Liu C P, Kappler J W, Marrack P
Howard Hughes Medical Institute, Department of Medicine, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206, USA.
J Exp Med. 1996 Nov 1;184(5):1619-30. doi: 10.1084/jem.184.5.1619.
T cells bearing the class II-restricted, DO-T cell receptor (TCR) are CD4+ if their thymocyte precursors are positively selected on the class II protein, IAd, but they are almost all CD4- after positive selection on a class II for which they have higher avidity, IAb. DO-TCR+ T cells mature in H-2b mice lacking CD4. CD4- DO-TCR+ T cells appear in H-2b mice at the same rate as their CD4+ counterparts appear in H-2d animals, suggesting that the CD4- cells are not the product of some minor pathway of thymocyte development and selection. In H-2b CD4 knock out mice expressing human CD2 under the control of the mouse CD4 promoter, mature DO-TCR+ cells did not express human CD2. These results suggest that the CD4-CD8-, DO-TCR+ mature T cells have developed without ever passing through the equivalent of a CD4+,CD8+ stage. The early expression of alpha/beta receptors (TCRs) on thymocytes in TCR transgenic mice may allow maturation of this type. Passage through the equivalent of the CD4+ CD8+, double-positive stage is not essential for differentiation of thymocytes into mature T cells.
携带Ⅱ类分子限制性DO-T细胞受体（TCR）的T细胞，如果其胸腺细胞前体在Ⅱ类蛋白IAd上进行阳性选择，则为CD4+；但如果它们在与其亲和力更高的Ⅱ类分子IAb上进行阳性选择，则几乎全部为CD4-。DO-TCR+T细胞在缺乏CD4的H-2b小鼠中成熟。H-2b小鼠中出现CD4-DO-TCR+T细胞的速率与H-2d动物中CD4+对应细胞出现的速率相同，这表明CD4-细胞并非胸腺细胞发育和选择的某些次要途径的产物。在小鼠CD4启动子控制下表达人CD2的H-2b CD4基因敲除小鼠中，成熟的DO-TCR+细胞不表达人CD2。这些结果表明，CD4-CD8-、DO-TCR+成熟T细胞在发育过程中从未经历过相当于CD4+、CD8+阶段。TCR转基因小鼠胸腺细胞上α/β受体（TCR）的早期表达可能使这类细胞成熟。经历相当于CD4+CD8+双阳性阶段对于胸腺细胞分化为成熟T细胞并非必不可少。
