Doctor of Philosophy

dissertationDuring acute infection, a CD4+ T cell response begins with the interaction between the T cell receptor (TCR) and its cognate antigen presented by major histocompatibility complex (MHC) class II on antigen presenting cells. The nature of these interactions impacts various aspects of T cell fate. Here we find that TCR signals influence the generation of Th1 memory cells. The transition of activated CD4+ T cells from effector to memory is associated with a significant decrease in TCR repertoire diversity. Particularly, a slow dissociation rate of TCR-antigen interactions, but not TCR avidity, corresponds to memory potential. Thus, long-lived TCR interactions with antigen during priming are a determinative factor in promoting Th1 memory differentiation. Once generated, memory T cells are maintained at stable levels. However, CD4+ memory T cells gradually decline in some mouse models of acute infection. We find that heterologous rechallenge of Th1 memory cells with a pathogen sharing only a CD4+ T cell epitope, which allows for robust boosting of memory T cells without rapid antigen clearance, leads to the generation of highly stable secondary Th1 memory cells that do not decline. Importantly, enhanced memory stability corresponds to the acquisition of high antigen sensitivity, often referred to as functional avidity, at the peak of the recall response. In contrast, homologous rechallenge of Th1 memory cells, where memory iv cells are weakly stimulated due to the limited antigen persistence, does not enhance function and stability of secondary Th1 cells. Upon heterologous rechallenge, the recall response of Th1 memory cells is characterized by the early emergence of secondary responders with high functional avidity, followed by functional avidity decay to the level similar to the parent memory cells. Unexpectedly, responding secondary effectors progressively lose their functional avidity when secondary infection is prolonged, which corresponds to the generation of poorly stable secondary memory cells. Functional avidity decay requires an extended period of both antigen presentation and infectious inflammation and correlates with the diminished magnitude of TCR signaling. Together, the recall response of Th1 memory cells is functionally dynamic, and the nature of secondary stimulation influences function and stability of secondary Th1 cells

Followership Characteristics among US Federal Government Employees

This paper was part of a PhD dissertation written by the author.Empowering collective action among leaders and followers in the US public sector has been encouraged to solve public problems in a complex and globalized society. However, without considering who the participants are, how much influence they have, and the various situations in which they find themselves, empowerment is not an adequate solution to existing public challenges. Understanding followership—the process empowered participants use to follow— is a prerequisite to understanding successful empowerment. This study examines followership as it is practiced within the US federal government. Data from the Federal Human Capital Survey data, which had 212,223 respondents and was administered by the Office of Personnel Management in 2008, were used. The results indicate that different followership styles are dominant in different agencies. Followership styles also differ depending on job rank, which also explains possible distinctions between different groups in public organizations

Factors Influencing Public Employee Engagement and Its Impact on Organizational Performance

The purpose of this study was to explore the factors influencing employee engagement and its possible outcomes. Using data from a large-scale survey of employees in 72 US federal government agencies, and several organizational factors in public setting as control variables, the study empirically tested three contextual factors(participative leadership support, organizational fairness, and supportiveness of organizational context) that influence employee engagement in federal agencies. The study also examined the mediating role of employee engagement between the three contextual variables and organizational performance. The results indicate that participative leadership support and supportiveness of organizational context predict employee engagement. In addition, employee engagement mediated the relationship between antecedents and organizational performance

Factors Influencing Public Employee Engagement and Its Impact on Organizational Performance*

Abstract: The purpose of this study was to explore the factors influencing employee engagement and its possible outcomes. Using data from a large-scale survey of employees in 72 US federal government agencies, and several organizational factors in public setting as control variables, the study empirically tested three contextual factors (participative leadership support, organizational fairness, and supportiveness of organizational context) that influence employee engagement in federal agencies. The study also examined the mediating role of employee engagement between the three contextual variables and organizational performance. The results indicate that participative leadership support and supportiveness of organizational context predict employee engagement. In addition, employee engagement mediated the relationship between antecedents and organizational performance