| Summary: | 博士 === 國立陽明大學 === 微生物暨免疫學研究所 === 88 === CD4+ T cells are divided into two subsets, Th1 and Th2, according to their cytokine profiles. Th1 cells produce mainly IL-2, TNF-b and IFN-g, but not IL-4, and are responsible for cell-mediated immunity. Th2 cells produce mainly IL-4, IL-5, IL-6 and IL-13, but not IFN-g, and provide efficient help for B lymphocytes to generate humoral immunity. The regulation of host immune response to Th1 or Th2 when host infected by pathogens play a critical role to determine the final outcome of each infections disease. Currently, the detection of Th1/Th2 response are determined by ELISA or intracellular cytokine staining, however these methods can not allow us to isolate viable Th1 and Th2 cells for subsequent functional studies or adoptive transfer. To overcome these problems, we try to use transgenic markers for the detection of Th1 and Th2 cells, as wells to find endogenous surface marker for Th1 and Th2 subsets. In the first part of this thesis, we generated mice transgenic for human Thy1 and murine Thy1.1 genes driven by IFN-g and IL-4 promoters, respectively, to resolve the fundamental problems in Th1/Th2 studies. In all the system tested in this thesis, the expression of these surface marker gene products can reflect the expression of the corresponding cytokines (with some temporal lag). The surface expression of the marker genes is readily this feature should permit isolation of viable the Th1 and Th2 cells by magnetic beads or cell sorter for subsequent functional analysis and adoptive transfer experiment. In addition, the transgenic surface marker will facilitate the detection of Th1 and Th2 cells by histochemical staining. In the second part, we found TRANCE, a member of tumor necrosis factor (TNF) superfamily, specifically expressed on activated Th1, but not Th2, CD4+ T cell. Moreover, the addition of soluble RANK.Fc fusion protein to inhibit the interaction of TRANCE (expressed on T cells) and RANK (expressed on antigen presenting cells, APCs) suppressed IFN-g secretion by activated Th1 cells, but it does not affect IL-4 secretion by Th2 cells. The suppressive effect of RANK.Fc fusion protein on IFN-g secretion by Th1 cells is only observed in the presence of APCs, but not in T cells activated by immobilized anti-TCRb mAb. Furthermore, immobilized RANK.Fc fusion protein can cross-link TRANCE expressed on Th1 cells and augments its ability to secrete IFN-g, indicating the presence of reverse signalling through TRANCE during T cells and APC interaction. The enhanced secretion of IFN-g via TRANCE correlates with the activation of p38 MAP kinase, and is inhibited by SB203580, a p38 MAP kinase-specific inhibitor. In addition to its role as ligand to activate dendritic cells, TRANCE can operate as receptor to transduce a p38 MAP kinase dependent signaling pathway to augment IFN-g secretion Th1 cells. Thus, the establishment of transgenic mice will become a valuable model system to study the differentiation of Th1 and Th2 cells, while the 烒everse signalling transduced by TRANCE on Th1 cells reveal the potential role of 舥everse signllaing in Th1/Th2 differentiation .
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