Mechanosensing in Naive CD4+ T cells

T cells are key players in adaptive immune response. Originating from the thymus, they seek and eliminate infected cells in various locations of our body. T cells are not anchorage-dependent in nature. However, in our body, cells are constantly under physiological stress. It is not yet known how natural changes in physical environment could affect T cell behaviors. This thesis focuses to study the role, pathway, and main mechanism of rigidity sensing in T cells. Most studies of T cell rigidity sensing have showed that T cell responses are sensitive to external forces. It is unclear whether T cells could generate forces, translate them to biochemical signaling, and regulate their function based on the physical sensing. We tested the idea by developing the use of substrate with varying modulus to analyze the impact of rigidity to T cell activation. We demonstrated that mouse naive CD4+ T cells were capable of sensing and transmitting information from substrate modulus, ultimately affecting the regulation of cytokine secretion, a key indicator of T cell activation. Interestingly, this cytokine secretion correlated with increasing substrate rigidity. This increased cytokine secretion diminished when T cells lost the ability to contract in sensing the underlying substrate rigidity. Contrary to the presumption that T cells are not able to regulate their function based on the forces applied to the environment, our study provides the first demonstration that substrate rigidity has a functional impact to naive CD4+ T cell activation. To understand the translation process from physical to biochemical signaling in T cells, we determined the signaling pathway that regulated T cell rigidity sensing. We found that T cell rigidity sensing was associated with the signaling molecules of the T cell receptor (TCR) complex, the central pathway of T cell response. Analysis of TCR signaling molecules revealed that T cell rigidity sensing was mediated downstream of the early signaling components in the TCR complex. Lastly, we developed a method of combining micron-scale patterning in elastic substrates to determine whether T cell mechanosensing was mediated from local adhestion sites or globally throughout the cell. Circular features of primary signal for naive CD4+ T cells were spatially segregated and patterned on elastic substrates to analyze T cell contractility in generating forces across the segregated primary signals, leading to sustained TCR triggering. We found out that T cell contractility failed to generate forces when the primary signals were arranged in equilateral triangle geometry, leading to loss of TCR triggering. This result shows that T cell rigidity sensing is mediated globally throughout the whole cell rather than locally from adhesion sites. Furthermore, the loss of TCR triggering by T cells when sensing the equilateral triangle geometry in elastic substrates opens up new ideas in characterizing force generation within the cell

Environmental Justice Inventory – Linn-Benton County, Oregon

The purpose of this inventory is to detail the state of environmental justice in the Mid- Willamette Valley in an up-to-date, centralized format. The inventory is based on information from various government sources, and a survey to gather first-person perspective to take a pulse of the wellbeing of our community. The Environmental Climate Justice committee of the Linn-Benton County NAACP commissioned this project to gather this information in order to make informed policy solutions to environmental justice issues experienced here in the Mid- Willamette Valley. This report will detail the methodology, findings from the survey and secondary sources, and some policy suggestions

T cell immunoengineering with advanced biomaterials

Recent advances in biomaterials design offer the potential to actively control immune cell activation and behaviour. Many human diseases, such as infections, cancer, and autoimmune disorders, are partly mediated by inappropriate or insufficient activation of the immune system. T cells play a central role in the host immune response to these diseases, and so constitute a promising cell type for manipulation. In vivo, T cells are stimulated by antigen presenting cells (APC), therefore to design immunoengineering biomaterials that control T cell behaviour, artificial interfaces that mimic the natural APC-T cell interaction are required. This review draws together research in the design and fabrication of such biomaterial interfaces, and highlights efforts to elucidate key parameters in T cell activation, such as substrate mechanical properties and spatial organization of receptors, illustrating how they can be manipulated by bioengineering approaches to alter T cell function

Mechanosensing in T lymphocyte activation.

Mechanical forces play an increasingly recognized role in modulating cell function. This report demonstrates mechanosensing by T cells, using polyacrylamide gels presenting ligands to CD3 and CD28. Naive CD4 T cells exhibited stronger activation, as measured by attachment and secretion of IL-2, with increasing substrate elastic modulus over the range of 10-200 kPa. By presenting these ligands on different surfaces, this report further demonstrates that mechanosensing is more strongly associated with CD3 rather than CD28 signaling. Finally, phospho-specific staining for Zap70 and Src family kinase proteins suggests that sensing of substrate rigidity occurs at least in part by processes downstream of T-cell receptor activation. The ability of T cells to quantitatively respond to substrate rigidly provides an intriguing new model for mechanobiology

