Van De Wiele C Justin, Marino Julie H, Murray Bryce W, Vo Stephen S, Whetsell Michael E, Teague T Kent
Department of Surgery, University of Oklahoma College of Medicine, Tulsa, OK 74135, USA.
J Immunol. 2004 Apr 1;172(7):4235-44. doi: 10.4049/jimmunol.172.7.4235.
Interleukin-7 is widely accepted as a major homeostatic factor involved in T cell development. To assess the IL-7 responsiveness of thymocytes involved in selection processes, we used a new sensitive flow cytometry-based assay to detect intracellular phosphorylation of STAT-5 induced by IL-7 in defined mouse thymocyte subsets. Using this method, we found the earliest thymocyte subset (CD4(-)CD8(-)CD25(-)CD44(+)) to contain both IL-7-responsive and nonresponsive cells. Transition through the next stages of development (CD4(-)CD8(-)CD25(+)CD44(+ and -)) was associated with responsiveness of all thymocytes within these populations. Passage of thymocytes through beta-selection resulted in a significant reduction in IL-7 sensitivity. In the next phases of development (TCR(-) and TCR(low)CD69(-)), thymocytes were completely insensitive to the effects of IL-7. STAT-5 phosphorylation in response to IL-7 was again observed, however, in thymocytes involved in the positive selection process (TCR(low)CD69(+) and TCR(intermediate)). As expected, CD4 and CD8 single-positive thymocytes were responsive to IL-7. These findings delineate an IL-7-insensitive population between the beta-selection and positive selection checkpoints encompassing thymocytes predicted to die by neglect due to failure of positive selection. This pattern of sensitivity suggests a two-signal mechanism by which survival of thymocytes at these checkpoints is governed.
白细胞介素-7被广泛认为是参与T细胞发育的主要稳态因子。为了评估参与选择过程的胸腺细胞对白细胞介素-7的反应性，我们使用了一种基于流式细胞术的新的灵敏检测方法，来检测在特定小鼠胸腺细胞亚群中由白细胞介素-7诱导的STAT-5的细胞内磷酸化。使用这种方法，我们发现最早的胸腺细胞亚群（CD4(-)CD8(-)CD25(-)CD44(+)）同时包含对白细胞介素-7有反应和无反应的细胞。向下一个发育阶段（CD4(-)CD8(-)CD25(+)CD44(+和-)）的转变与这些群体中所有胸腺细胞的反应性相关。胸腺细胞通过β选择后，白细胞介素-7敏感性显著降低。在发育的下一阶段（TCR(-)和TCR(low)CD69(-)），胸腺细胞对白细胞介素-7的作用完全不敏感。然而，在参与阳性选择过程的胸腺细胞（TCR(low)CD69(+)和TCR(中等)）中，再次观察到了对白细胞介素-7的STAT-5磷酸化。正如预期的那样，CD4和CD8单阳性胸腺细胞对白细胞介素-7有反应。这些发现描绘了一个在β选择和阳性选择检查点之间的白细胞介素-7不敏感群体，该群体包含预计因阳性选择失败而被忽视死亡的胸腺细胞。这种敏感性模式表明了一种双信号机制，通过该机制来控制这些检查点处胸腺细胞的存活。
