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KMID : 0617319980070010122
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Journal of Pharmacetical Sceiences Ewha Womans University
1998 Volume.7 No. 1 p.122 ~ p.127
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Thymocytes Positively Select Thymocytes in Human System
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Choi, Eun Young
Park, Weon Seo/Jung, Kyeong Cheon/Chung, Doo Hyun/Bae, Young Mee/Kim, Tae Jin/Song, Hyung Geun
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Abstract
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We previously demonstrated the expression of MHC class Ⅱ molecules in a significant percentage of human fetal and postnatal thymocytes [1]. These results, at that time, raised the question as to whether the MHC class Ⅱ molecules on immature thymocytes could actively be involve in the selection of immature T cells. We have developed a human reaggregate culture system to address this issue. Surprisingly, despite the fact that thymic epithelial cells (TECs) have been shown to be a major selecting cell type of positive selection, we were clearly able to see the involvement of MHC class Ⅱ^+ thymocytes during selection process through T-T interaction. In addition, maturation to single positive (SP) cells occurred only in the presence of MHC class Ⅱ molecules and immature thymocytes were found to be arrested at the double positive (DP) stage of differentiation by blocking of TCR recognition of MHC class Ⅱ molecules. All these results strongly suggest that human MCH class Ⅱ^+ thymocytes actively patticipate in the selection of the TCR repertoire, for which TCR recognition of peptide/MHC class Ⅱ may be an initial determining step. Human Immunology 54, 15-20 (1997).
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