Investigation of the role of cGAMP in differentiation of T lymphocytes

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buir.advisorGürsel, İhsan
dc.contributor.authorYıldız, Begüm
dc.date.accessioned2016-10-13T13:57:49Z
dc.date.available2016-10-13T13:57:49Z
dc.date.copyright2016-10
dc.date.issued2016-10
dc.date.submitted2016-10-13
dc.departmentDepartment of Molecular Biology and Geneticsen_US
dc.descriptionCataloged from PDF version of article.en_US
dc.descriptionThesis (M.S.): Bilkent University, Department of Molecular Biology and Genetics, İhsan Doğramacı Bilkent University, 2016.en_US
dc.descriptionIncludes bibliographical references (leaves 82-91).en_US
dc.description.abstractSTING is the pivotal mediator for the recognition of host and pathogenic cytosolic dsDNA as well as cyclic di-nucleotides metabolites from microbes. STING can either recognize DNA itself or sense the presence of cGAMP, which is converted from ATP and GTP upon DNA binding to cGAS enzyme. Not only strategy against intracellular pathogens makes STING an ideal target, but also the recognition of DNA from host cells has a significant role in tumor immunity. Previous studies demonstrated that DNA released from cancerous cells are internalized by innate immune cells such as macrophages and dendritic cells in tumor microenvironment and trigger the production of IFN-β and other pro-inflammatory cytokines including IL-6, TNF-α, and IL-12 through STING triggered signaling pathway. These cytokines then enhance cytotoxic activity of CD8+ T cells by further increasing IFNγ production. Since enhanced T cell immunity is the hallmark of vaccine adjuvants, cyclic di-nucleotides such as cGAMP become an important and effective vaccine adjuvants against intracellular pathogens and malignant cells. Although STING activating cyclic di-nucleotides are envisioned as novel and potent vaccine adjuvants, more thorough research is needed to unearth the mechanism of action of STING on different immune cells. Therefore, it will pave the way for the initiation of successful human trials. The important criteria while developing vaccine adjuvant are the magnitude, and the quality of an immune response and its toxic side effects. To identify these, members of the both innate and adaptive immune system should be taken into account. However, previous studies merely focus on the function and effect of cGAMP in innate immune cells such as macrophages, monocytes and dendritic cells. However, to date there is no explicit study investigating the effect of STING signaling cascade on T-cells. In the light of these findings, we aimed to investigate the direct effect and function of cGAMP on T lymphocytes. Since there were not any preliminary data, we firstly stimulated Pan T cells with cGAMP alone or together with various TLR ligands and then, checked the cytokine profiles and the viability of cells. Surprisingly, 2.5µg/ml dose of cGAMP had a toxic effect on T cell but not on bone marrow derived dendritic cells and macrophages. While cGAMP triggered cell death, interestingly IL-17 secretion from both CD4+ and CD8+ T cells was dramatically increased. Beside, cGAMP stimulation drastically increased CD4+ /CD8+ T cells ratio of Pan T cells population. Next, we sought to identify the source of IL-17. The IL17 inductive capacity of cGAMP was investigated on purified CD4+ T cells from mice. Unexpectedly, data revealed that cGAMP elicited apoptosis of CD4+ T cells. Moreover, there was no significant induction of IL-17 secretion. Next, we aimed to find a condition that will reduce the toxic effect of cGAMP, while maintaining IL-17 secretion. When Pan T cells were stimulated with cGAMP and R848 (a TLR7 ligand), the toxic action of cGAMP decreased while IL-17 secretion was enhanced. Lastly, the potency of T cells stimulated with cGAMP was investigated. According to our results, macrophages were activated in the presence of conditioned medium obtained from T cells stimulated with cGAMP. When taken together our findings point out that STING dependent direct activation of T-cells via cGAMP and its subsequent effect on macrophages might be utilized as an immunotherapeutic approach where IL17 induction is important and could be harnessed as vaccine adjuvants against mucosal infections or against cancer.en_US
dc.description.degreeM.S.en_US
dc.description.statementofresponsibilityby Begüm Yıldız.en_US
dc.embargo.release2018-10-13
dc.format.extentxix, 98 leaves : charts (some color)en_US
dc.identifier.itemidB154524
dc.identifier.urihttp://hdl.handle.net/11693/32463
dc.language.isoEnglishen_US
dc.publisherBilkent Universityen_US
dc.rightsinfo:eu-repo/semantics/openAccessen_US
dc.subjectcGAMPen_US
dc.subjectSTINGen_US
dc.subjectT lymphocytesen_US
dc.subjectApoptosisen_US
dc.subjectImmune responseen_US
dc.subjectAdjuvanten_US
dc.titleInvestigation of the role of cGAMP in differentiation of T lymphocytesen_US
dc.title.alternativeT lenfosit farklılıaşması üzerine cGAMP'ın rolünün incelenmesien_US
dc.title.alternativeT lenfosit farklılaşması üzerine cGAMP`ın rolünün incelenmesien_US
dc.typeThesisen_US

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Dept. of Molecular Biology and Genetics - Master's degree