Taghon Tom, Van de Walle Inge, De Smet Greet, De Smedt Magda, Leclercq Georges, Vandekerckhove Bart, Plum Jean
Department of Clinical Chemistry, Microbiology, and Immunology, Faculty of Medicine and Health Sciences, Ghent University, Ghent University Hospital, Ghent, Belgium.
Blood. 2009 Apr 2;113(14):3254-63. doi: 10.1182/blood-2008-07-168906. Epub 2008 Oct 23.
Notch signaling is absolutely required for beta-selection during mouse T-cell development, both for differentiation and proliferation. In this report, we investigated whether Notch has an equally important role during human T-cell development. We show that human CD34(+) thymocytes can differentiate into CD4(+)CD8beta(+) double positive (DP) thymocytes in the absence of Notch signaling. While these DP cells phenotypically resemble human beta-selected cells, they lack a T-cell receptor (TCR)-beta chain. Therefore, we characterized the beta-selection checkpoint in human T-cell development, using CD28 as a differential marker at the immature single positive CD4(+)CD3(-)CD8alpha(-) stage. Through intracellular TCR-beta staining and gene expression analysis, we show that CD4(+)CD3(-)CD8alpha(-)CD28(+) thymocytes have passed the beta-selection checkpoint, in contrast to CD4(+)CD3(-)CD8alpha(-)CD28(-) cells. These CD4(+)CD3(-)CD8alpha(-)CD28(+) thymocytes can efficiently differentiate into CD3(+)TCRalphabeta(+) human T cells in the absence of Notch signaling. Importantly, preselection CD4(+)CD3(-)CD8alpha(-)CD28(-) thymocytes can also differentiate into CD3(+)TCRalphabeta(+) human T cells without Notch activation when provided with a rearranged TCR-beta chain. Proliferation of human thymocytes, however, is clearly Notch-dependent. Thus, we have characterized the beta-selection checkpoint during human T-cell development and show that human thymocytes require Notch signaling for proliferation but not for differentiation at this stage of development.
在小鼠T细胞发育过程中，Notch信号对于β选择是绝对必需的，对于分化和增殖均如此。在本报告中，我们研究了Notch在人类T细胞发育过程中是否具有同样重要的作用。我们发现，在没有Notch信号的情况下，人类CD34(+)胸腺细胞可以分化为CD4(+)CD8β(+)双阳性（DP）胸腺细胞。虽然这些DP细胞在表型上类似于人类β选择细胞，但它们缺乏T细胞受体（TCR）-β链。因此，我们利用CD28作为未成熟单阳性CD4(+)CD3(-)CD8α(-)阶段的鉴别标志物，对人类T细胞发育过程中的β选择检查点进行了表征。通过细胞内TCR-β染色和基因表达分析，我们发现与CD4(+)CD3(-)CD8α(-)CD28(-)细胞相反，CD4(+)CD3(-)CD8α(-)CD28(+)胸腺细胞已经通过了β选择检查点。在没有Notch信号的情况下，这些CD4(+)CD3(-)CD8α(-)CD28(+)胸腺细胞可以有效地分化为CD3(+)TCRαβ(+)人类T细胞。重要的是，当提供重排的TCR-β链时，预选的CD4(+)CD3(-)CD8α(-)CD28(-)胸腺细胞在没有Notch激活的情况下也可以分化为CD3(+)TCRαβ(+)人类T细胞。然而，人类胸腺细胞的增殖明显依赖于Notch。因此，我们已经表征了人类T细胞发育过程中的β选择检查点，并表明人类胸腺细胞在这个发育阶段需要Notch信号来进行增殖，但不需要其进行分化。