Durable interactions of T cells with T cell receptor stimuli in the absence of a stable immunological synapse

T cells engage in two modes of interaction with antigen-presenting surfaces: stable synapses and motile kinapses. Although it is surmised that durable interactions of T cells with antigen-presenting cells involve synapses, in situ 3D imaging cannot resolve the mode of interaction. We have established in vitro 2D platforms and quantitative metrics to determine cell-intrinsic modes of interaction when T cells are faced with spatially continuous or restricted stimulation. All major resting human T cell subsets, except memory CD8 T cells, spend more time in the kinapse mode on continuous stimulatory surfaces. Surprisingly, we did not observe any concordant relationship between the mode and durability of interaction on cell-sized stimulatory spots. Naive CD8 T cells maintain kinapses for more than 3 hr before leaving stimulatory spots, whereas their memory counterparts maintain synapses for only an hour before leaving. Thus, durable interactions do not require stable synapses

Durable interactions of T cells with T cell receptor stimuli in the absence of a stable immunological synapse

T cells engage in two modes of interaction with antigen-presenting surfaces: stable synapses and motile kinapses. Although it is surmised that durable interactions of T cells with antigen-presenting cells involve synapses, in situ 3D imaging cannot resolve the mode of interaction. We have established in vitro 2D platforms and quantitative metrics to determine cell-intrinsic modes of interaction when T cells are faced with spatially continuous or restricted stimulation. All major resting human T cell subsets, except memory CD8 T cells, spend more time in the kinapse mode on continuous stimulatory surfaces. Surprisingly, we did not observe any concordant relationship between the mode and durability of interaction on cell-sized stimulatory spots. Naive CD8 T cells maintain kinapses for more than 3 hr before leaving stimulatory spots, whereas their memory counterparts maintain synapses for only an hour before leaving. Thus, durable interactions do not require stable synapses

Cutting edge: Synapse propensity of human memory CD8 T cells confers competitive advantage over naive counterparts

Memory T cells are endowed with multiple functional features that enable them to be more protective than naive T cells against infectious threats. It is not known if memory cells have a higher synapse propensity (SP; i.e., increased probability to form immature immunological synapses that then provide an entry into different modes of durable interaction with APCs). In this study, we show that only human memory CD8 T cells have remarkably high SP compared with naive counterparts. Such a dichotomy between naive and memory cells is not observed within the human CD4 or murine CD8 T cell population. Higher SP in human memory CD8 T cells allows them to outcompete and prevent naive CD8 T cells from getting recruited to the response. This observation has implications for original antigenic sin and aging of the immune system in humans

Cutting edge: Synapse propensity of human memory CD8 T cells confers competitive advantage over naive counterparts

Memory T cells are endowed with multiple functional features that enable them to be more protective than naive T cells against infectious threats. It is not known if memory cells have a higher synapse propensity (SP; i.e., increased probability to form immature immunological synapses that then provide an entry into different modes of durable interaction with APCs). In this study, we show that only human memory CD8 T cells have remarkably high SP compared with naive counterparts. Such a dichotomy between naive and memory cells is not observed within the human CD4 or murine CD8 T cell population. Higher SP in human memory CD8 T cells allows them to outcompete and prevent naive CD8 T cells from getting recruited to the response. This observation has implications for original antigenic sin and aging of the immune system in humans

Durable Interactions of T Cells with T Cell Receptor Stimuli in the Absence of a Stable Immunological Synapse

Summary: T cells engage in two modes of interaction with antigen-presenting surfaces: stable synapses and motile kinapses. Although it is surmised that durable interactions of T cells with antigen-presenting cells involve synapses, in situ 3D imaging cannot resolve the mode of interaction. We have established in vitro 2D platforms and quantitative metrics to determine cell-intrinsic modes of interaction when T cells are faced with spatially continuous or restricted stimulation. All major resting human T cell subsets, except memory CD8 T cells, spend more time in the kinapse mode on continuous stimulatory surfaces. Surprisingly, we did not observe any concordant relationship between the mode and durability of interaction on cell-sized stimulatory spots. Naive CD8 T cells maintain kinapses for more than 3 hr before leaving stimulatory spots, whereas their memory counterparts maintain synapses for only an hour before leaving. Thus, durable interactions do not require stable synapses. : T cells primarily form two types of adhesive junctions when interacting with stimulatory surfaces: stable synapses and motile kinapses. Mayya et al. demonstrate that durable interactions with antigen do not require formation of a stable synapse. Keywords: lymphocytes, migration, immunological synapse, kinapse, chemokines, adhesion, live imaging, micro-contact printin