Zhou T, Cheng J, Yang P, Wang Z, Liu C, Su X, Bluethmann H, Mountz J D
Department of Medicine, Division of Clinical Immunology and Rheumatology, University of Alabama at Birmingham, USA.
J Exp Med. 1996 Apr 1;183(4):1879-92. doi: 10.1084/jem.183.4.1879.
The Nur77/Nurr1 family of DNA binding proteins has been reported to be required for the signal transduction of CD3/T cell receptor (TCR)-mediated apoptosis in T cell hybridomas. To determine the role of this family of DNA-binding proteins in thymic clonal deletion, transgenic (Tg) mice bearing a dominant negative mutation were produced. The transgene consisted of a truncated Nur77 (deltaNur77) gene encoding the DNA-binding domain of Nur77 ligated to a TCR-beta enhancer resulting in early expression in thymocytes. Apoptosis of CD4+CD8+ thymocytes mediated by CD3/TCR signaling was greatly inhibited in the deltaNur77 Tg mice, compared with non-Tg littermates, after treatment with anti-CD3 or anti-TCR antibody in vivo and in vitro. Clonal deletion of self-reactive T cells was investigated in deltaNur77-Db/HY TCR-alpha/beta double Tg mice. There was a five-fold increase in the total number of thymocytes expressing self-reactive Db/HY TCR-alpha/beta in the deltaNur77-TCR-alpha/beta double Tg male mice. Deficient clonal deletion of self-reactive thymocytes was demonstrated by a 10-fold increase in the CD4+CD8+ thymocytes that expressed Tg TCR-alpha/beta. There was an eightfold increase in the CD8+, Db/HY TCR-alpha/beta T cells in the lymph nodes (LN) of delta Nur77-Db/HY TCR-alpha/beta double Tg compared with Db/HY TCR-alpha/beta Tg male mice. In spite of defective clonal deletion, the T cells expressing the Tg TCR were functionally anergic. In vivo analysis revealed increased activation and apoptosis of T cells associated with increased expression of Fas and Fas ligand in LN of deltaNur77-Db/HY TCR-alpha/beta double male mice. These results indicate that inhibition of Nur77/Nurr1 DNA binding in T cells leads to inefficient thymic clonal deletion, but T cell tolerance is maintained by Fas-dependent clonal deletion in LN and spleen.
据报道，DNA结合蛋白Nur77/Nurr1家族是T细胞杂交瘤中CD3/T细胞受体（TCR）介导的凋亡信号转导所必需的。为了确定该DNA结合蛋白家族在胸腺克隆清除中的作用，制备了携带显性负性突变的转基因（Tg）小鼠。转基因由截短的Nur77（δNur77）基因组成，该基因编码与TCR-β增强子连接的Nur77的DNA结合结构域，导致在胸腺细胞中早期表达。与非Tg同窝小鼠相比，在体内和体外用抗CD3或抗TCR抗体处理后，δNur77 Tg小鼠中由CD3/TCR信号介导的CD4+CD8+胸腺细胞凋亡受到极大抑制。在δNur77-Db/HY TCR-α/β双转基因小鼠中研究了自身反应性T细胞的克隆清除。在δNur77-TCR-α/β双转基因雄性小鼠中，表达自身反应性Db/HY TCR-α/β的胸腺细胞总数增加了五倍。表达Tg TCR-α/β的CD4+CD8+胸腺细胞增加了10倍，证明自身反应性胸腺细胞的克隆清除不足。与Db/HY TCR-α/β转基因雄性小鼠相比，δNur7-7Db/HY TCR-α/β双转基因小鼠淋巴结（LN）中的CD8+、Db/HY TCR-α/β T细胞增加了八倍。尽管克隆清除存在缺陷，但表达Tg TCR的T细胞在功能上呈无反应性。体内分析显示，δNur77-Db/HY TCR-α/β双转基因雄性小鼠的LN中，T细胞的激活和凋亡增加，同时Fas和Fas配体的表达也增加。这些结果表明，T细胞中Nur77/Nurr1 DNA结合的抑制导致胸腺克隆清除效率低下，但通过LN和脾脏中Fas依赖性克隆清除维持了T细胞耐受性。
