| Abstract |
In our body exists an internal clock, known as the circadian rhythm (CR), which resets every 24 hours. The CR affects all cells in our body, including white blood cells, such as T cells, that make up our immune system. Thus, the immune system's response to "threats" can be altered by the CR. In addition, the beta cells that produce insulin in the pancreas are also controlled by CRs. In Type 1 diabetes (T1D), some T cells attack the insulin-producing beta cells by recognising small pieces of protein, called peptides, as foreign. It is currently unknown what triggers this attack but one area being explored relates to the germs (bacteria) that live in our body. Evidence in children suggests that those at greatest risk for developing T1D have different bacteria present in their intestine and that this can change how the immune system, such as T cells, respond to them. Recently, it has been shown that bacteria can change the CR in the body through the immune system. Thus, bacteria may be a useful target for altering the CR to promote a healthier immune system, preventing the development of T1D. This has not been studied before. This research aims to understand how the bacteria in our bodies affect the CR of both T cells and the targeted insulin-producing beta cells. I hypothesise that bacteria can change the CR of both cell types, resulting in changes to the T cell's ability to destroy the beta cells. I will investigate this using the Non-obese diabetic (NOD) mouse model, which develops spontaneous T1D similar to humans. This work will be studied in 3 main aims: 1. Do bacteria change the CR in the insulin-producing beta cells making them more easily targeted by the T cells? 2. Do bacteria change the CR in the T cells making them better at destroying the beta cells? 3. Does disruption to the CR in the beta cells or CD8 T cells specifically alter the risk of developing T1D? I will study both NOD mice with bacteria and NOD mice that do not have any bacteria, called Germ-free (GF) mice. These mice will be used to identify the role bacteria have on the CR of both beta cells and CD8 T cells. All mice will be studied at two different time points to identify changes caused by the CR. Insulin-producing beta cells will be studied for their ability to produce insulin and will be investigated for the peptides they produce that may make them targets for the CD8 T cells. This will involve imaging NOD mice that have a fluorescent (coloured) signal after producing insulin, which allows them to be visualised. I will also introduce fluorescent bacteria into GF NOD mice allowing me to visualise whether the bacteria can enter the pancreas. I will also look at products bacteria produce that may alter the CR of the beta cells. CD8 T cells will be studied as they are the most common T cell found in the pancreas of humans with T1D. I will study a specific CD8 T cell that can recognise both a peptide produced by the beta cells and a similar peptide produced by bacteria. Recognition of either of these peptides will result in the CD8 T cells destroying the beta cells. CD8 T cells will be studied for their interactions with beta cells, their ability to destroy peptide-coated target cells and changes in energy usage that may help the cells become more damaging. I will also study how responses to bacteria at different time points of the CR can also affect the CD8 T cells. Finally, I will generate CR-deficient NOD mice and GF NOD mice in either beta cells or CD8 T cells specifically. These mice will be studied as mentioned above, as well as for their ability to develop spontaneous diabetes. This will help identify which cells (beta cells or CD8 T cells) may make better targets for future therapy. Understanding the CR and how it changes the cells may identify specific time points in which therapeutic success can be maximised. Given the increasing number of people diagnosed with T1D, and a lack of successful therapies, this is urgently needed. |
