Microbiology & Immunology - Theses
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ItemCharacterising novel cytotoxic T lymphocyte dysfunction by spatiotemporal analysis, and optimizing adoptive T cell therapy against cancer while preventing autoimmune side effect.( 2022)Adoptive cell therapy (ACT) is an emerging strategy for cancer treatment. However, ACT is not always successful because of various factors. In ACT using cytotoxic T lymphocytes (CTLs), T cell dysfunction is one of the most significant causes of failure. Our laboratory has previously discovered a novel type of T cell dysfunction, which we named “stunning”. We used a mouse model of ACT in the context of B-cell lymphoma. Here, mice were injected with Eu-myc lymphoma cells expressing ovalbumin (OVA) followed by injection of OVA-specific CTLs (OT-I CTL). In this model, we found that the presence of a large tumour burden led to rapid deletion and inactivation of OT-I CTLs in an antigen-specific manner. We hypothesised that at early stage after ACT, one CTL encounters a large number of antigen-presenting tumour cells within a short period of time, and this multiple interaction leads to stunning. Therefore, we aimed to investigate (1) How tumour cells and CTLs localise in organs, (2) Exact timing when stunning occurs, (3) How frequently CTLs interact with tumour cells, and (4) How CTLs behave after encountering tumour. In order to obtain these questions, we utilise both static (confocal) and dynamic (intravital) imaging techniques in this research. Using confocal fluorescence imaging, we found that in the spleen and lymph nodes, the proportion of antigen-specific CTLs that localised in T cell zones was decreased under a higher tumour burden. We next investigated the motility of CTLs in the lymph nodes by intravital imaging and found that motility was decreased in the context of high tumour burden. Accordingly, we propose the like between spatiotemporal characteristics of T cells and their dysfunction, which might be a potential therapeutic target. In addition to T cell dysfunction, another shortcoming of ACT is the potential for autoimmunity. If adoptively transferred CTL has specificity to an antigen that is shared with self cells, self-tissues are also susceptible to the attack by CTLs. Several clinical trials of ACT resulted in severe self-tissue destruction. Thus, balancing anti-cancer CTL responses with prevention of autoimmunity is paramount to the success of ACT. Typically, tumour-associated antigens are highly expressed in tumour cells compared to normal untransformed cells. Therefore, we hypothesised T cells with a lower affinity for antigen may be better candidates for use in ACT expecting that the T cell would only recognise the antigens on the tumour but not the ones on healthy tissues. We utilised OT-3 CTLs which express a lower affinity TCR than that of the OT-I cells. After optimising the concentration of IL-2 and cellular density for in vitro T cell priming, we found that OT-3 CTLs were still able to kill targets as effectively as OT-I CTLs. This provides evidence that low-affinity T cells may act as candidates for ACT.