Erlangen, Nürnberg, University, Diss., 2007. / Enth. 1 Sonderabdr. aus: AIDS ; 19. 2005.

Universiẗat, Diss., 2007--Giessen.

No description available.

IL-2 has multiple functions in T cell-mediated adaptive immunity. The stringent control of its expression is important for T cell activation, proliferation and the subsequent T cell clone contraction. Our lab has recently shown that the transcriptional repressor Blimp-1 is part of a negative feedback loop which controls IL-2 gene expression in mice. Understanding the molecular mechanisms of this signaling loop in T cells might help us to better understand the regulation as well as the role of IL-2 in T cell immunity. The human ortholog to murine Blimp-1 is termed PRDI-BF1 (each encoded by the respective Prdm1 gene). Both genes contain five zinc finger regions, whereby the first two zinc fingers are dispensable for DNA binding. In case of the human protein they are instead required to recruit the G9?Ñ methyltransferase to the gene promotor. We found that the human wild-type PRDI-BF1 protein suppressed IL-2 production in murine T cells, while deletion of the first two zinc fingers abolished this ability. Thus, a similar Blimp-1-mediated methylation mechanism might exist in IL-2 gene silencing. IL-2/IL-2R signaling is indispensable for Blimp-1 induction. PI-3Kinase and Stat5 are downstream of the IL-2 receptor complex and are known to contribute to IL-2 inhibition in T cells from C57BL/6 mice. However, activating only these two pathways are still not sufficient to induce Blimp-1 or suppress IL-2 expression in in IL-2R beta-/- mice. The Blimp-1-dependent IL-2 self regulatory loop is not functional in IL-2R beta-/-mice. In order to conveniently study this dysregulation we crossed these mice with a GFP transgenic strain in which the GFP transgene is under the control of IL-2 promoter sequence. In IL-2R beta-/-IL-2p-GFP mice about five times as many spleenic CD4+ T cells transcribe IL-2pGFP, compared to the littermate IL-2R beta+/-IL-2p-GFP control animals. And most of the GFP cells demonstrate activated phenotype (CD44HighCD62Llow). Blimp-1 is known as a master regulator of B cell terminal differentiation. Since a recent report indicated that IL-2 signaling via STAT5 constrains Th17 Cell differentiation, we speculated that Blimp-1 might play a similar role in effector T cell differentiation. In order to evaluate this possibility, activated CD4+ T cells from C57BL/6 mice were transduced with Blimp-1 and cultured under Th17 polarizing conditions. Blimp-1 overexpression in did not change the profile of IL-17 production.

The effectiveness of most chemotherapeutic regimens is limited by the toxicity of the therapy to normal healthy cells. Therapies to selectively modulate abnormal T cells bearing the interleukin 2 receptor (IL-2R) have been developed to treat diseases associated with aberrant immune response. This study describes the development and optimization of a targeted gene or oligonucleotide therapy vehicle to IL-2R bearing T cells for selective elimination of these cells. In this work, a monoclonal antibody to the IL-2R was used to target the oligonucleotide delivery vehicle which consisted of a polyamidoamine dendrimer. Optimization of the delivery vehicle involves understanding the factors that govern its association with oligonucleotide, the pathway of IL-2R endocytic trafficking, and the stability of the oligonucleotide in the biological milieu. Oligonucleotide stability in a cellular environment was examined intra- and extracellularly. Results showed that the rate of intracellular degradation of oligonucleotides was much greater than extracellular degradation. Binding of oligonucleotides to dendrimers was demonstrated as a function of dendrimer generation. The total binding capacities for dendrimers differed depending upon dendrimer size and surface group, whereas equilibrium binding affinity was comparable for all dendrimers tested. Binding of oligonucleotide delivery vehicle to the cell surface and subsequent internalization was inversely related to dendrimer size, and in all cases, significantly less than binding and internalization of the natural ligand for the IL-2R. Based on experimental results, a kinetic model of the delivery vehicle was derived which includedthe dependence of binding and internalization on dendrimer size and surface charge and intracellular degradation of oligonucleotide. Based on model predictions, we show that larger dendrimers carry more oligonucleotide than the smaller dendrimer vehicles, and delivery is more effective with larger vehicles. This work establishes our ability to predict the effects of different delivery vehicle properties on oligonucleotide delivery and aids in the development of design criteria for new vehicles for delivery of antisense, siRNA, or genes to IL-2R bearing cells.

Inducible LAK cell responses were studied in HIV-seropositive individuals lacking clinical symptoms, and overt AIDS patients. Inducible LAK cell responses have been operationally defined as, non-MHC-restricted and antigen-nonspecific cytotoxic activity observed following IL-2 stimulation. HIV-seropositive asymptomatic individuals exhibited an enhanced LAK cell response against HIV-infected targets while lysis of uninfected targets remained at control levels. LAK activity of AIDS patients however, was significantly diminished when compared to healthy controls. Immunomagnetic negative selection depletion experiments indicated that LAK cell activity is mediated primarily by CD56-expressing lymphocytes, both at the progenitor and effector cell level. Of interest, in HIV-seropositive asymptomatic individuals we observed the emergence of a second CD8-expressing cytotoxic population that mediates IL-2-induced non-MHC-restricted and antigen-nonspecific cytotoxicity. Overall we demonstrated that CD56-expressing LAK cells of HIV-seropositive patients exhibited a decreased ability to mediate cytotoxicity on a per cell basis against a panel of different targets. In vivo, this inhibition may be amplified by decreases in absolute numbers of CD56-expressing lymphocytes per ml of blood. HIV-infection therefore results in dramatic changes on the number, function and phenotype of the effector cells mediating IL-2 inducible LAK cell responses.

No description available.

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references.

Metabolic Syndrome (MetS), the clustering of obesity, high blood pressure, and disordered glucose and lipid/lipoprotein metabolism within a single individual, is associated with poorer cognitive function and dementia in later life. It has been hypothesized that cognitive impairment in MetS occurs primarily within the context of inflammation. MetS risk factors are also associated with thinning of the cerebral cortex. However, the mechanisms by which MetS and inflammation affect the brain are poorly understood. The present study used statistical mediation to examine the relationship between MetS risk factors, cortical thickness in a priori regions of interest (ROIs) and inflammation. ROIs in the inferior frontal, superior temporal, middle frontal, supra marginal, anterior cingulate and middle occipital regions were chosen from the previous literature. Serum levels of pro-inflammatory markers (interleukin 1, interleukin 2, interleukin 6 and C-Reactive Protein) were measured using enzyme-linked immunosorbent assays. Forty-three adults between the ages of 40 and 60 years underwent a health screen, neuropsychological testing and structural magnetic resonance imaging. A higher number of MetS risk factors was associated with thinning in the inferior frontal ROI (β=-0.35, p = 0.019). A higher number of MetS risk factors was also associated with higher levels of serum interleukin 2 (β=0.31, p=0.04). A higher level of serum interleukin 2 was also associated with reduced thickness in the inferior frontal ROI (β=-0.41, p=0.013). After accounting for the effects of interleukin 2, the number of MetS risk factors was no longer associated with cortical thickness in the inferior frontal ROI indicating successful statistical mediation and pointing towards a potentially important role for imflammation in linking MetS to cortical thinning and cognitive vunlerability. / text

published_or_final_version / Medicine / Master / Master of Philosophy