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Abstract

The overall goal of my thesis is to develop molecules to induce antigen-specic tolerance by co-opting endogenous tolerance mechanisms. To do this I developed antibody fragments that target the apoptotic pathway or the liver, and characterized the ensuing immune responses.In Chapter 1, I introduce the eld of immune tolerance. I discuss the mechanisms that the immune system employs to maintain tolerance to self, and avoid autoimmunity. I discuss the current standards of care in immunosuppression used to treat autoimmunity, allergy, transplantation, and prevention of anti-drug antibodies. Finally, I introduce emerging strategies that are in development to achieve antigen-specic tolerance. In Chapter 2, I expand upon a previously developed technique in the laboratory to target apoptotic erythrocytes for immune tolerance. I conduct phage display on mouse erythrocytes using a human antibody fragment phage library, and characterize the resulting erythrocyte-binding antibody fragments. I target antigen to erythrocytes and determine that delivery to this pathways yields profound and lasting T cell dysfunction, both in transgenic and endogenous T cells. I further characterize the mechanism of tolerance induction as occurring in the spleen, and for CD8 T cells by Batf3+ dendritic cells. In Chapter 3, I develop a method of targeting liver sinusoidal endothelial cells for their inherent tolerogenic properties. I conduct phage display on liver sinusoidal endothelial cell C-type lectin (LSECtin), for its specicity to LSECs in the liver. I characterize the Fabs from phage display, and determine that they are rapidly and specically internalized by LSECs. I target antigen to LSECtin, and determine that this pathway reduces presentation to T cells. I use protein engineering strategies to enhance antigen presentation by developing cathepsin-cleavable linkers and endosomal escape peptides. Finally, I encapsulate antigen in polymerosomes decorated with anti-LSECtin Fab, and enhance presentation by LSECs. In Chapter 4, I discuss the conclusions and future directions of this work. Furthermore, I discuss the limitations to the eld of antigen-specic tolerance, and oer potential strategies to overcome these limitations.

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