Analysis and modelling of immune cell behaviour in lymph nodes based on multi-photon imaging

This thesis presents quantitative studies of T cell and dendritic cell (DC) behaviour in mouse lymph nodes (LNs) in the naive state and following immunisation. These processes are of importance and interest in basic immunology, and better understanding could improve both diagnostic capacity and therapeutic manipulations, potentially helping in producing more effective vaccines or developing treatments for autoimmune diseases. The problem is also interesting conceptually as it is relevant to other fields where 3D movement of objects is tracked with a discrete scanning interval. A general immunology introduction is presented in chapter 1. In chapter 2, I apply quantitative methods to multi-photon imaging data to measure how T cells and DCs are spatially arranged in LNs. This has been previously studied to describe differences between the naive and immunised state and as an indicator of the magnitude of the immune response in LNs, but previous analyses have been generally descriptive. The quantitative analysis shows that some of the previous conclusions may have been premature. In chapter 3, I use Bayesian state-space models to test some hypotheses about the mode of T cell search for DCs. A two-state mode of movement where T cells can be classified as either interacting to a DC or freely migrating is supported over a model where T cells would home in on DCs at distance through for example the action of chemokines. In chapter 4, I study whether T cell migration is linked to the geometric structure of the fibroblast reticular network (FRC). I find support for the hypothesis that the movement is constrained to the fibroblast reticular cell (FRC) network over an alternative 'random walk with persistence time' model where cells would move randomly, with a short-term persistence driven by a hypothetical T cell intrinsic 'clock'. I also present unexpected results on the FRC network geometry. Finally, a quantitative method is presented for addressing some measurement biases inherent to multi-photon imaging. In all three chapters, novel findings are made, and the methods developed have the potential for further use to address important problems in the field. In chapter 5, I present a summary and synthesis of results from chapters 3-4 and a more speculative discussion of these results and potential future directions.

An interpretative phenomenological analysis of the lived experience of suicidal behaviour

Background: In Scotland, suicide prevention is a major public health challenge, with two people, on average, dying every day due to suicide. Any efforts to prevent suicide should be aided by research. Existing research on suicide is dominated by quantitative research that has largely focused on providing explanatory accounts of suicidal phenomena. Research providing rich and detailed accounts of suicidal behaviour among individuals who have directly experienced it is growing but remains relatively embryonic. This study sought to supplement existing understanding of attempted suicide specifically by exploring the processes, meaning and context of suicidal experiences among individuals with a history of attempted suicide. Methods: The study used a retrospective qualitative design with semi-structured in-depth interviews. Participants were patients (n=7) from a community mental health service in Glasgow, Scotland who had attempted suicide within the previous 12-month period. The interviews were transcribed verbatim and were analysed for recurrent themes using interpretative phenomenological analysis (IPA). Results: Three super-ordinate themes, each with inter-related sub-themes, emerged from the analysis. 1) “Intentions”: This theme explored different motives for suicide, including providing relief from upsetting feelings; a way of establishing control; and a means of communicating with others. 2) “The Suicidal Journey”: This theme explored how individuals’ thinking can change when they are suicidal, including feeling overwhelmed by a build-up of distress and a narrowing of their perspective. 3) “Suicidal Dissonance”: This theme explored how people can feel conflicted about suicide and can be fearful of the consequences of their suicidal behaviour. Conclusion: Participants’ accounts were dominated by experience of significant adversity and psychological suffering. These accounts provided valuable insights into the suicidal process, highlighting implications for clinical practice and future research.