京都大学 / 新制・課程博士 / 博士(医学) / 甲第23422号 / 医博第4767号 / 新制||医||1053(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 河本 宏, 教授 濵﨑 洋子, 教授 上野 英樹 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 新制・課程博士 / 博士(医学) / 甲第23381号 / 医博第4750号 / 新制||医||1052(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 河本 宏, 教授 濵﨑 洋子, 教授 上野 英樹 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

No description available.

Type 1 Diabetes (T1D) is a complex autoimmune disorder in which T cells destroy the pancreatic islets, leading to a loss of insulin production and hyperglycemia. The disease incidence has increased globally over the last decades, primarily in individuals with low to moderate genetic risk. There is evidence that environmental factors play a role alongside genetic risk to trigger the disease. An environmental factor that has global influence is adoption of the Western diet, characterized by increased consumption of n-6 fatty acids, including linoleic acid (LA), and decreased consumption of n-3 fatty acids. Increased n-6/n-3 ratios are associated with enhanced susceptibility to autoimmune diseases. We sought to understand how linoleic acid affects the survival and function of T cells from the non-obese diabetic (NOD) mouse, a model for T1D. We found that linoleic acid's presence during in vitro activation of T cells led to an increased expansion of the cells in culture. Additionally, CD4+ and CD8+ T cells activated in linoleic acid's presence produced increased levels of pro-diabetogenic cytokines, including Interleukin-21 (IL-21) and Interferon-gamma (IFN-γ). In contrast, linoleic acid reduced IL-10-producing CD4+ T cells, which are protective in T1D, significantly changing the balance between pro-and anti-inflammatory T cell subsets. Gene expression analysis of T cells exposed to linoleic acid during in vitro activation revealed decreased gene expression of lipid-regulated transcription factors, peroxisome proliferator-activated receptors (PPAR), PPARα and PPARγ. These data suggest a role for these transcription factors and their associated pathways in linoleic acid-mediated T cell functions. Finally, we tested whether the T cell fatty acid response is regulated by the cytokine IL-7, which modulates T cell immunometabolism. However, our data did not reveal a prominent role for IL-7 in regulating the T cell response to linoleic acid. Together, these studies add to evidence that fatty acids present in the microenvironment can directly alter T cell functions and that changes in dietary components may contribute to enhanced T1D susceptibility.

The magnitude and effectiveness of CD8 response against intracellular pathogens is directed by survival and apoptotic signals that govern the fate of T cells. XIAP is a bona fide endogenous inhibitor of apoptotic signals. In this thesis, I have investigated the role of XIAP at various stages of CD8 T cell response. I used both in vivo and in vitro models to show that XIAP acts in a CD8 T cell extrinsic and intrinsic manner to regulate the expansion and contraction phases of the CD8 T cell response, respectively. During the expansion phase, XIAP prevents the cell death of APCs to promote APC-T cell interaction and cytokine release, which facilitates the proliferation and survival of activated T cells. During the contraction phase, XIAP functions in a cell-intrinsic fashion to inhibit the proapoptotic signals in the activated CD8 T cells to prolong the immune response. Finally, I also demonstrate that the expression of XIAP in T cells is critical for their differentiation in to memory subsets. Overall, I present that XIAP plays a critical role in generating an effective CD8 T cell immune response.

No description available.

