T lymphocytes are a key aspect of the adaptive immune system, allowing the body to mount effective and long-lasting immune responses. Generally, there are two major types of T cells: CD8+ T cells, which are cytotoxic, and CD4+ T cells, which have many subsets but a majority are “helper” T cells which secrete cytokines to bolster the immune response. For T cells to function appropriately and efficiently, many signaling cascades are activated and inhibited to modulate a T-cell’s function and differentiation. These signals can come from strength and duration of T cell receptor binding, cell-cell interactions with antigen presenting cells and surrounding tissue, as well as from the present cytokine milieu. These signals are dynamic, complex, and can affect many different downstream pathways, making a holistic systems-biology approach the ideal strategy to study signaling in T cells. T-cell activation is normally short (1-3 days), however in some contexts such as cancer or infection, T-cell activation can be chronic (days to weeks) and lead to dysfunction, known as T-cell exhaustion. T-cell exhaustion is a clinically important cell state whereby T cells lose their effector functions (cytotoxicity and secretion of cytokines), proliferative ability, and upregulate many coinhibitory receptors (e.g., PD-1, TIM-3, LAG-3). T-cell exhaustion has been well studied, with some transcriptional drivers (e.g., TOX) and changes in metabolism (e.g., mitochondrial dysfunction) already identified. However, much of what has been discovered about T-cell exhaustion has been done in CD8+ T cells due to their direct role in antigen removal via cytotoxicity. CD4+ T cells are shown to also become exhausted and play an equally important role in the immune response for proper and complete neutralization of the pathogen, and many aspects of CD4+ T-cell exhaustion remain unclear. Here, I report on my quantitative global proteomic and phosphoproteomic studies of T-cell activation in human primary T cells, ranging from healthy acute physiological responses (i.e., hours to days) to dysfunctional long term chronic activation (i.e., days to weeks). I developed an in vitro model of CD4+ T-cell exhaustion and analyzed these cells using a multi-omic approach and uncovered pathways and proteins underlying the progression and demarcation of this understudied cell type. I identified novel CD4+ T-cell exhaustion-associated cell surface markers (e.g., CD276 and FLT-1), transcription factors (e.g., ZEB2), and implicated p300 as playing a role in epigenetic regulation of key exhaustion-associated genes. In addition, I investigated artificial activation signaling in a chimeric antigen receptor (CAR) expressing T-cell model, allowing us to tease apart differences in signaling to better fine tune this potent clinical tool. We compared the basal states of three different CARs and found that changing just one signaling domain can lead to drastic changes in T cells even before introduction of antigen. The resulting systems-level understanding of signaling mechanisms in T cells provides a valuable resource for the advancement of fundamental T-cell biology, for reprogramming T-cell signaling for desired output, and for developing immunotherapies to modulate immune signaling for clinical utility. / 2025-10-29T00:00:00Z
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/49435 |
| Date | 30 October 2024 |
| Creators | Lawton, Matthew Luke |
| Contributors | Emili, Andrew |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
| Rights | Attribution-NonCommercial-ShareAlike 4.0 International, http://creativecommons.org/licenses/by-nc-sa/4.0/ |
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