Browsing by Author "Linda Martin, Committee Member"

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    CD4+CD25+ Regulatory T Cells are Infected and Activated Phenotypically and Functionally During Acute Infection with Feline Immunodeficiency Virus.
    (2008-03-02) Mexas, Angela Marie; Gregg A. Dean, Committee Member; Linda Martin, Committee Member; Mary B. Tompkins, Committee Chair; Wayne A. Tompkins, Committee Co-Chair
    HIV-induced AIDS may be mediated by the activation of immunosuppressive CD4+CD25+ T regulatory cells (Tregs). Tregs have been shown to regulate CD4+ and CD8+ immune responses to HIV and FIV antigens in vitro. We tested the hypothesis that Tregs become infected and activated during the acute stage of FIV infection leading to the suppression of CD4+ T helper cell responses. Cats were experimentally infected with FIV-NCSU-1 and blood and lymph node biopsies were collected at 1 week intervals following inoculation. Real-Time PCR was used to determine plasma viremia and relative number of FIV copies in CD4+CD25+ and CD4+CD25- T cell subsets. Flow cytometry was used to assess the absolute numbers of each cell type and the expression of activation markers. Real-time RT-PCR was also used to assess relative increases in FoxP3 and TGF- mRNA levels over time. Treg suppression of IL-2 production in CD4+ T helper cells was assessed by ELISPOT assays and inhibition of cellular proliferation was assessed by incorporation of tritiated thymidine and CFSE. Our results show that peak viremia levels correlate with maximal infectivity in lymph node CD4+CD25+ populations. FIV-gag-mRNA levels are higher in CD4+CD25+ T cells than CD4+CD25- lymph node T cells. Activation of FoxP3 and increased expression of TGF1 in CD4+CD25+ cells correlates with peak plasma viremia and FIV-gag-mRNA levels in CD4+CD25+ T cells. Regulatory function can be detected in CD4+CD25+ T cells during the acute phase of FIV infection. Our findings support the hypothesis that early activation of immunosuppressor function in Treg cells may limit an effective anti-FIV response contributing to the establishment of the chronic infection and the immunodeficiency caused by this virus.
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    Differential Mucin Subtype Regulation and Anti-inflammatory Effects of Inducible Nitric Oxide Synthase in Stimulated Airway Epithelial Cells in Vitro
    (2005-07-28) Chorley, Brian Norris; Linda Martin, Committee Member; Frederick Fuller, Committee Member; Kenneth Adler, Committee Chair; Sarah Gardner, Committee Member
    This dissertation focuses on two critical functions mediated by the airway epithelium: mucus production and inflammatory mediation. Both processes are important for pulmonary defense, but may be deleterious to the surrounding airway if regulated inappropriately. In the first study, a novel monoclonal antibody developed against guinea pig Muc2 mucin and a commercially available anti-MUC5AC mucin antibody were characterized for use in guinea pig studies. Muc2 and Muc5AC mucin production was then measured in guinea pig tracheal epithelial (GPTE) cells stimulated with pro-inflammatory cytokines, TNF-α, IL-1β, and IFN-γ (cytomix). It was demonstrated that Muc2, but not Muc5AC, mucin secretion increased over constitutive production in cytomix-stimulated cells, but intracellular protein and mRNA increased similarly for both mucin subtypes. It was concluded that differential mechanisms for mucin subtype secretion are present in the guinea pig airway epithelium. This differential regulation of mucin subtype expression is an important finding, as it may affect the interactive properties of mucus in both normal and diseased airway. In the second study, the anti-inflammatory role of inducible nitric oxide synthase (iNOS) was evaluated in normal human bronchial epithelial (NHBE) cells. Using iNOSspecific inhibitor, cGMP-dependent kinase inhibitor, and exogenous nitric oxide and cGMPanalogue application, it was demonstrated that an iNOS/cGMP/PKG-mediated pathway suppresses granulocyte macrophage colon stimulating factor (GM-CSF), but not interleukin-8, expression in cytomix-stimulated NHBE cells. The third study demonstrated that an anti-inflammatory action of the β2-adrenergic agonist, (R)-albuterol, is dependent on iNOS. Through the use of small interfering RNA targeted against iNOS, it was demonstrated that (R)-albuterol, and not its inert enantiomer, (S)-albuterol, suppressed GM-CSF message and protein release in IL-1β/IFN-γ-stimulated NHBE cells by augmenting iNOS expression. In addition, through the use of various kinasespecific inhibitors and activators, it was demonstrated that (R)-albuterol-mediated iNOS augmentation requires protein kinase Cδ, but not cAMP or cGMP-dependent kinase, activity. Overall, this study identifies a novel pathway in which β2-adrenergic agonists may exhibit anti-inflammatory effects in the airway epithelium and surrounding milieu.