CD69 cell surface expression identifies developing thymocytes which audition for T cell antigen receptor-mediated positive selection |
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Authors: | Yamashita Iwao; Nagata Taeko; Tada Tomio; Nakayama Toshinori |
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Institution: | Department of Immunology, Faculty of Medicine, University of Tokyo 7-3-1 Hongo Bunkyo-ku, Tokyo 113, Japan |
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Abstract: | CD69, an activation marker that is rapidly inducedon mature T cells after stimulation through the T cell antigenreceptor (TCR) was found to be expressed on 10% of normal thymocytes.All of these CD69+ thymocytes express ß TCR, and theyinclude both TCRlowCD4+CD8+ and TCRhighCD4+CD8– or CD4–CD8+thymocytes. The CD69+ cells can be further segregated into heat-stableantigen (HSA)+TCR*HSA–TCRhigh and HSA+TCRhigh thymocytepopulations. None of CD69+ cells express the mature T cell markerQa-2. Thus CD69+ cells present in vivo appear phenotyplcallyto represent transitional cell populations between immatureTCRlowHSA+Qa-2– double-positive cells and mature TCRhighHSA–QA-2+single-positive cells. In addition, TCR engagement by MHC moleculesis required for CD69 expression in the thymus. Taken together,the CD69 + thymocytes appear to represent the cells auditioningin positive selection process or they are the cells that havebeen positively selected recently. Analysis of a TCR transgenicmouse model revealed an increased number of CD69+ thymocytesin a positively selecting thymus, whereas no CD69+ transgenicTCR+ thymocytes were observed in the non-selecting thymus. Basedon the results of this study, we suggest that the surface expressionof CD69 serves as a useful marker to identify and trace thosethymocytes that are engaged in the TCR-mediated positive selectionprocess in the thymus. |
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Keywords: | activation marker CD4+CD8+ thymocytes CD69 positive selection T cell antigen receptor |
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