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Dok proteins and CD28 regulate the development of yôNKT cells.

Yousefi, Mitra (2014). Dok proteins and CD28 regulate the development of yôNKT cells. Thèse. Québec, Université du Québec, Institut National de la Recherche Scientifique, Doctorat en virologie et immunologie, 252 p.

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In T cells, two members of the Dok family of adaptor proteins, Ook-1 and Ook-2, are predominantly expressed. Recent evidence suggests that they play a negative role in T cell signaling. In order to define whether Dok proteins regulate T cell development, we have generated transgenic mice overexpressing Ook-1 in thymocytes and peripheral T cells. For sorne expcriments wc also used mice deficient for the expression of both Dok-1 and Dok-2. In this research project we show that Ook overexpression negatively regulates the activity of the key components downstream ofTCR signaling such as LAT, ZAP-70, PLC-y and Erk. We also show that the overexpression of Ook-1 causes a dramatic reduction in the numbers of total, OP and SP thymocytes with an increase in the numbers of thymocytes in the DN stage, compared to WT controls. Further investigations indicated that this reduction is not due to an increased apoptosis in OP thymocytes in Ook-1 transgenic mice but rather a delay in the transition of thymocytes from the C04-C08- (ON) to C04+C08+ (OP) stage. More precisely, Ook-1 overexpression results in a block inside the ON stages by arresting thymocytes transition from ON3a to ON3b which are considered to be respectively the pre- and post-~ selection stages of T cell development. Moreover, Ook-1 overexpression promotes the development of yô T cells in the thymus, spleen, and li ver of the transgenic mice. This developmental promotion correlates with the lev el of Ook-1 overexpression and it is mainly due to the specifie expansion of the V y 1.1 + V6.l'. subset of yô T cells. Similar to their small population in WT mice, this expanded population of Vyl.1+ V6.3+ T cells in Ook-l Tg mice have also innate properties including rapid IL-4 production following stimulation. They express the transcription factor PLZF and they require SLAM-associated adaptor protein (SAP) for their development. Therefore, we concluded that Dok-1 promotes the development of yô NKT cells. Moreover, Ook-1 overexpression iii promotes the generation of an innate-like CD8+ T cell population. These cells express the transcription factor Eomesodermin, upregulate memory markers like CD44 and CD122 and produce IFN-y upon first stimulation. Thymie overproduction of IL-4 by y8 NKT cells is likely responsible for the innate conversion ofCD8+ thymocytes in Dok-1 Tg mice. We pursue our study to further characterize NKT cells by studying the signaling pathways that might be important for their development and maturation. We investigated the contribution of CD28 signaling in the functional development of ap and yô NKT cells in mice. We show that CD28 signaling promotes the thymie maturation of PLZF+ IL-4 producing NKT cells without any effect on their positive selection. Our results also show that CD28 signaJing positively regulates the LF A-1 expression on both ap and yô NKT cells. Using mixed bone marrow chimeric mice, we demonstrated that the developmental defect of yô NKT cells in CD28- deficient mice is cell autonomous. Moreover, in both wild type C57BL/6 and Dok-1 transgenic mice (with increased number of yô NKT cells), we show that the C028-mediated regulation of thymie IL-4 producing NKT cells promotes the differentiation of Eomes + CD44high innate-like COS+ T cells. Taken together, these findings reveal previously unappreciated mechanisms by which Dok-1 and C028 can be considered as important regulators of the innate immune response via controlling the NKT cell homeostasis and consequently the size of the immte-like C08+ T cell pool.

Type de document: Thèse
Directeur de mémoire/thèse: Duplay, Pascale
Mots-clés libres: lymphocyte ; T ; cellule ; tueuse ; immunite ; CD8
Centre: Centre INRS-Institut Armand Frappier
Date de dépôt: 17 mars 2016 20:27
Dernière modification: 17 mars 2016 20:27
URI: http://espace.inrs.ca/id/eprint/3352

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