18 research outputs found

    Neonatal Exposure to Thymotropic Gross Murine Leukemia Virus Induces Virus-Specific Immunologic Nonresponsiveness

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    Neonatal exposure to Gross murine leukemia virus results in a profound inhibition of the virus-specific T and B cell responses of adult animals. Animals exposed to virus as neonates exhibit a marked depression in virus-specific T cell function as measured by the virtual absence of in vivo delayed type hypersensitivity responses and in vitro proliferative responses to virally infected stimulator cells. Further, serum obtained from neonatally treated mice failed to either immunoprecipitate viral proteins or neutralize virus in an in vitro plaque assay, suggesting the concurrent induction of a state of B cell hyporesponsiveness. The specificity of this effect at the levels of both T and B cells was demonstrated by the ability of neonatally treated mice to respond normally after adult challenge with either irrelevant reovirus or influenza virus. The replication of Gross virus within both stromal and lymphocytic compartments of the neonatal thymus suggests that thymic education plays a key role in the induction of immunologic nonresponsiveness to viruses

    Derivation and characterization of SV40-transformed thymic stromal cells and their interaction with lymphoid stem cell populations in vitro

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    A panel of thymic stromal cell clones from SV40 transgenic mice was derived and characterized. This panel appears to include representatives of the thymic subcapsular cortex (thymic nurse cells), the deep cortex (cortical reticular cells) and the medulla (medullary interdigitating (IDC-like) cells and medullary epithelial cells), based on morphology, ultrastructural and surface antigen expression. All of the cell lines expressed the SV40-transgene, constitutively expressed Class I major histocompatibility complex (MHC) antigens, and expressed MHC Class II antigens upon induction with interferon-γ\gamma. The subcapsular cortical epithelial cell line supported Lyt-2\sp+, but not L3T4\sp+ cell differentiation in vitro from 14-day fetal liver cells. The thymic cortical reticular cell line or its conditioned medium induced T cell receptor (TcR) gene rearrangements and expression in cultured 14-day fetal liver cells. Sequence analysis revealed that some of the TcR β\beta transcripts were generated from V-D-J joining, and a small, but detectable fraction of these cultured fetal liver cells expressed cell surface TcR molecules. CM from several thymic stromal cell lines induced TcR gene rearrangements in a pre-T cell line; further analysis with the cortical reticular epithelial cell line suggested that these cells may activate recombinase enzyme(s) machinery in recombinase-negative pre-T cell lines. The thymus-derived cells elaborated a factor(s) that induced the proliferation of hematopoeitic stem cells from the fetal liver, bone marrow and fetal thymus, but not from neonatal thymus. Several of the thymic stromal cell lines elaborated factor(s) that induced stem cell differentiation along the granulocyte-monocyte lineage

    Derivation and characterization of SV40-transformed thymic stromal cells and their interaction with lymphoid stem cell populations in vitro

    No full text
    A panel of thymic stromal cell clones from SV40 transgenic mice was derived and characterized. This panel appears to include representatives of the thymic subcapsular cortex (thymic nurse cells), the deep cortex (cortical reticular cells) and the medulla (medullary interdigitating (IDC-like) cells and medullary epithelial cells), based on morphology, ultrastructural and surface antigen expression. All of the cell lines expressed the SV40-transgene, constitutively expressed Class I major histocompatibility complex (MHC) antigens, and expressed MHC Class II antigens upon induction with interferon-γ\gamma. The subcapsular cortical epithelial cell line supported Lyt-2\sp+, but not L3T4\sp+ cell differentiation in vitro from 14-day fetal liver cells. The thymic cortical reticular cell line or its conditioned medium induced T cell receptor (TcR) gene rearrangements and expression in cultured 14-day fetal liver cells. Sequence analysis revealed that some of the TcR β\beta transcripts were generated from V-D-J joining, and a small, but detectable fraction of these cultured fetal liver cells expressed cell surface TcR molecules. CM from several thymic stromal cell lines induced TcR gene rearrangements in a pre-T cell line; further analysis with the cortical reticular epithelial cell line suggested that these cells may activate recombinase enzyme(s) machinery in recombinase-negative pre-T cell lines. The thymus-derived cells elaborated a factor(s) that induced the proliferation of hematopoeitic stem cells from the fetal liver, bone marrow and fetal thymus, but not from neonatal thymus. Several of the thymic stromal cell lines elaborated factor(s) that induced stem cell differentiation along the granulocyte-monocyte lineage

    Micromachined Joule-Thomson coolers

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    A MEMS-based Joule-Thomson cold stage was designed and prototypes were realized and tested. The cold stage consists of a stack of three glass wafers. In the top wafer, a high-pressure channel is etched that ends in a flow restriction with a height of typically 300 nm. An evaporator volume crosses the center wafer into the bottom wafer. This bottom wafer contains the low-pressure channel thus forming a counter-flow heat exchanger. A design aiming at a net cooling power of 10 mW at 96 K and operating with nitrogen as the working fluid was optimized based on the minimization of entropy production. A batch of prototype coolers ranging from 20 to 40 mm was made for a flow of typically 1mgĊs-1 at a high pressure of 80 bar and a low pressure of 6 bar. The design and fabrication of the coolers will be discussed along with experimental results. A specific issue that will be addressed is the clogging of the restriction due to the deposition of ice crystals. Furthermore, introductory experiments with multistage microcoolers will be discussed. © 2008 American Institute of Physics
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