and protein synthesis of cytokines in human malignant glioma celllines (0-54 and U-251) was investigated. Primary MV infections led in both celllines to the induction of interleukin-1 fJ (ll-1 (3), interleukin-6 (IL-6), interferon-(3 (IFN-fJ), and tumor necrosis factor-a (TNF-a). ln contrast, persistently infected astrocytoma lines continually produced IL-6 (two out of 12 lines high Ievels) and IFN-ß, whereas only 1 out of 121ines synthesized TNF-a and none IL-1ß. The pathways for induction of IL-1fJ and TNF-a expression were not suppressed by the persistent MV infection, since IL-1ß and TNF-a could be induced by external stimuli Jike diacylglycerol analog plus calcium ionophore. lnterestingly, persistently infected astrocytoma cells synthesized considerably higher Ievels of ll-1ß and TNF-a than uninfected cells afteradditional external induction. These results suggest that in the centrat nervous system (CNS) of SSPE patients a percentage of persistently infected astrocytes may continually synthesize IL-6 and IFN-ß, and in the presence of additional external stimuli, as possibly provided by activated lymphocytes, might ovarexpress the inflammatory cytokines IL-1 ß and TNF-a. This may be of pathogenetic significance in CNS diseases associated with persistent MV infections.
To investigate the influence of inflammatory cytokines on the potential of peripheral nerves to regenerate, we analyzed the effect of interferon-y (lFN-y) and tumor necrosis factor-a (TNF-a) on the ability of immortalized Schwann cells to mediate outgrowth of neurites from primary DRG neurons. We found that IFN-y and TNF-a synergistically inhibited the neurite outgrowth-promoting properties of the Schwann cells by spedfically dowllregulating myelin-associated glycoprotein (MAG) at the levels of mRNA and cell surface protein by approximately 60%. Antibodies to MAG inhibited the outgrowth of neurites on Schwann cells to the same extent as treatment with the two cytokines. Since MAG appears to be involved in both neurite outgrowth and myelination, our findings may provide evidence for a mechanism, by wh ich inflammatory cytokines interfere with Schwann cell-neuron interactions.
Murine spienie T lymphocytes display maximal cellular myc gene (c-myc) expression already 3 h after concanavalin A timulation and sub equent down-regulation before the onset of DNA syntbesis. Stimulation by leucoagglulinin in the prcsence or absence of interleukin 2 Ieads to only low initiaJ Ievels of c-myc-specific RNA which, however, increase later on. A similar pattero of c-myc expression is shown by the Lyt- 2+ T cell subpopulation stimuiated with eilher concanavalin A or leucoagglutinin in the prescncc of interleukin 2. Although eH]thyn1idine incorporation was identical, the leucoagglutinin-stimulated Lyt-2+ T cells werc void of any demon. trable c-mycspeci. fic RNA at 3 h post-stimulation. Thus, the kinetics of c-myc expression in mause T lymphocytes arenot at all uniform, but depend on the mitogen and the subpopulation. [n contrast, lcvel8 of c-rasH•-spccific R A wcre always low at early times, always increased towards tbe onset ofDNA synthesis and down-regulationwas not observed.
Expression of the neural cell adhesion molecule and polysialic acid during early mouse embryogenesis
(1994)
The expression of the neural cell adhesion molccule (N-CAM) and a 2-8 linked polysialic acid (PSA), whieh is believed to be predominantly expressed on N-CAM, was investigated during early embryonie development ofthe mouse (embryonic days 7.5 to 10.0). By immunoeytoehemistry, in tissue sections, N-CAM and PSA were not detectable at embryonie day 7.5 but were expressed in the prominent body regions such as somites, unsegmented mesoderm, developing heart, and neuroectoderm at embryonie day 8.0 N-CAM and PSA immunoreaetivities were always predominantly associated with tbe plasma membrane. No tissue could be detected which was positive for PSA but negative for N-CAM. In Western blot analysis of whole embryos, by contrast, only the lightly sialylated and PSA-negative 180 and 140 kD isoforms of N-CAM werc present at embryonie day 8.0 and strong expression of PSA-bearing, heavily sialylated N-CAM was not detectable before embryonie day 10.0. In Western blot analysis of N-CAM immunoaffinity purifled from whole embryos and digested with neuraminidase as weil as in Northern blot analysis, the 120 kD isoform of N-CAM or its eorresponding mRN A were not expressed in detectable amounts during the time period investigated.