Clements J L, Cooper S M, Budd R C
Department of Medicine, University of Vermont College of Medicine, Burlington 05405, USA.
J Immunol. 1995 Jun 15;154(12):6372-81.
The inert quality of MRL-Ipr/Ipr (Ipr) peripheral CD4-CD8- (CD4-8-) T cells manifests primarily as an inability to proliferate or produce IL-2 in response to TCR or mitogenic stimulation. Yet these same cells do initiate early TCR-mediated signaling events, such as generation of inositol phosphates and increased intracellular calcium. They also display constitutively high levels of p59fyn and CD3 zeta tyrosine phosphorylation. The generation of second messengers in T cells normally leads to downstream signaling that results in transcriptional activation of the IL-2 gene. We, therefore, compared the activation state of the IL-2 gene promoter region in freshly isolated and stimulated Ipr CD4-8- T cells with that of normal T lymphocytes. Levels of the octamer, NF-kappa B (p50-p65 heterodimer), and AP-1 transcriptional factors are constitutively elevated in freshly isolated Ipr CD4-8- T cells, consistent with the activated phenotype of these cells. Upon stimulation with mitogens, formation of the transactivating complex, nuclear factor of activated T cells (NF-AT), occurs with normal kinetics in Ipr CD4-8- T cells. Yet, the levels of the activating NF-AT complex never reach those observed in similarly stimulated normal T cells. Furthermore, nuclear extracts from Ipr CD4-8- T cells display high levels of a novel specific binding activity at the NF-AT site, which is present at much lower levels in freshly isolated normal T lymphocytes. Upon mitogenic stimulation, the binding activity of the novel NF-AT-binding factor is rapidly down-regulated in normal T cells, but persists at high levels in Ipr CD4-8- T cells. These two abnormalities at the NF-AT site provide a potential mechanism to account for the defect in IL-2 production from Ipr CD4-8- T cells.
MRL-Ipr/Ipr（Ipr）外周CD4-CD8-（CD4-8-）T细胞的惰性主要表现为在受到TCR或丝裂原刺激时无法增殖或产生IL-2。然而，这些细胞确实会启动早期TCR介导的信号事件，如肌醇磷酸的产生和细胞内钙的增加。它们还持续显示高水平的p59fyn和CD3 ζ酪氨酸磷酸化。T细胞中第二信使的产生通常会导致下游信号传导，从而导致IL-2基因的转录激活。因此，我们将新鲜分离和刺激的Ipr CD4-8- T细胞中IL-2基因启动子区域的激活状态与正常T淋巴细胞的激活状态进行了比较。在新鲜分离的Ipr CD4-8- T细胞中，八聚体、NF-κB（p50-p65异二聚体）和AP-1转录因子的水平持续升高，这与这些细胞的激活表型一致。在用丝裂原刺激后，Ipr CD4-8- T细胞中活化T细胞核因子（NF-AT）转活化复合物的形成以正常动力学发生。然而，活化的NF-AT复合物的水平从未达到在类似刺激的正常T细胞中观察到的水平。此外，Ipr CD4-8- T细胞的核提取物在NF-AT位点显示出高水平的新型特异性结合活性，而在新鲜分离的正常T淋巴细胞中该活性水平要低得多。在丝裂原刺激后，新型NF-AT结合因子的结合活性在正常T细胞中迅速下调，但在Ipr CD4-8- T细胞中持续保持高水平。NF-AT位点的这两个异常情况为解释Ipr CD4-8- T细胞IL-2产生缺陷提供了一种潜在机制。
