Date of Award

12-2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Program

Biomedical Sciences

Track

Microbiology, Immunology, and Biochemistry

Research Advisor

Benjamin Youngblood, PhD

Committee

Yong Feng, PhD; Kevin Freeman, PhD; Stephen Gottschalk, M.D.; Mark Hatley, M.D., PhD

Keywords

antitumor CD8 T cells;epigenetic regulation;T cell exhaustion;TCR signal strength;Tpex self-renewal

Abstract

Durability of an antitumor immune response is mediated in part by the persistence of progenitor exhausted CD8 T cells (Tpex). Tpex serve as a source for the pool of effector T cells that tend to have a short lifespan or eventually become dysfunctional in uncleared tumors. In contrast to the short-lived feature of their daughter cells, Tpex are able to preserve their quantity and developmental potential through a process of self-renewal. Previous research has demonstrated that Tpex can even self-renew in the absence of their cognate antigen. However, it remains unknown how T cell receptor (TCR) engagement impacts the self-renewal capacity of Tpex in settings of continued antigen exposure. Given that many cancer cells lack antigens capable of effectively engaging with TCRs, it is important to understand whether and how TCR engagement strength regulates the preservation of Tpex and their terminal differentiation during tumor progression. To investigate this, I established multiple murine tumor models, including Lewis lung carcinoma, which elicit an optimal or attenuated TCR signal in CD8 T cells. Longitu- dinal phenotyping and single-cell transcriptomics of tumor-specific T cells revealed that formation and maintenance of the Tpex reservoir in tumor-draining lymph nodes (tdLN) is dependent on optimal TCR engagement. Despite the generation of central memory-like T cells in tdLN under suboptimal priming, replenishment of tumor-infiltrating Tpex is abrogated. Moreover, adoptive transfer of optimally primed Tpex into a tumor setting with attenuated TCR stimulation significantly accelerates their terminal differentiation. This TCR-reinforced Tpex development and self-renewal is coupled to proximal position- ing to dendritic cell niches and epigenetic imprinting that involves increased chromatin accessibility at Egr2 and Tcf1 target loci. Collectively, my dissertation work reveals a previously unappreciated and coun- terintuitive role of TCR stimulation in preserving Tpex and highlights TCR-dependent self-renewal of Tpex during tumor progression. These results provide fundamental insight into T cell exhaustion and have important implications for the development of cancer vaccines that target tumor-epitopes with varying TCR binding avidities.

Declaration of Authorship

Declaration of Authorship is included in the supplemental files.

ORCID

0009-0002-1031-0435

DOI

10.21007/etd.cghs.2023.0649

Additional Files
2023-036-Lan-DOA.pdf (124 kB)
Download

Available for download on Saturday, December 06, 2025

Share

COinS