Controlling T cell activation through manipulation of cytoskeletal balance
Abstract/Contents
- Abstract
- T cells must remain sensitive enough to respond to even a single low-affinity peptide presented on an antigen presenting cell while maintaining an activation threshold high enough to prevent spurious activation. Effector and memory T cells have a significantly lower activation threshold than naive T cells, enabling the former to rapidly mount a recall response and clear the nascent infection. While many differences in protein expression and localization between effector, memory, and naive T cells have been discovered, the cellular mechanisms underlying the variable activation threshold are largely unknown. Chapter 2 examines the effects of local stimulation on T cell activation and cytoskeletal regulation. I delivered local signals to naive and effector T cells using an atomic force microscope to measure the generation of force by T cells and the mechanical properties of their cortical cytoskeleton. I found that effector T cells are mechanically soft (reduced elastic modulus) compared to naive cells and that cells contacted with an anti-CD3--coated cantilever have slower stress relaxation kinetics. The latter result suggests active rearrangements of the cortical cytoskeleton. I discovered that effector T cells flux more calcium than naive T cells, but the timing and tempo of calcium flux do not differ. T cells push and pull in response to this local stimulation and produce oscillatory forces with 50-100s periods. Chapter 3 examines global cytoskeletal regulation in T cells. Cells soften within one hour of activation, requiring actin remodeling. This cytoskeletal softening is a general feature of T cell activation, observable whether the cells are activated with anti-CD3, peptide-pulsed antigen presenting cells, or \emph{in vivo} immunization. Cytoskeletal softening was durable, persisting in lymphoblasts several days after removing TCR stimulation and in memory phenotype T cells, suggesting that the cortical cytoskeleton is a `storage' mechanism controlling the threshold of activation. This softening process occured downstream of CD28 costimulation, particularly requiring Rho kinase (ROCK) to maintain basal cytoskeletal stiffness and PI3K to soften the cytoskeleton. Inhibitors of ROCK made T cells mechanically soft without activation, and those cells had larger lamella and flux more calcium. Overall, this work demonstrates bidirectional regulation of T cell activation and the cortical actin cytoskeleton. A mechanically stiff cortex antagonizes activation of naive T cells, raising the activation threshold. Durable softening of the cytoskeleton in effector and memory T cells thus represents a physical mechanism to `store' the activation state of the cell and reduce the threshold.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2014 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Bruce, Marc Amor |
|---|---|
| Associated with | Stanford University, Program in Immunology. |
| Primary advisor | Butte, M. (Manish) |
| Thesis advisor | Butte, M. (Manish) |
| Thesis advisor | Davis, Mark |
| Thesis advisor | Lewis, Richard (Richard Sheridan) |
| Thesis advisor | Melosh, Nicholas A |
| Advisor | Davis, Mark |
| Advisor | Lewis, Richard (Richard Sheridan) |
| Advisor | Melosh, Nicholas A |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Marc Amor Bruce. |
|---|---|
| Note | Submitted to the Program in Immunology. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2014. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2014 by Marc Amor Bruce
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