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UBC Theses and Dissertations

Developing next-generation regulatory T cell therapeutics Lam, Avery Justin

Abstract

CD4⁺FOXP3⁺ regulatory T cells (Tregs) control inflammation and enforce self-tolerance to maintain immune homeostasis. Adoptive Treg cell therapy holds promise for a variety of immune-mediated conditions, including transplant rejection and autoimmune disease. The last decade has seen an increased appreciation for Treg heterogeneity and hence an untapped potential for therapeutic Tregs with tailored functional profiles. We aimed to enable the development of next-generation Treg cell therapies by investigating novel Treg functions, optimizing gene editing tools, and interrogating the parameters essential for optimal Treg stability and efficacy. First, we examined the potential of human Tregs to directly mediate tissue repair. In contrast to mouse models, human Tregs did not express the IL-33 receptor ST2, but Tregs engineered to overexpress ST2 exhibited several tissue-reparative features, including amphiregulin expression and a heightened ability to induce M2-like macrophages. Second, we optimized a CRISPR-based approach to knock-out/knock-in genes in human Tregs. Using this method, we found that the master transcription factor FOXP3 had subset-specific roles in regulating mature Treg function and a limited role in maintaining lineage identity. Finally, we applied genome editing in human Tregs to interrogate the role of the transcription factor Helios, implicated in mouse Treg stability. Human Tregs that spontaneously downregulated Helios expression during in vitro expansion exhibited phenotypic and functional instability, but CRISPR-based Helios-knockout Tregs did not exhibit discernable functional defects. Overall, this work highlights important species-specific considerations in the translation of biology to therapy and offers a method to explore future mechanistic questions in human Tregs. 

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