Thy-1 functions as a signal transduction molecule in T lymphocytes and transfected B lymphocytes

Thy-1, a glycoprotein of relative molecular mass 25,000 (25K), is a major constituent of the cell surface of mouse thymocytes, peripheral T cells and neurones. In man, Thy-1 is present on neurones and on a small percentage of thymocytes, but is absent from peripheral T cells. The amino-acid and complementary DNA sequences of Thy-1 indicate that it has a structure similar to an isolated V (variable region) domain of immunoglobulin. Although the function of Thy-1 is unknown, the ability of different anti-Thy-1 monoclonal antibodies to activate murine T cells or induce functional changes in neuronal cells in vitro suggests that Thy-1 is involved in transmembrane signalling. We now show that crosslinking of murine Thy-1 triggers a rapid rise in the cytoplasmic free calcium concentration ([Ca2+]i), not only in murine T cells and Thy-1.2-transfected human T cells, but also in murine B-lymphoma cells transfected with the murine thy-1.2 gene. These results indicate that the generation and transduction of the signal leading to the rise in [Ca2+]i is independent of the T-cell receptor and other T-cell-specific molecules. The preservation of the [Ca2+]i-modulating function of Thy-1 in various lymphoid cells of two species further suggests that the necessary signal either originates in the Thy-1 molecule itself or is generated in concert with a highly conserved molecules(s) associated with Thy-1.     

Thy-1-mediated T-cell activation requires co-expression of CD3/Ti complex

In addition to monoclonal antibodies against the CD3 (T3)-T-cell antigen receptor (CD3/Ti) complex, several other monoclonals directed towards distinct cell surface structures on human (CD2 (T11) and Tp44) and murine (Thy-1, TAP, and Ly-6) T lymphocytes are capable of activating T cells. It has been proposed that such structures may function as alternative pathways of stimulation. To examine directly whether any relationship exists between Thy-1-dependent activation phenomena and T-cell activation mediated through the CD3/Ti complex, we have transfected several CD3/Ti- variants of the human T-cell line Jurkat with the murine Thy-1.2 gene. Our data indicate that in CD3/Ti-, Thy-1.2+ transfectants, monoclonal antibodies against Thy-1.2 can induce a rise in cytoplasmic free calcium ([Ca2+]i), but fail to stimulate interleukin-2 (IL-2) production. The only defect in these variant cell lines responsible for the inability to produce IL-2 in response to Thy-1 stimulation was in the expression of the CD3/Ti complex, because replacement of defective Ti alpha- or beta-chain genes reconstributed both surface expression of CD3/Ti and responsiveness to Thy-1 in the IL-2 production assay.     

用于数据库新兴应用程序的逻辑

逻辑与数据库及信息系统之间的关系是广泛和长期存在的。对于数据库理论家而言，逻辑是一个统一的框架。在该框架内可以理解数据模型和查询语言的语义学；允许对它们的可表达性进行比较；并且应用高度开发的数学逻辑工具给出深入的理解。随着数据库系统管理的信息类型日益丰富．数据库和信息系统的逻辑价值也就更加突出。异构和分布式数据源包括了从遗传序列到具有丰富时态的结构；从结合文本与数据的半结构文件到有关复杂组织协同进程的信息。