Kashiwakura J, Suzuki N, Nagafuchi H, Takeno M, Takeba Y, Shimoyama Y, Sakane T
Department of Immunology and the Department of Medicine, St. Marianna University School of Medicine, Kawasaki, Kanagawa 216-8511, Japan.
J Exp Med. 1999 Oct 18;190(8):1147-54. doi: 10.1084/jem.190.8.1147.
Differentiation of human T cells into T helper (Th)1 and Th2 cells is vital for the development of cell-mediated and humoral immunity, respectively. However, the precise mechanism responsible for the Th1 cell differentiation is not fully clarified. We have studied the expression and function of Txk, a member of the Tec family of nonreceptor tyrosine kinases. We found that Txk expression is restricted to Th1/Th0 cells with IFN-gamma producing potential. Txk transfection of Jurkat T cells resulted in a several-fold increase of IFN-gamma mRNA expression and protein production; interleukin (IL)-2 and IL-4 production were unaffected. Antisense oligodeoxynucleotide of Txk specifically inhibited IFN-gamma production of normal peripheral blood lymphocytes, antigen-specific Th1 clones, and Th0 clones; IL-2 and IL-4 production by the T cells was unaffected. Txk cotransfection led to the enhanced luciferase activity of plasmid (p)IFN-gamma promoter/enhancer (pIFN-gamma[-538])-luciferase-transfected Jurkat cells upon mitogen activation. Txk transfection did not affect IL-2 and IL-4 promoter activities. Thus, Txk specifically upregulates IFN-gamma gene transcription. In fact, Txk translocated from cytoplasm into nuclei upon activation and transfection with a mutant Txk expression plasmid that lacked a nuclear localization signal sequence did not enhance IFN-gamma production by the cells, indicating that nuclear localization of Txk is obligatory for the enhanced IFN-gamma production. In addition, IL-12 treatment of peripheral blood CD4(+) T cells enhanced the Txk expression, whereas IL-4 treatment completely inhibited it. These results indicate that Txk expression is intimately associated with development of Th1/Th0 cells and is significantly involved in the IFN-gamma production by the cells through Th1 cell-specific positive transcriptional regulation of the IFN-gamma gene.
人类T细胞分化为辅助性T（Th）1细胞和Th2细胞分别对于细胞介导免疫和体液免疫的发展至关重要。然而，Th1细胞分化的确切机制尚未完全阐明。我们研究了非受体酪氨酸激酶Tec家族成员Txk的表达和功能。我们发现Txk表达仅限于具有产生γ干扰素潜力的Th1/Th0细胞。用Txk转染Jurkat T细胞导致γ干扰素mRNA表达和蛋白产生增加数倍；白细胞介素（IL）-2和IL-4的产生未受影响。Txk的反义寡脱氧核苷酸特异性抑制正常外周血淋巴细胞、抗原特异性Th1克隆和Th0克隆的γ干扰素产生；T细胞产生的IL-2和IL-4未受影响。Txk共转染导致有丝分裂原激活后，质粒（p）γ干扰素启动子/增强子（pIFN-γ[-538]）-荧光素酶转染的Jurkat细胞的荧光素酶活性增强。Txk转染不影响IL-2和IL-4启动子活性。因此，Txk特异性上调γ干扰素基因转录。事实上，激活后Txk从细胞质转位至细胞核，而用缺乏核定位信号序列的突变Txk表达质粒转染细胞不会增强细胞的γ干扰素产生，这表明Txk的核定位对于增强γ干扰素产生是必不可少的。此外，用IL-12处理外周血CD4(+) T细胞可增强Txk表达，而用IL-4处理则完全抑制其表达。这些结果表明，Txk表达与Th1/Th0细胞的发育密切相关，并通过对γ干扰素基因的Th1细胞特异性正向转录调控，显著参与细胞的γ干扰素产生。
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