京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22147号 / 医博第4538号 / 新制||医||1039(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 濵﨑 洋子, 教授 竹内 理, 教授 髙折 晃史 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Regulatory T cells (Tregs), lymphocytes that suppress immunological reactions, are of great interest for our comprehension of basic immunology and as a therapeutic agent to treat immune-mediated pathologies. Understanding the physiology of these cells will help to inform clinical strategies targeting Tregs. In order to study the homing of human Tregs, we utilised genetic engineering to drive expression of fluorescent protein in human Tregs, permitting in vivo cell tracking. We optimised a protocol for lentivirus-mediated transduction of human Tregs during in vitro expansion, to generate high yields of stably-engineered cells. After infusing labelled cells into a humanised mouse model of skin allotransplantation, we detected human Tregs within a human skin graft by PCR and visualised Tregs moving in the graft, in a live mouse, by two-photon microscopy. Through reverse genetic analyses, we explored molecular mechanisms that allow Tregs to respond adaptively to environmental cues. Neuropilin-1 (NRP1), a transmembrane co-receptor, has been implicated in the function of mouse Tregs. Tregs transduced with shRNA to knock down NRP1 were severely impaired in their capacity to suppress cell proliferation in vitro and to prolong allograft survival in a humanised mouse model. qRT-PCR analysis revealed that transcription the gene encoding the anti-inflammatory cytokine IL-10, and the autophagy-associated genes BECN1, COPS4 and MAP1LC3B, was significantly diminished in NRP1-deficient Tregs. We concluded that in human Tregs, NRP1 is necessary for suppressive function, most likely via regulation of NRP1-dependent regulation of cytokine production and metabolism. Having identified a molecular target via which Treg function might be potentiated, we explored methods to target such molecules for cell therapy applications. Tregs engineered to over-express IL-10, but not NRP1, exerted significantly enhanced suppression of cell proliferation in vitro. Thus, relatively straightforward genetic engineering, compatible with generation of therapeutic cell yields, could be exploited to improve the efficacy of Treg cellular therapy.