Thesis (Ph. D.)--University of Chicago, Committee on Immunology, June 2001. / Includes bibliographical references. Also available on the Internet.

Interluekin-23 (IL-23) is a pro-inflammatory cytokine critical to the regulation of innate and adaptive immune responses. The main role for this cytokine is in the proliferation and differentiation of the IL-17 producing CD4 T helper cell, Th17. Virus infection deregulates IL-23 expression and function, but little is known about the mechanism behind this phenomena. Here, I demonstrate a reduction of Toll like receptor (TLR) ligand-induced IL-23 expression in lymphocytic choriomeningitis virus (LCMV)-infected bone marrow-derived dendritic cells (BMDCs), indicating that a function of these cells is disrupted during virus infection. I propose a mechanism of TLR ligand-induced IL-23 expression inhibition upon LCMV infection via the deactivation of p38, AP-1, and NF-κB. Further analysis revealed a direct relationship between LCMV infection with the IL-10 and SOCS3 expression. To understand IL-23 function, I characterized IL-23-induced JAK/STAT signalling pathway and IL-23 receptor expression on human CD4 T cells. My results demonstrate that IL-23 induces activation of p-JAK2, p-Tyk2, p-STAT1, p-STAT3, and p-STAT4 in CD4 T cells. For the first time I show that IL-23 alone induces the expression of its own receptor components, IL-12Rβ1 and IL-23Rα, in CD4 T cells. Blocking JAK2, STAT1, and STAT3 activation with specific inhibitors detrimentally effected expression of IL-23 receptor demonstrating that activation of JAK/STAT signalling is important for IL-23 receptor expression. I also addressed the effect of viral infection on IL-23 function and receptor expression in CD4 T cells using cells isolated from HIV positive individuals. These studies were based on earlier reports that the expression of IL-23 and the IL-23 receptor are impaired during HIV infection. I demonstrate that the phosphorylation of JAK2, STAT1, and STAT3 induced by IL-23, as well as IL-23 receptor expression are deregulated in CD4 T cells isolated from HIV positive individuals. This study has furthered the understanding of how the expression and function of IL-23 is regulated during viral infections. / Thesis (Ph.D, Microbiology & Immunology) -- Queen's University, 2011-08-24 07:52:24.898

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.

Cytokines play an important regulatory role during immune responses against pathogens. The outcome of an induced cytokine pattern is determined by many factors. It strongly depends on the nature of the pathogen and the host’s ability to control the quality and strength of cytokine signals. In pulmonary infection with Cryptococcus neoformans T helper (Th) 1 and Th17 cell subsets and their associated cytokines confer protection, whereas a Th2-biased response with production of interleukin (IL) -4 confers susceptibility. Since inappropriate Th responses often lead to death in immunosuppressed human patients, especially HIV-1 infected patients, this work aimed to elucidate mechanisms of Th2 induction and regulation by assessing the Th2 hallmark cytokine IL-4 in an experimental model of cryptococcosis. Therefore, a kinetic study of IL-4 expression during 70 days after intranasal infection was performed in susceptible mice. The analyses included characterization of pulmonary leukocytes and Th cell cytokine profiling. IL-4 profiling revealed Cryptococcus-specific IL-4 production not before six weeks after infection. This unexpected finding was further validated by equal results observed in a kinetic study done in IL-4 reporter mice. These mice express a green fluorescent protein simultaneously to IL-4 expression in the same cell and this protein can be detected by flow cytometry. Two cellular sources of IL-4 were identified: Th2 cells were found as expected, but also, as shown for the first time, eosinophilic granulocytes could be demonstrated to secrete IL-4. Next, the influence of eosinophils on pulmonary inflammation and disease development was investigated using ΔdblGATA-1 mice constitutively devoid of eosinophilic granulocytes. Experiments with infected ΔdblGATA-1 mice revealed novel regulatory functions of eosinophils in cryptococcosis. In the absence of eosinophils pulmonary Th cell recruitment was significantly diminished. In addition, Th2 polarization was reduced in ΔdblGATA-1 mice as shown by reduced numbers of Th2 cells expressing the Th2-related surface marker T1/ST2 and reduced albeit not absent IL-4 production by Th cells. In addition to reduced IL-4 production, in the absence of eosinophils Th cells with enhanced interferon-γ and IL-17 production were observed. However, control of pulmonary fungal growth was only slightly enhanced in the absence of eosinophils and dissemination of cryptococci to the brain was unaltered. This may be related to the shared IL-4 production by not only eosinophils but also Th2 cells. Blocking more than one cellular source of IL-4 could be required to prevent immunopathology. To test the hypothesis of gradual IL-4-dependent immunopathology, experiments were conducted using mice expressing only one allele of the IL-4receptor (R) alpha (α) chain (+/-) instead of two (+/+). Indeed, mono-allelic expression of the IL-4Rα resulted in an intermediate expression of the IL-4R on the surface of myeloid and lymphoid cells indicating a gene-dosage effect for IL-4R expression. Infected IL-4Rα+/- mice displayed reduced susceptibility as compared with IL-4Rα+/+ mice, and IL-4Rα-/- mice completely lacking IL-4R expression were found to be protected with survival for the complete time period of the experiment (i.e. up to 275 days). Reduced susceptibility found in infected IL-4Rα+/- mice was associated with decreased serum levels of immunoglobulin E, reduced mucus production by airway epithelia, attenuation of airway hyper-reactivity, and reduced formation of alternatively activated macrophages in lung parenchyma – pathophysiological features, which are typically found in experimental models of asthma but also in asthma of humans and animals. Since no up-regulation of IL-4R by the infection with Cryptococcus neoformans was found, the experimental pulmonary infection model used appears to be a very sensitive low-level IL-4 system. This work highlights the outstanding role of IL-4 and its different cellular sources as well as its receptor in cryptococcosis and provides novel insights into pathogenesis. Moreover, a cellular (i.e. eosinophils) and a molecular (i.e. IL-4R) target for treatment of this mycosis and possibly of asthma is provided.

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Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2006. / Härtill 3 uppsatser.

Regensburg, Univ., Diss., 2008

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 174-206). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Chicago, Pritzer School of Medicine, Committee on Immunology, June 2000. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--Virginia Commonwealth University, 2009. / Prepared for: Dept. of Biochemistry. Bibliography: leaves 147-171. Also available on the Internet.