ORCID

https://orcid.org/0000-0002-6856-2603

Date of Award

11-9-2023

Author's School

Graduate School of Arts and Sciences

Author's Department

Biology & Biomedical Sciences (Immunology)

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

Natural Killer (NK) cells are innate lymphocytes known for their role in recognizing and killing virus-infected or tumor cells without prior sensitization. NK cells express a variety of inhibitory and activating receptors that control their effector functions. Once activated by target cells, cytokines, or activating receptor ligation, NK cells are capable of potent IFN-γ secretion in addition to direct cytotoxicity mediated by perforin and granzymes. Because of their anti-tumor function, NK cells are currently utilized in promising immunotherapy approaches. NK cells develop in the bone marrow and arise from the common lymphoid progenitor, which also gives rise to T, B, and innate lymphoid cell (ILC) lineages. ILCs and NK cells share a closer progenitor that further gives rise to a NK progenitor that differentiates into mature NK cells. Most NK cells circulate in the blood and throughout the lymphoid organs while ILCs are tissue-resident. A main differentiating factor that distinguishes an NK cell from other ILCs is that NK cells express both Eomes and T-bet while ILCs only express either Eomes or T-bet, depending on the ILC type. Eomes and T-bet are transcription factors in the T-box family, defined by their T-box DNA binding domains. Eomes and T-bet are the only two T-box family transcription factors expressed by lymphocytes. T-box family transcription factors, including Eomes, are important for embryogenesis and early development. Eomes and T-bet specifically have been shown to regulate NK cell development. Nevertheless, while well-studied in their role in regulating NK development in mice, the impact of Eomes and T-bet deletion on mature NK cells is currently unknown. Furthermore, while there have been various mouse models studying Eomes and T-bet in NK cells, they used hematopoietic or constitutive knockout models that led to NK cell developmental defects, which precluded genetic loss-of-function studies on mature NK cells. As studies investigating the impact of gene deletion on mature NK cells have been limited by a lack of appropriate models, there is a gap in our knowledge about Eomes and T-bet’s role in mature murine NK cell homeostasis and function, especially in human NK cells. We hypothesized that Eomes and T-bet expression are required for mature NK cells to retain their homeostasis and function. To investigate this, we utilized a tamoxifen-inducible, NK cell specific mouse model that overcome previous mouse models’ limitations to study the impact of lacking either one or both of Eomes and T-bet on mature murine NK cells. In addition, we used CRISPR/Cas9 to genetically delete Eomes and T-bet individually and together from mature human NK cells. In both mouse and human settings, we demonstrated that persistent T-bet and Eomes expression are required to maintain mature NK cell homeostasis and function. Particularly in primary human NK cells, T-bet and Eomes expression are critical to maintain NK cell identity. This study contributes to a deeper understanding of mechanisms governing NK cell homeostasis and function, which will ultimately allow for identification of novel ways to enhance NK cell immunotherapies.

Language

English (en)

Chair and Committee

Todd Fehniger

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