Show simple item record

dc.contributor.advisorYankee, Thomas M.
dc.contributor.authorZhang, Elizabeth Yan
dc.date.accessioned2012-06-03T13:53:42Z
dc.date.available2012-06-03T13:53:42Z
dc.date.issued2011-12-31
dc.date.submitted2011
dc.identifier.otherhttp://dissertations.umi.com/ku:11761
dc.identifier.urihttp://hdl.handle.net/1808/9710
dc.description.abstractCD8+ T cells are the branch of the adaptive immune system responsible for recognizing and killing tumor cells or cells infected with intracellular pathogens, such as Listeria monocytogenes (LM). However, when CD8+ T cells target our own tissues, they can cause autoimmune diseases, such as type I diabetes, rheumatoid arthritis. For CD8+ T cells to fulfill these functions, the T cell receptors (TCRs) on CD8+ T cells must recognize pathogens or antigens presented on the surface of target cells. TCR ligation triggers multiple signaling pathways that lead to the activation and proliferation of CD8+ T cells. The goal of our research is to define the TCR-proximal signaling events that regulate CD8+ T cell-mediated immunity. To accomplish this goal, we are focusing on an adaptor protein Gads, which is critical for optimal TCR-mediated calcium mobilization. We reported the first analysis of the function of Gads in peripheral naïve CD8+ T cells. To examine the function of Gads in CD8+ T cell mediated immune responses, we crossed Gads-/- mice with mice expressing an MHC class I-restricted transgenic TCR recognizing ovalbumin (OVA). The transgenic mice are called ovalbumin-specific T cell receptor-major histocompatibility complex class I restricted (OT-I) mice. We investigated the effect of Gads on the proliferation of CD8+ T cells following stimulation with peptide antigen in vivo and in vitro. We stimulated splenocytes from Gads+/+ OT-I and Gads-/- OT-I mice with the peptide agonist. The experiments revealed that Gads is required for optimal proliferation of CD8+ T cells. The regulation of Gads is most evident at the early time points of proliferation. Then we demonstrated that Gads-/- CD8+ T cells have impaired TCR-mediated exit from G0 phase of the cell cycle. In addition, Gads-/- CD8+ T cells have delayed expression of c-myc and the activation markers CD69 and CD25, upon stimulation with peptide antigen. Next, we investigated how Gads affects CD8+ T cell-mediated immunity in the context of infection with LM. We adoptively transferred naïve CD8+ T cells from Gads+/+ OT-I mice and/or Gads-/- OT-I mice into congenic wild-type hosts. Then the recipient mice were infected with recombinant LM expressing ovalbumin (rLM-OVA). The CD8+ T cells from OT-I mice recognize and respond to the ovalbumin provided by this strain of LM. By using this system, we investigated how Gads regulates the activation of antigen-specific CD8+ T cells as well as the expansion and memory phases of CD8+ T cell-mediated immune responses following infection with rLM-OVA. We also examined the recall response of CD8+ T cells after the secondary encounter with the same pathogen. Our data demonstrated that Gads regulates the expression of activation markers CD69 and CD25 of antigen-specific CD8+ T cells but Gads is not required for the onset of accumulation of antigen-specific CD8+ T cells following infection. However, Gads is critical to sustain the expansion of CD8+ T cell-mediated immune response following infection. Although the differentiation of naïve CD8+ T cells into memory cells is independent of Gads, Gads is required for an optimal recall response. Our data indicating that Gads regulates the initiation of proliferation of CD8+ T cells upon TCR ligation by peptide antigen seemed to contradict with our in vivo infection data showing that Gads is not required for the initiation of expansion of CD8+ T cell population. In order to explain the "discrepancy", we hypothesized that the homotypic interactions among CD8+ T cells compensate for Gads deficiency at the initial stage of accumulation of antigen-specific CD8+ T cells upon infection. Our data indicated that the need for Gads in cell cycle progression of CD8+ T cells when total splenocytes were stimulated could be overcome by stimulating purified CD8+ T cells. These data suggested that the homotypic interactions among CD8+ T cells facilitate the TCR signaling so as to compensate for Gads deficiency in promoting cell cycle entry and proliferation. To conclude, the role of Gads in TCR-mediated activation and proliferation of CD8+ T cells is dependent on the interactions of CD8+ T cells and their partners. Interestingly, if CD8+ T cells interact with non-CD8+ T cells, Gads regulates the kinetics of cell cycle entry; however, if CD8+ T cells interact with other CD8+ T cells, Gads is dispensable for cell cycle entry of CD8+ T cells. Overall, these studies will help us better understand how TCR-proximal signaling regulates the activation of CD8+ T cells.
dc.format.extent269 pages
dc.language.isoen
dc.publisherUniversity of Kansas
dc.rightsThis item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
dc.subjectImmunology
dc.subjectCd8+ t cells
dc.subjectGads
dc.subjectTcr signaling
dc.titleTHE ROLE OF ADAPTOR PROTEIN GADS IN CD8+ T CELL-MEDIATED IMMUNITY
dc.typeDissertation
dc.contributor.cmtememberBenedict, Stephen H.
dc.contributor.cmtememberParmely, Michael J
dc.contributor.cmtememberQiu, Jianming
dc.contributor.cmtememberVines, Charlotte
dc.thesis.degreeDisciplineMicrobiology, Molecular Genetics & Immunology
dc.thesis.degreeLevelPh.D.
kusw.oastatusna
kusw.oapolicyThis item does not meet KU Open Access policy criteria.
kusw.bibid7643129
dc.rights.accessrightsopenAccess


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record