Mycobacterium tuberculosis infection is one of the leading causes of mortality worldwide. One third of the population is estimated to be infected, however only 5-10% of those individuals can transmit the disease. While T cell immunity initially limits mycobacterium growth, it is unclear why T cell immunity fails to sterilize the infection and prevent subsequent recrudescence. One hypothesis is T cell exhaustion is mediating the failure of T cell immunity late during infection. Here we show the development of T cell exhaustion during chronic infection, and that the inhibitory receptor T cell-immunoglobulin and mucin domain containing 3 (TIM3) mediates the development of T cell exhaustion. TIM3 accumulates on the surface of T cells throughout the course of infection and there is a subsequent decrease in effector cytokine production, such as IL-2, TNFα, and IFNγ. Furthermore, antibody blockade of TIM3 restores T cell function and improves bacterial control. Our results show that TIM3 is mediating T cell exhaustion during chronic TB infection and leading to suboptimal bacterial control.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Facial nerve axotomy (FNA) in immunodeficient mice causes significantly more facial motoneuron (FMN) loss relative to wild type (WT), indicating that the immune system is neuroprotective. Further studies reveal that both CD4+ T cells and interleukin 10 (IL-10) act centrally to promote neuronal survival after injury. This study first investigated the roles of IL-10 and CD4+ T cells in neuroprotection after axotomy. CD4+ T cell-mediated neuroprotection requires centrally-produced IL-10, but the source of IL-10 is unknown. Using FNA on IL-10 reporter mice, immunohistochemistry was employed to identify the IL-10 source. Unexpectedly, axotomy induced astrocyte production of IL-10. To test if microglia- or astrocyte-specific IL-10 is needed for neuroprotection, cell-specific conditional knockout mice were generated. Neither knockout scenario affected FMN survival after FNA, suggesting that coordinated IL-10 production by both glia contributes to neuroprotection. The effect of immune status on the post-FNA molecular response was studied to characterize CD4+ T cell-mediated neuroprotection. In the recombinase-activating gene2 knockout (RAG-2-/-) mouse model of immunodeficiency, glial microenvironment responses were significantly impaired. Reconstitution with CD4+ T cells restored glial activation to normal levels. Motoneuron regeneration responses remained unaffected by immune status. These findings indicate that CD4+ T cell-mediated neuroprotection after injury occurs indirectly via microenvironment regulation. Immunodysregulation is evident in amyotrophic lateral sclerosis (ALS), and FMN survival after FNA is worse in the mutant superoxide dismutase (mSOD1) mouse model of ALS. Further experiments reveal that mSOD1 CD4+ T cells are neuroprotective in RAG-2-/- mice, whereas mSOD1 whole splenocytes (WS) are not. The third aim examined if the mSOD1 WS environment inhibits mSOD1 CD4+ T cell glial regulation after axotomy. Unexpectedly, both treatments were equally effective in promoting glial activation. Instead, mSOD1 WS treatment induced a motoneuron-specific death mechanism prevalent in ALS. In conclusion, the peripheral immune system regulates the central glial microenvironment utilizing IL-10 to promote neuronal survival after axotomy. Astrocytes, specifically, may be responsible for transducing peripheral immune signals into microenvironment regulation. Additionally, the immune system in ALS may directly participate in disease pathology.

Indiana University-Purdue University Indianapolis (IUPUI) / The adaptive arm of the immune system is necessary for facial motoneuron (FMN) survival after facial nerve axotomy (FNA). CD4+ T cells mediate FMN survival after FNA in an interleukin-10 (IL-10) dependent manner, but are not themselves the cellular source of neuroprotective IL-10. The aims of this study are to elucidate the neuroprotective capacity of cell-specific IL-10 expression, and to investigate the manner in which CD4+ T cells participate in IL-10 signaling after FNA. Immunohistochemistry revealed that FMN themselves were constitutive producers of IL-10, and astrocytes were induced to make IL-10 after FNA. Il10 mRNA co-localized with microglia before and after axotomy, but microglial production of IL-10 protein was not detected. To determine whether any single source of IL-10 is critical for FMN survival, Cre/Lox mouse strains were utilized to selectively knock out IL-10 in neurons, astrocytes, and microglia. In agreement with the localization data reflecting concerted IL-10 production by multiple cell types, no single cellular source of IL-10 was necessary for FMN survival. Gene expression analysis of wild-type, immunodeficient, and immune cell-reconstituted animals was performed to determine the role of the immune system in modulating the central IL-10 signaling cascade. This revealed that CD4+ T cells were necessary for full upregulation of central IL-10 receptor (IL-10R) expression after FNA, regardless of their own IL-10R beta (IL-10RB) expression or IL-10R signaling capability. Surprisingly, the ability of CD4+ T cells to respond to IL-10 was critical for their ability to mediate neuroprotection. Adoptive transfer of IL-10RB-deficient T cells resulted in increased central expression of genes associated with microglial activation, antigen presentation, T cell co-stimulation, and complement deposition in response to injury. These data suggest that IL-10RB functions on the T cell to prevent non-neuroprotective immune activation after axotomy. The conclusions drawn from this study support a revised hypothesis for the mechanisms of IL-10-mediated neuroprotection, in which IL-10 serves both trophic and immune-modulating roles after axotomy. This research has implications for the development of immune-modifying therapies for peripheral nerve injury and motoneuron diseases. / 2 years (2021-05-24)