Zhang Meifen, Vacchio Melanie S, Vistica Barbara P, Lesage Sylvie, Egwuagu Charles E, Yu Cheng-Rong, Gelderman Monique P, Kennedy Michael C, Wawrousek Eric F, Gery Igal
National Eye Institute and National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
J Immunol. 2003 Apr 15;170(8):3954-62. doi: 10.4049/jimmunol.170.8.3954.
We have previously shown that transgenic (Tg) mice expressing either soluble or membrane-bound hen egg lysozyme (sHEL or mHEL, respectively) under control of the alphaA-crystallin promoter develop tolerance due to thymic expression of minuscule amounts of HEL. To further address the mechanisms by which this tolerance develops, we mated these two lines of Tg mice with the 3A9 line of HEL-specific TCR Tg mice, to produce double-Tg mice. Both lines of double-Tg mice showed deletion of HEL-specific T cells, demonstrated by reduction in numbers of these cells in the thymus and periphery, as well as by reduced proliferative response to HEL in vitro. In addition, the actual deletional process in thymi of the double-Tg mice was visualized in situ by the TUNEL assay and measured by binding of Annexin V. Notably, the apoptosis localized mainly in the thymic medulla, in line with the finding that the populations showing deletion and increased Annexin V binding consisted mainly of single- and double-positive thymocytes. Interestingly, the thymic deletional effect of sHEL was superior to that of mHEL in contrast to the opposite differential tolerogenic effects of these HEL forms on B cells specific to this Ag. Analysis of bone marrow chimeras indicates that both forms of HEL are produced by irradiation-resistant thymic stromal cells and the data suggest that sHEL is more effective in deleting 3A9 T cells due mainly to its higher accessibility to cross-presentation by dendritic APC.
我们之前已经表明,在αA-晶状体蛋白启动子控制下表达可溶性或膜结合型鸡卵溶菌酶(分别为sHEL或mHEL)的转基因(Tg)小鼠,由于胸腺中微量HEL的表达而产生耐受性。为了进一步探讨这种耐受性产生的机制,我们将这两种Tg小鼠品系与HEL特异性TCR Tg小鼠的3A9品系进行交配,以产生双转基因小鼠。两种双转基因小鼠品系均显示HEL特异性T细胞缺失,这通过胸腺和外周中这些细胞数量的减少以及体外对HEL增殖反应的降低得以证明。此外,通过TUNEL检测原位观察并通过膜联蛋白V结合进行测量,双转基因小鼠胸腺中的实际缺失过程得以显现。值得注意的是,细胞凋亡主要定位于胸腺髓质,这与显示缺失和膜联蛋白V结合增加的群体主要由单阳性和双阳性胸腺细胞组成的发现一致。有趣的是,与这些HEL形式对该抗原特异性B细胞相反的差异致耐受性效应形成对比的是,sHEL的胸腺缺失效应优于mHEL。对骨髓嵌合体的分析表明,两种形式的HEL均由抗辐射的胸腺基质细胞产生,并且数据表明sHEL在删除3A9 T细胞方面更有效,这主要是由于其对树突状抗原呈递细胞交叉呈递的更高可及性。