Ericsson P O, Teh H S
Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada.
Int Immunol. 1995 Apr;7(4):617-24. doi: 10.1093/intimm/7.4.617.
The role of the protein tyrosine kinase (PTK), p56lck, in T cell development was evaluated by mating TCR transgenic mice with transgenic mice that expressed lckF505, a constitutively activated form of p56lck which is under the control of the lck proximal promoter element. The TCR transgenic mice expressed either a receptor specific for the male antigen presented by Db (H-Y TCR) or a receptor specific for pigeon cytochrome c peptide presented by I-Ek class II MHC molecules (AND TCR). The lckF505 transgene caused lower TCR expression in immature CD4+CD8+ thymocytes from normal and TCR transgenic mice. Consistent with the conclusion that activated p56lck causes lower TCR expression, the PTK inhibitor, herbimycin A, was able to restore TCR expression to normal levels in CD4+CD8+ thymocytes from TCR/lckF505 doubly transgenic mice. However, despite lower TCR expression, calcium mobilization was only moderately reduced in CD4+CD8+ thymocytes from H-Y TCR/lckF505 doubly transgenic mice. Furthermore, negative selection of CD4+CD8+ thymocytes expressing the H-Y TCR occurred efficiently in H-Y TCR/lckF505 doubly transgenic male mice despite lower TCR levels. By contrast, analysis of H-Y TCR/lckF505 and AND TCR/lckF505 doubly transgenic mice showed that positive selection in these mice was reduced by 4- to 5-fold by the lckF505 transgene. The smaller proportion of cells that were positively selected in doubly transgenic lckF505 mice expressed normal levels of TCR but higher levels of the appropriate CD4 or CD8 co-receptor molecule. These results indicate that the positive selection of thymocytes is regulated by the enzymatic activity of p56lck.
通过将T细胞受体（TCR）转基因小鼠与表达lckF505的转基因小鼠杂交，评估蛋白酪氨酸激酶（PTK）p56lck在T细胞发育中的作用。lckF505是p56lck的一种组成型激活形式，受lck近端启动子元件的控制。TCR转基因小鼠表达的受体要么对由Db呈递的雄性抗原具有特异性（H-Y TCR），要么对由I-Ek II类主要组织相容性复合体分子呈递的鸽细胞色素c肽具有特异性（AND TCR）。lckF505转基因导致正常和TCR转基因小鼠未成熟CD4+CD8+胸腺细胞中TCR表达降低。与激活的p56lck导致TCR表达降低的结论一致，PTK抑制剂赫曲霉素A能够将TCR/TCR/lckF505双转基因小鼠CD4+CD8+胸腺细胞中的TCR表达恢复到正常水平。然而，尽管TCR表达降低，但H-Y TCR/lckF505双转基因小鼠的CD4+CD8+胸腺细胞中的钙动员仅适度降低。此外，尽管TCR水平较低，但表达H-Y TCR的CD4+CD8+胸腺细胞在H-Y TCR/lckF505双转基因雄性小鼠中仍能有效地进行阴性选择。相比之下，对H-Y TCR/lckF505和AND TCR/lckF505双转基因小鼠的分析表明，lckF505转基因使这些小鼠中的阳性选择减少了4至5倍。在双转基因lckF505小鼠中被阳性选择的细胞比例较小，这些细胞表达正常水平的TCR，但表达较高水平的相应CD4或CD8共受体分子。这些结果表明胸腺细胞的阳性选择受p56lck酶活性的调节。
