Title: Utilizing a novel magnetically actuated variable rigidity platform to investigate mechanosensing within T cell activation
Description: Immune system functionality and lymphocyte activity are gaining traction as a relevant therapeutic source for potentially addressing diseases such as cancer and autoimmune disorders. One such promising technique, adoptive cell therapy, revolves around successful ex vivo T cell activation and the ability to elicit a specific immune response. Key studies have recently suggested that mechanical forces play an important role in the ability of T cells to expand and proliferate and that T cell activation is sensitive to the mechanical properties of activating substrates. T cells initiate adaptive immune responses through interactions with antigen presenting cells (APCs). When T cells interact with APCs, they form the immune synapse, a multistep process that leads to downstream signaling and cellular function. Previous research has suggested that this process is both dynamic and mechanically sensitive. Gaining insight into the mechanisms through which T cells carry out mechanosensing and the associated effector functionalities will be advantageous in developing approaches for controlling T cell activation through mechanics and will allow for more accurate and efficient methods of promoting cell expansions for targeted therapies.

This dissertation serves to generate a new mechanically dynamic 3D system to be utilized towards these understandings and contribute to the fields of immunology and mechanobiology. We first establish the development of a novel variable rigidity system actuated by magnetic field application. Validation experiments conclude that this device provides rapid, dynamic, and reversible control of substrate rigidity, without affecting the physical or biochemical properties of the system. The novel system is first used to explore mechanistic activity of T cells during activation in the face of a dynamic biomechanical environmental; we discover that T cells modulate the deflection and protrusive nature of their physical behaviors towards their targets in response to variable rigidity changes. We then utilize the magnetically driven system to characterize the biological mechanisms involved in these mechanosensitively associated behavior phenotypes. We demonstrate that activation patterns of T cells, defined by cytokine secretion profiles and TCR stimulation, correspond with varying cellular deformation directionality of activating substrates of variable increasing rigidity.

In this process we discover a possible rigidity threshold upon which TCR triggering is sustained. Furthermore we reveal cytoskeleton components associated with identified mechanosensitive behaviors that cells produce in response to dynamic biomechanical cues. Together this work highlights the dynamic physicality and biomechanical mechanisms of T cell activation in response to a variable rigidity environment. These conclusions reveal insights into T cell mechanosensing activity within the natural mechanically complex atmosphere of the body. Encompassing those understandings, this thesis will help address current scientific gaps between mechanobiology and immunology and advance the biomechanical parameters of cell expansion driven adoptive immunotherapies.